Welds austenitic stainless steel

Considering the success of detecting crack tip echoes from defects at the near probe surface, future work will deal with the detection and sizing of defects on the far probe surface. Future work also relates to carrying out defect sizing in anisotropic austenitic stainless steel welds and... 

Figure 8. SANS-scan over 08H18N10T austenite stainless steel welded and base metal forward cross section I0i (per cm3) for large defects Rgl 20nm, colour scale in units of cm"1. Right and left pieces are base metal and joint metal in between (coupled triangles).

Delong W. T., Ferrite in austenitic stainless steel weld metal. Weld. Res. Suppl. 53 (1974), 273s —286s... 

Ironically, their reasoning that the hardened, heat-affected zone of the 5-Cr steel would have ductile, austenitic stainless steel weld metal on one side of it and ductile, 5-Cr steel parent metal on the other, is equally valid in the rejected case where the weld met is carbon steel. 

S.W. Borenstein. Microbiologically influenced corrosion failures of austenitic stainless steel welds. Materials Performance, Vol. 27, No. 8, pp. 62-66, 1988. 

Ino] Inoue, H., Koseki, T., Ohkita, S., Tanaka, T., Effect of Solidification on Subsequent Ferrite-to-Austenite Massive Transformation in an Austenitic Stainless Steel Weld Metal , ISIJ Int., 35 (10), 1248-1257 (1995) (Calculation, Experimental, Morphology, Phase Diagram, Phase Relations, 23)... 

In order to preclude microfissuring in austenitic stainless steel welds, RCPB components are consistent with the recommendations of Regulatory Guide 1.31 as follows ... 

Table 3.1-63 Weldability of austenitic stainless steels welding methods not in parentheses are to be preferred...

Hardness, Impact Strength. Microhardness profiles on sections from explosion-bonded materials show the effect of strain hardening on the metals in the composite (see Hardness). Figure 8 Ulustrates the effect of cladding a strain-hardening austenitic stainless steel to a carbon steel. The austenitic stainless steel is hardened adjacent to the weld interface by explosion welding, whereas the carbon steel is not hardened to a great extent. 

The most widely used austenitic stainless steel is Type 304, known as 18—8. It has excellent corrosion resistance and, because of its austenitic stmcture, excellent ductihty. It may be deep-drawn or stretch formed. It can be readily welded, but carbide precipitation must be avoided in and near the weld by cooling rapidly enough after welding. Where carbide precipitation presents problems. Types 321, 347, or 304L may be used. The appHcations of Types 304 are wide and varied, including kitchen equipment and utensils, dairy installations, transportation equipment, and oil-, chemical-, paper- (qv), and food-processing (qv) machinery. 

Austenitic stainless steel 3(3. If (1) the carbon content by analysis is greater than 0.10 percent or (2) the material is not in the solution-heat-treated conchtion, then impact testing is required for design temperatures below-29 C (-20 F). See Note 2. ib. When materials are fabricated or assembled by wel(hng, the deposited weld metal shall be impact-tested for design temperature below —29 C (—20 F) unless cou(htious conform to Note 2. 3. The material shall be impact-tested. See Note 2. 

Poor Weldability a. Underbead cracking, high hardness in heat-affected zone. b. Sensitization of nonstabilized austenitic stainless steels. a. Any welded structure. b. Same a. Steel with high carbon equivalents (3), sufficiently high alloy contents. b. Nonstabilized austenitic steels are subject to sensitization. a. High carbon equivalents (3), alloy contents, segregations of carbon and alloys. b. Precipitation of chromium carbides in grain boundaries and depletion of Cr in adjacent areas. a. Use steels with acceptable carbon equivalents (3) preheat and postheat when necessary stress relieve the unit b. Use stabilized austenitic or ELC stainless steels. 

A somewhat similar phenomenon is knife-line attack which may be observed after welding titanium or niobium stabilised austenitic stainless steels. In this case there is a very narrow band of severe intergranular attack along the interface between the parent metal and the fusion zone. During welding, the parent metal immediately adjacent to the fusion zone is heated to just below the melting point and both chromium carbides and niobium or titanium carbides dissolve completely. On cooling rapidly, the conditions are such that when relatively thin sections are welded, neither chromium carbide nor niobium or titanium carbide have time to precipitate. If the weld is now... 

Fig. 1.9(a) Curves showing the variation of temperature with time at various points adjacent to a fusion weld in an austenitic stainless steel and (b) weld decay in an unstabilised austenitic... 

The corrosion of stainless steel welds has probably been studied more fully than any other form of joint corrosion and the field has been well reviewed by Pinnow and Moskowitz , whilst extensive interest is currently being shown by workers at The Welding Institute. Satisfactory corrosion resistance for a well-defined application is not impossible when the austenitic and other types of stainless steels are fusion or resistance welded in fact, tolerable properties are more regularly obtained than might be envisaged. The main problems that might be encountered are weld decay, knifeline attack and stress-corrosion cracking (Fig. 9.29). 

The electrochemical examination of fusion joints between nine pairs of dissimilar metal couples in seawater showed that in most cases the HAZ was anodic to the weld metals" . Prasad Rao and Prasanna Kumarundertook electrochemical studies of austenitic stainless steel claddings to find that heat input and 5Fe content significantly affected the anodic polarisation behaviour under active corrosion conditions whilst Herbsleb and Stoffelo found that two-phased weld claddings of the 24Cr-13Ni type were susceptible to inter-granular attack (IGA) as a result of sensitisation after heat treatment at 600°C /pa was unaffected by heat input. 

With some materials, there are specific heat treatments that are known to reproduce the worst effects of the heat of welding. It is recommended, therefore, that in tests made to qualify a material for a particular service environment, in addition to the exposure of welded test specimens in order to observe effects of welding heat, specimens should be included that have been given a controlled abusive or sensitising heat treatment. As an illustration, austenitic stainless steels may be held at 650-700° forO-5-1 h, followed by testing for susceptibility to intercystalline attack as in ISO 3651-1 or -2 1976. 

Knife-line Attack severe highly localised attack (resembling a sharp cut into the metal) extending only a few grains away from the fusion line of a weld in a stabilised austenitic stainless steel, which occurs when the metal comes into contact with hot nitric acid and is due to the precipitation of chromium carbides. 

Weld Decay localised attack of austenitic stainless steels at zones near a weld, which results from precipitation of chromium carbides. 

The selection of materials for high-temperature applications is discussed by Day (1979). At low temperatures, less than 10°C, metals that are normally ductile can fail in a brittle manner. Serious disasters have occurred through the failure of welded carbon steel vessels at low temperatures. The phenomenon of brittle failure is associated with the crystalline structure of metals. Metals with a body-centred-cubic (bcc) lattice are more liable to brittle failure than those with a face-centred-cubic (fee) or hexagonal lattice. For low-temperature equipment, such as cryogenic plant and liquefied-gas storages, austenitic stainless steel (fee) or aluminium alloys (hex) should be specified see Wigley (1978). 

A 269 Seamless and Welded Austenitic Stainless Steel Tubing for General Service... 

A 312 Seamless, Welded, and Heavily Cold Worked Austenitic Stainless Steel Pipes [Note (2)]... 

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