US2158652A - Steel - Google Patents

Description

Patented May 16, 1939 I UNITED'STATES "PATENT OFFICE STEEL Frederick M. Becket, New York, and Russell Franks, Niagara Falls, N. Y., assignors'to Elec- -tro Metallurgical Company, a corporation of West Virginia No Drawing. Application December 21, 1938,

Serial No. 246,995

3 Claims. ((71. 75-423) This invention relates to steels, and provides affected the toughnessof the steels," or failed new and improved steels characterized by novel to prevent coarsening of the grain size at eleand commercially valuable properties. This apvated temperatures, during fabrication for in-. plication contains subject-matter in common stance, or both. The coarsening of the grain 5 with our application Serial No. 87,006, filed June is considerably aggravated in a case carburizing 24, 1936, process, and in such a process the addition of We have discovered that the addition of cocolumbium to the steel is especially advantalumbium in amounts between 0.02% and 1% to geous, as illustrated by the data in Table I which so-called plain carbon and certain low algives the experimentally determined grain numloyed steels efiects a marked and surprising her (A. S. T. M. Specification E 19-33) of the 10 improvement in the properties of such steels. cases of a series of steels after carburizing for One important effect of the columbium addition eight hours at each-of three different temperais to refine the grain-size of the steel, and this tures. In each case, the grain size of the core grain refinement is retained and maintained was smaller than that of the case. even at elevated temperatures up to and some- Table I 15 what above the critical range. Another effect, which is doubtless at least in part a result of the grain refinement, is the improvement of the tensile strength of many of the steels. Further,

Composition of steel (remainder Grain No. of case after cariron) burizing 8 hours- 20 the impact strength is increased, and this im Pep Pep Pep Pep Pep M M M 20 provement .15 marked even at subzero temperaent cent cent cent cent 925 1, 2

0 Mn Si Cb Ni 0. c. o.

tures. There is also an increase in the resistance of the steels to rusting and hot oxidation. The

machinability and the deep-drawing and cold 8- rolling characteristics of the steels are im- 0111 0147 0 31 0.10 3145 6to9 6to9 stos 25 proved. The hardenability of the steels by heat 8- g3 g3 2-33 fizz treatment is somewhat decreased, and there is less distortion of the steel when it is rapidly cooled from. elevated temperatures. The ratio $332 g i figi gfi efiegt rouihly of yield point to maximum stress is increased, 2 g o timum fg f g up a 30 the increase depending upon the columbium and r p o um 0 carbon contents of the steels: the increase is optmmm content depends i on the carbon greater in the steels having the lower carbon contgnt of a Steel The gram refinement and columbium contenta maximum .carbon steel reaches substan- 35 I Steels included in our invention are those Em igi f gfif g gr g z gg 35 containing up to 1% carbon, up to 1% silicon. 1 i b te u up to 2% manganese, 0.05% to 5% nickel, 0.02% um a r 9 5 e at about 018% to 0.5% columbium, remainder ir0n columbium; and a 0.5% carbon steel at about Suitable amounts of columbium to be added to g moderate excess of 40 these steels according to the present invention lumbmm above t e opum'um and below the 40 are from 0.02% to 0.5% columbium, and the most imam Specifiedabove (1%) will not ordinarily useful range is within the limits 0.05% to 0.25%. adrersely affect the Pmperties 0f the Steel to a In general, the greater amounts of columbium serwus extent should ordinarily be used in the steels containing The influence of columbium on e t i e and 'the greater amounts of carbon, within the ranges impact Properties 0f the Steels un r o s de a- 45 specified above, V tion is indicated by the data appearing inTable o of t t, valuable -ti of t II which shows the experimentally determined columbium containing steels of the invention yield point in thousands of p u d per square is that of retaining its normally fine grained inch maximum e s in thousands of structure at elevated temperatures, which proppounds p Square inch pe a 50 erty is attained without detrimentaliy affecting elongation in a 2 h gage length (Eland other important physical properties, The xreduction in area (R. A. all on 0.505 inch pedients heretofore customarily employed to rediameter A. S. T. M. standard tensile test pieces; fine the grain size of carbon and low-alloyed and also the Izod impact value in foot pounds steels have, in most cases, either detrimentally as determined on a standard Izod machine with 55 an initial energy level of foot pounds and a standard specimen one centimeter square provided with a 45 notch.

