US2711959A - Welding steel for developing high surface hardness under impact - Google Patents

Description

l I 2,711,959 I I p p} WELDING STEEL FOR DEVELOPING HIGH SURFACE HARDNESS UNDER IMPACT William T. De Long, West Manchester Township, York County, and Gustaf A. Ostrom, Paradise Township, York County, Pa., assignors to The McKay Company, Pittsburgh, Pa, in corporation of Pennsylvania No Drawing. Application November 3, 1954, Serial No. 466,661 r 4 Claims. (61. 75-128) This invention relates to welding steel, i. e., steel which can be weld-deposited, which has important improved characteristics. Our improved welding steel is superior to previously existing welding steels in developing surface hardness and has other superior properties.

Austenitic steels of a number of analyses have been used successfully for hard facing applications. The steels suitable for such use, being austenitic or largely so, have a relatively low level of hardness as deposited but have the property of work hardening under impact to higher surface hardness levels which resist wear. The utility of such steels to resist wear therefore depends upon (1) the original hardness level; (2) the speed with which hardness is increased under impact; and (3) the level of increased hardness produced under impact.

An undesirable property in such steels for many applications is the property of deforming or squashing down which the steel undergoes in developing its hardened surface. That property is especially undesirable in applications such as deposits on rail ends, switch frogs, etc., in which the metal should remain standing up in place as it develops its hard surface.

Since the development of the Hadfield manganese steels about 1886 various modified and improved austenitic type steels have been developed and used. They have manifested dilfering combinations of physical properties and have had utility but they have left much to be desired. There is a crying need for significant improvements in physical properties which will bring about improved performance.

5 ltd TABLE I Prior hard surfacmg welding steels No l 2 3 C .70 .70 .50 Or 18 18 Mn 14 4 4 i 4 9. 9. 5 N .05* .05* .05* Mo 1. 5 Tensile (lbs/sq. in.) 125, 000 116, 000 116, 000 Yield (lbs/sq. in.) 00 90,000 91, 000 Elongation 4 15 15 Shrinkage on Impac .068 050 .050 'tial 13 27 27 I as 3s 36 *Estimated.

2,?ll359 Patented June 23, 1955 Table I is a tabulation of the properties of three known alloy steels numbered consecutively from 1 to 3, inclusive. They are typical austenitic type alloy welding steels now widely used for hard surfacing. No. 1, sold under various names including Hardalloy 118, is a nickel-manganese steel based on the old Hadfield steel analyses (similar steels are being used with molybdenum at the relatively low level of approximately 1% substituted for all of the nickel and with properties rather similar to the nickelmanganese alloys). The physical properties appearing in the table show that the metal is quite soft as deposited with a yield strength of less than half the tensile strength. Under impact the surface hardness of the metal increases. A laboratory test which has been developed for such materials is to subject a standard sample rod to 2500 blows of foot-pounds each. The hardness of the pounded metal is compared with the initial value to show the rate of increase, and the amount of squashing down which has occurred is also measured.

The final hardness shown under the hammer test values would continue to increase, if the test were continued, to a maximum value between and Rc at 80,000 blows. The additional squashing which would occur after the first 2500 blows is negligible as compared with the squashing effected by the first 2500 blows. Under the pounding test (2500 25 foot-pound blows) the l-lardallay 118 went from a surface hardness of 13 Re to 39 Re and at the same time the standard specimen decreased .068 in height.

Steels Nos. 2 and 3 of Table i, sold under the trade names Frogalloy M and Frogalloy C, respectively, are modified 188 type austenitic hard facing materials of higher cost than No. 1. Although Nos. 2 and 3 have a little lower tensile strength, they show higher yield strength, higher hardness as deposited and less squashing or shrinkage under the standard pounding test. Because of these properties the Frogalloy deposits or closely similar analyses have been considered superior for many hard facing uses. The properties of these modified l8-8 analyses were the best that had been developed in the field of austenitic welding steels for producing hard surfaces prior to the present invention.

We have discovered that superior properties can be developed by the proper balancing of chromium, manganese and nickel coupled with carbon and nitrogen within defined limits, and that further improvement in properties can be obtained by addition of molybdenum and/or tungsten, and/or vanadium and/or columbiurn within defined limits.

