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 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
(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. Plate was process 100 ed from two heats which had no significant difference in composition except in manganese content. This difference was considered inconse quential. For the studies on GMA welding, 1/16 in. diam bare electrode was in itially processed from the standard analysis 450 without any special handling except for the routine care given bright drawn wire. A pair of 12 in. long by 4 in. wide by % in. thick plates of annealed 450 beveled 30 deg from the vertical with no land were butted together with 1/16 in. copper backing under the joint. During all welding the plates were held in a rigid fixture. The re sulting Vee groove was filled with the standard analysis electrode by multi ple pass GMA welding. Eight to ten beads were required to fill the groove. The base of the groove was then 100 500 removed by hand grinding and TIME TO FAIL, HOURS replaced with a single bead. Fig. 2 — The effects of welding/heat treatment on the resistance of 450 alloy to hydrogen Parameters for this welding are embrittlement by 0.1% NaCI plus 0.5% HAc plus H2S shown as trial #1 in Table 2. In this and other GMA welding, power input and the rate of filler metal feed were selected to produce spray metal more than 8 randomly dispersed Ar+02 shield as opposed to Ar + He. transfer across the arc. Some droplet pores 3/64 to 4/64 in. per 6 in. length There were variations in electrode transfer was indicated, however, by of weld. feed rate but these proved to have no arc noise and spatter. (b) No more than 15 randomly dis significant effect on the amount of Following removal of weld metal persed pores 2/64 in. to 3/64 in. porosity. X-ray examination showed overfill, radiographs of the welds were diam per 6 in. length of weld with no some plates welded in the third trial to obtained at 2% sensitivity as de more than 20 randomly dispersed contain less porosity than allowed by scribed by ASTM Std E142-68. pores up to 2/64 in. diam per 6 in. of the above standard, but porosity was Porosity in excess of that allowed by weld. not eliminated or consistently re MIL Std 775-A Ships was observed. Additional Vee grooves were weld duced to an acceptable level by these This standard was used as a basis for ed with the same setup and filler additional efforts. acceptance because of its critical limi metal as above but with other In a further attempt to eliminate the tations which are listed below for Vt in. parameters as seen in trials 2, 3 and porosity, 1/16 in. bare electrode was to 1 in. thick plate: 4. As noted for the additional welding, processed for a special heat of alloy (a) No more than 15 randomly dis parameters were varied to investi 450 containing an addition of 0.10% persed pores of all sizes up to 1/16 in. gate the effects of constant voltage as titanium. Welds were deposited with diam per 6 in. length of weld with no opposed to constant current and an this filler in the 450 plate much the
WELDING RESEARCH SUPPLEMENT! 419-s Table 5 — Mechanical Properties for 450 Alloy Welds and Base Metals in the Conditions Shown
Frac Charpy V 0.2 ture impact YS, UTS, loca strength, Type weld ksi ksi % El. %RA tion(a) NTS/UTS(b) ft-lb
Welded + Aged 900F(C) GMAW 176 182 12 45 P 0.98-1.24 7 SMAW (lime) 153 177 9-15 8-45 W-P 0.93 5 SMAW(titania) 163 177 8 14 W 0.77 4 SAW 179 185 12 48 p 0.99 5
W (e) Welded + Annealed V Aged 900 F
GMAW 180 189 14 46 w 1.49 18 SMAW (lime) 181 192 7-13 18-50 W-P 1.29 5,8, 12 SMAW(titania) — 194 7 9 W 1.10 4,5, 10 SAW 182 190 3 7 w 0.89-1.29 10
Base Metal — Annealed + Aged 900F,C)
Longitudinal 176 185 16 58 1.61 37 Transverse 174 182 13 46 — 1.55 19
(a) P = in base metal plate; W=in weld. (b) Notch tensile strength divided by the ultimate tensile strength. (c) 900 F, 1 hr, air cool (d) 1900 F. 1 hr. water quench
