The Iron Age 1940-03-14: Vol 45 Iss 11

— Managing Editor Machinery Editor OLIVER MOFFETT CAMPBELL JAMES London, England MEYER SANDERSON Toronto, Ontario LEROY ALLISON Newark, N. J. St. Louis Publication Office Chestnut and 56th Sts., Philadelphia, Pa., U.S.A. HILDRETH, GEORGE GRIFFITHS, EVERIT TERHUNE, VAN DEVENTER, J. H. VAN DEVENTER President and Editor BAUR Vice-President and General Manager News Editor Metallurgical Editor Art Editor Associate Editors PHAIR Washington Editors ELLIS Resident District Editors Pittsburgh Chicago SHERMAN Cleveland Detroit Editorial Correspondents Cincinnati FRAZAR FIDRMUC Boston Hamburg, Germany CHARLES Post Milwaukee San Francisco CLYDE ENNIS Birmingham I’. TURNER, JR. Buffalo DIX, Manager Reader Service ADVERTISING STAFF Robert F. Blair. § 621 Union Bldg., Cleveland B. L. Herman, Chilton Bldg., Phila. H. K. Hottenstein, 1012 Otis Bldg., Chicago H. E. Leonard, 239 W. 39th St.. New York Peirce Lewis. 7310 Woodward Ave., Detroit C. H. Ober. 239 W. 39th St., New York Fitzgerald Db. C. Warren, P. O. Box 81, Hartford, Conn. Don F. Harner, 1595 Pacifie Avenue, Long Beach, Cal. Member, Audit Bureau of Circulations Member, Associated Business Papers Indexed in the Industrial Arts Index. Published every Thursday. Subscrip- tion Price: United States and Pos- sessions, Mexico, Cuba, $6.00; Can- ada, $8.50; Foreign, $12.00 year. Single copy, 25 cents. Annual Num- ber $1.00. Cable Address, Owned and Published CHILTON COMPANY (Incorporated) Editorial and Executive Offices OFFICERS AND DIRECTORS C, A. MUSSELMAN, President Vice-President Vice-President Vice-President Vice-President S. BAUR, Vice-President WILLIAM BARBER, Treasurer JOUN BLAIR MOFFETT, Secretary JULIAN CHASE, THOMAS L,. KANE, G. C. BUZBY, P. M. FAHRENDORF HARRY DUFFY FINDLEY Editor Emeritus RICCIARDI ROBERT BINGHAM Roy 239 West 30th St., New York, N. Y., U.S.A THE Contents March 14, 1940 Unlimited Frontiers Interpretation Test Results Theory and Practice Slag Control Process Control Aircraft Spotwelding Heat Resisting Steels Cutters, Small Tools and Gages Manufacture Fish Hooks Tool Engineers Annual Meeting Couldn't Done Hand the Assembly Line Washington News THE NEWS BRIEF Statistics Metal Working Activity Rate Activity Capital Goods Weekly Ingot Operating Rates Plant Expansion and Equipment Buying New Industrial Literature Just Between Two Products Advertised Index Advertisers Copyright, 1940, by Chilton Company (Inc.) 106 114 132 134 162 q x Ss $ 44 ‘ . ‘ 7 Production Costs Cut with Certified Alloy Steels You can depend better results less time when your heat treater guided the Ryerson alloy data charts. These charts show him the exact properties the steel with which working and tell him how get the de- sired results. does not have test. takes chances. Spoilage eliminated and sound dependable job high accuracy and uniformity assured. addition saving production costs, the Ryerson Certified Alloy plan benefits the Purchasing Depart- ment they can keep detailed record the exact Principal products stock for Im- mediate Shipment include— Bars, Structurals, Plates, Iron and Steel Sheets, Tubing, Shafting, Strip Steel, Alloy Steels, Tool Steels, Stainless, Babbitt, Welding Rod, etc. IRON AGE, March 1940 analysis every alloy purchased. Thus possible duplicate particularly desirable close range specifica- tions repeat orders. The Metallurgical Department benefitted too for they can call for any reasonable physical requirement and sure the Heat Treater can produce the desired result. Ryerson Certified Steels also include carbon, tool and stainless steels that meet definite quality standards. They offer many advantages steel users. Let tell you the complete story. Write for booklet. Joseph Ryerson Son, Inc. Plants at: Chicago, Milwaukee, St. Louis, Cincinnati, Detroit, Cleveland, Buffalo, Boston, Philadelphia, Jersey City. 5 ... THE IRON AGE ... MARCH 14, 1940 ESTABLISHED 1855 Vol. 145, No. Unlimited Frontiers HAVE heard some the younger men our industry complain that their grandfathers got all the breaks. That they lived and worked while our frontiers were still expanding and times when man who was able and willing open new territory could make fortune, comfortable living least job Men who think like that today are the wrong track. They are not altogether blame for being there, however, since many our prominent public figures—mostly zeros themselves when you sum them up—are dinning that defeatist philosophy our ears day and night. Grandfather did have advantage. There were New Dealers his day who made him think that his fellow citizens owed him living. knew that was him sink swim, proceeded learn toswim without teacher. Grandpa cultivated initiative and used it. Grandpa did open new physical frontiers. fought the Indians, worked hours day, opened the West, squatted settled wherever the land offered him oppor- tunity. When found would not yield him living, which was often, moved another place, under his own steam and not ona Government ticket. Grandpa sweated summer and froze winter. did not have steam heat air conditioning heat cool him. adapted himself his times and his environment. And his reward, and large, was meagre. Usually was short life and hard one. Harder than most our young men today could endure. Well, they don't have to. These are different times and our physical frontiers are mostly all opened except remote places like Alaska. But there are other frontiers opened that are unlimited. Unlimited their extent and also the reward gained those who open them. The opening our physical frontiers gave agricultural products and raw mo- terials such coal, iron, copper and gold. Gave much these basic materials that there are limits now for the new pioneers who discover new ways use them. Any bright young man today who willing emulate his grandfather initiative and determination and who will work hard with his head grandfather worked with his hands will find the new frontiers far richer reward than the old ones were. But get that reward, will have fight the Indians. The Indians defeatism, discouragement and the hope something for nothing. } | ey 2 j \ | => Heart the newest Automatic Gear Shift cylinder, 4-inch diameter cup, drawn depth. And the call for 8000 parts per day. Ordinary sheets caused tremen- dously high breakage rates. acceptable rejection figure was fixed three per cent. When Inland Hot Rolled Sheets were used, the breakage was brought down average less than one per cent! That kind performance nothing new with Inland Sheets. why manufacturers come depend Inland Sheets reduce production costs. They the job better. They cut waste the bone. They help you keep output right schedule. Inland metallurgists are available work out similar economies for you. Write today. SHEETS STRIP TINPLATE BARS PLATES FLOOR PLATES STRUCTURALS PILING RAILS TRACK ACCESSORIES REINFORCING BARS Production cost went down when Inland Hot Rolled Sheets were used form this vacuum cylinder. First draw. Blank Second draw. and cup. Draw inches. Trim flash. Embossed, punched and drilled. 