US1938221A - Steel alloy - Google Patents

Description

Patented Dec. 5, 1933 STEEL ALLOY Jamaal. Glll,hatrobe,h.,adgnortovauadim- Aliens tionofl'ennsy teelcompany,llatrobe.ra.,aoomnlnnla No Drawing. Application Mal-ch10, 1932 Serial No. 509,355

1 Claim. (01. 15-1) My invention has for its object the. production of an alloy steel that is particularly adapted for themakingof dies whicharetobeused inthe die casting of aluminum base alloys. I

5 There has been a need by the die casting industry for an alloy steel that is suitable for the making of dies in which articles of aluminum base alloys were to be cast. oftentimes the cost of cutting the dies is very costly; many dies costing from $500.00 to $1500.00 each in machining cost alone. It is, therefore, very essential that the steel used in making these dies have certain definite physical properties which will permit long-continued use of the dies without excessive deterioration thereof.

Such a steel should have air hardening properties; should show little movement or distortion on hardening; the surface of the steel should not readily develop checks when subjected to alternate heating and cooling; it should withstand to a fair degree the erosion of molten aluminum base alloys; should have easy machinability in the annealed condition, and should be of such alloy content that its cost is not prohibitive.

My invention has for its object the provision of a die and an alloy for making the same, which possesses the various desirable features heretofore referred to.

Generally stated, the alloy comprises a steel having a carbon content of from .20% to .50%, a silicon content of from .10% to 1.50%, a manganese content of from .10% to 1.00% a tungsten content of from 50% to 2.00%, a chromium content of from 3.00% to 8.00%, a molybdenum content of from .50% to 2.75%. This composition has been found to fulfill the above requirements to a high degree.

In actual practice I have found that a heat of my steel which analyzed-- Percent Carbon .28 Silicon 1.27 Tungsten .99 Chrnmium 4.76 Molybden 1.50 Manganese .28

when hardened to a Brinell hardness 61 532 showed a yield point of 258,000 lbs. per sq; inch; a tensile strength of 270,000 lbs. per sq. inch;

area, when tested at room temperature Fahr.

Another heat of my steel having the following composition:

Percent 12% elongation in 2, inches, and 42% reduction in was forged into a block. 16" X12" x4". The face of this block 167x12? was machined smooth and flat to an accuracy of one thousandths of an inch. This block of steel was then heated to a temperature of 1900 degrees Fahr. and cooled in as still air. A hardness reading then made across the lace ofthis block from the center to the outside edge showed a uniform Brinell hardness of 532, while the distortion from flatness across the face of the block was less than one-half thou- '70 sandths of an inch.

This uniformity in hardness and lack of distortion results largely from the inclusion of the molybdenum content. If the molybdenum were omitted and the tungsten content increased even to as high as 5.000%, the desired hardness and resistance to distortion could not be secured. The usefulness of this steel is largely dependent upon its ability to harden uniformly in air and show a negligible distortion on hardening.

Furthermore, a heat of steel of similar composition but not containing tungsten showed practically the same characteristics as when the tungsten was present. The tungsten, however, has been added to obtain better wear resistance 35 and slightly greater hardness at elevated temperatures.

4 My steel when tested by the Charpy impact, using a standard Charpy impact test block, required 17 foot pounds to break the specimen at a temperature of 200 degrees Fahn; 16 foot pounds to break the specimen at 500 degrees Fahr., and 15% foot pounds to break the specimen at 800 degrees Fahr.

My steel when tested for erosion in molten 05 aluminum showed high resistance to the action of aluminum.

I have added from .50 to 2.00% nickel to my steel and found that the toughness of the steel was improved without detracting from its other characteristics.

I claim as my invention:-

A die for use in the die-casting of aluminum base alloys, composed of a steel alloy containing Carbon... .20% to .50% Silicon .10% to 1.50% Manganese -1 .10% to 1.00% Chromium 3.00% to- 8.00% Molybdenum -1 1.50% to 2.75% Tungsten .50% to 2.00% Nickel 50% to 2.00%

and the remainder mainlyiron.

' JAMES P. GILL.