same as before — note trial #5, Table 2. X-ray examination, at the 2% sensi Table 6 — Mechanical Properties for 450 Alloy Weld and Base Metals tivity level, showed no porosity in these welds. Additional GMA welding in the Conditions Shown. with the titanium treated wire repro Frac Charpy V duced the same favorable results. 0.2 ture impact For the SMA welding, both lime and YS, UTS, % El., Loca strength, titania covered 5/32 in. diam elec Type weld ksi ksi 4D %RA tion (a) ft-lb trodes of the standard analysis 450 Welded + Aged 1150 F(b) were prepared. Coverings with the composition required to maintain the SMAW (lime) 88 138 19 62 P 27 desired weld metal analysis were for SMAW (titania) 92 141 20 58 P 21 mulated through preliminary welding. SAW 92 140 20 62 P 21 Beads were deposited by the SMA (e) (b) process in Vee grooves in the 450 Welded + Annealed + Aged 1150F plate formed the same as for GMA welding, welding parameters being 23 SMAW (lime) 87 137 21 62 P 30 volts and 140 amperes. The maxi SMAW (titania) 87 138 23 52 W 27 mum interpass temperature was 250 SAW 84 137 21 59 W 24 F. One exception in the Vee groove (c) (bl Base Metal — Annealed + Aged 1150F preparation was a Vs in. root opening and V* in. thick backing of 450. In Longitudinal 92 145 22 67 95 these instances, 20 to 25 beads were Transverse 92 145 20 62 32 required to fill each groove. Weld metal overfill and the backing were machined from one plate for each (a) P=in base metal plate; W=in weld. type of covering. Radiographs of the (b) 1150 F, 4 hr, air cool (c) 1900 F, 1 hr. water quench prepared welds, obtained at the 2% sensitivity level, showed no porosity and only a single indication of en trapped slag. For submerged arc welding a entrapment was seen in these plates. 1900 F plus aged at 900 F, and (f) titania type flux which would maintain All welding for this study was com welded plus annealed at 1900 F plus the desired 450 weld metal composi pletely free from hot cracking. aged at 1150 F. Test specimens were tion was formulated by preliminary cut with the long axis transverse to the welding. Using this flux and 5/32 in. Evaluation — Weld Metal Proper direction of welding with the weld cen diam standard analysis 450 elec ties tered in the gage section — Fig. 1. trode, Vee grooves in the 450 plate Tensile properties, Charpy V-Notch Test results are listed in Tables 3 prepared the same as for the SMA (CVN) impact strengths and hard through 6. Values reported are the av welding were welded at 32 volts, 510 ness traverses were obtained for each erage of duplicate tests except where amperes direct current-reverse po weld metal in the following condi there was lack of duplication. In these larity and 14 to 20 ipm travel. Eight tions (a) as welded, (b) welded plus instances individual results are beads were deposited in each groove. aged at 900 F, (c) welded plus aged at recorded. It is observed that test Weld surfaces were prepared and x- 1150 F, (d) welded plus annealed at results are tabulated to show first the rayed as before. No porosity or slag 1900 F, (e) welded plus annealed at effect of welding and then the condi-
420-s | SEPTEMBER 1973 Table 7 — Fracture Toughness Data for 450 Alloy Welds and Base Metals lest Toughness values Metal Direction Heat treatment temp. ksi-^Tn. % shear GMA weld Transverse Welded + aged 900F'b) 72 F 48,51,55 0, 0, 0 GMA weld Transverse Welded + aged 900 F -60F 53,51,55 0, 0, 0 GMA weld Transverse Welded + annealed(a) 72 F 54, 56, 56, 60 9, 11,11, 14 + aged 900 F Base metal Longitudinal Annealed|a,+ aged 900 F 72 F 65, 72, 74, 75 11, 12, 12, 14 Base metal Longitudinal Annealed + aged 900F -60F 55,57,64 7, 9,12
(a) 1900 F, 1 hr. water quench (b) 900 F. 4 hr, air cool
Table 8 — Cantilever Beam Stress Corrosion Data for 450 Alloy Welds and Base Metals in 3.5 W/O NaCI at pH of 3.6 at Room Temperature
stress intensity, Hours to fail specimen Direction Condition ksiYin". Environment Base Metal Longitudinal Annealed 5, 6 Transverse Welded + annealed + aged 900F(b) 58.2.60.3 Air — Transverse Welded + annealed + aged 7,8 1(d) (d) 900 F 90% of avg of 5 and 6 3.5 w/o NaCI 809 /944 9 Transverse Welded(a,+ aged 900 F* b) 52 Air — 10 Transverse Welded + aged 900 F 90% of 9 3.5 w/o NaCI 315 disc. 11 Transverse Welded + aged 900 F 95% of 9 3.5 w/o NaCI 800NB,e) (a) 1900 F. 1 hr, water quench (b) 900 F, 4 hr, air cool (c) Discontinued. (d) Failed out of the notch due to crevice corrosion, {e) NB-no break. tion of heat treatment. obtained for the SMA welds than for aged conditions when data for base GMA weld metal was also eval GMA and submerged arc welds. This metal fractures are not included in the uated for fracture toughness at R.T. difference can be correlated to the comparison — Table 5. and -60 F, for resistance to stress greater number of weld beads and the In the 900 F aged condition mar corrosion cracking using precracked reannealing effect of the heat from ginal differences in strength, ductility cantilever beam specimens, and for welding. The highest weld metal elon and toughness were observed among resistance to hydrogen embrittle- gation and reduction in area were ob the SMA and submerged arc welds. ment. Because of the limited material tained on GMA welds while the low Annealing prior to aging at 900 F in available