US2141016A

US2141016A - Alloy steel

Info

Publication number: US2141016A
Application number: US111616A
Authority: US
Inventors: Payson Peter
Original assignee: Individual
Current assignee: Individual
Priority date: 1936-11-19
Filing date: 1936-11-19
Publication date: 1938-12-20
Anticipated expiration: 1955-12-20

Description

Patented Dec. so, 1938 Qumran sures 1,141,016 my s'mar. retel- Pawn, New Yul-1;, N. r.

Na Application November is, was,

Serial No. 111,616

13 claims. (01. ire-e1 This invention relates to improvements in heat, oxidation and corrosion resisting steels adapted for such uses as valves, valveseat inserts and related parts 'of internal combustion engines, 5 high speed and other cutting, forming and shearing tools, hot work dies, die casting dies, and

more generally for use in articles requiring great strength, hardness and resistance to corrosion, oxidation and scaling at elevated as well as at atmospheric temperatures.

' This application is a continuation in part 'of my copending application Serial No. 83,451, filed June 4, 1936, which in turn is a continuation in part of my applications for Letters Patent Nos.

2,009,974 and 2,051,415.

In my patents aforesaid I have described a series of steels, having the properties above .noted, containing about 18 toi35% chromium, about 1 to 10% of metal of the group consisting of nickel 20 and manganese, and about 1 to 10% or metal of the group consisting of molybdenum, .tungsten and silicon, characterized in undergoing a change in phase or in structure when maintained for a period-usually a matter of hours-at elevated temperature within the approximate range of- 1200 to 1800 F., whereby they acquire outstanding and distinguishing characteristics as compared to known steels and also as compared to the characteristics of these same steels prior to such heat treatment. Such steels when so treated acquire high hardness-up to C 65 Rockwel1 or more for some analyses-as compared to their hardness prior to such heat treatment and following usualrolling, forging or annealing operations.- Elevated temperature measurements have shown that these steels actuallyharden at heat, their elevated temperature hardness being superiorto that of known steels and their hardv ness on cooling being substantially independent of the rate of cooling. When so hardened these steels undergo no substantial reduction in hardness after heating to temperatures as high as 1400" or 1600 F. or even higher for someanalyses, and this irrespective of the number, duration or temperature of individual heats.

Whereas according to the information of my patentsaforesaid, at least one of the elements nickel and manganese'and at least one of the elements molybdenum, tungsten and silicon in addition to chromium within the percentage limits noted, is required for imparting heat hard= enability, myfurther investigations have established' that straight chrome steels are susceptible to such hardening provided chromium is present in sufficient amount, i. e. in excess of about 35%; 5

and also that steels containing about 18 to 35% chromium-and which are,thereby substantially non-heat hardenable on the basis of their chromium contents alone, can be rendered so by adding the aboveelements in the manner taught 10 by my patents aforesaid; or by adding about 1 to 10% silicon, about 1 to 10% molybdenum or its equivalent tungsten, or about 1 to 15% of metal of the group comprising silicon, molybdenum and tungsten, as taught by this application. 15

These latter steels difier from those of'my patents aforesaid in that metal of the group consisting of nickel and manganese is not required for imparting heat hardenable properties of such steels.

It is shown in my patents aforesaid that heat 20 'hardenability of the steels therein described, in-

creases with increasing content of the alloying elements other than carbon within the limits therein stated. The same is true of the steels constituting the subject matter of this applica- 25 tion, as isshown by the following data:

' Table I I Effect of chromium on hardenability of straigh 30 chrome steels. C 12%; other elements present in usual amounts.

I on Hardnem small 35 Cr r cant pe Alter 10 hrs.

sees

M1811 Effect on .hardenability or adding i"? enable by adding silicon in suflieient amount,

the hardenability increasing with further increase of this element.

Hardness: Rockwell Si per cent Ai'ter 16 hrs.

As rolled at 14000 Steels which contain insuihcient chromium for heat hardening, may thus be rendered so hard- Table 11 Effect on hardenability o! adding.molybde- V num to chrome steel. 0 about .14; Cr about 30%; elements other than Mo present in usual Y amounts.