Table II shows the results of tests made with certain improved welding steels which we have developed.

TABLE II Improved welding steels Estimated.

n A Jr a Referring to steel No. 6 of Table H, with that analysis steel vanadium is approximately twice as powerful as pound test values and hardness levels before and after molybdenum. Tungsten and columbium can be subpounding are approximately the same as for the modified stituted respectively for all or part of the molybdenum 188 type (Nos. 2 and 3 of Table I) but the tensile and vanadium. The limits for molybdenum and/or strength, yield strength and elongation are much im- 6 tungsten plus 2 vanadium and/or columbium are set as proved. a function of the carbon content by positive values of Steels Nos. 4 and 5 of Table II, which we developed, the expressions given; negative values are treated as zero. are toward the ends of the chromium-manganese area With regard to other elements, the austenitizers copfound to be most useful and show that while the properper and cobalt may be present in limited quantities. ties vary somewhatahigh general level is maintained over lU Silicon will normally be present in quantities up to 1.5 the ranges evidenced. or even 2% since it is present in the commercial ma- To obtain the benefits of our invention the chromium terial available as core wire and is usually used as a content of the welding steel should be in the range deoxidizer in the coatings of coated welding electrodes. 11-21% while the manganese is in the range 949%, and Other strong carbide formers such as tantalum "or tiwhen to this base area of chromium and manganese car- 15 tanium could theoretically be substituted for the carbide bon and alloy additions are made within defined limits formers listed but are hard to recover in weld deposits. combinations of properties are developed which are out- The deposit analyses disclosed can be produced by the standing. A narrower preferred base area is chromium various methods of manual and automatic welding, as, 14-19% and manganese l418%. For example, steels for example, shielded arc, inert arc, submerged are or Nos. 7, 8 and 9 of Table II, which we developed, taken acetylene. as a grgup h very high tensile and yield strengths, While we have described certain present preferred emgood elongation, good resistance to shrinkage on impact, bodiznents of the invention it is to be distinctly underhigh initial hardness and good final hardn Th i stood that the invention is not limited thereto but may properties average far beyond those hi h h b be otherwisevariously embodied within the scope of the found in the chromium-nickel or austenitic manganese P alloys heretofore available. The effect of carbon, chromi-= W6 Claim: 1 um, manganese, nickel and alloy additions has been A s fi Whlch unqer lmliact develops hlgh studied extensively to find the approximate limits within i f f' fi h excesllfe S hrmkage havmg which the benefits of our invention are obtained. Table 90 tdnuafly followmg Composition III shows the broad and preferred ranges of elements for C .2 to .85 accomplishing our improved results. Mn 9 to 19%.

TABLE III Broad Range Preferred Range 14 to 18% Oto 2%. 16 to 22% 14 to 19% .10 50.25%

v and/or Cb .I. 1.10 and/0r W+2(V and/0r Cb).

0 to 2%. IMO-.60) to 10(C.10)%.

1 0 stands [or percent of carbon in the alloy. Only positive values of the parenthetical expressions in this line are significant, negative values are treated as zero.

We have found that two relationships are important. Ni Q to 4% The first is the balance between the austenitizers (C, Mn, N Mn-i-ZNi 13 to 22%, Ni, N) and ferritizers (Cr, W, Mo, Cb, V). This balan Cr 11 to 21%. must be adequate to produce a strong matrix. With all N 0 to 30%, the austenitizers near the low limits of their ranges and Mo and/0r W 0 to 5%. the ferritizers near the high limits of their ranges the V and/or Cb 0 to 2%.

