US3660080A - Austenitic alloy and weld - Google Patents

Abstract

Sound, ductile austenitic alloy and weld of high strength in the as-welded condition. The alloy essentially consists of an ironchromium-nickel-manganese austenitic matrix with a second phase comprising a columbium compound, the columbium-rich phase serving to host non-metallic impurities such as phosphides, sulphides, silicides and borides and preclude their depositing in the austenitic grain boundaries. The alloy contains about 12% to 30% chromium, about 10% to 55% nickel, about 5% to 15% manganese, up to 3% molybdenum, carbon about 0.03% to .20%, nitrogen about 0.03% to 0.30%, with 0.5% to 4.5% columbium and/or 1% to 7% tungsten, and remainder iron, this amounting to at least about 22%.

Description

United States Patent Espy, Ronald H. et al.

[ 51 May2,1972

[54] AUSTENITIC ALLOY AND WELD [72] Inventors: Ronald R, Espy, Randallstown; Elbert E.

[73] Assignee:

[52] U.S.Cl ..75/128 A, 75/1286 [51 Int. Cl 1 ..C22c 39/20 [58] Field ot'Search ..75/128 A, 128 N, 128, 125

[56] References Cited UNITED STATES PATENTS 2,892,703 6/1959 Furman ..75/128 A 3,152,934 10/1964 Lula ....75/l28 N 3,201,233 8/1965 Hull ..75/128 N 3,306,736 2/1967 Rundell ..75/128N 3,495,977 2/1970 Denhard ..75/128N Primary Examiner-l-lyland Bizot Attorney-John Howard Joynt [5 7] ABSTRACT Sound, ductile austenitic alloy and weld of high strength in the as-welded condition. The alloy essentially consists of an ironchromium-nickel-manganese austenitic matrix with a second phase comprising a columbium compound, the columbiumrich phase serving to host non-metallic impurities such as phosphides, sulphides, silicides and borides and preclude their depositing in the austenitic grain boundaries. The alloy contains about 12% to 30% chromium, about 10% to 55% nickel, about 5% to 15% manganese, up to 3% molybdenum, carbon about 0.03% to 20%, nitrogen about 0.03% to 0.30%, with 0.5% to 4.5% columbium and/or 1% to 7% tungsten, and remainder iron, this amounting to at least about 22%.

9 Claims, No Drawings AUSTENITIC ALLOY AND WELD As a matter of introduction, our invention in a sense is a companion to that described and claimed in the copending Application Ser. No. 491,880 of Denhard-Espy, filed Sept. 30, 1965, and entitled Stainless Steel Resistant to Stress Corrosion Cracking, now US Pat. No. 3,495,997, issued Feb. 17,

1970 and relates to the austenitic iron-chromium nickel-man austenitic corrosion-resistant alloy of high strength and good ductility over a wide range of operating temperatures."

Another object is the provision of a fully austenitic stainless steel of good workability which is readily weldable and which in the as-welded condition is possessed of good tensile strength, ductility and resistance to impact, all over a wide' temperature range, that is, from about 320 F. up to about A further object is the provision of a weld metal and weld which are sound and free of defects and which are strong, ductile and of good impact strength.

Other objects of our invention in part will become readily apparent in the course of the description which follows and in part will be more particularly pointed to.

Accordingly, our invention in general may be considered to reside in the combination of elements, in the composition of the ingredients, and in the relation between the same, all as described herein and particularly set forth in the claims made at the end of this specification.

BACKGROUND OF THE INVENTION In order to gain a better understanding of certain features of our invention, it may be noted at this point that most 'of the iron-chromium-nickel alloys which are fullyaustenitic, and particularly the fully austenitic chromium-nickel stainless steels, are inclined to develop cracks as a result of welding. Hot cracks will develop when these alloys are heated to a tem perature of some 2,300 F., especially those alloys in the form" of heavy section. Even in the lighter sections, where'bending or other relief of stress is restrained, cracks also are likely to tial amount. Moreover, in applications where'a wholly nonmagnetic structure is necessary, as in electrical instruments,

instrument panels, and the like, not even a small amount of' delta-ferrite can be tolerated because of the ensuing magnetic effects. Perhaps even more importantly, we find that a'ferritecontaining alloy develops sigma phase at elevated temperatures, with resulting loss in mechanical properties, and even causing hot-working difficulties.

And while the nickel-base alloys and many of the chroniumnickel-base alloys of the prior art are fully austenitic and free of delta-ferrite, we find that these alloys also are inclined to develop cracks as a result of a welding operation. This we attribute to the appearance of low melting compounds along the grain boundaries. The appearance of these compounds is especially pronounced in welds or weld deposits as the weld metal solidifies and cools during the course of the welding operation. The low melting compounds particularly involved are found to be phosphides, silicides and borides and, to a' lesser extent, the sulphides. Such compounds formingin the grain boundaries weaken the metal, particularly causing a loss of hot tensile strength, resulting in the occurrence of hotcrack defects.

