Weldability and Weld Metal Capabilities of a New Precipitation-Hardenable Alloy Alloy 450, a martensitic stainless steel age-hardenable beyond the strength of Type 410, with corrosion re­ sistance comparable to Type 304, can be joined using conventional welding procedures. BY L. P. MYERS, C. V. PRESTOWITZ AND H. C. CAMPBELL ABSTRACT. Using filler materials used with the standard filler metal. same degree of simplicity is not to be especially compounded to overcome Good properties are obtainable found in their physical metallurgy. porosity and maintain alloy content, a with all of the processes studied here. Although widely recognized and new precipitation hardenable mar­ The best mechanical properties were used for such diverse applications as tensitic stainless steel called alloy 450 shown by GMA welds annealed be­ turbine blading and conveyor belts, may be successfully welded by many fore aging. the alloy designated 450 is a rela­ standard arc welding processes and tively new development. A limited put into service after a simple aging Introduction description of the alloy placing it in treatment at 900 to 1500 F (4 hr at Research experimental welding is perspective therefore appears de­ temperature, air cooled). For opti­ required on any new alloy when sirable. mum properties combining high cor­ definite information on the weldability Alloy 450 belongs to that group of rosion resistance with weld tough­ and weld metal capabilities of the alloys known as the martensitic pre- ness and strength the weldment must alloy are required. This is particularly cipitation-hardenable stainless steels. be annealed at 1900 F (1 hr, water relevant to the highly alloyed This family of alloys is characterized quenched) and then aged. precipitation-harden able stainless by a predominately martensitic matrix Porosity appears in GMA welds un­ steels. While certain of these steels in all conditions of heat treatment in­ less the filler metal contains addi­ are engineered for simplicity and cluding the annealed state. Although tional deoxidizers (on the order of ease of handling in the fabricators' the martensitic reaction is commonly 0.1% Ti). Standard filler metal seems shop, it can be readily stated that the used to develop high strength and satisfactory for GTA welds. Covered electrodes for shielded metal-arc welding need to be formulated with certain elements reinforced to offset losses experienced in the arc. A simi­ Table 1 -• Typical Room Temperature Mechanical Properties of Wrought Plate larly reinforced granular flux is re­ 0.2% YS, UTS, % El., quired for submerged arc welding, Alloy Heat Treatment ksi ksi 4D % RA Hardness 450 Annealed <a> 115 140 14 58 28 HRC 450 Annealed + aged 900 F ' 182 192 14 58 42 HRC L. P. MYERS is Supervisor, Stainless Steel 450 Annealed + aged 1150 F(c) 90 140 20 65 28 HRC Research, Carpenter Technology Corp., Type 304 Annealed(d) 30 85 60 70 81 HRB Reading, Pa. C. V. PRESTOWITZ is Tech­ Type 410 Hardened and tempered'6' 150 195 15 55 42 HRC nical Director, Arcos Corp., Philadelphia, Pa. H. C. CAMPBELL, formerly Director of Research and Technology, Arcos Corp., is Manager, Education, AWS, Miami. (a) 1900 F (1 hr) water quench Paper was presented at the 54th AWS (b) 900 F (4 hr) air cool (c) 1150 F (4 hr) air cool Annual Meeting held at Chicago during (d) 1950 F - water quench April 2-6, 1973. (e) 1800 F(1 Inr ) oil quench + 300 F (1 hr) air cool WELDING RESEARCH SUPPLEMENT! 417-s hardness, martensite with relatively Table 2 — Welding Parameters for 450 Alloy (Gia s Metal Arc Welding) low hardness and ease of fabrication can be obtained by restricting the Root Opening 1/16 in. amount of carbon (and to a lesser ex­ Electrode Gap 3/4 in. tent nitrogen) available for dissolu­ Maximum Interpass Temperature 250 F tion at the annealing temperature. Ac­ a (b b b (b cordingly, carbon is limited or stabil­ Trial < > Trial > Trial< > Trial < >' Trial > no. 1 no. 2 * no. 3 no. 4 no. 5 ized to some extent in all martensitic precipitation hardenable stainless Cover gas, cfh 30Ar + 10He 30Ar + 10He 40 Ar+2%02 40Ar+2%O , 40Ar+2%O steels including 450. Electrode (450), 1/16 in. Std Anal. Std Anal. Std Anal. Std anal. Ti-anal. Feed, ipm 225 195 216 205 180 The principal elements in 450 are Voltage, V 33 33 (const) 30 (const) 30 (const) 30 (const) Cr, Ni, Cu, Cb, Fe, Mo. Total alloy Current, A (reverse content, as well as the amount of any polarity) 320 (const) 300 300 300 300 one element, is closely controlled