3 22—THE IRON AGE, March 14, 1940 NTERPRETATION test results must necessarily involve considera- tion the application the steel other materials service. One set properties might entirely suitable for one type service but distinct failure might result another applica- tion. Neither will one test, quently more than one, not properly chosen, always serve satisfactory measure the suitability article for the service intended. Merely list all the tests that have been applied steel products would take more time and space than would justified since many are suit- able for specific applications only. The most that can done discuss the more common tests and include some more special type illustrate the value results obtained from tests suit the particular conditions. the final analysis, the performance the steel during fabrication and the history the finished article assem- bly service are the only complete tests that omit unanticipated factors that lead erroneous interpretation results. Very probably tests were orig inated prevent the repetition pre- vious failures finished products. these have been added numerous other tests such those determine suit- ability for various operations during fabrication, uniformity product not necessarily the finished condition, comparison different compositions, suitability for new developments re- quiring special properties not previous- employed, etc. Most these might still considered incidental the de- sire manufacture product that will j ESTS alone are little worth determining the suitability material for given application—the proper tests must chosen and the results interpreted correctly. The different phys- ical tests, their characteris- tics and the results obtained for various metallic articles are all treated herein, this the first section two-part article. ° ° ° not result undue failure service. perhaps the failure keep this original purpose mind that has re- sulted the misapplication and misinterpretation test results many cases. number such mis- interpretations will mentioned later connection with the different types tests. general may said that the best test for finished product outside actual service one which tests the full size part, preferably assembled part unit, under conditions ap- proaching nearly possible those obtaining service. Frequently this can done but other cases there are limitations and difficulties the way. Parts may large that they could not tested without sectioning, the design might require special equip- ment not available the number parts one design would not justify the cost destruction any them. Many the conditions prevailing service may unknown, known, ° ° ° McMULLAN Youngstown Sheet Tube Co., East Chicago, Ind. ° ° ° difficult reproduce accelerated tests. certain that our engineers are unable calculate the occur assembled units under dynamic loads and frequently the effect de- flection point load application not taken into consideration. The de- signer, course, cannot held re- sponsible for intentional overloading service beyond the rated capacity. doubt too, tests complete assemblies can lead erroneous results. in- stance mind that one the large automotive companies which sev- eral years ago thoroughly tested its radiators for cooling capacity driv- ing cars the dry, hot, Southwest States. Yet, after selling them the public, many complaints overheated radiators came from New England States. Similar complaints have escaped proving ground tests. The human factor from the test operator, the driver these cases, enters such tests also. The lack suitable test methods the uncertainty interpretation re- sults may offered explain why, when the final decision made de- sign procedure, frequently more re- liance placed copying, with suit- able modifications, article proc- ess that has proved successful the past, than placed the results calculation and standard tests. That method reality follows the natural Neither can denied that such procedure carries with many the mistakes and needless precautions the past that might eliminated THE IRON AGE, March 14, | | a é i i | — by ‘ 4 ia te. bat £ 4 ) x 4 suitable tests. Testing complete article assembled unit, course, really only test the weakest unit and testing comparison one part unit with another could lead vicious cycle. The writer has been told that the front axle one the early automobiles was designed making changes until the car could driven against brick wall with such force that the tires would rupture be- fore damage the axle would result. the comparative strength the tires and axle from the results, what would eventually happen the next step should build tires that would not rupture before the axle Quality and Uniformity Tests general might divided into those which determine the quality and uniformity product more less unfinished state, regardless subsequent fabricating service re- quirements, and those which determine suitability for more specific fabricating operations and types service. Qual- ity and uniformity tests include chem- ical analyses, microscopic examina- tions, grain size and hardenability, but these are beyond the intended scope this paper. the intention dis- cuss tests, although chemical means may used make istics. character- AND Fracture Tests: Etch tests are widely used check for the presence blow holes, large inclu- sions, porosity,’ dendritic patterns, internal ruptures, blooms, billets, bars, castings