For many welding applications there are available a number of nickel-base alloys, these containing the ingredients chromiumand manganeserSee, for example, the alloy described in the Witherell U.S. Pat. No. 3,113,021 of Dec. 3, 1963, typically analyzing'about 18.5% to 21.5% chromium, about 2.75% to 3.25% manganese, about 2.25% to 2.75% columbium, about 0.2% to about 0.5% titanium, with iron up to about 2%, carbon up to about 0.08%, silicon less than about 0.3%, alu-' minum less than 0.08%, and remainder'nickel, this in the amount of about 69.5%(Patent, column 3, lines 56 through 63). The alloy is costly because of the high nickel content; And because of the'high nickel content it is difficult to work in the mill. Moreovenin many instances thealloy is found to be sensitive to hot-cracking in the weld metal.

An object of my invention, therefore, is the provision of a fully austenitic iron-chromium-nickel-manganese alloy possessing a good combination of strength, ductility and impact resistance which is suited to applications over a wide range of temperatures, which alloy readily lends itself to welding 'by known and accepted techniques, including electric-arc welding in controlled atmosphere, and which, indeed, is itself suited to applications as a weld-metal, as in thewelding of highly alloyed'stainless steels and other alloys, as, for example, the known 20-45-5 alloy (about 20% chromium, about 45% nickel, about 5% manganese, and remainder iron) and the 21- 6-9 (about 21% chromium, about 6% nickel, about 9% manganese, and remainder iron), which alloy and weld are sound and free of defects, having properties compatible with those of the unwelded base metal.

SUMMARY OF THE INVENTION Now'referring moreparticularly to the practice of our invention, we provide an iron-chromium-nickel-manganese alloy which essentially contains'particular amounts of the ingredients'carbon and/or nitrogen,-together with columbium and/or tungsten. The further ingredients sulphur, phosphorus, silicon and'boron, commonly present in stainless steel and like alloys, are maintained within practical but controlled amountspln the alloyof our invention there is employed chromium'in the amount of about 12% to 30% and preferably about 12%to 25%, nickel in the amountof'about' 10% 'or 15% to 55% and preferably about 12% to 45% or more especially about 20%'to about45%, manganese in'the amount of about 5% to 15% and'preferably about 9% to 13%, andat least one of the ingredients columbium in the amount of about 0.5% to 4.5%, preferably about 1% to about 4%, or tungsten in the amount of about 1% to 7%, preferably about 3% to about 7%,

with iron amounting to about 22% to 72%, usually about 22% to about 66%. In our alloy carbon necessarily is present, this in the amount of about 0.03% to 0.20% and preferably 0.03% to 0.15% or 'even' about 0.04% to about 0.12%. Nitrogen is present in the amount of about 0.03% to 0130% or'about 0.03% to about0.25% or even about 0.06% to about 0.25%. The sum of the ingredients carbon'and nitrogen amounts to at least about 0.15% where the columbium content amounts to only about 0.5% or the tungsten content only about 1%, and at least about 0.10% where the columbium content is about 1%. The ingredients phosphorus and sulphur are present in residual amount, the phosphorus being in amounts up:to about 0.020% andthe sulphur in amounts up to about 0.020% or even to about 0.035%. Boron ordinarily is less than 0.001%, although where columbium'and/or tungsten are on the'high side, boron purposely may be added to improve the hot-workability of the metal, but in an amount not exceeding 0.007%.

The silicon content of the alloy should not exceed 0.75%, and

for best results is maintained at a value less than 0.65%, this usually ranging from 0.30% to 0.60%. Where desired, molybdenum may be employed in amounts up to about 3%.

Our alloy is austenitic. But we find that columbium and/or tungsten introduced in large amount go to form columbiumrich or tungsten-rich compounds, as thecase maybe, with the iron, carbon and nitrogen present. The columbium compound or tungsten compound is in the nature of a second phase which exists along and with the primary austenitic phase. And this second phase serves to break up the grain structure and distribute the phosphides, sulphides, borides and silicides which form in the melting and teeming of the metal, this within the grains rather than at the grain boundaries. Microscopic examination clearly reveals a distribution of these compounds within the second phase; the grain boundaries of the alloy thus remain substantially uncontaminated.v Strength, ductility and high impactresistance thus are assured. Moreover, we find that with the assured freedom from the precipitation of phosphides, sulphides, borides and silicides in the austenitic grain boundaries, there is little tendency for them to nucleate and foster corrosive attack. While we prefer not to be bound by a theoretical explanation, it is our view that where it is columbium that is employed, the second phase is a columbium carbide, or perhaps columbium nitride or even a columbium-iron-carbon-nitrogen compound. Where tungsten is employed, it is thought that the second phase is a tungsten carbide or a tungsten nitride, or even some tungsten-iron-carbon-nitrogen compound.

In our iron-chrornium-nickel-manganese-columbium/tungsten alloy the composition is in every sense critical. For we find that where one or more of the ingredients is eliminated, or, indeed, where any significant departure is made from either the assigned minimum values or required maximum values, the desired combination of properties is no longer had. More particularly, chromium is employed in the amount of about 12% to about 30%, preferably some 13% to about 25%. With a chromium content less than about 12%, corrosion-resistance suffers. And where the chromium content exceeds about 25%, and certainly where'it exceeds about 30%, hotworkability directly suffers. Moreover, with the excessive chromium content the metal is inclined to become ferritic, particularly where the nickel content approaches the low side of the permissible range.