mechanical properties are little or no better than those Mo and/or W+2(V and/ of the modified 18-8 type welding steels mentioned above. or Cb) i0 c ,70 to 10 c+ For this reason limits as to the effective sum or" the in which in the expressions C.70 and C+.20 C man anese and the nickel are included in Table III. The h total value of manganese plus 2 nickel defines the effect i i g g gg p gi i z g igg g g gz g g :5;

z I ul .1 l 1 fi g g gg gs ifi gg gg gfi zg sfi z ggg sh g l meal significant, negative values being treated as zero; the pm The second important relationship is that between car- 33 I fif j i Whlch g substan bon and the strong carbide formers (Cr, W, Mo, Cb, V). 2 5 ;$15 gi gifii g i fi 35,2 2 hi h To illustrate assume that an optimum balance has been r g found between the austenitizers and the ferritirers to form Surface hardness W, thout excessive Shnnkage havmg I P f e a'good matrix such as is present in steel No. 6 of Table "mmldny fOnOv mg Composltlon II; as more strong carbide former is added carbon should C .35 to .85%. be added in small amounts to maintain the alloy balance. Mn 14 to 18%. Guidance for maintaining the required relationship is Ni 0 to 2%. given in Table III in which the quantities of molybdenum P Mn-i-ZN i 16 to 22%. and/or tungsten, and/ or vanadium and/ or colurnbium ll) Cr 14 to 19%. which may be employed are specified as a function of the N .10 to .25%. carbon content. Carbon and nitrogen exert their usual Mo and/ or W 0 to 5%. strong austenitizing action and the carbon range specified V ,and/ or Cb 0 to 2%.

is needed to maintain the hardness level and wearing Mo and/or W+2(V and/ quality developed in the welding steel. In our welding or Cb) 10(C.60) to 10(C.10)%.

in which, in the expressions C-.60 and C.l0, C stands for the per cent. of carbon in the welding steel and only positive values of such expressions are significant, negative values being treated as Zero; the balance, except for impurities which do not substantially affect the properties of the steel, being iron.

3. An article comprising a structure having welded thereto a deposit which under impact develops high surface hardness without excessive shrinkage having substantially the following composition:

C .20 to .85%. Mn 9 to 19%. Ni 0 to 4%. Mn+2Ni 13 to 22%. Cr 11 to 21%. N G to 30%. Mo and/or W 0 to 5%. V and/or Cb 0 to 2%. Mo and/or W]2(V and/ or Cb) lO(C,70) to 10(C+.20)%.

in which, in the expressions C.70 and C+.20, C stands for the per cent. of carbon in the welding steel and only positive values of the expression C-.70 are significanhnegative values being treated as zero; the balance, except for impurities which do not substantially afieet the properties of the steel, being iron.

4. An article comprising a structure having welded lit thereto a deposit which under impact develops high surface hardness without excessive shrinkage having substantially the following composition:

or Cb) 10(C-.60) to lO(C-.l0)%.

in which, in the expressions C.60 and C.10, C stands for the per cent. of carbon in the Welding steel and only positive values of such expressions are significant, negative values being treated as zero; the balance, except for impurities which do not substantially affect the properties of the steel, being iron.

References Cited in the file of this patent UNITED STATES PATENTS 2,671,726 Jennings Mar. 9, 1954 2,698,785 Jennings Jan. 4, 1955 FOREIGN PATENTS 152,291 Austria Jan. 25, 1938

Claims (1)

1. 3. AN ARTICLE COMPRISING A STRUCTRE HAVING WELDED THERETO A DEPOSIT WHICH UNDER IMPACT DEVELOPS HIGH SURFACE HARDNESS WITHOUT EXCESSIVE SHRINKAGE HAVING SUBSTANTIALLY THE FOLLOWING COMPOSITION: C---------------------- .20 TO .85% MN--------------------- 9 TO 19%. NI--------------------- 0 TO 4%. MN+2NI----------------- 13 TO 22%. CR--------------------- 11 TO 21%. N---------------------- 0 TO .30%. MO AND/OR W------------ 0 TO 5%. V AND/R CB------------- 0 TO 2%. MO AND/OR W+2(V AND/ OR CB)------------- 10(C-.70) T 10(C+.20)% IN WHICH, IN THE EXPRESSIONS C-.70 AND C+.20, "C" STANDS FOR THE PER CENT. OF CARBON IN THE WELDING STEEL AND ONLY POSITIVE VALUES OF THE EXPRESSION C-.70 ARE SIGNIFICANT, NEGATIVE VALUES BEING TREATED AS ZERO; THE BALANCE, EXCEPT FOR IMPURITIES WHICH DO NOT SUBSTANTIALLY EFFECT THE PROPERTIES OF THE STEEL, BEING IRON.