and other steel and iron products. The deleteri- ous nature several these defects self-evident but the effect others more obscure. dendritic pattern one the latter and there exists difference opinion its effect. While more pronounced some types steel than others, dendritic wrought products frequent- amount hot work has been done and the pattern probably will eliminated further hot working, such forg- ing, follow. When the pattern due to, accompanied by, carbide segregation high carbon steels, such high speed steel, definitely harmful mechanical properties. Thermal cracks, internal ruptures, bursts variously named, also are harmful mechanical properties but they too may eliminated sequent hot work which welds them shut. Blow holes and porosity due gas also weld hot working the 24—THE IRON AGE, March 1940 surfaces not become contaminated. macro etch are usually considered harmful. Banding flow lines forgings are more harmful when such direction receive trans- verse stresses. The adverse effect defects castings depends greatly their nature, size and location re- gard thickness section and tensity stress. Etching used also bring out surface defects such seams, laps and grinding cracks. Sulphuric, hydro- chloric and other etching acids that liberate hydrogen may actually develop cracks where none existed, prior etching show grinding cracks highly hardened steel. Cracks thus de- veloped probably follow lines high internal stress. Nitric acid, the other hand, will make visible only those cracks actually present before etching, and the etching deep enough will entirely remove shallow cracks. Fig. illustrates how etching tests may used reveal surface defects produced during fabrication. When copper present steel, surface checks occur when the steel hot worked. The samples shown were forged down bars from small cast- ings. They are low alloy steels about 0.40 per cent carbon and contain 0.70 and 1.00 per cent copper that order from left right. This effect can diminished eliminated the addition nickel amounts equal greater than the amount copper present. Fracture tests may used deter- mine the uniformity and quality metal products. Fracture may either parallel transverse grain flow. Sometimes specimens are hardened be- fore the test made. the fracture reveals the same kind in- formation the etch test, but the etch test usually more comprehensive. Many the tests described under the next heading are used for deter- mining quality and uniformity also. Fabrication and Performance The tests described may used determine suitable for fabricating operations performance service, both, and for the most part attempt will made classify them that basis. the writer’s opinion that the more usual types service which steel products are subjected require tests re- vealing one more the following properties. Tensile strength, shock re- sistance, notch sensitivity, and wear resistance. Endurance tests the same characteristics under repeated loading. More special service applica- tions require knowledge corrosion resistance, creep rate high tempera- tures, etc. Tests FoR TENSILE STRENGTH: The tensile strength can measured variety ways. The standard tensile test specimen machined 0.505- in. diameter probably the most familiar and widely used—also the re- sults are widely common practice larger specimens take the specimen from point half way between the center and surface. Since many machine structural parts are stressed bending tor- sion rather than simple tension, the stresses developed service are pro- portional the distance from the neutral axis. such values the halfway point may have little value. The tendency toward lower alloy shallow hardening steels has resulted products with surface hardness 400 500 Brinell and perhaps 250 Brinell the center, as, for example, certain automotive axle that case the hardened shell, which really determines strength the shaft, may less than thick. This too thin from which chine test specimen, but test taken from any other location little value. machine test specimen first and then harden brings the problem warpage and also sets distribution. Some other test, such torsion test the complete shaft, far more value under the circum- stances. the other extreme, the properties near the center large piece may most interest when machining done after ment, as, for example, drilled and splined holes, deep slots, The surface condition finish may have pronounced bearing tensile properties. Sucker rods put into service with their surface the hot rolled condition. Both ductil- ity and tensile strength are affected decarburization and surface tions. tensile test short length bar more suitable than one that has been machined down standard size. must kept mind in- terpreting results, also, that surface scratches, sharp corners, threads, etc., decrease allowable stresses. Threaded bolts, studs, etc., should tested full size finished products possible. The writer has seen butt welds tested cutting strips across the weld and pulling them tensile ma- chine cases where service conditions | if \ } IG. tests show surface checking developed hot working copper containing steels. The samples shown (natural size) contain 0.40 and 0.35, 0.70 and per cent copper from left right. imposed practically stresses either the weld material the rection tested. While the tensile test did serve somewhat check the uniformity the formance, bend test wider speci men would quicker, cheaper and more informative. The may offer definite figures standard method, but definite percentages unsuitable standard not help much applying results. means the tensile test, the elastic limit, yield point, elongation and reduction area are obtained also. The foregoing remarks apply the interpretations placed these results well the maximum tensile strength. The elastic limit value since represents the safe load without permanent deflection. Its usefulness diminished the fact that more difficult determine and, especially heat treated steels that have been given low draw, its location may depend the sensitivity the instrument used and the care taken making the readings. also more affected internal stresses present which may altered re- moval material during machining additional stresses may set the machining, stamping method used form the test speci- men. The elastic limit determined may therefore even further er- ror from that the article whole than either the tensile strength yield point. Both the nature the yield point and its numerical value are importance forming operations flat products. High Factors Affecting the Plastic De- formation Sheet and Strip Steel and Their Relation the Deep Drawing Joseph Winlock and Ralph Leiter, Trans actions A.S.M., Vol. XXV, No. 163. 