Steels welding

The ultrasonic testing of anisotropic austenitic steel welds is a commonly used method in nondestructive testing. Nevertheless, it is often a problem to analyze the received signals in a satisfactory way. Computer simulation of ultrasonics has turned out to be a very helpful tool to gather information and to improve the physical understanding of complicated wave phenomena inside the samples. 

The radiographs were made from austenitic (titanium- or niobium-stabilised nickel chromium steels) welds that were double-wall penetrateted by x-rays of 130kV. The wall thiekness is in the range of 8 to 12 mm. 

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... 

Austenitic Steel weld has a well defined transcrystalline (oriented) macrostructure with continuously changing orientation of the crystal axis - from the periphery towards the centre the angle between the axis of the crystal and the axis of the weld is changed from 90 to 0 degrees. Weld metal eould be possible to approximate in the form of a discrete combination of crystals with parallel axes of the crystallites. 

As the weld metal solidifies, impurity elements are rejected into the molten weld pool, eg, sulfur and phosphoms in steel welds (Fig. 7) (8). The final weld metal to soHdify, located along the weld centerline at the surface of the weld, has increased levels of these elements, which act to lower the... 

Lead and its alloys are generally melted, handled, and refined in cast-iron, cast-steel, welded-steel, or spun-steel melting ketdes without fear of contamination by iron (qv). Normal melting procedures require no dux cover for lead. Special reactive metal alloys require special alloying elements, duxes, or covers to prevent dross formation and loss of the alloying elements. 

Attack at welds due to bacteria is possible, but it is not nearly so common as is often supposed. Because of residual stresses, microstruc-tural irregularities, compositional variation, and surface irregularities, welds show a predisposition to corrode preferentially by most corrosion mechanisms. Attack is common along incompletely closed weld seams such as at butt welds in light-gauge stainless steel tubing (Fig. 6.9A and B). Attack at carbon steel welds may occur. Figure 6.10 shows a severely corroded carbon steel pipe from a service water sys-... 

Weld attack. Welds are often more susceptible to corrosion than other areas (see Chap. 15, Welds Defects ). Welds may contain porosity, crevices, high residual stresses, and other imperfections that favor attack. Carbon steel welds are usually ditched by acid attack (Fig. 7.10). 

Cautions. Certain types of stainless steel welds are metallurgically designed to form two compositionaUy distinct phases to reduce the... 

Figure 15.9 Cross section of stainless steel weld showing crevice corrosion along a site of incomplete fusion. (Magnification 15x.)...

Galvanic corrosion may occur at stainless steel welds if sensitization has taken place or if welding has produced unfavorable dissimilar phases (see Chap. 15, Weld Defects, particularly Case History 15.1). These forms of microstructural galvanic corrosion do not involve the joining of two different metals in the usual sense. 

Figure 28.6 shows the fatigue properties of structural steel welds. The fatigue limit stress range of 120 MPa for the best class of weld is a good deal less than the limiting range of 440 MPa for the parent steel (Fig. 28.5). And the worst class of weld has a limiting range of only 32 MPa ...

Fumes from stainless steel welding Stainless steel fabrication operations... 

Figure 2-4C. Forged steel welded-end fittings. By permission, Tube Turn Technologies, Inc.

Mild steel welded Mild steel sectional Cast iron sectional Reinforced concrete... 

Of these four, the mild steel welded tank is the most popular and is widely used for every type of application. 

Sandor, P., Resistance to Intercrystalline Corrosion in Stainless Steel Weld Metal , Anticorros. 

Maraging steel welds are somewhat less resistant than base plate. U -bend exposure of 1 240 MNm strength welds survived for up to 2 years in seawater while at 1 380 MNm failures occurred in 2-18 months. ... 

Of more serious practical significance is iron contamination of nickel-clad steel welds. Tables 3.39 and 3.40 show the increase in corrosion of various nickel-iron alloys which may occur when coupled to nickel in... 

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). 

Fig. 9.29 Corrosion sites in stainless steel welds. The typical peak temperatures attained during welding (°C) are given at the foot of the diagram. Note that knifeline attack has the appearance of a sharply defined line adjacent to the fusion zone...

Recently, attention has been directed to a study of the problem of grooving corrosion in line-pipe steel welded by high frequency induction or electric resistance welding. In sea water, it seems to be related to high sulphur content in the weld zone, the type of environment, its temperature and velocity The importance of sulphur is significant since Drodten and... 

Controlled additions of N have been made to 439 steel weld metal to prevent IGA whilst additions of Y or Ce to an 18Cr-12Ni steel have been found to be beneficial ". In the case of TIG-welded Mo-containing stainless steels, <7-phase formation can be responsibe for IGA in hot oxidising acids ). 

The Standards, Measurements and Testing Programme of the European Commission launched a few years ago a project dealing with the development and, ultimately, the production of air filters realistically exposed to welding dust occurring during stainless steel welding (Christensen et al. 1999). This project resulted in the production and certification of a batch of 1100 filters for the Cr (VI) content (40.16 0.60 pg/g dust) (CRM 545). In addition, the total leachable Cr content ( 39.37 1.30 pg/g dust) was certified as a means to check for total Cr recovery. 

Figure 1.10. This shows a 3DAP atom map across a grain boundary in a neutron irradiated 15KkMFA Russian pressure vessel steel weld. It reveals significant levels of P, Mn, Mo and C segregation, which correlate with poor mechanical properties exhibited by these materials.

Estimate the thickness required for the component parts of the vessel shown in the diagram. The vessel is to operate at a pressure of 14 bar (absolute) and temperature of 300°C. The material of construction will be plain carbon steel. Welds will be fully radiographed. A corrosion allowance of 2 mm should be used. 

Steel welding-neck flanges for nominal pressure ratings of 6, 10, 25, 40 bar. 

STEEL WELDING NECK FLANGES Nominal pressure 6 bar (1 bar = 105 N/m2)... 

Report on the Effect of Stainless Steel Weld Overlay or Cladding on Hydrogen Attack of Underlying Steel, Materials Properties Council, New York, September 1984. 

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