US2379988A - Steel alloys - Google Patents

Description

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STEEL ALLOYS Filed'Feb. 22, 1944 Mn+ l.5x Ni INVENT Carl P08 BY Maurice C. Fe izer ATTORNEY Patented July 10, 1945 s'rasr. more,

Carl a. rim and Maurice c. Fetzer, Wyomilsing,

assignors to The Carpenter Steel Company,

Beading,

Pa., a corporation of New Jersey Application February 22, 1944, Serial No. 523,408

2 Claims.

This invention relates to air-hardening steels.

It is an object oi the invention to produce a steel which will harden in air to a Rockwell C hardness of at least 55.

It is a further object to produce a steel which will harden in air to a Rockwell C hardness of at' least about 55 in large sections or pieces-for example, pieces having a size at least as large as those typified by sections four inches round b four inches long.

It is a further object to produce a steel which will air-harden to a Rs: hardness of at least 55 from temperatures of 1600 degrees Fahrenheit and lower, in large sections or pieces-for example, pieces having a size at least as large as those typified by sections four inches round-by four inches long.

It is a further object to produce a steel having the hardening properties above set forth and, in addition, having unusually high toughness.

It has been found that the combination of properties above set forth can be obtained in a steel by employinga combination of certain a'lloying components, with a particular range of carbon content, and restricting the total alloy content between certain limits. The alloying elements employed are manganese, chromium, and

molybdenum. Nickel may be substituted fora portion of the manganese to the extent and in the manner hereinafter indicated.

The nature and scope of the invention will be defined in the claims and described by reference to the accompanying diagram, which is a trilinear or pseudo-ternary diagram, showing the interrelationship between the alloying elements, manganese, chromium, and molybdenum, in a steel in which the total alloy content varies from about 4 to about 6 per cent., and in which the carbon is limited to a range of about 0.40 per cent. to about 0.60 per cent.

The area of the invention is that lying within the line CDEFGB passing through the following series of points:

A preferred alloy lying substantially at the center of the said area, and having a total alloy (Mn+Cr+Mo) content of about 4 per cent. to 5 per cent. is shown by the following commercial melting limits:

Per cent Carbon 0.40 to 0.80 Manganese 2.35 to 2.65 Chromium 0.35 to 0.65 Molybdenum 1.10 to 1.40

Alloys above the line ABCwill air-harden to an Rc of at least in sizes at least four inches round by four inches long, from temperatures not. over 1600 F., and, in addition, anneal satisfactorily provided the total alloy content be limited within the range of 4 to 6 per cent. If the total alloy content is less than about 4 per cent., alloys above (and below) the line will not harden as above described, and if the total alloy content is greater than 6 per cent., alloys above the line ABC have the hardenability characteristics above mentioned, but lack annealability.

Therefore, alloys lying above the line ABC and limited as to total alloy content and carbon content as described, have a combination of the kind of hardenability mentioned and annealability. However, for certain purposes those alloys are not tough enough.

Within the area delineated by the line CDEFGB, the alloys having a total alloy content of 4 to 6 per cent. possess not only annealability and hardenability as above described, but also exceptionally high toughness. It is those alloys which constitute the subject-matter oi the present invention.

To illustrate the contrast in toughness between typical alloys lying inside and outside said area.

TABLE I Per cent. alloying elements based on the steel {at gent llo a lg elemetntst e on o 0 con en a Point on y Total alloy content 4 Total alloy content 6 diagram a Per cent Per cent Per cent Per cent Per cent' Per cent Per cent Per cent Per cent 11 Cr Mo Mn Cr Mo Mn 0: Mo I 61 N 30 2. 44 Nil 1. 56 3. 66 Nil 2. 34 75 Nil 25 3. 00 Nil 1.00 4. 50 Nil 1. 50 v 74 l0 l6 2. 05 0.40 0. 64 4. 44 0.60 0.96 19 16 2. 50 0. 76 0. 64 3. 90 1. l4 0. 96 55 10 26 2. 20 0. 1. 04' 3.30 1.14 1.56 51 13 30 2. 04 0. 52 1. 44 3. 06 0. 78 2. l6

the following additional specific examples are given:

TABLE II Alloys having 4.25 per cent total allow content mama or AREA Percent Percent Percent Impact, Rockwell All? Mn Cr Mo it.-lbs. o

280 2. 46 46 1. 33 26 63 300 2.90 .04 .78 2a 64 304 3. 25 Ni! 1. 12 20 55 OUTSIDE OF AREA 288 2. 13 1.03 1. 09 12 54 292 3.20 1.02 Nil 55 296 2. 24 2.01 Nil 12 55 Alloys having 5.35 per cent total alloy content INSIDE OF AREA Percent Percent Percent Impact Rockwell Mn 01' M6 lt.-lbs.' c

281 3. 20 .82 1.30 19 55 301 3.65 v .79 .92 20 64 305 4.05 Nil 1.41 21 64 OUTSIDE OF AREA (Carbon 0.50 per cent.silicon normal).