The nickel content of our alloy is in the amount of about on the low side to about 55% on the high. With a nickel content less than about 10% the stability of the metal is adversely affected, the alloy inclining to become ferritic. And with nickel exceeding about 55%, the hot-workability is adversely affected. And, even more importantly, we are inclined to the view that'the solubility of the metal for carbon and nitrogen, two essential ingredients, is adversely affected, nickel objectionably decreasing the solubility of the'metal for both. The nickel content for best results amounts to about 15% to about 40%.

A manganese content of about 5% to about 15% is required, for with a manganese content less than about 5% I feel that there is insufficient support for the necessary nitrogen content. And with manganese exceeding about 15% we feel that ferrite is introduced at elevated temperatures. Moreover, the corrosion-resistance suffers. For best results manganese is employed in the amount ofabout 9% to about 13%.

lron is a necessary and essential constituent in my alloy, this amounting to about 22% to about 72%. The iron serves as a vehicle for the carbon and nitrogen present and, moreover, is thought to be one of the ingredients present in the columbium/tungsten second phase. At least about 22% iron is required for the purposes noted; iron should not exceed about 72%, however, in view of the necessary requirements for chromium, nickel, manganese and columbium/tungsten. In general, the iron content ranges from about 22% to about 55%.

In our alloy, as noted above, at least one of the ingredients columbium in the amount of 0.5% to 4.5% or tungsten in the amount of about 1% to about 7% is necessary in order to serve as a basis for the required second phase. A columbium content less than about 0.5% is insufficient for that purpose. And a columbium content exceeding about 4.5% adversely affects the hot-workability of the metal. And the excessive columbium content moreover is inclined to result in undesired hardening, that is, age-hardening or precipitation-hardening, as .the metal is cooled from elevated temperatures. While the excessive columbium content increases the tensile strength, it adversely affects the ductility and impact-resistance. In general,

the same may be said with respect to the tungsten content; less 1 than about 1% tungsten is insufficient and a tungsten content exceeding about 7% creates undesired problems in working the metal, in giving an undesired hardening in cooling from high temperature, and in loss of corrosion-resistance.

Although the carbon content of our alloy ranges from about 0.03% to 0.20%, for best results there is employed a carbon content of 0.04% to 0.12%. A carbon content less than about 0.04%, and certainly one less than about 0.03%, affords insufficient carbon for the required second phase noted. And a carbon content exceeding 0.12%, and particularly one exceeding about 0.15%, adversely affects corrosion-resistance. In general, the same may be said with respect to the ingredient nitrogen, at least 0.03%, and preferably 0.06% nitrogen being required in order to contribute to the second phase noted, but nitrogen exceeding about 0.25%, and certainly in excess of 0.30%, adversely affects ductility and impact-resistance.

DESCRIPTION OF THE PREFERRED EMBODIMENTS While, as noted above, the alloy of our invention broadly ranges in composition from about 12% to about 30% chromium, about 10% to about 55% nickel, about 5% to about 15% manganese, with carbon about 0.03% to about 0.20%, nitrogen about 0.03% to 0.30%, phosphorus in amounts up to about 0.020%, sulphur in amounts up to about 0.035%, and any boron in an amount not exceeding 0.007%, and with columbium in the amount of 0.5% to about 4.5% and/or tungsten in the amount of about 1% to about 7%, withremainder iron, there are a number of more limited compositions in which a best combination of properties is enjoyed. In all, however, the alloy is fully austenitic, strong, tough and ductile. Moreover, the alloy is suited to applications throughout a wide temperature range. The alloy is readily weldable and, in point of fact, peculiarly suited to applications as a weld filler materia1, giving a sound weld which is possessed of a good combination of properties in the as-welded condition.

One of the preferred alloys according to our invention es sentially consists of about 12% to about 15% chromium, about 18% to about 24% nickel, about 9% to about 13% manganese, with about 0.06% to about 0.15% carbon, about 0.03% to 0.20% nitrogen, about 1.5%. to about 3.5% columbium, phosphorus not exceeding about 0.020%, and remainder iron. More specifically, this alloy essentially consists of about 13% to about 14% chromium, about 18% to about 22% nickel, about 10% to about 11% manganese, about 0.03% to about 0.11% carbon, about 0.06% to about 0.20% nitrogen, with about 1.5% to about 3.5% columbium, and about 49% to about 57% iron. Both the preferred and the specific alloy are considered to be stainless steels, fully austenitic, and sufficiently corrosion-resistant for most applications. They are suited to a variety of welding applications, particularly as a filler material. And in the as-welded condition are strong, tough and ductile.