for these tests evaluation of est were for submerged arc welds. creased yield, ultimate tensile and im corrosion properties was restricted to SMA welds deposited from lime type pact strengths but had no consistent the three severe test conditions in this electrodes showed somewhat im effect on ductility. In these conditions study, i.e., as welded, welded plus 900 proved ductility over weld metal of heat treatment the effect of an F, and annealed plus aged at 900 F. deposited from titania type elec nealing was inadequately demon Properties are listed in Tables 7 and 8 trodes. Impact tests showed superior strated because of base metal tensile and on Fig. 2. results for the GMA weld metal rela fractures for some specimens. tive to the other welds which were not Mechanical tests on weld metal in Discussion of Test Results appreciably different one from an the 1150 F aged condition indicated Examination of the hardnesses ob other. little or no significant difference tained from traverses on the welded It is further seen in Table 4 that an between SMA and submerged arc plates reveals some difference be nealing increased weld metal ductility welds either as welded plus aged or tween base metal, heat-affected zone and impact strength while de annealed plus aged. Marginal in and weld for the welded and welded creasing the difference among the creases in elongation and impact plus aged conditions. As might be ex tensile properties of the weld metals strength were produced by an pected for a precipitation hardenable compared to the welded condition. nealing relative to the properties for alloy, the largest gradient was ob The increases in impact strength for specimens aged from the welded served for the welded condition. To a SMA and submerged arc welds were condition. For want of test material, large degree, the differences in hard less than might be expected based on GMA weld metal was not included in ness due to welding were eliminated the increases in elongation and re the 1150 F aging treatment. by annealing at 1900 F. duction in area. Comparison of weld metal proper No difference in ultimate tensile Tensile and impact tests showed ties to corresponding test data for strength among the four weld metals GMA welds to be superior to the other base metal shows that the tensile and was seen for the welded condition — weld metals for the welded plus 900 F impact properties of 450 alloy GMA Table 4. Lower yield strengths were and welded plus annealed plus 900 F weld metal closely approached, and WELDING RESEARCH SUPPLEMENT! 421-s Table 9 — Chemical Analyses % (450 Alloy) 0, Metal C Mn Si P S Cr Ni Cu Mo Cb Ti ppm Fe (b) % in. plate #1 .035 b 1/16 in. electr.— no Ti .035 .69 .33 .020 .004 14.83 6.42 1.50 .77 .75 90/150< > bal b 1/16 in. electr. — Ti .033 .37 .27 .003 .005 14.93 6.43 1.52 .81 .75 .10 90/150< > bal b 5/32 in. electr.(°> .035 .69 .33 .020 .004 14.83 6.42 1.50 .77 .75 90/150 < > bal — (b 5/32 in electr.(d) .031 .36 .26 .015 .008 15.26 6.54 1.49 .77 .84 — 90/150 > bal GMA weld — no Ti .033 .65 .33 .021 .005 14.89 6.43 1.50 .77 .73 , 243/264 bal GMA weld —Ti .031 .33 .21 .010 .005 14.81 6.53 1.48 .80 .72 ,05 327 bal SMA weld — Titania .036 .66 .42 .028 — 15.80 6.24 1.36 .92 .79 — 862/895 bal SMA weld — Lime .045 .37 .35 .028 — 15.88 6,36 1.39 .89 .89 — 750/784 bal SA weld .033 .42 .53 .025 .005 15.09 6.59 1.44 .82 .72 — 920 bal (a) Same heat, ingot sample (b) Typical range. (c) For GMA weld. fd) For submerged arc weld. & HNjIP ,,=*? A ^W^v^"f, %^A-A • •&£&*••< IP Fig. 4 — (Above) Microstructure of 450 alloy wrought metal, % in. thick plate, longitudinal direction, annealed 1900 F. Etchant: ferric and cupric chlorides in aqua regia and alcohol. X250, not reduced Fig. 3 — Microstructure of 450 alloy weld metal: (left, top) welded condition; (left, bottom) welded plus annealed 1900 F. Etchant: ferric and cupric chlorides in aqua regia and alcohol. X250, not *r- reduced in some instances exceeded, the lime and titania electrodes were com The ductility and impact strength of transverse properties of the % in. parable to transverse % in. plate submerged arc welds aged at 1150 F plate. Two exceptions are seen, these properties but only in tensile proper were about the same as for trans being the low impact and notch ten ties obtained for the annealed, welded verse plate specimens. In the other sile strengths for the weld metal in the plus 1150 F, and annealed plus 1150 F conditions of heat treatment the prop welded plus 900 F condition. By and conditions. In the other conditions of erties listed in Tables 4, 5 and 6 for the large, the toughness of