2“Taylor Speed and Its Relation Reduction Janitzky, Transactions A.S.M., Vol. XXVI, No. 1122. elongation and dropping load carry ing capacity result local extension and stretcher strains contrast more uniform flow metal when the sharp break the curve The point, connection with other properties such elongation and tensile strength, important forming operations and static struc- tures, some yielding may permit redistribution stresses and more stable structure rupture occur. Yield point may little interest dynamic parts. Close dimensional maintenance many moving parts necessary and they would valueless the elastic limit were exceeded; also, any definite yield treated alloy steels and many carbon steels well. Reduction area and elongation are measures the ductil- steel. They are important connection with redistribution stresses, already mentioned. While ordinarily thought only connec- tion with stresses that cause perma- nent deformation, they should not overlooked elsewhere. Sharp notches, threads, concentrate stresses, but steels with high elongation and reduc- tion permit better load distribution and minimize danger sudden fail- ure. Reduction area has been re- ported measure machinability hardness the machinability becomes poorer with increase reduction area. has been found that, the com- mon steels uniform quality, tensile strength varies directly Brinell hardness regardless the com- position the steel. The proportion varies little different hardness levels but the tensile strength aver- ages about 500 times the Brinell hard- 4 4 ¥ 4 : § similar relationship between strength and other hardness values the material uniform hardness. Hardness checks therefore offer quick and easy means determining approximate tensile strength and may apply surface layers and parts size from which tensile tests could not taken. Also they may non- destructive compared with de- structive tensile test. Bend tests and torsion tests may substituted for standard specimens determine tensile strength. Unless the steel highly hardened, however, torsion failure more apt occur shear. The usual formula for bending loads gives unit tensile stress values for outside fibers considerably higher than maximum values obtainable from standard ten- sile specimens. Because uneven load distribution with maximum stress the surface, bend test specimens may more sensitive surface con- ditions than tensile tests should remembered selecting samples, choosing the direction loading and interpreting results. Bend tests and specimens, with per- haps the exception cast iron, have not been standardized the extent that tensile tests have been. The ca- pacity testing machines such that larger specimens can used for bend and torsion tests frequently making possible the use full size specimens such, for example, automotive front rear axle parts assemblies bending torsion. The interpreta- tion results from standard bend torsion test specimens machined out for test purposes only subject the same errors mentioned connec- tion with standard tensile tests. impact tests study the effect rapid application load. While the THE IRON AGE, March 14, 1940—25 n aE. 4 A > 7 | rat | | \ } more commonly used specimens are notched, notched bar and impact tests are not synonymous the latter may used unnotched specimens and any rate load application may employed with notched bars. Since the desire design keep away from notches and sharp corners, notched im- pact tests usually are not designed simulate serviceconditions. They should interpreted tests establish the relative values various compositions, heat treatments, case depths, etc., under shock loads and the sensitivity various ma- terials surface imperfections. Pre- liminary treatments must considered as, for example, only relatively few degrees difference drawing tem- perature not other properties might cause consider- able difference impact results. Also the temperature which the test made important, for wide fluctua- tions may occur impact values within rather narrow temperature zone. The minimum temperature reached service should govern the interpretation results. Since im- pact specimens are smaller and simpler design than the tensile speci- men and the notch can located any side, possible get tests near the surface specimens cut from shallow hardening steel. Impact tests have been applied test specimens many sizes and shapes including finished sults such cases can applied only Torsion Impact Properties Greene, Transactions A.S.M., Vol. XXIII, No. 861. 26—THE IRON AGE, March 1940 that testing automotive ring gear teeth clamping the gear rigidly fixture and dropping known weight from measured heights strike tooth the pitch line. The inten- tion indicate what shock the gear will stand service. Results are dif- ficult interpret since shocks such severity not occur service be- cause the cushioning effect rub- ber tires, wind-up shafts, They can value comparison against standard test faulty design, in- ternal stresses, case depths and imper- 2—Progressive fractures shaft stressed torsion. Grooves and sharp corners act stress raisers. diam- fections surface finish the blow can controlled strike the cor- rect location each time. more recent development im- pact testing the torsion impact test. Small specimens have been used for single blow tests steels, and the results indicate that greater sensitivity the effects low draw temperatures shown the torsion test. This said aid the selection proper heat treating pro- cedure for tools.