Table [1 Composition of steel (remainder iron) Tulane M El. R.A.

9' 7 Izod 9.30 g; 9, %Cb Y.P. M.s. 5 5;; mm

Qumdled in of! from800 0., draamin m M 0.

0.16 0.36 0.16 3.49 None 74 99.5 22 49 46 0.17 0.47 0.31 3.45 0.10 53 102 21 30 57 0.18 0.45 0.25 3.5 0.18 56 100 27 64 52 Queaded in waterfront 876 0., drawn in air M550 0.

0.37 0.40 0.17 3.52 None 116 129 7.5 21 23 0.34 0.35 0.13 3.45 0.084 101 113 16 47 40 0.32 0.45 0.25 3.5 0.13 97 115 22 60 41 Quendled in oil from 860 0., drawn in air at 495 C.

0.51 0.70 0.25 3.5 None 104 7 16 3.8 0.47 0.80 0.31 3.42 0.084 191 12 37 8 0.51 0.75 0.25 3.5 0.18 170 183 11 38 15 0.54 0.76 0.25 3.5 0.46 170 184 12 41 11 Air-cooled from 850 CW C 0.10 0.36 0.16 an None s4 77 32 e2 61 0.17 0.47 0.31 3.45 0. 70 82 27 50 73 0.18 0.45 0.25 3.5 0.18 65 84 31 65 78 0.37 0.40 0.17 3.52 None 68 97 17 J0 29 0.34 0.35 0.13 3.46 0.084 72 94 25 43 37 0.32 0.45 0.25 3.5 0.13 69 94 27 54 47 0.51 0.76 0.25 3.5 None 94 134 2 5 3.5 0.47 0.80 0.31 3.42' 0.084 102 144 10 15 5 0.51 0.75 0.25 3.5 0.103 77 124 20 45 29 0.54 0.75 0.25 3.5 0.462 82 131 17 36 19 sense that high chromium steels, for instance,

are oxidation resistant, the increase in resistance will be valuable in many uses of the steels.

The articles of the invention include articles deep-drawn from the steel of the invention; articles having a core containing less than 0.5% carbon and a carburized case containing more than 0.8% carbon, and 0.02% to 0.5% columbium throughout; parts of machines and of other apparatus, required to withstand stress at moderately elevated temperatures; articles, composed of the steel of the invention, designed for use to resist impact shock at subzero temperatures; and pressure vessels, composed of the steel of the invention, designed to withstand two or three dimensio'nal stress at subzero temperatures.

It will be appreciated that the specific examples herein are given by way of illustration, and that the invention is not limited to or by such examples.

We claim:

1. Steel containing carbon in an amount not exceeding 1%, manganese in an amount not exceeding 2%, silicon in an amount not exceeding 1%, 0.05% to 5% nickel, and 0.02% to 0.5% columbium, remainder iron; the columbium acting to impart to said steel a fine-grained structure which persists at all temperatures up to and somewhat above the critical range.

2. Steel containing carbon in an amount not exceeding 0.6%, manganese in an amount not over 2%, silicon in an amount not over 1%, 0.05% to 5% nickel, and 0.05% to 0.25% columbium, remainder iron; the columbium acting to impart to said steel 8. fine-grained structure which persists at all temperatures up to and somewhat above the critical range.

3. Case carburized article having a core containlng less than 0.5% carbon and e. carburized case containing more than 0.8% carbon, the core and case being composed of steel containing, aside from carbon, manganese in an amount not over 2%, silicon in an amount not exceeding 1%, 0.05% to 5% nickel, and 0.05% to 0.25% columbium, remainder iron; the colwnbium acting to impart to said carburized article a fine-grained structure, increased ductility, and increased impact strength.