longitudinal heat treatment, both tensile and im submerged arc procedure were well plate metal specimens exceeded that pact properties of these weld metals below the properties for transverse of the GMA welds. were lower than corresponding plate plate specimens. SMA welds deposited from both properties. Table 7 reveals that the fracture 422-s I SEPTEMBER 1 973 ^ ilSSiSs^^ V 8 / i • its- aHKffir- IMIK i F/'g. 5 — Electron microfractographs of 450 alloy annealed plus aged 900 F: (left) dimple fracture surface, X1900, not reduced; (right) quasi-cleavage fracture surface, X2700, not reduced. Carbon extraction replicas; etchant: 10% bromine in methanol toughness of GMA weld metal in the trode and plate analyses are listed in columnar grains, the appearance of a welded plus 900 F aged condition was Table 9. Some differences between small amount of dendritic ferrite and lower than that of the aged base metal the composition of the electrode some grain boundary carbide con when tested at room temperature. At materials and corresponding weld sisting of discrete particles generally -60 F there was no appreciable dif metals are noted. SMA welding in aligned parallel to the primary direc ference between the two metals. The creased Cr and Cb but only due to ex tion of solidification. As annealed, toughness of the weld metal in the an cessive reinforcement of these ele each structure was recrystallized with nealed plus aged condition was ments in the electrode coverings. no appearance of ferrite, but the prior slightly higher at room temperature Such increases in Cr and Cb would grain boundary carbide was still pres than listed for the welded plus aged have no appreciable effect on ent. condition. In addition, the material an wrought metal properties and would Closer examination of the micro- nealed before aging, showed consid not be expected to have any signifi structures showed small differences, erable ductility as indicated by shear cant effect on weld metal properties. especially between the GMA and the lip whereas there was a lack of ductili Oxygen was increased in all weld remaining welds, which would be ex ty for the welded plus aged material. metals, being the lowest for GMA pected to have some effect on me As illustrated in Table 8, pre- welds and highest for submerged arc chanical properties. GMA weld metal cracked cantilever beam specimens welds. contained less grain boundary car of weld metal in the welded plus 900 F The weld compositions reported bide, showed the smallest grain size and annealed plus 900 F aged condi are all well within the control range in and the least evidence of the col tions stressed 90% to 95% of the Kicin 450 alloy except for the oxygen con umnar structure after the anneal, and 31/2% NaCI showed no stress corro tent. Therefore, satisfactory weld was essentially free of oxides which sion cracking after times up to 944 properties are to be expected, modi was not the case for SMA and sub hrs. In the same test, base metal aged fied by the effect of oxygen. In the merged arc welds. SMA and sub at 900 F showed no evidence of range found (up to 900 ppm), oxygen merged arc welds were quite similar cracking after 1190 hrs. It is ob reduces toughness. The effect can be one to another, even under close served in Table 8 that stress intensity seen in Tables 4, 5 and 6, where the examination. varied with heat treated condition and Charpy V-Notch impact strength de The microstructure of the % in. test metal; however, similar test times creases inversely with the oxygen: plate as annealed is shown in Fig. 4. without failure were interpreted as the highest strength for GMA, then SMA The apparent difference between this same resistance to stress corrosion lime covered and lowest strength for and weld metal in the same condition cracking, since test stresses were SMA titania covered, and sub is observed to be the smaller grain equal when computed as a per merged arc (which had the highest size for the plate. centage of the KlG oxygen). The resistance of 450 weld metal, in Electron Microfractography the welded and welded plus 900 F Metallographic Examination Fractured notched tensile speci aged condition, to hydrogen em- Photomicrographs illustrating the mens of each weld metal, notched in brittlement by a solution of 0.1% microstructure of the four weld metals the weld, revealed a mixture of dim NaCI plus 0.5%) acetic acid saturated in the welded and welded plus an pled and quasi-cleavage fracture sur with H2S was less than typically ob nealed conditions are seen in Fig. 3. faces for all specimens in both the served for annealed and