US2378991A - Cold rolled manganese steels - Google Patents

Description

Patented June 26, 1945 2,378,991 COLD ROLLED MANGANESE STEELS Russell Franks, Niagara Falls, N. Y.', assignor to Electro Metallurgical C of West Virginia ompany, a corporation No Drawing. Application July 22, 1942,

Serial No. 451,893

8 Claims. (Cl. 148-31) There is a large and increasing demand for structural materials having very high strengths per unit of weight and per unit of volume, and great toughness and ductility. The principal de-. mand has been by the makers of aircraft and other vehicles, but the advantages of high- I strength, light-weight structures are gaining recognition in other fields.

Plastic-bonded non-metallic materials, aluminum-base alloys, and magnesium-base alloys are widely used to obtain a combination of great strength with light weight, but for many purposes the structures gained by a high ratio of strength to weight.

Austenitic type chromium nickel stainless steels, cold-rolled to a high tensile strength, have also gained considerable favor for the manufacture of airplanes, railway cars, and other structures. These steels are very tough and ductile, and offer the advantage not only of a high ratio of strength to weight but also of a high ratio of strength to volume. They are, moreover, very resistant to corrosion and ordinarily do not require surface-protection against the weather.

Several special alloy steels, containing but a few per cent of alloying ingredients, and submitted to strengthening heat treatments, have been used for a limited number of purposes, for instance, airplane tubing and railway trucks, wherein a high ratio of strength to weight is important; but such steels when welded and not specially annealed have not had enough toughness and ductility at very high strength levels to adapt them to all uses in the field of highstrength, light-weight structures.

An object of this invention is to provide a new material having a very high strength per unit of weight and per unit of volume, and great toughness and ductility.

Another object is to use in cold drawing, forming operations.

Another object is to'provide novel cold drawn, cold rolled, and otherwise cold formed steel articles; and a further object is to provide such steels and articles progressive rusting.

In a search for steels which would achieve the objects of the invention, the so-called Hadfleld manganese steels containing 10% to 14% manganese wcreinvestigated. The results were disappointing throughout the composition range. because the material cracked after relatively light cold rolling. Raising the manganese content to 16%, 17.5%. and 18% did not obviate this dimculty. when the manganese content rose to ll2.0% or 30%, the material was dimcult to hot n A provide a new steel for cold rolling, and other cold I have discovered, however, that a manganese which are also resistant to,

built of such materials are undesirably bulky, thus ofisetting to a degree the advantage steel which is readily hot rolled, and is readily cold rolled or otherwise cold worked, and which haswhen sufliciently cold worked a very high strength and excellent ductility and toughness, can be obtained if the manganese content is maintained within certain narrow, critical limits, and if copper or both copper and nickel are added in certain small, critical proportions. I have also discovered that these steels have a substantial resistance to progressive rusting, which resistance can be considerably enhanced, without ill eilect on the physical properties, by

the addition of a small proportion of chromium.-

The invention comprises steel articles of manufacture in the condition produced by cold drawing, cold rolling, or similar cold forming operations, containing manganese between 15.5% and 20%, preferably between 16% and 18%, between 0.25% and 4.5% nickel, preferably 1% to 2.5% nickel, and between 0.25% and 2.5% copper, preferably 0.5% to 1.75% copper, and preferably also containing chromium, remainder substantially iron. The resistance of these articles to progressive rusting is enhanced by the presence of chromium in a proportion between 0.25% and 7%. preferably 1% to 4%.

By "remainder iron and remainder substantlally iron" as used herein and in the appended claims, I mean to include not only chemically pure iron but also iron containing the common impurities and incidental ingredients found in ordinary steels. For instance, carbon may be present in a proportion from 0.01% to 1% or somewhat higher without greatly altering the characteristics of the steel, although it is prefen'ed that the carbon content be less than 0.35%. Nitrogen in a Proportion up to about 0.15%, phosphorus up to about 0.2%, sulfur up to about 0.05%, silicon up to about 1%, and residual-deoxidlzers, scavengers, and grain refiners, such as calcium, may also be present.

The steels ot-the invention, described above, can be hot forged and hot rolled readily, without checking, cracking, or tearing, and can be cold worked, without intermediate or subsequent annealing at high temperatures, to obtain a very high strength while retaining great toughness and high ductility.

The strength and ductility of the steels of the invention are illustrated by the tensile test data in Table A, obtained .on several typical steels within the composition limits described herein. The test data were obtained on standard coupon samples of cold-rolled strips. the amount of coldrolling being indicated in the table.

Department specification No. 41821.

The coupon samples were each 0.035 inch thick, and were Table A Composition (remainder iron) Tensile test data I I Yield Tensile Percent Percent Percent Percent Percent Percent Percent 11 Ni Cu Cr. red. E strengih' el.

p. s. 1. p. s. i.

16.5 0.10 i 1. 0 25 30 114, 300 172, 200 20 16. 5 0.10 1.0 35 28 139, 000 195, 500 18 16.0 0. 0.75 0. 75 35 26 141, 000 161, 500 -6 16.0 0.12 1.00 0. 50 35 26 144,000 195, 200 16.0 0.13 1.00 1.00 U) 35 123,600 184,500 17 16. 5 0.10 2.60 1.15 97,300 148, 200 18 16. 5 0. l0 2. 60 1. l5 5) 27 132, 500 170, 400 13 17. 5 1. 04 4.15 2.12 35 27 157, 000 184, 700 11 16.0 0.10 0. 75 0.75 3.0 35 26 130,000 174,000 9 15.8 0.25 1.10 0. 73 3.1 35 26.5 135,000 ,000' 22 16.0 0.20 2.00 1.00 3.0 25 28 115, 500 160,500 15 16.0 0.20 2.00 1.00 3.0 35 26 142,500 180,500 -l0 l6. 8 0. 13 2.06 1. l0 3. 2 35 28 114,000 175,000 21 None.

