US2009974A - Alloy steel and method of making same - Google Patents

Description

Patented July 30, 1935 PATENT OFFICE- ALLOY STEEL AND METHOD OF MAKING SAltlE Peter Payson, New York, N. Y., assignor to Crucible Steel Company N. Y., a corporation of No Drawing.

13 Claims.

, My invention resides in the discovery of. a new steel and in a method for hardening the same. The new steel is hardenable by said method up to 0" 65 Rockwell or more; it does not suite-r any substantial permanent reduction in hardness after heating as high as 1600 F., or in some instances to even higher temperatures; and thereby distinguishes from all known steels of which I am aware.

In addition, the new steel possesses a degree of hardness at temperatures of 1100 to 1800 F. or higher, which is superior to that of all known steels. The new steel is, moreover, resistant to corrosion, oxidation and scaling at elevated temperatures. It is, accordingly, exceptionally well adapted for such uses as valves and valve seats for internal combustion engines, hot work dies. die casting dies, high speed and other cutting, shearing, and forming tools, and the like.

Of the known steels, the austenitic chromenickel alloys with or without additions of molybdenum, tungsten, titanium vanadium, silicon, etc., will retain their initial hardness when tempered up to 1600 F., but such steels are incapable of high hardness comparable to that of the steels of my invention. The available normally ferritic steels hardened in accordance with recognized practices, temper or soften when reheated after hardening. Although certain of. these steels may. be so hardened initially as to be susceptible to a slight carbide precipitation hardening at some retempering temperature up to about -1100 F., they soften rapidly as the temperature is increased above 1100 F. D

I have discovered, however, that certain ferrochrome alloys containing nickel-likemetal, such as either or both of nickel and manganesaand containing molybdenum-like metal, such as either or both of molybdenum and tungsten, in appropriate proportions, are susceptible to hardening by heating, with the resulting advantages and to the degree of hardness characterizing my invention as aforesaid.

Steel conforming to the invention may be produced for example by alloying about 18% to 35% chromium, about 1% to 10% nickel-like metal, about 1% to 10% molybdenum-like metal, with ferro-metal, and heating within the approximate Application February 15, 1935,

Serial No. 6,645

1 America, New York,

New Jersey REISSUED temperature range of 1200 to 1800 F. for an interval required to secure a desired hardening. The resulting hardness of the new steel is substantially unaffected by the rate of cooling.

The new steel may contain carbon in amounts ranging from the lowest percentages found in commercial steels, for example .03% ,up to about 1.0%.

The alloying ingredients are preferably combined in such relative proportions as to render the steel initially ferritic, and by "initially ferritic I mean ferritic in the as annealed, as cast, as rolled, or as forged condition.

It will be understood that it is the treatment by adding chromium, molybdenum-like metal and nickel-like metal-in the proportions stated and the heat hardening, which distinguish the steel of my invention and the process of treating the same from those heretofore known, and that iron or steel containing the usualimpurities within commercial tolerances and also other ingredients for imparting thereto well known characteristics of commercial steel alloys, are to be considered as a ferro-metal to which my invention may be applicable. Thus broadly stated the new steel of my invention will contain the following, preferably in proportions to render the steelinitially ferritic:

Chromium, about 18% to 35% Steel conforming to the information above set forth may be readily rolled or forged into any of. the usual shapes imparted to iron or steel, and is likewise useful in cast form.

The degree of hardness acquired by the new steel in consequence of the heat hardening depends in part on the particular composition as well as on the prehardened condition, on the hardening temperature employed, and on the duration of heating, in the manner .indicated by Tables I to IX, inclusive, presented and referred to hereinafter.

The heat hardening is accompanied by a marked reduction in magnetic permeability of the steel, and hence presumably, by .some phase change from an initially ferritic to a substantially non-ferritic state, as is evidenced by:

TABLE I Efiect of heat treatment on hardness and magnetic changes [Steak-1% C, 6.0% Ni, 30.0% Cr, 7.5% Mo] Hardness- Maximum Rockwell induction 0" gausses As rolled 36 6600 Reheated 1400 F., 1 hour. air cooled 63 810 Reheated 1400 F., 15 hours, air cooled".-. 64 800 Reheated 1000 F., 2 hours, air cooled- 64 800 Reheated 1800" F., 2 hours, air cooled. 64 760 Reheated 2000 F., 2 hours, air cooled.. 32 8900 1 For magnetizing force of 300 oersteds.

