US2331900A - Steel alloy and die block - Google Patents

Description

Patented a. 19, 1943 2,331,900 r STEEL ALLOY AND DIE BLOCK 7 William. F. Fink], Chicago, 111., assignor to A. Finkl & Sons Company, Chicago, 111., a cornotation of Illinois No Dr awing. Application April 4, 1942,

Serial vNo. 437,711

4Claims; (Cl. 75-128) This invention relates to improvements in steel alloys which are particularly adapted for use in die blocks employed for hot work forging processes and die blocks made fromsuch alloys, and has for its principal objects to producea steel alloy combining the special characteristics necessary for such usage, including facility and economy in manufacture, and in particular. a greaterresistance to heat checking, scoring and abrasion.

The improved alloy has been developed to overcome the difficulties of heat checking, scoring and abrasion which have been encountered with dies used in hot work forging processes, and in particular in hot pressing and upsetting operations. These forging operations subject dies to the most rigorous and exacting conditions known because of the extremepressure and variations in temperatures encountered. The die must remain in contact with the work at extremely high temperatures for relatively long periods of time, and is usually cooled as by water, between successive operations.

Some of the most commonly used types of steel alloys heretofore employed for the particular purposes above mentioned are disclosed in my prior Patents Nos. 1,464,174, 2,104,979 and 2,104,980. The steels of the latter two patents include small amounts of copper, in addition to chromium, nickel and molybdenum, as broadly disclosed in-the first patent. Other alloys con taining other alloying elements such as tungsten,-

cobalt, titanium and vanadium, have also been employed to some extent for similar purposes.

- It has been found, however, that these prior alloy steels are not wholly satisfactory for the reasons above suggested, and in addition are relatively costly to manufacture. For instance, coppersilicon as the principal alloying elements, all confined within relatively narrow ranges. The preferred ranges of the principal alloyingelements of this special steel are as follows:

Per cent Carbon .45to .60 Molybdenum .90 to 1.10 Chromium .85 to 1.15 Manganese .45 to .65 Silicon .50 to 100 Nickel 1.00 to 1.75

Other elements of a more or less residual character may also be present in small fractions, as

is often the'case in special alloy steels of this class.

As an example of steel alloy made in accordance with my present invention, the following analysis may be cited:

It will be observed that the ranges of the several alloying elements and the typical analysis above set forth difier from the alloy broadly disclosed in my prior Patent No. 2,104,980, by the elimination of'copper as a substantial alloying bearing steels require much more critical handling for heating in preliminary forging or rolling, due to their tendency to hot shortness, so that special treatment of such steels is essential to their successful operation. Other alloying elements such as vanadium, cobalt and tungsten, impart a tendency to crack the die in service on alternate heating and cooling of the die. The last named alloying elements also, of course, add to the expense of initial manufacture.

In carrying out my present invention for the particular purpose above indicated, I utilize molybdenum, chromium, nickel, manganese and element and by specifying the molybdenum, chromium and silicon contents within much narrower limits. I find that the especial characteristics essential for use under the extreme operating conditionsherein set forth, can only be obtained satisfactorily by limiting the percentages of the several alloying elements within the narrow ranges specified for each.

Heat checking may be described as 2. development of small cracks extending in various directions on and near the surface of the die, which follow more or less crystalline patterns, and eventually cause the surface to break down by chipping of the cracked surfaces. Such cracking is attributed largely to the high temperatures and the extreme variations in temperatures to which the die surface is subjected. Scoring and abrasion, as the terms imply, are closely allied to heat checking, and are especially troublesome I .50 to 1.00%, nickel from 1.00 to 1.75%, and the under the especially rigorous conditions of hot balance substantially all iron.

forging processes, where the steelpbjects 9r wgrk- 2. A steel alloy which comprises as its alloybeing forged are relatively hard and of-low plasf; ing elements carbon approximately 50% molybticity. The development of these defects in the '5 denum approximately 1.00%, chromium approxidie surfaces has therefore beeirone of the 1m mately 100%} manganese approximately .55%, portant limiting factors 'determining. the eflec-' f silicon approximately 30%, nickel approximately five life of d e 'dln 0li 01'k. ;;1 have demon- 11.50% and the.balance substantially all iron.

strated, however; that these defects,.jcan'- be 'IIQJA die*- block {for hot work f orging characradially reduced by the use of my improved nlloy 10' terized by its resistance to heat'checking, scors e t increasing t e i e da ee p e I 'ing and abrasion," made of a steel alloy which tion of each die sinking. Comparisons of diesof comprises as; its alloying elements carbonrangthe above analysis under most severe conditions 1 ing from .45 to .60%, molybdenum from .90-t0 of quantity production in hot pressing opera- 1.10%, chromium from .85.]:0 1.15%, manganese tions have shown an increase or 20% overave 1'5 from .45 to..65%, silicon from .50 to 1.00%, nickel age production life from the best types of alloyy from 1.00 t 1.75%, and

steels heretofore available for similar purposes.

Due to the advantages above set forth, dies made from my improved analysis have already largely susperseded all other dies in hot pressing and upsetting processes in this country, and

also have been widely adopted in other types of w w the balance'substantially al-l iron. 2

4.-A.die block for hot work iorging characterized by its resistance to heatchecking, scoring 20 and abrasion madeof a steel alloy which comprises as its alloying elements carbon approximately 50%, molybdenum approximately 1.00%,

chromium approximately 1.00%, manganese approximately .55%, silicon approximately .80%,

25 nickel approximately 1.50%, and the balance substantially all iron.

- WILLIAM F. FINKL.