A further preferred alloy, this likewise being considered a stainless steel, essentially consists of about 15% to about 22% chromium, about 10% to about 22% nickel, about 7% to about 13% manganese, about 0.05% to about 0.12% carbon, about 0.03% to about 0.20% nitrogen, about 1.5% to about 2.5% columbium, with remainder substantially iron. Because of the increased chromium content this alloy enjoys excellent corro' sion-resistance, along with good strength, ductility and toughness in the as-welded condition. Moreover, the alloy is suited to applications where there is encountered a rather wide range of operating temperatures.

7 Another preferred alloy essentially consists of about 16% to about 21% chromium, about 35% to about 45% nickel, about 9% to about 13% manganese, phosphorus not exceeding about 0.020%, with carbon about 0.06% to about 0.12%, nitrogen about 0.06% to about 0.20%, columbium about 1% to about 4%, and remainder substantially iron, this amounting to at least 22%. This alloy enjoys good stress-corrosion crack-resistance in combination with good weldability. Where desired, molybdenum may be added in amounts up to about 3%.

A still further preferred alloy essentially consists of about 22% to about 27% chromium, about 18% to about 23% nickel, about 9% to about 13% manganese, with a carbon content of about 0.06% to about 0.10%, a nitrogen content of about 0.06% to about 0.20%, a columbium content of about 1% to about 2%, and remainder substantially iron. Perhaps the outstanding virtue of this alloy is its combination of corrosion-resistance, strength and toughness over a wide range in temperatures, that is, from about -320 F. to about 1,500 F.

in applications involving a welding of the 20-45-5 grade of stainless steel (about 20% chromium, about 45% nickel and about 5% manganese, with remainder substantially iron) we prefer an alloy essentially consisting of about 17% to about 22% (more broadly about 12% to about 25%) chromium, about 30% to about 45% (or more especially about 35% to about 40%) nickel, about 5% to about 12% (or especially about to about 12%) manganese, about 0.03% to about 0.20% (or more particularly about 0.06% to about 0.12%) carbon, about 0.03% or 0.04% to about 0.20% nitrogen, about 1% to about 3% or 4% columbium, up to about 3% molybdenum, and remainder substantially iron, this amounting to at least 22%, more particularly about 22% to about 42% iron. Boron may be added in amounts up to about 0.007% where desired. This alloy has especially good corrosion-resisting characteristics which make it suited to marine applications. For a best combination of properties this alloy essentially consists of about 19.5% to about 20.5% chromium, about 44.5% to about 45.5% nickel, about 5% to about 6% manganese, about 0.03% to about 0.05% carbon, about 0.03% to about 0.06% nitrogen, about 1.5% to about 2% columbium, and remainder substantially iron.

1n the welding of the 21-6-9 grade of stainless steel (about 21% chromium, about 6% nickel, about 9% manganese and remainder iron) our preference is for an alloy essentially consisting of about 12% to about 27% (more particularly about 24% to about 26%) chromium, about 17% to about 24% (or more particularly about 20% to about 22%) nickel, about 9% 'lensile propertics,-fracture appearance and microstructure of the alloys of these alloys, with high nickel content, give a sound weld which is fully austenitic, tough and ductile in the as-welded condition, even where subjected to duty at low temperatures.

As particularly illustrative of the alloy of my invention we give belowin Table 1(a) the chemical compositions of some nine alloys, four according to our invention and five of composition outside of our invention, in which'there are forcefully revealed the effects of manganese, columbium and carbon on the production of crack-free welds. The compositions in every case are those of the deposited weld metal.'The tensile properties and a notation respecting the appearance of the fractured tensile specimens, as well as the amount of a second phase present in the alloy, are given in Table 1(b).

TABLE I B Chemical composition of nine austenitic stainless steel weld deposits Specimen N o. 0 Mn P S Si Cr Ni C b N 9. 35 .009 .005 .40 20.20 11.90 .31 1. 9.1 .012 .011 .40 13.46 20.69 .05 9. 71 .008 .011 .45 13. 79 19.19 .04 9. 03 .007 013 19 13. 28 19. 83 14 11.88 .001 .010 64 13.110 19. 3. 17 .22 1. 31 005 014 52' 13. 84 20. 27 1.9 1 .01 11.111 012 007 38 13.11 .21. .25 .2. (I8 .03 ll. 31 013 U119 .37 2-1. 65 .21. .2-1 1.50 05 11.88 .67 1.10

Alleys of the invention. Alloys of the invention enjoying.' it best cenihinntion of properties.

The tensile properties of the weld compositions of table 1(a) in the form of weld specimens of 0.505 inch diameter are reported below in Table 1(b). There are given the ultimate tensile strength in kilopounds per square inch (ksi), the yield strength in ksi, the percent elongation in 2 inches, and the percent reduction in'area. Also reported is the appearance of the fractured tensile specimens, with percent indication of the number of microfissures or hot-cracks which occurred at the time of welding each specimen and which later show up as defects on the face of the fractured specimen. Additionally, there is indicated the volume percent of a second'phase which is observed in the microstructure of each specimen, these by visual estimate at 300x.