- ments other than Cr, Si,

Hardness: Rockwell 0" Mo per cent After 16 hrs.

As mum at 1400' r.

Heat hardenability may be thus imparted to an otherwise non-heat hardenable chrome steel by adding sufficient molybdenum.

Table IV Effect on hardenability of adding molybdenum to chrome-silicon steels and of adding silicon to chrome-molybdenum steels. C about. .15%; ele- Mo present in usual amounts.

Hardness: Rockwell 0 61 Or Si Mo D61 per per cent cent cent Alter 18 hrs.

As rolled at 29.6 3. a 23 45 29. 1 4. 4 27 55 2s. 2 a. 4 4. 7 32 c1 25. 2 a. 1 2.4 1 27 41 24. 4 4. 1 2. a a4 45 24. 4 5. 1 1. 7 33 48 29.9 3.1 1.5 27 51 f 29. c 3. 1 a 5 27 5e 28. 2 3.4 4. 7 32 e1 Comparison of the heat hardening for steel '3 increases with increasing silicon keeping the chromium and molybdenum about constant.

Similarly the results for steels 'l to 9 inclusive, show that hardenability increases with increasing molybdenum keeping the chromium and silicon about constant.

Table .v

Effect on hardenability of varying the. chromium content in steels containing either or both of silicon and molybdenum. 0 about 15%; elements other than Cr, vSi and Mo present in usual amounts.

Hardness: Rockwell "C" or Mo Art 13 hrs er at 14oo F.

19. 0 5. 6 4. 7 37 44 23. s 3. 7 4. 7 31 52 25. 7 4.3 4.8 30 5e 28. 2 3. 4 4 7 32 01 37. 2 1. 8 1. 2 26 63 4o. 7 .9 0 24 e5 Hardenability thus increases with increasing chromium.

Table VI Effect of carbon onhardenability. Cr about 28.5%; Si about 4%; Mo about 1.7%; elements other than C present in usual amounts.

Hardness: Rockwell "0 0 percent After 16 hrs.

As rolled at F.

Increasing the carbon content therefore does not increase hardenability.

The data of Tables I to VI inclusive, thus establish that: Chromium is the dominant element as regards hardenability, and if present in sumcient amount, 1. e., in excess of about 35%, none of the other elements above referred to need be present, although additions thereof enhance hardenability. As the chromium content is decreased, other elements such as silicon, molybde num and tungsten, must be added in increasing amounts for imparting a given hardenability, additions of such elements being requisite where the chromium is below about 35%. In general, hardenability increases with increasing additions of the individual alloying elements other than carto such hardening in appreciable degree. This relationship may be formulated as follows: steels are heat hardenable when the sum comprising two-thirds the chromium content plus twice the silicon content plus the molybdenum content divided by twenty-five exceeds unity., Designating this as the Hardenability Ratio or more briefly as H. R., this relationship may be expressed more concisely as follows: (1) For hardenability The data presented below embracing a wide range of analyses conform to this relationship and tend to substantiate it as a rule of general applicability to such steels.

. ampliiythose 01 Tables I to V1, inclusive, and

Table VII i Hard- And, my lisrdneas ttockwcii bill Ratio: .42 411011011. 11.11. 101100 411400 1 CHROMIUM 10.0 To 20.0 INCLUSIVE 0131101411114 20.1 To 22.0 INCLUSIVE e 0 .00 20.2 4.0 0 .00 25 20 4 .10 21.0 0.7 0 1.10 02 40 011110141004 22.1 To 24.0 mcwsrvn CHROMIUM 24.1 m 20.0 mowsrva .14 25.0 2.0 0 .04 15 14 .14 24.0 0.0 0. .00 20 20 .14 25.7 4.4 0 1.04 00 40 .12 25.0 4.0 0 1.05 24 40 .15 24.0 5.4 0 1.10 01 4s .14 24.0 1.0 4.0 .02 20 .11 25.7 2.0 1.7 .02 10 1s .12 25.2 0.1 2.4 1.02 27 41 .10 24.4 4.1 2.0 1.00 04 45 .10 25.7 4.0 40 1.22 00 50 .14 24.4 5.1 1.7 1.10 00 4s OHROMIUM 20.1 To 20.0 INCLUSIVE OHROMIUM 20.1 T0 00.0 mcl usivn CHROMIUM 00.1 m 00.0 INCLUSIVE CHROMIUM OVER 00.0 55

