Key points of cold processing technology of duplex stainless steel pipe

1, the yield strength of duplex stainless steel is twice as tall as austenitic stainless steel, small deformation, than the latter should be adopted when cold rolled must choose appropriate speed and sent to the amount, try to reduce the longitudinal uneven wall thickness and rolling fold. When cold drawing, the steel pipe reduction ratio should not be too large.

2, duplex stainless steel pipe's middle softening and finished products by continuous roller hearth heat treatment furnace with water cooling device (the exit), prohibit using electrical contact heating, which is not easy to control temperature, heating up fast, easy to overtemperature, make the ferritic phase quantity to exceed bid, especially when rolling thin wall pipe, once the control is not good, easy to produce bamboo-like uneven thickness, although this kind of wall thickness is not mean not (generally not more than 0.1 mm). In electrical contact when heated, thin wall parts rapidly warming, caused by local over temperature, make the ferrite quantity increase greatly, appear even single-phase organization, coarse grained ferrite reduces the corrosion resistance, acid pickling, then this will produce local pickling, make steel scrap.

3. Solid solution treatment of two phase stainless steel pipes is very critical, not only to eliminate the residual stress of the cold machining of the double-phase stainless steel pipe, but also to ensure the proper two phase ratio and the surface quality of the finished pipe. The uniformity of heat treatment need to pay attention to the material temperature and enough time of heat preservation, avoid the insufficient solution of duplex stainless surface residual stress is too high, resulting in some medium caused by stress corrosion.

4. For the biphase stainless steel, which is mainly used for the stress corrosion, it is necessary to make the delivery of the solid solution pickling and avoid the abrasive delivery. When the surface distribution of steel pipe has small cracks, folding and other defects, it needs to be cleaned by the whole pipe. After the grinding, the double - phase stainless steel pipe needs to be reprocessed by the resolvent. The shear stress in residual stresses generated by grinding is the main stress that produces SCC damage.

Source: China Duplex Stainless Steel Pipe Manufacturer - Yaang pipeline Industry Co., Limited (www.yaang.com)