TABLE 111 Efiect on hardenabilzty of prehardening condition [Steelz- .07% o, 5.2% Ni, 27.6% Cr, 1.2% Mo] Rockwell O hardness After reheating for indicated Prehardening condition Initial time at 14000 R hardness 1 hr. 4 hrs. 16 hrs. hrs.

As rolled 35 42 48 49 50 As annealed at:

1800 F. for 1 hr- 18 2A 38 44 47 2200 F. lot 1 hr 18 20 31 40 46 Other factors remaining constant, maximum hardness is secured for steels having a carbon TABLE II HardnessRockwell 0" Type of steel percentage As hardened Hardness alter reheating 1 k132i}; at temperatures indicated by heating at 1400 F for 16 hrs Cr Ni Mo 600 800 1000 1200 1400* 1600 1800 In contrast to this performance, known steels of comparable initial hardness either soften progressively with increase of tempering tempera ture, or are subject to variation in hardness for reheating temperatures up to about 1100 F., and

content below approximately 1.0%, but the hardness is increased progressively by additions of chromium, manganese, molybdenum or tungsten within the limits specified as is shown by Tables IV and IX inclusive, as follows:

TABLE IV Efiect of carbon on hardenability Cr constant at 24.0% Cr constant at 27.

Ni constant at 5.0% Ni constant at 5.0 7?

Mo constant at 3.0% Mo constant at 4.5%

o Hardness, Rockwell O Hardness, Rockwell "C" Annealed Hardened Annealed Hardened .07 max. 18 38 .0! max. .10/.15 19 42 .10/.l5 32 6 311.25 24 34 fill/.25 24 51 301.36 23 36 .80/35 25 47 Tm: V Tun: 1x

Eflect of Or on hardenability fl W n m l i! C constant a: 27.3% max.

r cons an a C constant at.10/.l57

Niconstam at Ni constant at 5.0% Mo constant at 4.5%

Hardness, Rockwell C Hardness. Rockwell "C w or Annealed Hardened Annealed Hardened 2.0 18 36 4.0 21 37 18 15 23 6.0 23 46 21 21 46 24 25 47 27 24 55 24 A comparison of the results in Tables VIII and IX shows that as regards its eiIect on harden- TABLE VI Efiect of Ni on hardenability C constant at.l0/.l5% C constant at .10/.15% Cr constant at 27.0% C! constant at 27 .07 Mo constant at 1.5% Mo constant at 4.5%

Hardness, Rockwell C Hardness, Rockwell 0 Ni Ni Annealed Hardened Annealed Hardened TABLE VII ability, tungsten may be substituted in whole or Efiect of Mn on hardenab'ility C constant at .10% max.

Cr constant at 27.0% Mo constant at 4.5%

A comparison of the results in Tables VI and VII shows that as regards its efiect on hardenability, manganese may be substituted in whole or in part for nickel.

in part for molybdenum.

The choice of proportions in each instance depends, of course, on the nature of individual applications.

The new steels,.particularly those containing relatively high percentages of chromium, nickel and molybdenum, or their equivalents, are more resistant than are the known steels to many acids and other corroding media, and are, moreover,

- highly resistant to oxidation and scaling at elevated temperatures.

In the appended claims by the term nickellike metal", I mean to include either or both of nickel and manganese; by the term molybdenum-like metal I mean to include either or both of molybdenum and tungsten; and by the term balance substantially all iron I means to include iron and steel containing commercial impurities.-

TABLE VIII Efi'ect 0] Mo on hardenabz'lity C constant at .10]. 15% Cr constant at 27. 0%

G constant at .10]. 15% Cr constant at 27. 0% Ni constant at 6. 0%

Ni constant at 2. 5%

Hardness, Rockwell 0" Hardness, Rockwell "0" Annealed Hardened Annealed Hardened What is claimed is:

1. An alloy steel containing: about 18% to 35% chromium, about 1% to nickel-like metal, about 1% to 10% molybdenum-like metal, carbon up to about 1.0%, and the balance substantially all iron, in proportions to render said steel initially ferritic, said steel being hardened by heating within the approximate temperature range of 1200 to 1800 F.