TABLE 10) Till): lei

Appearance of fractured tensile specimens Average Percent MF 1 on Breaks 2 on phase in Specimen U.'1.S Y.S., elong. Percent fractured side of micro- No. K s 1 K s.i. 2 R. face specimen structure 73 57 18 16 3 Several 5 83 63 31 39 0 None 5 MF=Micr0fissures or hot-cracks which occurred at the time of welding show up as defects on the face of the fractured specimen.

2 Breaks on side of specimen are a good measure of weld deposit soundness.

Ihis was mostly micro condition, a condition where fracture occurs along the grain boundary in tensile loading.

Alloys of the invention.

b Alloys of the invention enjoying a best combination of properties.

or 10% to about 12% manganese, with a carbon content of about 0.03% to about 0.12% (or about 0.06% to about 0.l0% carbon), a nitrogen content of about 0.03% toabout 0.30% (more especially about 0.06% to about 0.20% nitrogen), with about 1.5% to about 3% (or even about 1% to about 2%) columbium, and remainder substantially iron, although molybdenum may be present in amounts up to about 2%. And, here again, for a best combination of properties, however, we employ an alloy essentially consisting of about 21% chromium, about 20% nickel, about 9% manganese, with a carbon content of about 0.03% to about 0.06%, a nitrogen content of about 0.03% to about 0.10%, with about 1.5% to about 2% columbium, and remainder substantially iron. We find that lnnoting the results reported in'Table 1(b) above for the austenitic stainlesssteel weld depositsof composition according to Table.l(a), itwill be immediately seen that the first four specimens reveal many microfissures on the fractured tensile specimen face, as well as numerous breaks in the side of the specimens. Moreover, it will be seen that all are singularly free of a second phase. These are the alloys which are free of the ingredient columbium. They'are clearly outside of the composition of the alloys according to my invention.

The alloys Nos. 839, 813, 805 and 806 of Tables 1(a) and 1(b), which contain the required critical amount of the ingredient columbium, fully answer to the requirements of the invention. All four specimens are free of fractured defects on the fractured tensileface. And all four specimens contain a certain amount of the required second phase. Although two of the specimens (Nos. 839 and 805), having carbon contents of 0.060% and 0.066% respectively, with respective columbium contents of 3.17% and 1.50%, disclose a single break on the side near the fracture, this evidencing a microfissure or hotcrack at the time of welding, the single occurrence is acceptable. The specimens Nos. 813 and 806 with somewhat higher carbon contents (Nos. 813 with carbon 0.077% and columbium 2.08% and No. 806 with carbon 0.100% and columbium 1.10%) are singularly free of defect. It is in the alloys of the composition of these specimens in which a best combination of properties is had.

' The single remaining specimen (No. 816) is not acceptable,

even though a second phase is present; the number of microfissures on the fractured face is great, and the number of breaks on the side of the tensile specimen is excessive. l attribute the unacceptability of this alloy to the objectionably low manganese content of 1.31%; in other regards the com position meets that of the acceptable alloys.

A further series of weld deposits of differing compositions is given below in Table ((1). In these alloys the chromium content ranges from some 13% to with nickel from about 1 1% to 21%. For purposes of comparison there additionally is included an alloy of the standard AlSI Type 310 (chromium about 25%, nickel about 20%, manganese 2% max., silicon 1.5% max., carbon 0.25% max., and remainder iron).

TAB LE II (a) A study of the results reported in Table ll(b), this with respect to the compositions reported in Table ll(a), rather clearly reveals that a composition according to the standard AlSl Type 310 shows many microfissures on the fractured face of the tensile specimen and many breaks on the side of the specimen. There is no evidence of the presence of a second phase. The alloy, of course, is well outside of the composition of the alloys of my invention in that there is an absence of columbium and a wholly insufficient amount of manganese. Moreover, the phosphorus content appears to be excessive.

So, also, two further specimens (Nos. 843 and 851) are unacceptable even though containing sufficient columbium and sufiicient manganese. One reveals defects in the fractured face, evidencing microfissures or cracks occurring at the time of welding, and both reveal an excessive number of breaks on the side of the specimen. ln both specimens boron is present in significant added amount, this being on the order of some 0.002% to 0.007%. And in both the nitrogen content is objectionably low and there is an objectionably high phosphorus content, this latter amounting to 0.029% for the one and 0.021% for the other.

As to the'remaining alloys, all are acceptable, although it is noted that a best combination of properties, with freedom from microfissures on the fractured face and freedom from breaks on the side of the specimen is had with the alloys of the higher columbium contents and higher carbon or carbon plus Chemical composition of nine further austenitic stainless steel weld deposits Specimen N o. 0 Mn 1 S Si Or Ni B 1 Cb W N l Boron in wire used for weld filler:

X-N0t added, content generally .001%. YAdded, content may vary from approx. .002 to .007%. n Alloys oi the invention. Alloys of the invention enjoying a best combination of properties. a Ta .85. Mo 1.82.

with examination at 300x. Here again, the properties are re- 55 ported for weld deposit specimens of 0.505 inch diameter.