annealed Structures for the other conditions of welded plus aged 900 F and welded plus aged wrought metal — Fig. 2. heat treatment investigated in this plus annealed plus aged 900 F condi The decrease, however, might be ex work are not included since the tion — note Fig. 5. Other conditions of pected based solely on the lower appearance of 450 alloy at the lower treatment, generally being more duc toughness of weld metal in these con magnifications of the light micro tile, were not examined. In this work ditions of heat treatment. scope are not significantly changed the amount of dimple surface, i.e. by aging. As viewed under the light ductile fracture, was increased by an Chemical Analyses microscope the weld metals ap nealing prior to aging as compared to A complete chemical analysis was peared quite similar one to another welded plus aged condition. obtained on weld metal deposited by for the two basic conditions of treat GMA welds in the welded plus an each type of welding. Weld, elec ment. As welded, each weld showed nealed plus aged condition showed WELDING RESEARCH SUPPLEMENT! 423-s .Tr*, Sr^W^ **»>. •r^y f-%M^W'S.\ AL: •••1A M^ :k t, fck l»*r vP?"*M F/g. 6 — Electron microtractographs of 450 alloy weld metal annealed 1900 F plus aged 900 F showing the effect of welding on the number of CbC, Cb (CON) platelets, X2700, not reduced. Carbon extraction replicas; etchant: 10% bromine in methanol. (a) GMA weld; (b) SMA weld, lime type; (c) SMA weld, titania type; (d) submerged arc weld about the same amount of dimpled Conclusions and Summary properties for 450 alloy can be re surface as aged 900 F wrought metal, (1) Multiple bead GMA welds of lated in part to increasing weld metal that is an estimated 75%. The amount the standard analysis 450 deposited oxygen and a corresponding in of dimpled surface was estimated at in 450 base metal can be expected to crease in Cb (CON) precipitate. 65 to 70% for the SMA lime type weld contain a significant amount of po (5) Welding decreases, somewhat, and 50 to 60% for the SMA titania and rosity. This porosity can be pre the resistance of 450 to hydrogen em- submerged arc welds. vented by the use of 450 alloy elec brittlement by a solution of 0.1 % Varying amounts and mor trode treated with a special addition NaCI + 0.5% HAc + H2S but has no phologies of precipitates were ob of titanium. Although not investi apparent deleterious effect on resis served on the fractures of both gated in this work, other special addi tance to stress corrosion cracking in wrought and weld metals, the pre tions may have the same beneficial an aqueous solution of 31/2% NaCI at cipitates consisting in large part of Cb effect. room temperature. carbonitrides (CON) plus Fe3Cb3C (2) Alloy 450 can be successfully (6) Annealing after welding is re type M6C carbides as identified for x- welded by SMA and submerged arc quired to obtain the best possible 450 ray diffraction. Electron microtracto procedures using the standard analy weld metal properties irrespective of graphs revealing the effect of welding sis 450 electrodes without the occur the type welding in this study. on the amount of these precipitates — rence of gross defects. Successful Acknowledgements see Fig. 6 — show an increase in the welding of the alloy by these proced The authors gratefully acknowledge the Cb (CON) platelets which parallels the ures requires the use of properly for support of their respective companies dur decrease in dimpled fracture area ob mulated coverings, fluxes and ing this study. The electron microfractog- served above. As might be expected, welding parameters. raphy and related studies by the Applied the amount of weld metal carboni (3) The best 450 alloy weld metal Physics Group, Carpenter Technology Re trides increases with the increases in mechanical properties observed in search Laboratory and the help extended weld metal oxygen seen in Table 9. this study were obtained by GMA by Frank Dilmore and co-workers at Arcos The decreasing levels of mechanical welding followed by SMA welding with Corporation are especially appreciated. properties due to welding, especially lime covered electrodes, SMA Reference SMA and submerged arc types can welding with titania covered elec 1, Henthorne, M„ DeBold, T. A., and be correlated, in large part, to the in trodes and finally submerged arc Yinger, R. J., "Custom 450 — A New High creases in weld metal oxygen and welding using titania type flux. Strength Stainless Steel", Corrosion/72 — resulting precipitation of Cb (CON). (4) Decreasing levels of weld metal Paper Ho. 53, pp. 1-23. 424-s | SEPTEMBER 1973