to Travel speed, ipm 12 12-15 12-18 12-18 12-17 obtain the desired combination of No. specimens 4 1 3 2 4 mechanical properties and corrosion No. pores in 6 in. over 15 over 15 over 15 over 15 Note <c> resistance coupled with a single phase matrix for several conditions of (a) Manual welding (b) Mechanical welding heat treatment. (c) Essentially no pores Basic mechanical properties show a yield strength for the annealed con­ dition approximately four times that for Type 304 and, after aging to maxi­ Table 3 — Weld Hardness Data, Rockwell C, Measured at Three Locations mum hardness, a yield strength mod­ for Each Specimen <a) erately in excess of that for fully hard­ ened Type 410 (tempered 300 F). The Welding process used and type of electrode covering, where applicable yield strength of the 1150 F aged con­ dition, which provides maximum re­ Heat treated condition GMAW SMAW-lime SMAW-titania SAW sistance to stress corrosion crack­ 1 2 3 1 2 3 1 2 3 1 2 3 ing and maximum thermal stability, is As welded 30 36 37 29 33 31 29 34 34 31-34 29-35 29-33 somewhat less than that for the an­ Annealed (1900 F)(b) 29 29 28 28 28 28 27 27 28 28 29 27 nealed condition — note Table 1. The Welded + aged (900 F)lc> 42 39 42 41 40 42 41 39 42 41 39 41 corrosion resistance of the alloy is Annealed (1900 F) comparable to Type 304 in those en­ + aged (900 F) 42 42 42 41 42 41 41 41 42 41 41 41 vironments in which 450 would com­ Welded + aged monly be used (Ref. 1). (1150 F)(d) _ _ _ 28 29 31 28 29 32 28 28 31 The acceptance of alloy 450 for Annealed (1900 F) numerous applications and its po­ + aged (1150 F) 28 29 29 28 29 30 28 28 29 — — — tential for others created a need for welding technology and data on weld fa) Location of hardness measurements: 1 = plate. '2 in. from HAZ: 2= HAZ: 3 = weld. (b) 1900 F, 1 hr. water quench metal capabilities. At the outset of this (c) 900 F, 4 hr air cool work it was assumed that basic (d) 1150 F. 4 hr air cool welding procedures would be appli­ cable to the alloy. It remained to be seen, however, what problems might be encountered when welding the Table 4 — Mechanical Properties for 450 Alloy Welds and Base Metals alloy by several common methods. In in the Conditions Shown addition, it was necessary to evaluate 450 weld metal integrity and de­ Frac­ Charpy V termine the mechanical and cor­ 0.2 ture impact rosion properties of weld metals. YS, UTS % El., loca- strength, Laboratory and production experi­ ,a) Type weld ksi ksi 4D %RA tion ft-lb ence showed that sound gas-tung­ sten-arc welds can be consistently As Welded Condition obtained with no unusual effort. For GMAW 133 153 14 49 W 33 this reason, the present welding was SMAW (lime) 104 151 10-16 16-61 W-P 16 confined to multiple bead weld­ SMAW(titania) 119 151 7 14 w 11 ments using a filler metal. SAW 130 152 5-13 5-50 W-P 12 The principal study was divided into three phases, the first dealing A ..(b) Welded + Annealed with gas metal-arc welding (GMAW) coupled with the selection of a GMAW 116 137 16 63 w 65,83 suitable filler metal, the second deal­ SMAW (lime) 118 144 16 56 25 w ing with shielded metal-arc welding SMAW(titania) 123 145 16 55 p 15 SAW 120 142 12 50 17 (SMAW) coupled with the selection of w the best covering for the electrodes Base Metal — Annealed Ci and finally, submerged arc welding (SAW). Longitudinal 120 141 17 65 102 The weldments were studied in the Transverse 118 139 13 47 34 as-welded condition and in five heat treated conditions: (a) W^weld: P= bare metal plate. • Annealed, which produces the (b) 1900 F (1 hr) water quench highest resistance to corrosion; 418-s | SEPTEMBER 1 973 • Aged (at two temperatures) di­ rectly after welding, which de­ velops quite satisfactory hard­ ness with minimum effort; • Annealed and Aged (two temperatures), which produces the most uniform mechanical properties. The two aging temperatures were : (1) 900 F, which hardens the alloy to the maximum strength level, with yield strength exceeding 170 ksi; (2) 1150 F, which provides the maximum resis­ tance to stress corrosion cracking and the maximum thermal stability. Welding Procedure Plate % in. thick by 4 in. wide and the electrode used in this study were processed from production size air heats melted in a fifteen ton capac­ ity electric arc furnace. The plate was annealed 1 hr at 1900 F, water Fig. 1 — Location of test specimens in welded plate quenched, and ground on both sides to remove the scale from hot working and heat treating.