US2253385A

US2253385A - Steel

Info

Publication number: US2253385A
Application number: US376420A
Authority: US
Inventors: William E Mahin
Original assignee: Westinghouse Electric and Manufacturing Co
Current assignee: CBS Corp
Priority date: 1941-01-29
Filing date: 1941-01-29
Publication date: 1941-08-19
Anticipated expiration: 1958-08-19

Description

, HESS.

. Patented Aug. 19, 1941- Westinghouse Electric & Manufacturing Company, East Pittsburgh, Pa., a corporation of Pennsylvania No Drawing. Application January 29, 1941, Serial No. 376,420

, Claims. (01. 75-128);

Thisinvention relates to articles of manufacpressing and permanent molding operations.

. Toolsteel employed heretofore as dies for hot pressing and permanent: molding operations where the tool is repeatedly heated at temperatures of more than 1000 F. have failedin a relatively short time by cracking, warping or washing. In general, it can be said that while the steels of previously known compositions have high hardness at elevated temperatures, they particularly to intergranular oxidation, to have a long life. Intergranular oxidation results in development of points of stress concentration which cause surface cracking. Surface cracks the die .or mold.

Tool steels with high tungsten contents have long been known to possess very high red hardness, that is, high hardness at relativelyhigh temperatures. Likewise steels with high chromium contents have been known to possess high resistance to oxidation at relatively high temperatures together with moderately high red hard- The high tungsten steels have never been "ture and particularly to steel suitablefor hot bined in a steel in relatively high proportions, a steel is produced having a toughness, hardness and resistance to oxidation which renders it suitablefor use as a die for hot pressing and permanent molding operations at repeated high temperatures.

.are not sufliciently resistant to oxidation, and

' grow inwardly and ultimately lead to failure of considered oxidation-resistant and therefore have usually been limited. in use to applications where temperatures inservice do not exceed a temperature of approximately 1200 F.

Contact surfaces oi'dies and molds used for hot pressing and molding or casting, particularly of non-ferrous metals and alloys probably reach temperatures well in excess 0f l000 F. At these higher temperatures, ordinary tool steels containing high tungsten but relatively low chromium contents do not possess adequate oxidation resistance. On the other hand, previously.

known high chromium steels with relatively low contents of other hardening elements do not possess red hardness for most tool applications.

It is an object of this invention, therefore, to provide a steel having a high hardness at elevated temperatures, together with resistance to oxidation.

Another object of this invention is to provide a alloys.

characteristics desired in' a die, the steel may be subjected to a heat treatment, preferably after steel having a. high tungsten and a high chromium content which will have a high hardness at elevated temperatures together with resistance to oxidation.

Other objects of this invention will become apparent from the following description and the The following table sets forth the broad ranges in percent by weight within which the several a1- loying elements may be present:

Percent Carbon 0.05 to 0.50 Manganese 0.15 to 3.00 Silicon 0.20 to 1.00 Chromium 8.00 to 20.00 Tungsten l 8.00 to 20.00 Vanadium; 0.10 to 4.00

th remainder being substantially all iron, together with such alloying impurities as are sometimes found in alloy steels.

A somewhat narrower range of percentages in which the several alloying elements may be present are as follows Percent Carbon. 0.05 to 0.30 Manganese 0.15 to 0.50 Silicon 0.20 to 0.50 Chromi m 11.00 to 15.00 Tungsten 11.00 to 15.00 V n m 0.10 to 1.00

the remainder being substantially all iron, to gether with such alloying impurities asare sometimes found in alloy steels.

Steels having the composition given in the foregoing tables are found to be satisfactory when formed into dies for hot pressing and permanent molding operations, and particularly such operations on hot non-ferrous metals and In order to give the steel certain of the having been formed to thepredetermined shape of the die. Where desired, the finishing of machining operations may be applied "to the die after the heat treatment.

The heat treatment may comprise quenching the steel in oil or air from a temperature between 2100? F. and 2350 F. and then subjecting it to a tempering treatment at a temperature between 1100 F. and 1300 F. for a suflicient period of time to develop its hardness. A preferred heat treatment is to quench the steel from a temperature between 2250 F. and 2300 F. and temper it at a temperature of about 11200 F'.

In making the steel-for forming the dies, it is Percent Percent Percent Percent Percent Carbon 25 20 20 24 l2 Manganese.. .25 .16 .27 .28 .25 Silicon 25 21 36 38 25 Chromium 12. 12. l3 12. 02 12. 60 12. 00 Tungsten- 8. 00 12. 71 12. 62 12. 89 12. 00 Vanadium-..- .50 .46 .43 .43 .50

it being understood that the remainder of the composition of each of the specific examples given is substantially all iron together with such alloying impurities as are sometimes found in alloy steels.

As previously stated, it is found that the high chromium and high tungsten constituents cooperate to impart high red hardness and high oxidation resistance to the finished product. The vanadium and silicon constituents function primarily as deoxidants in the making of the steel and the vanadium is thought to impart resistance in the steel against grain coarsening during the heat treatment of the alloy. The higher contents of vanadium may also assist in developing red hardness. The manganese is thought to impart forgeability characteristics to the alloy. For most of the applications embodied by this invention, the lower carbon contents as set forth are thought to develop adequate hardness and to aid in obtaining a steel having greater toughness than would be obtained with the higher carbon contents. However, it is not desired to be limited in application of the principles herein set forth to the lower carbon contents.

Dies formed from high chromium and high tungsten steel referred to hereinbefore are found to be resistant to oxidation. checking, warping and washing. These dies may have a useful life of from twelve to fifteen times the life of the dies formed from the conventional high tungsten, low chromium steels such as, for example, the tungsten, 3% chromium, 50% carbon, and .50%

vanadium steel available on the market at the present time when subjected to operations entailing the repeated heatings at temperatures of over 1000 F. The high chromium, high tungsten steel dies of this invention are particularly useful in the hot pressing of copper parts and permanent molding of aluminum bronzes.

I claim as my invention:

1. A tool steel suitable for hot pressing and permanent molding operations formed from an alloy composed of 8% to 20% chromium, 8% to 20% tungsten, 0.10% to 4% vanadium, 0.20% to 1% silicon, 0.15% to 3% manganese, 0.05% to 0.5% carbon and the balance substantially all iron.

2. A toolsteel suitable for hot pressing and permanent molding operations formed from an alloy composed of 11% to 15% chromium, 11% to 15% tungsten, 0.10% to 1% vanadium, 0.2% to 0.5% silicon, 0.15% to 0.5% manganese, 0.05% to 0.3% carbon and the balance substantially all iron.

3. A tool steel suitable for hot pressing and permanent molding operations formed from an alloy composed of about 12.62% chromium, about 12.62% tungsten, about 0.43% vanadium, about 0.36% silicon, about 0.27% manganese, about 0.20% carbon and the balance substantially all iron.

4. A tool steel suitable for hot pressing and permanent molding operations comprising an alloy composed of 8% to 20% chromium, 8% to 20% tungsten, 0.10% to 4% vanadium, 0.20% to 1% silicon, 0.15% to 3% manganese, 0.05% to 0.5% carbon, and the balance substantially all iron formed to a predetermined shape and heat treated to give high hardness, the steel being characterized in that it is resistant to oxidation.

5. A tool steel comprising an alloy of 8% to 20% chromium, 8% to 20% tungsten, 0.10% to 4% vanadium, 0.20% to 1% silicon, 0.15% to 3% manganese, 0.05% to 0.5% carbon and the balance substantially all iron which has been quenched from a temperature between 2100 F. and 2350 F. and tempered at a temperature between 1100" F. and 1300 F.