All specimens drawn 1 hr. at 450 F.

The compositions of the alloys given in Table II are shown by their position on the Mn-Cr-Mo pseudo-ternary diagram of Fig. 1, the numbers on the diagram being the numbers identifying the alloys in Table II. v

Table II illustrates the toughness exhibited by the alloys inside and outside of the prescribed area. All specimens were air-hardened and then drawn at 450 F. The mm, square impact specimens were air-hardened from 1550 F., using a cooling rate equal to that of a piece two inches round by eight inches long. The specimens were then-drawn at 450 F. for one hour, and the values given in Table II above represent the average of three breaks. Rockwell 0 hardnesses after air-hardening and drawing at 450 F. are also given in Table II. The impact test used. to measure toughness was identical with the well-known Izod test, except that a Guillery notch was used instead of the more common v-notch. The Guillery notch is semi-circular, with a radius of .0625". The notch depth is the same as that of the standard V-notch.

It has been further discovered that a portion of the manganese can be substituted by nickel, and that not only does the substitution permit maintenance of the above-mentioned properties 01' air-hardenability in large sections and annealability and toughness, but also that substantial additional toughness is obtained, provided the following criteria be observed:

AThe nickel must not exceed about 1.50% nor be less than about 0.5%...

B-The manganese must not be less than about 1.25% and not greater than about 3.75%.

C-The nickel is substituted in the ratio of about 1.0% nickel for 1.5% manganese.

relation which is shown between manganese. I

5 chromium, and molybdenum in the accompanying ternary diagram, and the limits oi the relation between manganese and nickel, tor steels having total alloy contents of 4.6 per cent., respectively, are those shown by the following table:

Tun: HI

4% total alloy content 0 total alloy content Per cent of total alloy at cent of total alloy content of (Mn+1. 6 content of (Mn+l.6 XND XI) PercentMn-.--- 1.25 2.25 1.25 220 1.25 an 2.20 PercsntNi .50 .60 1.17 .60 1.17 .60 1.50

This table may be explained by pointing out that for a steel having a total alloy content 0! about 4 per cent. and in which the manganese plus is times the nickel amounts to 50 percent. of the total alloy content, the nickel must be about 0.5 per cent. and the manganese about 1.25 per cent. For a steel having the same total alloy content and in which the manganese plus 1.5 times the nickel amounts to about '75 per cent. of the total alloy content, the manganese may vary from a minimum of about 1.25 per cent. to a maximum of about 2.25 per cent, corresponding to a maximum of about 1.17 per cent. nickel to a minimum of about 0.50 per cent. nickel,

For a steel having a. total alloy content or about 6 per cent. and and in which the manganese plus 1.5 times the nickel amounts to about 50 per cent. of the total alloy content, the nickel may vary from about 0.50 to about 1.17 per cent., corresponding to a manganese content of about 2.25 to 1.25 per cent. For a steel having the same total alloy content and in which the manganese plus 1.5 times the nickel equals about 75 per cent. of the total alloy content, the nickel may vary from about 0.50 per cent. to about 1.50 per cent corresponding to a manganese content of about 3.75 to 2.25 per cent.

To further illustrate the relationships, consider a steel having a total alloy content of about 4 per cent.

Mn+1.5 Ni=50% of total alloy content =2-% of steel Ni 0.5% and 1.5% 1 Ni=.-1.5 Mn Mn 1.25% and 3.75% Maximum manganese that may be substituted by nickel:

2.00-1.25=0.75% an %Ni=1.50- .0.50

0.75% is also the minimum manganese to be substituted since Ni 0.5 Therefore, the minimum and maximum nickel equals about 0.50%. The minimum nickel in this case is set by requirement A, and the maximum by requirements B and O, the total alloy content and the tact that the Mn+1.5 Ni=50% x total alloy content. The minimum and maximum manganese content is about 1.25% for the same reasons.