5 Referring to the data of Table VII, in every instance that the hardenability' ratio is unity or less, the corresponding, steel undergoes little or no increase in hardness after being heat treated; whereas inevery instance that the ratio exceeds unity the hardness of the corresponding steel is greatly enhanced by heat treating. And generally speaking, the analyses which are susceptible to the greatest heat hardening are those for which the hardenability ratio is largest.

The data of Table VII embrace a wide range of compositions for steel containing chromium both with and without silicon, molybdenum or both; so that the above rule appears to be of general applicability as a criterion of hardenability tor such steels. Ihe data of the table, moreover.

lend further support to the conclusions derived therefrom as above stated.

"As was the case with the steels of my patents aforesaid, heat hardening of the steels described herein is a function of time at temperature, and

-in general is more readily secured and to an increased degree if the steel is in the "as forged" or "as rolled condition before hardening, as compared to hardening from the as annealed condition, as appears from:

Table VIII Analysis Rockwell "0 Hardness Pre-heat.l1ardened eon-amen Time. hrs. at 1400 F.

C Si Cr M0 .10 0.00 04.00 40101100 25 25 02 42 40 47 1850 F.anneal 20 20 20 34 43 45 .12 8.10 25.22 2.43 ASX'OHBd 27 27 28 30 36 42 M l850 lianneaL. 24 -25 25 28 29 33 39 As heretofore stated, such steels afterbeing heat hardened, undergo no substantial reduction in hardness after heating to temperatures as high as about 1400 F. or more, as shown by:

Table IX Rockwell C hardness O Si Cr Mo hASt Aft/0r reheating 16 hours at-- 88 Egg 000 000" 1000 1100* 1200" 1400 F. F. F. F. F. F.

' seats and related parts of internal combustion engines. v ,t

As shown by the data contained in Table VIII,

heat hardening of the steels above described is maintaining the same at ele-- vated temperature within the approximate range of 1200 to 1800 F., until a desired hardening. has been imparted. It is immaterial in this connection whether the steel is held within this temperature range while cooling from some higher temperature, such as that of forging. extruding, etc., or is elevated to temperature 1 within this range from some lower temperature for hardening. Also, it is not essential, although preferable, that hardening'be effected at reasonably constant temperature within the hardening range; the temperature may be permitted to increase, decrease,- or fluctuate during this treatment. All such modes of treatment are intends ed to be embraced in the appended claims by the recital of a steel "characterized in being hardened by heating within the approximate temperature range of 1200 to 1800 F. f

Also reference to molybdenum in the claims is intended to include its equivalent, tungsten.

Although silicon is classified as a non-metal, or metalloid, by certain authorities, it nevertheless has the attributes of a metal in the steels oi.

accomplished by the specification and claims herein.

What I claim is: I

1. An alloy steel, characterized in being hardened by maintaining the same at temperature within the approximate range of 1200 to.1800 F. until hardened, and in thereafter undergoing no substantial reduction in hardness after heating to any temperature up to about 1400 F., said steel containing about 18 to 35% chromium, under 1% of nickel and manganese, and about 1 to 15% ofmetal of the group consisting of silicon and molybdenum, the balance of said steel consisting principally of iron.

2. An article subjected to use to elevated temperatures at least a portion of which is made of a steel according to claim 1.

3. A cutting, forming or shearing tool at least a portion of which is made of a steel according to claim 1.

4. A valve or valve element for internal combustion engines at least a portion of which is made of a steel according to claim 1.