TABLE II (b) nitrogen contents (Nos. 833, 844 and 852). Specimen 833, although having a carbon content of 0.047%, has a nitrogen content of 0.18%, with a columbium content of 2.28%, which it is felt gives the desired substantial amount of the second phase, some 5% to 10% by volume. The alloys of even higher carbon plus nitrogen content (Nos. 789, 802 and 803), while acceptable, are not absolutely free of defect. For example, specimen No. 789, which contains tungsten in the amount of 3.5% as a substitute for columbium, with carbon 0.041% and nitrogen 0.24%, reveals but a small amount of the second phase and two breaks on the fractured face and a trace of a second phase for the nine weld deposits of Table II (2.)

Appearance of fractured Tensile properties tensile specimens Average percent Percent second Percent MF 1 on Breaks 2 on phase in Specimen U.'1.S Y. elong. Percent fractured side of micro- N 0. K s.1 K s.1 2 RA. face specimen structure 789 a 99 33 46 1 833 N 96 77 26 38 7 844 b 97 79 11 11 7 802 82 26 25 1 803 n 04 73 26 34 7 843 87 70 18 10 5 H51. 8'. (i3 '31 30 1 H51. N7 lit) 21') 33 4 'l \'|u-. 3111 8'11 131 .32 Ill 1) 1 MI" Mh-rullssnros or lml t'l'lll'iih' which occurred at tho llnw of welding show up as /\|lu i of the invention. Alloys of the invention unjoying n ln'sl. combination of propel-tics.

break on the side of the specimen. Because of a minimum number of breaks the alloy is acceptable. Specimen No, 802, with columbium 0.48% and tantalum 0.85%, along with carbon 0.110% and' nitrogen 0.28%, while acceptable, clearlyv falls short of the combination of properties had with the best compositions (Nos. 833, 844 and 852). it appears that while tantalum is acceptable as a partial'substitute for columbium, the results had leave something to be desired; it is with the columbium addition that a best combination of properties is realized.

Another series of austenitic weld deposits, these of about 17% to 21% chromium, about 30% to 45% nickel, about 4% to 12% manganese, all of which contain columbium, with or without the further ingredient molybdenum, and remainder iron, was subjected to mechanical test and examination. The chemical composition of these alloys, twelve in number, including one of the standard AlSl Type 330, which is free of columbium, is given below in Table lll(a). The tensile properties of the weld deposits of 0.505 inch diameter, as well as the appearance of the fractured tensile specimens and the amount of second phase present in the microstructure when examined at 300x are given in Table lll(b) which follows.

TABLE lll(a) Chemical composition of twelve austenitic weld deposits A review of the test resultsset out in Table lll(b) above, this with regard to the composition of the specimens as given in Table lll(a), reveals that the alloys of high nickel content and the required chromium and manganese contents, as well as the required columbium and carbon contents, are characterized by the presence of a second phase and a desired freedom from defects on the fractured face. Such freedom from defect evidences a freedom from microfissures or cracks occuringat the time of welding. A study of the results also reveals in these alloys an acceptable minimum number of breaks on the side oi the specimens. A best combination of results. of course, is had in those compositions (Nos. 823 and 845) evidencing a complete freedom from face defect and side breaks of the fractured specimens.

Although. as indicated, best results are had with compositions free of break. others (Nos. B and 826) are acceptable. These additionally contain a small amount of boron, this on the order of 0.002% to 0.007%, for the purpose of improving thehot-working characteristics of the metal. While it appears that the boron additionin a measure adversely affects the properties to some slight extent, this conclusion must be tempered by the further observation that the specimen No. 806

Specimen No. C Mn 1" S Si (Jr Ni B Cl) Mo N B u r 061 12.10 010 008 60 17. 83 38. 50 Y 1.13 03 101 4. 42 .010 .013 .78 10. 40 38. 70 X 3. 00 .02

. ll 10. 81 008 .010 57 1 .1. 811 30. 54 Y 3. (l4 2. 77 02 050 5. 23 008 020 47 20. 24 I 44. 00 X l. 511 2. (i1 03 I Boron in wire used for weld filler:

X-Not added, content generally .001%. YAdded, content may vary from approx. 002% to 007%. Alloys of the invention. Alloys of the invention enjoying a best combination of properties.

The mechanical properties of the weld deposits of Table. lll(a) are presented below in Table lll(b). There are reported tionally, there is'indicated the volume percent of a second phase when examined by microscope at 300x. The properties are reported for weld deposits of 0.505 inch diameter.

TAB LE III (b) reported in Table 1(a), although not there reported, does, in fact, contain boron in the amount of 0.002% to 0.007% and, as reported in Table 1(b) is free of defect. The acceptable steels essentially consist of about 17% to about 21% chromium, about 30% to about 45% nickel, about 5% to about 12% manganese, about 0.05% to about 0.20% carbon, with silicon not exceeding about 0.75%, nitrogen at least 0.03%, up to 0.007% boron, columbium about 1.5% to 3%, and remainder substantially iron, this amounting to at least about 22%.

