US2474766A - Alloy steel - Google Patents

Description

Patented June 28,` 1949 (Cl. 'i5-423) 7 Claims.

Thisnventin frtes t-'lit steers and more "paitlnlarly tvo Tow alloy; tensile strength steels adapted for ntnf ctmt'ff` trates 'suite maar weidingty t'fnfn al methods.

f'Afrtherfobjt of fthe vent' n'is the provisidn'nfsuth 'an alloy 'stt' "n a `'specific lion'ileinaticir'l5 `ofy alltiu'yiirgl el'een'ts can be varied Within definite "ranges ttclvlrrvi'tle proper Weldalldilityand strength y'for i'a'r'yirig thicknesses of bate.

The ffore'goin'g 'objects' are 'achieved I:in the prsentnvention by the prei'zislc'i` Lofi afew A'and useful tomltinationfor` 'allowing leriientsfwmch to'- gether with iron are combined to give an alloy steel having the desi/fable tensile properties, toughness Aand `dut'stility "common lto present day rW 'alloy or niild alloy-steels together with iinprovedweldin'g characteristics.

fHigh tensile ialloy'stels intended for welded plate fabrication have heretofore `beensubject to serious shortcomings. `yWhen a plate of steel is Welded by gas, nt'allior'carbon arc, or electrical resistance inetlids, a'ae 1vcalled the heat affectdzone, nxt Ito theffused Weld'` metal, is heated t"t/inpe`ratres vra'iigir'ig fron the lower criticaflpont up to the-melting rangeof the a1- loy. nfterthe welding operation, `'as this zone cools, the steeltherein may under certain conditions become excessively hard, even to the extentudf :acquiring crlckstwhichrare sometimes 'referred to'r'as :underbead J'cracks. The 'hardening j tendencyin the w heat affecteazoneis aggravated when the carbon content:of'thefalloyfis increased ,Qra certain alloying elements are added to raise the strength of the steel.`

In the p'a'st'; it has beenrnecessary for the steel industry todoptoneor more costly and laboriols expediente` "to avoid excessive hardening and cracking duringweldingmoperations. One `such expedient to .restrict they. carbont content of `the steel` to 4less than about 0.12per cent, The actual percentage of certain widely used alloy steels;` fabricated -'into tpl'ate'is fabut'fOlOQ to 0.1 l 'per cnt. Whenltlecarbon ntentfis restricted 'in 'this 'frxiannen "itfi'sn'fnecessary-tb add lrelatively large 'and Acostly-zt11"1'c1iit;s of 1"alloying: elements tof provide strengthinf the lultilnate composition. "Presentfcomrnercialhighrtensile'isteels intended fior Welding c'contain 'relatively large f amounts of "ffmanganese, vchronuin, artiekel; rccpper., and tpnosto prehat them, 'er to.l emiploiexpensive electrodes.

According tbV purfinve'n cwy alleys-steel is prvidledrofnigh fterfsil@properties-tand ofr'siitable 'euctnity `Satin-1tinignness witnutftr'eehardfenability common to the manganese steels of the pirfrt. Qur steels contain between 0.12 and 0.201-per`fcentl carbon `andbetween l `0.40 ialtid'OlQO percentmanganese.-

Wherasfin the'rpr-ior artf,-steelswith 290 cent manganeselsslhif tiloenlfsftilsf ry frornthe-pirit of viewofstifng l vflfcyi'ld-pint, We *have discovereda combination o allo ""g "elrnentsvvhich enables-us tolimitthe"` e `content to 0290 per cent or .below-r whil the same tiineobtaining the necessari/physicalSpiperties.

` Our invention obviates `the necessityfofff'addii'g any chromium in obtaining the desired propirties 'and "pf tb'-iep VtloW `as possibleLaridfinaiyfcase, iit'irilperfent of the steel.

mild imprvern'erit 'in strengthtitvitnouttcitically increasingthe thardra'bilitymf mirc-steels. Thus,

inches, we sometimes find it desirable to increase Y the tensile strength f the ultimate composition by the addition of nickel suicient to raise the total nickel content to between 0.50 and 1.0 per cent. Such addition does not critically increase the hardening characteristics of the alloy in the *Y heat affected zone of the weld;

the total phosphorus is maintained below a maximum of 0.08 per cent.