In the fOTegOing e. p r e t e i 20 pression. The tabular headings correspond to cates the percentage reduction in thickness of section effected by cold rolling before testing; E indicates the initial tangent modulus of elasticity ,in millions of pounds per square inch; yield strength p. s. i." represents the yield strength in tension, measured at 0.2% permanent set, in pounds per square inch; tensile strength p. s. i. represents ultimate tensile strength in pounds per square inch; and per cent el." represents percentage elongation of the tensile test specimen in rupture, in an initial gauge length of two inches.

Although the steels of the present invention are suitable for lightweight high strength members in the cold rolled condition, still further improvement in certain physical properties may be effected by subjecting the cold rolled steel to a low temperature heat treatment between 100 C. and 250 C. A suitable treatment is at 200 C. for 24 hours. At the lower end of the temperature range a somewhat longer time is required to efiect'the desired result, whereas the time may be lessened at the higher temperatures of the range. At the higher temperatures of the range, some benefit may be derived from heating for as short a period as 30 minutes. In other instances, particuthose of Table A. Buckling stress in p. s. 1. represents the load in pounds per square inch at which the test specimens buckled under compressive loading.

It will be noted from Table C that, the as rolled and heat treated specimens, marked 3" under the column headed condition," show a higher yield strength in both tension and compression than corresponding specimens cold rolled but not heat treated, marked A" in the same column. This effect is particularly pronounced in the specimens tested under compression. These specimens show an increase in yield strength of from 30,000 to 50,000 pounds per square inch over the untreated specimens.

The materials of this invention may be welded by the common welding methods, including the various spot electrical resistance welding meth0ds,'electric arc welding, and oxyacetylene torch welding. This characteristic is of particular value, because welding is usually faster and cheaper than riveting. The material 'need not be annealed after welding.

Table B I larly at the lower temperatures of the range it Com osition (remainder iron) say be desirable to heat for as long as 100 hours. N D

St 0 o. th illustrative of the marked improvement of 0 Percent Percent Percent Percent Percent e ow temperature heat treatment on the stress- Mn Ni 01- Cu 0 Stmm a acteristics. of the steels are given in Tables B d 10. 40 1.13 0.10 Table B ts typical steels of the present inven i5 3 8 81% 111011 d Table C comprises comparative physical 15.33 1.00 3.21 1.10 010 ta of the steels in both the as rolled and the as 55 10.4 1.10 s. 10 0.68 0.21 rolled and heat treated condition, Data are list-. ed for p ysical tests in both tension and com- Table C Tension Compression Per- S l C nd- 13%? {1011' Yield Tensile Per- Yield Buckling E strength, strength, cent E strength. stress. p. 0.1 p. 0.1 cl. p. 0.1. p. 0.1

as A as 100,000 105,000 10 21 100,000 115,200 35 B 20.1 140,200 187,000 10 20 150,200 195,000 25 a 20 114,500 169,900 13 21 30,000 143,200 25 B 28 130,000 100,000 22 s5 .4 28 148,500 mean a 28 112,000 178,300 35 B 30 158,800 214,000 1 20 160,600 206,200 as A 21 123,000 184,600 11 as 109,000 112.500 35 B 211 140,000 181,800 11 21 143.300 185.00 35 A 21 114,000 110,000 21 as 87,600 150.000 :15 a 00V 130,000 110,000 10 21 110.500 100.400 35 .4 21 130,000 187,800 22 23 00,000 100.210 as 1s as 144,000 105,000 1s as 145,000 113,000

A-As cold rolled. B-As cold rolled plus 24 hours at 000 0. followed by air cooling.

I claim: 1. Steel article of manufacture in the condition produced by cold drawing, cold rolling, or similar cold forming operations, comprising mangation produced by cold drawing. cold rolling, or.

similar cold forming operations, comprising manganese between 16% and 18%. nickel between 1% and 2.5%, copper between 0.5% and 1.75%, remainder substantially iron.

3. Steel article of manufacture in the condition produced by cold drawing, cold rolling, or similar cold forming operations, comprising approximately 16% manganese, 1.5% nickel, 0.75% copper, remainder iron.

4. Steel article of manufacture, resistant to progressive rusting, in th condition produced by cold drawing, cold rolling, or similar cold forming operations, comprising manganese between 15.5% and 20%, nickel between 0.25% and 4.5%, copper between 0.25% and 2.5%, chromium between 0.25% and 7%, remainder substantially iron.

5. Steel article of manufacture, resistant to progressive rusting, in the condition produced by cold drawing, cold rolling, or similar cold forming operations, comprising manganese between 16% and 18%, nickel between 1% and 2.5%, copper between 0.5% and 1.75%, chromium between 1% and 4%, remainder substantially iron.

6. Steel article of manufacture, resistant to progressive rusting, in the condition produced by cold drawing, cold rolling, or similar cold forming operations, comprising approximately 16% manganese, 1.5% nickel, 0.75% copper, 3% chromium, remainder iron.

7. A cold formed, high strength article composed of a steel containing manganese between 15.5% and 20%, nickel between 0.25% and 4.5%, copper between 0.25% and 2.5%, remainder substantially iron, said article being in the condition resulting from heating within the range of 100 C. to 250 C. for a time between minutes and hours.

8. A cold formed, high strength article composed of a steel containing manganese between 15.5% and 20%, nickel between 0.25% and 4.5%, copper between 0.25% and 2.5%, chromium between 0.25% and 7%, remainder substantially iron, said article being in the condition resulting from heating within the range of 100 C. to 250 C. for a a time between 30 minutes and 100 hours.

RUSSELL FRANKS.