* Large flywheel types machines have been constructed for single blow tests small shafts standard specimens one inch diam- eter. Even these tests not closely simulate service conditions failure use more likely occur fatigue rather than from single blow. The shock resistance ratings various steels may different order, when tested under blows that not cause permanent distortion, they would tested blows that produce permanent distortion frac- ture. Since the only useful properties are those exhibited before failure occurs, would not reasonable for many applications develop tests that would show what steel iron prod- ucts can withstand without rather than determine the energy ab- sorbed when failure does Thus highly hardened silico-manganese steels give good account themselves shear blades, chipping chisels, ete., where shock loads are very severe, yet the usual destructive tests would show low impact values. The high elastic limit such steels permits relatively large elastic distortion without failure. mentioned, notched bar tests are used for various rates load application and for different kinds tests such impact, bend, endurance, torsion, etc. The effect the notch local- ize raise stresses, and this becomes more severe with the sharpness and depth the notch. Failure occurs when the cohesive strength exceeded before deformation sets in. All steels break brittle manner the notch severe enough. The notch may therefore varied test the relative notch sensitivity steels ments that make satisfactory products tensile strength and other prop- erties. The test especially applicable designs necessitating sharp notches such threads and service condi- tions that may stretches, nicks, etc. Somewhat akin the notch effect that protrud- ing fins, sharp corners, etc. These too may serve local stress raisers present critical location, and there- fore the point origin fatigue and other failures. Fig. shows fatigue failure grooved shaft driven key. The large crescent shaped fatigue failure originated the bottom the cir- cumferential groove progressed Another small fatigue frac- ture started the sharp corner the keyway. Both conditions, the groove and the sharp corner, served stress raisers. Materials high damping capacity are said less sensitive the in- fluence surface notches. Damping tests measure the rate damping out vibrations. common test proce- dure set torsional vibrations cylindrical Stresses are kept below the elastic limit. Damping the result dissipation energy the form heat. Ed. Note:—Next week the author will conclude with discussions hardness and wear resistance, torsion tests, endurance tests, bend, shear, compression, cupping and high temperature tests. | > ‘ ° PHILBROOK Assistant Superintendent Metallurgy and Inspection, and Research Metallur- Respectively, Wisconsin Steel Works, International Harvester Co. ° problems slag control occupy more and more the attention open- hearth men, now that analyses steels are becoming increasingly rigorous. These problems are treated this article. During the past three weeks the authors have covered slag formation, transfer iron oxides, measurement oxidizing power, elimination carbon from the bath, rate oxidation slag and bath, effect temperature, elimination silicon and manganese, and removal phosphorus. Herein, conclusion, some observations are made the removal sulphur, and extensive details are presented slag control." EMOVAL SULPHUR: not the intention this paper discuss sulphur removal any detail. Sulphur not much prob- production rimming steels for severe deep-drawing application, particularly view the present trend toward deliberate specification sulphur con- tents 0.055 0.065 per cent for better machineability high quality forging and alloy steels. well known that any extensive removal sulphur from liquid iron steel requires highly basic slag, high temperature, and reducing condi- tions. The basic open hearth process operates all times under oxidizing conditions, and its ability remove sulphur therefore limited and some- what uncertain. far the best prac- tice selection and control insure low sulphur scrap, low sulphur iron, and low sulphur fuel. When sulphur troubles are encountered, neces- sary abandon otherwise desirable principles slag control favor high basicity and increase time and temperature, divert the heat some less exacting specification this possible. The function practical slag con- ° trol quality killed steel arrive rapidly possible the end the refining period heats, which course the point which furnace de- oxidation starts, with minimum oxides the steel bath. the same time this minimum should obtained without excessive build-up oxides the slag which may possibly transferred the bath during the fur- nace deoxidation. The primary reason for desiring low oxide content the steel bath this point that the basic open hearth process the furnace deoxidation must carried out the use reducing elements, such manganese, silicon and aluminum, which form solid liquid reaction products the bath. order pro- duce satisfactorily clean steel, these reaction products must almost en- tirely removed allowing them float the surface the bath. While this process gravity separation taking place, more reaction products are being formed from the oxides dif- fusing into the bath from the slag, and therefore the time which can al- lowed for this gravity separation THE IRON AGE, March 14, 1940—27 1 | a a a » : ‘ ~ Pouring slag pancake test. definitely limited. the FeO content the bath low, relatively few non- metallic inclusions are during furnace deoxidation, and. importance from cost standpoint, the amount deoxidizers required achieve the de- sired FeO content the steel leaving the furnace will reduced. The Refining Period the previous text attempt has been made show that the basic open hearth process operates accord with definite laws chemical equilibrium. Any artificial disturbance the nat- ural approach equilibrium, created manipulation the slag, will purely transitory effect, and when correction once started the fur- nace system will proceed ac- celerated rate until the same conditions have been established would have resulted without the application control, unless the readjustment stopped the tapping the heat further manipulation which will postpone the adjustment only tempo- The only exception this statement the accelerated removal carbon during the early part the refining time the use ore, be- cause this reaction rendered non- reversible the removal the flame the carbon