The further specimen Nos. 812, 827, 829, 831, 834, 835, 849 and Type 330 are not acceptable. in specimen No. 812,

Tensile properties, appearance of fracture and percent second phase for the weld specimens of composition according to Table I11(a)' Appearance of fractured tensile specimens Average Tensile properties percent Percent second Percent MF 1 on Breaks on phase in Specimen U.T.S., Y.S., elong. Percent fractured side of microo. K 5.1. K st. 2' RA. face specimen structure MF=Microfissures or l1ot-cracks which occurred at the time of welding show up as defects on the face of the fractured tensile specimen.

2 Breaks on side of tensile specimen are a good measure of weld deposit soundness.

Alloys of the invention. Alloys of the invention enjoying a best combination of properties.

the manganese content is unacceptably low, even though, a second phase is present and but two microfissures appear on the fractured face; the ductility is a bit low and corrosion-resistance suffers.

The compositions of the specimen Nos. 827, 829, 831', 834, 835 and 849, as well as the specimen of AlSl Type 330, contain an objectionable number of breaks on the side. of each tensile specimen, the specimen No. 849 and A181 Type 330 additionally revealing objectionable weld defects as gauged by the condition of the fractured face. We attribute the shortcomings of the specimen Nos. 827 and 829 to an objectionably low nitrogen content; that of No. 831 to the high phosphorus content of 0.020% in combination with high silicon; and of specimen Nos. 834 and 835 to the high silicon contents of 1.15% and 0.85%, respectively, this in combination with boron for the specimen No. 834. The deficiencies of specimen No. 849 we attribute to the low manganese content of 4.02%, and to some extent the presence of boron. The inadequacy of the standard AlSl Type 330 is felt to lie in the very low manganese content of 1.72% and the absence of both columbium and tungsten.

We feel that perhaps the necessary importance of the resence of the ingredient manganese and that of carbon and columbium, with particular relation between the same, is best illustrated by presentation of test results on fusion welds made in grooved bar samples. In every case the composition of bar and head is the same, this amounting to about 20% chromium, about 20% nickel, with phosphorus in the amount of about 005%, sulphur in the amount of about 0.010% and silicon in the amount of about 0.50%. Weld deposits were examined on a series of welds of the three groups about 0.75% manganese, about manganese and about manganese, with columbium contents of about 0.50%, about 1% and about 2% at each manganese level. Samples with carbon contents of about 0.05% and about 0.15% were examined for each manganese and columbium figure.- The composition of the various specimens and the degree of cracking reported for the weld deposit in each case are given below in Table IV.

TABLE IV phosphorus, sulphur and silicon low, are acceptable. It is noted, however, that where carbon is on the low side, that is, about 0.05%, a best combination of properties is had where the columbium content amounts to about 2% (Heat Nos. 6698-1, 6701-1 and 6702-1 Where the carbon is on the high side, however, that is, about 0.15%, the best combination of properties is had where columbium amounts to at least about 0.50% (Heat Nos; 6696-2 and 6699-2), or about 1% (Heat Nos. 6697-2 and 6700-2), or about 2% (Heat Nos. 6698-2, 6701-2 and 6702-2). In all of these alloys the weld deposit is free of cracking, both in the crater area and in the center area of the weld bead. These results also obtain for the two highnitrogen grades (Heat Nos. 6702-1 and 6702-2, with nitrogen contents, respectively, 0.14% and 0.24%).

Thus, in conclusion, it will be seen that we provide in our invention an iron-chronium-nickel-manganese alloy and weld which is austenitic and which in the as-welded condition is strong, sound and ductile. The alloy in the form of weld wire is particularly suited to the welding of the known 21-6-9 and 20- -5 chromium-nickel-manganese alloys and others, producing sound, ductile welds of high strength.

Inasmuch as many embodiments may be made of our invention and many modifications made of the embodiments set out above, it will be understood that all matter described herein is to be taken as illustrative and not by way of limitation.

We claim 1. Austenitic alloy essentiallyconsisting of about 12% to about 15% chromium, about 18% to about 24% nickel, about 9% to about 13% manganese, about 0.06% to about 0.15% carbon, about 0.03% to about 0.20% nitrogen, about 1.5% to about 3.5% columbium, phosphorus not exceeding about 0.020%, and remainder substantially iron.

2. Austenitic alloy essentially consisting of about 13% to about 14% chromium, about 18% to about 22% nickel, about 10% to about 11% manganese, about 0.03% to about 0.11% carbon, about 0.06% to about 0.20% nitrogen, about 1.5% to about 3.5% columbium, and about 49% to about 57% iron.

3. Austenitic alloy essentially consisting of about 15% to Degree of cracking in weld deposit Crater Center of Heat No. 0 Mn Cr Ni Cb N area ead I .78 19. 18 20. 17 .50 05 Very heavy. Moderate. 73 19. 69 20. 12 49 .06 Heavy 68 19. 81 19. 93 97 .05 Heavy .64 20.42 20.13 .73 .05 Moderate 0. .67 19. 83 20. 06 1. 88 04 Moderate- 0. 70 20.42 20.03 1. 51 .04 Light 0. 4. 20.24 19. 88 .53 1 0. 4. 28 20. 12 20. 06 53 4. 86 20.40 20.07 1.09 4. 20.41 20. 15 1.06 4. 81 20. 31 20. 09 2. 20 4. 46 20, 14 20.27 2. 18 10. 01 20. 03 20. 21 63 9. 92 20. 28 20. 08 62 10. 11 20. 10 20.21 1.13 10. 10 20. 13 20.06 1.09 9. 96 20. 14 20. 24 2. 13 10.02 20. 17 20.29 2. 16 10. 16 20. 08 20. 17 2. 20 10.25 20. 13 20. 19 2. 24

* Alloys of the invention. I b Alloys of the invention enjoying a best combination of properties.