Our steels contain between 0.50 and 1.50 per cent silicon and in formulation of individual heats *according to our invention we prefer to adjust the amdunt of manganese employed within l the limits above stated in proportion to the amount of silicon. Thus, when 0.50 per cent of 1 silicon is employed we use in the neighborhood of 0.40 per cent of manganese which is near the lower limit of the operable range of amounts,

while, on the other hand, when higher percentages of silicon are employed, the amount of manganese is proportionately increased.

In our steels, improved welding properties are obtained by the addition of titanium in conjunction with another alloying element. The element used in conjunction with titanium can be molybdenum or vanadium or columbium or zirconium. The amount of titanium employed is between 0.03 and 0.20 per cent of the steel and the amount of the additional element used in conjunction therewith is between 0.10 and 0.45 per cent.

Thus, a steel prepared according to our invention will conform to the following analysis:

Chromium 0.20 maximum The remainder is iron containingimpurities incidental to the commercial production of steel.

We have found that alloy steels within the foregoing ranges will provide a high tensile steel having yield strengths comparable to or `superior to other high strength steels now used in the industry together with greatly reduced hardenability characteristics under the influence of welding. Thus, careful hardness measurements made with a Knoop or Vickers diamond indenter scarcely ever-show a hardness in excess of 300 in the heat effected zone after welding. Likewise, steel formulated with the above alloying ingredients in the range of proportions stated exhibit freedom from underbead cracking even ,under severe welding conditions. i

of our invention, we have discovered that a combination ofY carbon, manganese, and'silicon within the above ranges together'with a combination of titanium and another allo-ying element selected from the group consisting of molybdenum, zirconium, vanadium and columbium provides a novel combination of high strength and improved weldabilityfin steel together with freedom from objectionable alloying elements. In practicing our invention, titanium is combined with one of the elements in the aforesaid group in a ratio of about 1 part titanium to between 3 and 8 parts of said element. Thus, the steel may contain, for example, 0.10 per cent vanadium and 0.03 per cent titanium, or as another example 0.05 per cent titanium may be combined with 0.18 per cent molybdenum, and a third example is the use of 0.04 per cent titanium with 0.12 per cent zirconium. In using columbium, we prefer to employ about 0.40 per cent in conjunction with 0.05 per cent titanium. We prefer that the amount of titanium plus the amount of one of the aforesaid four elements with which it is combined should be limited to a total of between 0.13 and 0.50 per cent of said steel.

It will be seen that alloy steels made in accordance with these principles readily provide considerably higher yield points together with improved weldability than is possible under the present art. For example, practically all the present commercially deyeloped high strength steels are made to-only 45,000 p. s. i. minimum in plates over one-half inch thick. Using our invention we have readily produced seven-eighths inch thick plates-ihaving yield points of 50,000 to 63,000 pounds per square inch. A steel prepared in these ranges had the following chemical analysis and physical properties:

A preferred composition for the production of one-half inch plate of improved welding characteristics is obtained from a heat corresponding to the following analysis:

Percentage Carbon 0.14 Manganese 0.65 Silicon 0.75 Molybdenum 0.18 Titaniume 0.05 Phosphorus 0.06 maximum Sulphur 0.04 maximum For a more detailed presentation of the advantages of low weld hardenability coupled with high-tensile strength properties, reference is made to our article entitled: Some observations on the welding of manganese steels, Thei Welding Journal Research Supplement, October, 1944.

Steels conforming to the analyses herein de- In order more particularly to denne the nature ,scribed and claimed .exhibit Jominy curves very similar to that shown for heat 421 in Fig. 7 of the reference article.

Having thus described our invention with the aid of illustrative examples, it is to be understood that our invention is not to be taken as limited thereto, the scope of the invention being dened by the appended claims wherein the particular ranges of amounts specined may be, of course, subject to slight variations Without departing from the spirit of the invention.