monoxide formed. Even this case, the same conditions iron oxide the slag and bath and rate carbon drop will established some lower carbon content would apply the same carbon content were reached without ore. Since any unbalance during the re- fining period the natural striving the bath-slag-flame system toward equilibrium does not result any last- ing beneficial effect. would seem more the point assist the furnace system reach the desired end point the most direct way. Any system practical slag control must first provide for removal phosphorus point below the de- sired maximum, Certain definite limits the minimum percentages lime and iron oxide the slag, and definite fluidity characteristics are required for phosphorus elimination. “V” ratios 2.2 2.5 offer safe working range insure removal phosphorus. ratio 2.5 greatly exceeded, the viscosity the slag also greatly increased, the action the furnace retarded, the heat transfer the bath lessened, and the iron oxide content the slag increased. The lime necessary arrive “V" ratio this range 2.2 2.5 may derived all from the original charge, deficiency lime may charged, and additions burnt lime may subsequently made. Theoreti- cally, knowing the weights and analyses the components the metallic late the exact quantity lime which would required form the desired slag from such charge. This pro- cedure would exactly the same which has been practised suc for many years. impossible make accurate practice. major portion the charge steel scrap heterogeneous nature, and its exact composition can- not obtained analysis but can only roughly estimated. Under some conditions operation, such taking hot metal from several blast furnaces through large mixers, accurate estimate may made the composition the hot metal which will added some hours subsequent charging the furnace. When hot metal taken from one blast fur- nace. even the best estimate may far trom correct when the time comes charge the hot metal, due unex- pected “swings” the blast furnace. less important the fact that the Creased Lime Ratios 1.2 1.6 28—THE IRON AGE, March 14, 1940 Furrowed Lime Silica SLAG PANCAKES Lime Silica Ratios 2.1 Intermediate Ratios 2.4 Basic slags are finishing slags with Lime over 2.4 > i | ‘ amount lime actually the slag may very appreciably more less than the quantity charged, be- cause lime remaining on, picked from the bottom. Since, shown above, even the most accurate and detailed calculations the composition the charge which practical make fail give reli- able figures which base the lime charge, the best solution the prob- lem charge either what past prac- tice shows the minimum quantity lime for phosphorus removal, deliberately charge deficiency lime, and add lime required during the course the heat. Since the oper- ator faced with choice charg- ing too much or too little lime, it seems preferable charge deficiency be- cause simple matter add more lime required, but impossible re- move excess lime. suggested neutralize excess lime additions silica sand; however, such cedure unnecessarily increases the slag volume, and can recommended only much lime inadvertently present. The procedure charging deficiency lime has been practical only since able method, such the “pancake” method, for estimating the basicity slag. Shaping-Up Slag order take full advantage the practice charging deficiency lime, would desirable de- velop experiment relationship which would enable the operator, be- fore the heat was melted, estimate the actual amount lime which would brought up. With this knowledge, would able add part the make-up lime period when the slag was highly acid and thus mini- mize its erosive action banks, and the same time get head- start shaping his slag. the authors’ knowledge such has not yet been developed prac- tical basis, but seems entirely feasi- ble with the aid visual examination slag cakes. The process the slag should begin soon the greater part the lime up, but be- fore the heat entirely The use fluorspar very beneficial facilitating the solution lumps calcined limestone, and spar usually necessary obtain the desired fluidity this period when the slag rather Cook, Open Hearth Slag Transactions the American Society for Metals, 25, pp. 325-416 (1937). and low iron oxides. Some care and experience the use spar necessary avoid over-sparring this time, which might lead exces- sive fluidity later stage. Changes the basicity the slag the lime periodic “pancake” tests. Spar imparts etched appearance the surface the slag cakes, which must con- sidered the interpretation the tests. Corrective additions burnt lime should made when estimated that solution the remaining lime will not bring the value the slag 5.0 paring slag conditions existing various plants, for translates into numerical values such indefinite terms “fluid,” “creamy,” and “viscous.” The range slag fluidity desired dur- ing the refining period corresponds the Herty Viscosimeter. For the same reasons which make difficult calculate the lime charge necessary give slag desired basicity melt, plus additional com- plications arising from differences degree oxidation with variations the physical condition the scrap, has been found that impossible Value slag on wm Lime boil Time Compromise Refining period Kill Tap Fig. 7—Schematic comparison slag control practices. the desired range 2.2 2.5. The amount burnt lime required effect given increase the ratio will depend primarily upon the slag volume and also upon the slag compo- sition, and additions must upon actual experience, but with the usual practice 125 150 ton heats, 1000 Ib. burnt lime complete solution will increase the ratio 0.2 0.4. Fig. schematic diagram com- paring ideal and basicity practices with the compromise which may obtained practical operation. The use “pancake” tests conjunction with the melters judg- ment the fluidity the slag from its appearance the furnace has largely eliminated the need for mea- sure slag viscosity, such Herty for control pur- poses. The Herty Viscosimeter was valuable tool the time was in- troduced, and still useful for com- proportion the scrap and pig iron the charge such way that the carbon content the bath melt will the exact amount required for proper refining the heat. Making