Annealing stainless steel

Figure 4-428. Intergranular corrosion of sensitized (improperly annealed) stainless steel. (From Ref. [185].)...

For example, the small amounts of chlorides in most extern pipe insulations can be leached out by exposure to weather and become concentrated at the pipe wall. Temperature may be difficult to measure, let alone control, especially during startup or shutdown when gradients exist. Residual stresses usually are present in a relatively low yield strength material like annealed stainless steel pipe. A pipe bumped in shipment or sprung or cold bent in fitting can have all the stress needed. 

Fig. 1. Temperature dependence of critical property ratios for uniaxial composite laminates and annealed stainless steel (a) ratio of thermal conductivity to Young s modulus (b) ratio of thermal conductivity to tensile yield strength (c) ratio of Young s modulus to density (d) ratio of tensile yield strength to density.

Furnaces for vertical strip or strand (wire) do not have a conveyor, per se, because the strip or wire can be pulled over a series of rollers after it has been threaded through the furnace. A catenary furnace is a continuous horizontal furnace most often used for annealing stainless-steel strip. A long, thin load is supported by rollers at the entrance and exit, and therefore hangs in the shape of a catenary curve within the furnace. (See box on page 132 and fig. 4.10.)... 

These atmospheres are used for annealing stainless steel and... 

IGSCC has been a concern in the BWR community since first detected in the late 1950 s in annealed stainless steel fuel cladding and in the mid-1960 s Type 304 stainless steel recirculation piping. In the late 1980 s IGSCC was detected in reactor internal components, i.e. shroud head bolts, core shrouds, access hole covers, etc. More recent experience from the world wide BWR fleet indicates that cracking of vessel internals has become more widespread than previously thought. 

Fig. 8. Stress—rupture curves for annealed H-grade austenitic stainless steels. AISI numbers are given (see Table 3). Rupture iu 10,000 h (35). To convert...

Zirconium is a hard, shiny, ductile metal, similar to stainless steel in appearance. It can be hot-worked to form slabs, rods, and rounds from arc-melted ingot. Further cold-working of zirconium with intermediate annealings produces sheet, foil, bar wire, and tubing. Physical properties are given in Table 3. 

Structural Properties at Low Temperatures It is most convenient to classify metals by their lattice symmetiy for low temperature mechanical properties considerations. The face-centered-cubic (fee) metals and their alloys are most often used in the construc tion of cryogenic equipment. Al, Cu Ni, their alloys, and the austenitic stainless steels of the 18-8 type are fee and do not exhibit an impact duc tile-to-brittle transition at low temperatures. As a general nile, the mechanical properties of these metals with the exception of 2024-T4 aluminum, improve as the temperature is reduced. Since annealing of these metals and alloys can affect both the ultimate and yield strengths, care must be exercised under these conditions. 

Austenitic stainless steels are the most corrosion-resistant of the three groups. These steels contain 16 to 26 percent chromium and 6 to 22 percent nickel. Carbon is kept low (0.08 percent maximum) to minimize carbide precipitation. These alloys can be work-hardened, but heat treatment will not cause hardening. Tensile strength in the annealed condition is about 585 MPa (85,000 Ibf/in"), but workhardening can increase this to 2,000 MPa (300,000 Ibf/in"). Austenitic stainless steels are tough and ducdile. 

When stress-relief-annealing 300 series stainless steel components, care must be taken to avoid slow cooling through the sensitization range (see Weld Decay in this chapter). 

Stainless steel t>pe 304 Ni 9.0 c 0.08 Annealed cold-rolled 35 85 60 160 General purpose, weldable ... 

Type 316 stainless steel, annealed 316 stainless steel, annealed, 20% R. of A. 316L stainless steel, annealed A 18/8/Ti stainless steel, annealed A Ntmonic P.E.16... 

Intercrystalline corrosion was a serious problem with the austenitic stainless steels early in their development since carbon contents then were relatively high, e.g. En58J contained up to 0.12type stainless steel contained up to 0.08 Vo C. The problem in relation to surgical implants has been reported by Scales eta/. and as a result of this and several other reports the British, American and International Standards specified the use of a 316S12 type austenitic stainless steel which contains 0.03 Vo C max. The use of the lower carbon content stainless steels as specified in the various standards has now eliminated the problem of sensitisation of implants. If manufacturers do use the 0.08% C versions they have to be very careful with the forging temperatures or anneal the prostheses afterwards. 

Niobium is always found in nature associated with tantalum and it closely resembles tantalum in its chemical and mechanical properties. It is a soft ductile metal which, like tantalum, work hardens more slowly than most metals. It will in fact absorb over 90% cold work before annealing becomes necessary, and it is easily formed at room temperature. In addition, welds of high quality can be produced in the metal. In appearance the metal is somewhat similar to stainless steel it has a density slightly higher than stainless steel and a thermal conductivity similar to 1% carbon steel. 

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