We claim:

1. A low alloy, high tensile steel suitable for the production of plates having improved weldability, said steel containing 0.12 to 0.20 per cent carbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon, 0.08 per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20 per cent maximum chromium, from a trace to 1.0 per cent nickel, from a trace to 0.35 per cent copper, 0.03 to 0.20 per cent titanium, 0.10 to 0.45 per cent of an element selected from the group consisting of molybdenum, zirconium, vanadium and columbium, the remainder being substantially all iron.

2. A low alloy, high tensile steel suitable for the production of plates having improved weldability, said steel containing 0.12 to 0.20 per cent carbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon, 0.08 per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20 per cent maximum chromium, from a trace to 1.0 per cent nickel, from a trace to 0.35 per cent copper, titanium and an element selected from the group consisting `of molybdenum, zirconium, vanadium and columbium, the ratio of the amount of titanium present to that of said element being between 1 to 3 and 1 to 8 and the total amount of titanium and said element being from 0.13 to 0.50 per cent of said steel, the remainder being substantially all iron.

3. A low alloy, high tensile steel suitable for the production of plates up to about one inch thick having improved weldability, said steel containing 0.12 to 0.20 per cent carbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon, 0.08 per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20 per cent maximum chromium, 0.25 per cent maximum nickel, from a trace to 0.35 per cent copper, 0.03 to 0.20 per per cent titanium and 0.10 to 0.45 per cent of an element selected from the group consisting of molybdenum, zirconium, vanadium and columbium, the remainder being substantially all iron.

4. A low alloy, high tensile steel suitable for the production of plates from about 3A inch thick to about 21/2 inches thick having improved Weldability, said steel containing 0.12 to 0.20 per cent carbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon, 0.08 per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20 per cent maximum chromium, 0.50 to 1.0 per cent nickel, from a trace to 0.35 per cent copper, 0.03 to 0.20 per cent titanium and 0.10 to 0.45 per cent of an element selected from the group consisting of molybdenum, zirconium, vanadium and columbium, the remainder being substantially all iron.

5. A low alloy, high tensile steel suitable for production of plates having improved Weldability, said steel containing 0.12 to 0.20 per cent carbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon, 0.12 to 0.25 per cent molybdenum, 0.03 to 0.20 titanium, 0.08 per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20 per cent maximum chromium, from a trace to 1.00 per cent nickel and from a trace to 0.35 per cent copper, the remainder being substantially all iron.

6. A low alloy, high tensile steel suitable for the production of plates having improved weldability, said steel containing 0.12 to 0.20 per cent carbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon, 0.10 to 0.20 per cent zirconium, 0.03 to 0.20 per cent titanium, 0.08 per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20 per cent maximum chromium, from a trace to 1.00 per cent nickel and from a trace to 0.35 per cent copper, the remainder being substantially all iron.

7. A loW alloy, high tensile steel suitable for the production of plates having improved Weldability, said steel containing 0.12 to 0.20 per Cent carbon, 0.40 to 0.90 per cent manganese, 0.50 to 1.50 per cent silicon, 0.20 to 0.45 per cent columbium, 0.03 to 0.20 per cent titanium, 0.08 per cent maximum phosphorus, 0.04 per cent maximum sulphur, 0.20 per cent maximum chromium, from a trace to 1.00 per cent nickel and from a trace to 0.35 per cent copper, the remainder being substantially all iron.

ALVIN G. WAGGONER. WILLIAM B. BROOKS.

REFERENCES CITED The following referenlces are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 1,261,743 Churchward Apr. 2, 1918 1,839,157 Mathesius Dec. 29, 1931 2,040,189 Strauss May 12, 1936 FOREIGN PATENTS Number Country Date 118,263 Switzerland Dec. 16, 1925 OTHER REFERENCES Alloying Elements in Steel, pages and 66; edited by Bain, published in 1939 by the American Society for Metals, Cleveland, Ohio.

Making, Shaping and Treating of Steel, 5th edition; edited by Camp and Francis, published in 1940 by The Carnegie-Illinois Steel Corporation, Pittsburgh, Pa.

Metals and Alloys, February 1939, pages 48 and 49.