Oxide Additions general, more satisfactory practice charge little more car- bon than necessary, rather than too little. The extra carbon which thus obtained may removed rapidly additions ore. Although mathemati- cal calculations may made de- termine the amount ore required reduce the carbon from given point lower value, this information has been known from practical observation most open hearth operators since long before the theories were in- vented. The reactions which ore removes carbon from the bath have been cov- ered the theoretical discussion THE IRON AGE, March 1940—29 A I | SQN ce — — | ray 1.0 | | | =, there, the effect accelerate the rate carbon drop until the added oxygen has been removed from the bath; but eventually the FeO content the bath and slag, and the rate carbon drop, will become the same would have obtained the same amount carbon had been removed more slowly oxidation the flame alone. For this reason, the addition ore not detrimental steel any grade sufficient time allowed for the oxygen thus introduced worked out the bath the carbon boil. safe rule add ore high quality forging and alloy heats during the last two hours before tap. Oxide additions may made the form lump ore, fine ore, mill scale. Lump ore preferable most cases because penetrates through the slag and much reacts directly the steel bath, thus eliminating the time lag required for solution the slag and transfer the added FeO the steel bath the usual convection and diffusion process. Mill scale does have some beneficial effect helping flux lime floaters before the slag shaped up. There frequently some time lag before the effect such scale additions becomes apparent bath, followed very sudden drop carbon after the scale might have been thought have been dissipated. For this reason, the use hard ore for removing carbon from the bath and spar for shaping the slag con- sidered better practice for qual- ity heats. recommended that the greater part the estimated ore re- 5000 Ib., included the first addi- tion. One-half hr. should allowed ascertain its effect before further ore used, the additions being tapered off such way that the carbon drop does not get beyond the melter’s control. Mill scale has been recommended various times for “iron oxide control” the slag, and believed that the practice has been misconstrued some extent. effort was made the theoretical discussion show that the active iron oxide content the slag determined the carbon content the bath and the ability the slag and bath react normally through the convection process. The total iron con- 30—THE IRON AGE, March 14, 1940 tent the slag affected also the basicity because the formation stable calcium ferrites. The total iron content the slag is, and should considered, result the control slag basicity and viscosity conjunc- tion with the carbon content the bath, and should not object specific control itself. The reason for adding mill scale not increase the iron oxide content the slag end itself, but bring the carbon and oxygen content the bath given point, work- ing “equilibrium” with the slag, faster than the same point would reached oxidation the flame alone. Be- cause remains the slag and does not carry siliceous impurities into the bath, mill scale permissible later stages the heat, where the use ore would prohibited. Furnace Deoxidation the end the refining period the heat, when the carbon has been lowered the desired point, and the phosphorus and sulphur are below the desired maximum, the heat for furnace deoxidation. desir- able slow the transfer oxygen from the slag during the deoxidation period the furnace, and this can done increasing the viscosity, “thickening up” the slag addition burnt lime. case the furnace deoxidation practice used calls for interval min. between the addition the deoxidizers and tap, the addition burnt lime for thick- ening the slag may made just prior the introduction the de- oxidizers. When the deoxidation prac- tice used calls for longer interval than min. between start fur- nace deoxidation and tap, neces- sary increase the basicity the slag somewhat before the final addi- tion burnt lime. the basicity not increased, the solution the added lime will take place rapidly that the end the longer deoxida- tion period the slag will have thinned out such extent that serious re- oxidation the bath will take place and thus nullify the effect the de- oxidizers added. the heat allowed “open-up” before tapped, the FeO accumulated the slag during furnace deoxidation may all trans- ferred the bath with disastrous re- sults. Therefore, when short deoxida- tion period used, the recommended basicity ratio 2.2 2.5 for the re- fining period may carried until im- mediately prior the furnace deoxi- dation which time two three pans burnt lime are added. When long deoxidation period say min. used, additions burnt lime should started hr. more before the furnace block, increasing the basicity the slag around 3.0 3.5 ratio, dependent upon the time interval used. One three additional pans burnt lime may then charged just before the furnace deoxidizers are added. actual practice, many varia- tions furnace deoxidation practice exist, due different grades and types steel and different combinations deoxidizers, that only general recom- mendation can made the final condition the slag just prior fur- nace deoxidation. Although this final conditioning the slag must based upon the deoxidation practice em- ployed, the general principles slag control during the should very generally applicable all grades killed steel any shop, since they are aimed arriving the furnace deoxidation period with the lowest oxygen content the bath and slag the shortest possible time. The recommended practices for slag control may very briefly summar- ized follows: (1) Charge slight deficiency lime and make additions burnt lime range 2.2 2.5 “V” value during the refining period. (2) Maintain fluid slag (viscosity Viscosimeter) within the sicity range during the refining period the use fluorspar. (3) Charge heats melt somewhat above the desired melt carbon, and use hard ore required reduce the car- bon rapidly. ore added quality heats during the last hr. be- fore tap. (4) Thicken the slag addi- tions burnt lime