No'rE.-All compositions contain about 005% phosphorus, about 010% sulphur and about .50% silicon.

A review of the results presented above in Table IV quickly reveals that the alloys having a manganese content of about 0.75% are in no way acceptable; cracks ranging from very heavy to moderate are found in all of these specimens (Heat Nos. 6900-1-2, 6901-1-2 and 6902-1-2).

All of the alloys with a manganese content of either about 5% or about 10% with carbon contents of about 0.05% or about 0.15% and columbium contents of about 0.50%, about 1% or about 2%, along with chromium in the amount of about 20%, nickel about 20%, nitrogen at least 0.04%, and

amounting to at least about 22%.

5. Austenitic alloy essentially consisting of about 16% to about 21% chromium, about 35% to about 45% nickel, about 9% to about 13% manganese, phosphorus not exceeding about 0.020%, about 0.06% to about 0.12% carbon, about 0.06% to about 0.20% nitrogen, about 1% to about 4% columbium, up to about 3% molybdenum and remainder substantially iron this amounting to at least about 22%.

6. Austenitic alloy essentially consisting of about 22% to about 27% chromium, about 18% to about 23% nickel, about 9% to about 13% manganese, about 0.06% to about 0.10% carbon, about 0.06% to about 0.20% nitrogen, about 1% to about 2% columbium, and remainder substantially iron.

7. Austenitic alloy essentially consisting of about 24% to about 26% chromium, about to about 22% nickel, about bon, about 0.03% to about 0.30% nitrogen, about 1.5% to about 3% columbium, up to about 2% molybdenum, and remainder substantially iron.

9. Austenitic alloy essentially consisting of about 12% to about 25% chromium, about 12% to about 45% nickel, about 9% to about 13% manganese, about 0.03% to about 0.15% carbon, about 0.03% to about 0.30% nitrogen, about 3% to about 7% tungsten, and about 22% to about 72% iron.

Claims (8)

1. 2. Austenitic alloy essentially consisting of about 13% to about 14% chromium, about 18% to about 22% nickel, about 10% to about 11% manganese, about 0.03% to about 0.11% carbon, about 0.06% to about 0.20% nitrogen, about 1.5% to about 3.5% columbium, and about 49% to about 57% iron.
2. 3. Austenitic alloy essentially consisting of about 15% to about 22% chromium, about 10% to about 22% nickel, about 7% to about 13% manganese, about 0.05% to about 0.12% carbon, about 0.03% to about 0.20% nitrogen, about 1.5% to about 2.5% columbium, and remainder substantially iron.
3. 4. Austenitic alloy essentially consisting of about 17% to about 21% chromium, about 30% to about 45% nickel, about 5% to about 12% manganese, silicon not exceeding about 0.75%, about 0.05% to about 0.20% carbon, about 0.06% to about 0.20% nitrogen, up to 0.007% boron, about 1.5% to about 3% columbium, and remainder substantially iron, this amounting to at least about 22%.
4. 5. Austenitic alloy essentially consisting of about 16% to about 21% chromium, about 35% to about 45% nickel, about 9% to about 13% manganese, phosphorus not exceeding about 0.020%, about 0.06% to about 0.12% carbon, about 0.06% to about 0.20% nitrogen, about 1% to about 4% columbium, up to about 3% molybdenum and remainder substantially iron, this amounting to at least about 22%.
5. 6. Austenitic alloy essentially consisting of about 22% to about 27% chromium, about 18% to about 23% nickel, about 9% to about 13% manganese, about 0.06% to about 0.10% carbon, about 0.06% to about 0.20% nitrogen, about 1% to about 2% columbium, and remainder substantially iron.
6. 7. Austenitic alloy essentially consisting of about 24% to about 26% chromium, about 20% to about 22% nickel, about 10% to about 12% manganese, about 0.06% to about 0.10% carbon, about 0.06% to about 0.20% nitrogen, about 1% to about 2% columbium, and remainder substantially iron.
7. 8. Austenitic alloy essentially consisting of about 12% to about 27% chromium, about 17% to about 24% nickel, about 9% to about 12% manganese, about .03% to about 0.12% carbon, about 0.03% to about 0.30% nitrogen, about 1.5% to about 3% columbium, up to about 2% molybdenum, and remainder substantially iron.
8. 9. Austenitic alloy essentially consisting of about 12% to about 25% chromium, about 12% to about 45% nickel, about 9% to about 13% manganese, about 0.03% to about 0.15% carbon, about 0.03% to about 0.30% nitrogen, about 3% to about 7% tungsten, and about 22% to about 72% iron.