'5. An alloy steel, characterized in being hardened in excess of C 32 Rockwell by maintaining the same at temperature within the approximate range of 1200 to 1800 F. until so hardened, said steel being so hardenable While in the as forged, rolled or annealed condition, the resulting hardness of said steel being substantially independent of the rate of cooling from the hardening temperature, and said steel thereafter undergoing no substantial reduction in hardness after-heating to any temperature up to about 1400" F., said steel containing about 18 to 35% chromium, less than 1% of nickel and manganese, and about 1 to 15% of metal of the group consisting of silicon and molybdenum, ,the balance of said steel consisting principally of iron.

6. An alloy steel characterized in being hardened by maintaining the same at temperature within the approximate range of 1200 to 1800 F. until hardened, and in thereafter undergoing no substantial reduction in hardness after heating to any temperature up to about 1400 F., said steel containing: about 18 to 35% chromium, under 1% of nickel and manganese, and about 1 to 15% silicon, the balance of said steel consisting principally of iron.

'7. An alloy steel characterized in being hardened by maintaining the same at temperature within the approximate range of 1200 to 1800 F. until hardened, and in thereafter undergoing no substantial reduction in hardness after heating to any temperature up to about 1400 F., said steel containing: about 18 to 35% chromium, under 1% of nickel and manganese, and about 1 to 15% molybdenum, the balance of Said stee consisting principally of iron.

8. An alloy steel characterized in being hardened by maintaining the same at-temperature within the approximate range of 1200 to 1800 F. until hardened, and in thereafter undergoing no substantial reduction in hardness after heating to any temperature up to about 1400 F., said steel containing: about18 to 35% chromium, under 1% of nickel and manganese, and about 1 to 15% of metal of the group consisting of silicon and molybdenum, the percentage sum of the molybdenum content, twice the silicon content and two-thirds the chromium content divided by twenty-five exceeding unity, the balance of said steel consisting principally of'iron.

9. A heat hardened alloy steel, hardened by maintaining the sameat elevated temperature within the approximate range of 1200 to 1800 F. and characterized in undergoing no substantial reduction in hardness on subsequent heatingto any temperature up to about 1400 F., said steel containing: about 18 to 35% chromium, under 1% of nickel and manganese, and about 1 to 15% of metal of the group consisting of silicon and molybdenum, the balance of said steel consistingv principally of iro'n.

10. A heat hardened alloy steel, hardened by maintaining the same at elevated temperature within the approximate range of 1200 to 1800" F. and characterized in undergoing no substantial reduction in hardness on subsequent heating to any temperature up to about 1400" F., said steel having a hardness in excess of C 32 Rockwell and containing: about 18 to 35% chromium, under 1% of nickel and manganese, and about 1 to 15% of metal of the group consisting of silicon and molybdenum, the balance of said steel consisting' principally of iron.

11. A heat hardened alloy steel, hardened by maintaining the same at. elevated temperature within the approximate range of 1200 to 1800" F. and characterized in undergoing no substantial reduction inhardness on subsequent heating to any temperature up to about1400 F., said steel containing: about 18 to 35% chromium, under 1% of nickel and manganese, and about 1 to 15% silicon, the balance of said steel consisting principally of iron.

12. A heat hardened alloy steel, hardened'by maintaining the same at elevated temperature within the approximate range of 1200 to 1800 F. and characterized in undergoing no substantial reduction in hardness on subsequentheating to any temperature up to about 1400 F., said steel containing: about 18 to=35% chromium, under 1% of nickel and manganese, and about 1 to 15% molybdenum, the balance of said steel consisting principally of iron.

13. A heat hardened alloy steel, hardened by maintaining the same at elevated temperature within the approximate range of 1200 to 1800- F. andcharacterized in undergoing no substantial reduction in hardness on subsequent heating to any temperature up to about 1400 F., said steel containing: about 18 to 35% chromium, under 1% of nickel and manganese, and about 1 to 15% of metal of the group consisting of silicon and molybdenum, the percentage sum of the molybdenum content, twice the silicon content and two-thirds the chromium content divided by twenty-five exceeding unity, the balance of said steel consisting principally of iron.

PETER. 'PAYSON.