When, however, the Mn+1.5 Ni equals about 75% of the total alloy content (said total alloy content remaining fixed at about 4% of the weight of the steel), both the nickel and mannickel ganese may vary within certain limits as shown by the above table and explained as follows:

Mn+ 1.5 Ni=75 x total alloy content =3% of the steel Maximum manganese that may be substituted= e.co-1.25=1.75% 7Ni 1 177 o "'1.50

Therefore, the maximum nickel is about 1.17 per cent., and the minimum manganese about 1.25 per cent.

in accordance with the principles of this invention is shown as follows:

Percent by weight of steel Additional examples of nickel-containing alloys according to the present invention are as follows:

Team: IV

Alloys containing maximum manganese content [Percent Ni=0.50 percent] Percent. alloying elements based on the steel Percent. e110 g elements based on tot alloy content i Point on diagram Total alloy content 4 percent Total alloy content 6 percent Percent Mn+ Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent 1.5 X Ni Gr Mo Mn Ni Or Me n Ni Cr Mo 61 Ni] 39 1. 69 50 Nil 1.56 2. 91 0. 50 Nil 2. 34 75 Nil 25 2. 25 50 Nil 1. 00 3. 75 50 N11 1. 50 74 16 2.20 .50 .40 .64 3.69 .50 .60 .90 65 l9 l6 1. 85 50 76 B4 3. .50 1. 14 96 55 19 26 1. 45 50 76 l. M 2. 55 50 1. 14 1. 50 51 13 36 1. 29 50 52 1. 44 2. 21 50 78 2. 10

Alloys containing minimum manganese content [i. e., percent Mn l.25% and percent Ni l.50%]

Percent.allcying elements based on the steel Percentnlloyigifi elements based on total cy content Point on diagram Total alloy content 4 percent Total alloy content 6 percent Percent Mn+ Percent Percent Percent Percent Percent Percent Percent Percent Percent Percent 1.5 X Ni Cr Mo Mn Ni Cr Mo Mn Ni Cr Mo 61 Nil 39 1.25 0.80 Nil 1.56 1. 41 1.50 Nil 2. e4 75 Nil 1. 25 1. 16 Ni] 1. 00 2. 25 1. 50 N 11 l. 50 74 10 16 l. 25 1. 14 0. 64 2. 19 1. 0. 00 00 65 19 16 1.25 .90 .70 .64 1.65 1.50 1.14 .08 19 26 1. 25 63 76 i. 04 1. 25 1. 36 -1. 14 1. 50 51 13 30 1. 25 53 52 1. 44 1. 25 1. 21 78 2. l0

Mimimum nickel is 0.50% (Requirement A) which may be substituted for 0.75% Mn.

Mn+1.5 Ni =3% of steel 1.5x Ni =.75%

Mn=2.25% maximum Percent alloy components ggg ggg Toughness Rockwell 0 Mn Cl M0 N1 F l .10 3. 00 0. 75 0. 85 Ni] 4. B0 20 a 54 l. 50 0- 75 0- 85 1- 00 4- 30 54/56 illustrative .range of compositions where is substituted for a part or the manganese m It is to be noted that the maximum nickel content within the range of .50 to 1.50%, which can be used as replacement for the manganese content, is dependent upon the total alloy content-i. e., Mn+l.5 Ni+Cr+Mo-because or the restrictions A and B above. We have found that the manganese content must be greater than about 1.25% to obtain the above air-hardenlng properties in large sections, and that the nickel content mustnot be greater than 1.50% to obtain alloys which can be commercially annealed. The minimum amounts of nickel to be substituted for manganese-i. e., 50% nickel-is about the least nickel which leads to a. significant gain in toughness as compared with those nickelfree manganese-chromlum-molybdenum alloys delineated by the lines CDEFGB in Fig. 1.

It will be apparent that total alloy content means per cent manganese plus per cent chromium plus per cent molybdenum plus 1.50 times per cent nickel.

This is a continuation-in-part of our copending application Serial No. 497,312, illed August 4. 1943.

What is claimed is: 1. An air-hardening steel capable of being annealed to a condition sunlciently soft for commercial machining requirements and capable of being hardened in sections having a size at least as great as those typified by sections four inches round by four inches long, to yield a product having high toughness, said steel containing 0.40 to 0.60 per cent. carbon, a total alloy content oi 4 to 6 percent. and the balance principally iron, and in which steel the relationship between the alloying elements, chromium, molybdenum, and manganese plus 1.50 times the nickel content is such as to define a point lying within the area delineated by the line CDEFGB. on the accompanying pseudo-ternary diagram, passing through the iollowing series oi points:

asvacss and inwhich the nickel is not less than about 0.5 per cent. and not greater than 1.5 per cent. by weigh and in which the manganese is not less than about 1.25 per cent. and'not greater than about 8.75 per cent. by weight.

2. An air-hardening steelcapable of being airhandened i'rom temperatures not ove 1600 degrees Fahrenheit to a Rc hardness of at least 55 in sections having a size at least as great as those typified by sections four inches round by four inches long, to yield a product having a high toughness, such steel containing .40 to .60 per cent. carbon, .80 to 1.20 per cent. nickel, 1.80 to 2.10 per cent. .75 to 1.00 per cent. chromium, and .90 to 1.20 per cent. molybdenum and the balance principally iron.

CARL 3. POST. MAURICE 0. mm.

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