2. An alloy steel containing: about 18% to 35% chromium, about 1% to 10% nickel-like metal, about 1% to 10% molybdenum-like metal, carbon up to about 1.0%, and the balance substantially all iron in proportions to render said steel initially ferritic, said steel being hardened by heating within the approximate temperature .range of 1200 to 1800 F., and developing its maximum hardness after heating within said range.

3. An alloy steel containing: about 18% to 35% chromium, about 1% to 10% nickel-like metal, about 1% to 10% molybdenum-like metal, carbon up to about 1.0%, and the balance substantially all iron in proportions to render said steel initially ferritic, said steel being hardened by heating within the approximate temperature range of 1200 to 1800 F., and the resulting hardness of said steel being substantially unafiected by reheating below about 1400 F.

4. An alloy steel containing: about 18% to 35% chromium, about 1% to 10% nickel-like metal, about 1% to 10% molybdenum-like metal in proportions to render said steel initially ferritic, carbon up to about 1.0%, and the balance substantially all iron, said steel being hardened by heating within the approximate temperature range of 1200 to 1800 F., and the resulting hardness of said steel being substantially unafiected by reheating below about 1800 F.

5. An alloy steel containing: about 18% to 35% chromium, about 1% to 10% nickel, about 1% to 10% molybdenum, carbon up to about 1.0%, and the balance substantially all iron in proportions to render said steel initially ferritic, said steel being hardened by heating within the approximate temperature range of 1200 to 1800 F.

6. An alloy steel containing: about 18% to 35% chromium, about 1% to 10% manganese, about 1% to 10% molybdenum, carbon up to about 1.0%, and the balance substantially all iron in proportions to render said steel initially ferritic, said steel being hardened by heating within the approximate temperature range of 1200 to 1800 F.

7. An alloy steel containing: about 18% to 35% chromium, about 1% to 10% nickel, about 1% to 10% tungsten, carbon up to about 1.0%, and the balance substantially all iron in proportions to render said steel initially ferritic, said steel being hardened by heating within the approximate temperature range of 1200 to 1800 F.

8. An alloy steel containing: about 18% to about 1% to 10% tungsten, carbon up to about 1.0%, and the balance substantially all iron in proportions to render said steel initially ferritic, said steel being hardened by heating within the approximate temperature range of 1200 to 1800 F.

9. The method of producing a heat hardened alloy steel consisting of about 18% to 35% chromium, about 1% to 10% nickel-like metal, about 1% to 10% molybdenum-like metal, and carbon up to about 1.0%, and the balance substantially all iron in proportions to render said steel initially ferritic, said method comprising: heating said alloy within the approximate temperature range of 1200 to 1800 F. to harden.

10. The method of producing a heat hardened alloy steel consisting of about 18% to 35% chromium, about 1% to 10% nickel-like metal, about 1% to 10% molybdenum-like metal, and carbon up to about 1.0%, and the balance substantially all iron in proportions to render said steel initially ferritic, said method comprising: heating said steel within the approximate temperature range of 1200 to 1800 F. for an interval required to secure substantially maximum hardening of said steel.

11. An article made of a heat hardenable alloy steel, resistant to corrosion, oxidation and sealing, and containing: about 18% to 35% chromium, about 1% to 10% nickel-like metal, about 1% to 10% molybdenum-like metal,carbon up to about 1.0%, and the balance substantially all iron in proportion to render said steel initially ferritic, said steel being hardened by heating within the approximate temperature range of 1200 to 1800 F.

12. An article made of a heat hardenable alloy steel, resistant to corrosion, oxidation and sealing, and containing: about 18% to 35% chromium, about 1% to 10% nickel-like metal, about 1% to 10% molybdenum-like metal, carbon up to about 1.0%, and the balance substantially all iron in proportion to render said steel initially ferritic, said steel being hardened by heating within the approximate temperature range of 1200 to 1800 F., and the resulting hardness of said steel being substantially unaffected by reheating below about 1400 F.

13. An article made of a heat hardenable alloy steel, resistant to corrosion, oxidation and sealing, and containing: about 18% to 35% chromium, about 1% to 10% nickel-like metal, about 1% to 10% molybdenum-like metal, carbon up to about 1.0%, and the balance substantially all iron in proportion to rendersaid steel initially ferritic, said steel being hardened by'heating within the approximate temperature range of 1200' to 1800 F., and the resulting hardness 01 said steel being substantially unaflected by reheating below about 1800 F.

PETER PAYSON.