just prior charg- ing furnace deoxidizers, order decrease the rate transfer FeO the bath. = 4 | | | ° ° HIBERT Consolidated Aircraft Corp., San Diego, Cal. ° ° ° considered the design engi- neer the shear strength per weld, which the load necessary shear single spot between two sheets that are stressed Table (see article last week) gives the mini- mum shear strength requirements for various spot welded materials. These data have been garnered from various sources, and the actual shear strength per weld will average much higher strength shown the same table based two-thirds the minimum shear strength—these values may used until approved design require- ments are established. When two more sheets unequal thickness are welded the values for the thinnest gage are used, The common error designing spot weld parts the failure allow cient edge distance spacing welds too close together. The distance from the center the weld the edge the sheet should not any case less than four times the thickness the thinnest gage welded. The width the flange overlap the seam should not less than eight times the thickness the thinnest gage welded the joint. For more than two thick- nesses sheet welded together, both the minimum flange depth and the min HAT the requirements are for successful air- craft spot welding, the weld- ing variables, time current dwell, diameter and shape electrodes, pressure, contact resistance and current density were all dealt with last week. Herein, the second and last section this report, the author presents data the design spot welded parts, equipment necessary, per- sonnel and inspection pro- cedure. imum edge distance, given Table should slightly increased. TABLE Spacing Data for More Than Two Thicknesses Metal Minimum Minimum Edge Flange Thickness Distance Depth 0.014 in. less 1/16 in. in. 0.030 in. less in. in. 0.046 in. less in. 0.078 in. less in. The minimum allowable spacing spot welds the same the minimum flange depth, given Table II. Spacing many cases, approxi- mately the same slightly less than similar riveted construction. any event, spacing should not designated less than increments. Spot welds are usually placed eye, and therefore only approximate spacing should called for. For instance, in. approximately, in. approximate- ly, etc. typical spacing for 18-8 stainless steel would in. apart, and in. for non-structural parts aluminum alloys. Sheets varying thickness may spot welded, and several sheets four and five may spot welded simultaneously. Combinations gages that vary widely may make job im- practical and should avoided. hard and fast rules can given, but ratio thin thick greater than aluminum alloy may consid- ered impractical. course, with steels the ratio may much greater steel welding not critical for alu- minum alloys. Different combinations thicknesses should kept min- imum any one part, each combi- nation requires different setting current and pressure the spot weld- ing machine. Welds aluminum alloys are noto- riously weak tension and torsion, consequently welds should applied THE IRON AGE, March 14, 15, | — tle that they are stressed shear only. Torsion and tension stresses may occur design where one weld isolated would welding the ends corru- gated section angle with but one weld each corrugation. such in- stances the material free work be- tween each weld, causing failures. Stainless steel may considered the ideal material for spot welding, the welds are strong either shear, ten- sion, torsion. With sufficient num- ber welds properly spaced, 100 per cent efficiency the joint may realized. Cost per weld has been given Size and design parts present limitations for stainless steel, port- able tools and various unique setups can utilized. With aluminum alloys differ- ent story, for here most the welds are effected fixed machine high electrical capacity, and many special tricks the trade cannot employed. set any limits the size and shape objects that can accommodated spot welding equipment hardly possible special equipment may designed reach relatively inacces- sible places. The thought bear mind for aluminum alloys the larger the parts welded the less positive re- sults will obtained. For this rea- son and also from cost standpoint, parts should small and easily acces- sible. thickness in. for one sheet 32—THE IRON AGE, March 1940 Total thickness can greater than in. long the stack does not con- tain gage heavier than in. Spot welding aluminum alloys limited the following alloys the Army and Navy bureaus: 17ST clad, 24ST Alclad, and 53ST for extruded shapes. Drawings must submitted for approval each spe- cific part and recently only ap- proval for non-structural parts was granted. The correct symbol indicate spot welds drawings the dollar sign ($) with but one cross bar, order distinguish spot welds from rivets. aluminum alloys use rivet each end and rivets regular intervals, prevent tension failures from starting. With steels there necessity for doing this except for aid assembling. Spot welded parts subject vibra- they were riveted construction. Seam and spot welded tanks have passed the requirements Army and Navy vibration tests. Cowling has been welded and has been service for over three years without evidence failure. Equipment The equipment required welding consists machines, elec- trodes, timing control, heat control, pressure control The requirements, course, are deter- NTERIOR view the radio room com- mercial ship built for American Ex- port Lines. The ventilating ducts, conduit boxes, switch panels and radio table are all spot welded mined the nature the material equipment sufficient electrical pow- er, and general the best results are obtained when high current passed through the work short period time. Nominal name plate kva ratings are usually one-half the maximum output the machine, and ratings are determined multi- plying secondary volts secondary amperage. Secondary amperage as- peres and turn ratio. The amount secondary volts necessary welding machines found from the formula. Secondary Volts VArea (secondary amperes) The area, this case the cross- sectional area between the welding arms, consequently the area the smaller the capacity needed. The larger this area the less efficient the machine, d