Rolling heat treatment process

The metallurgical processing of the steel (hot and cold rolling, heat treatments, welding, surface treatments) may dramatically modify the pitting resistance of a steel grade as well. The effect of heat treatments on the phase equilibrium, recrystallization, and minor... 

In alloy steels, particularly if these have been slowly cooled after rolling, the carbides in the as-roUed condition tend to be massive and are difficult to dissolve on subsequent austenitization. The carbide size is subject to wide variations, depending on the rolling and slow cooling. Here, again, normalizing tends to estabUsh a more uniform and finer carbide particle size that faciUtates subsequent heat treatment. Although an expense, this process provides more uniform quaUty in the finished product. 

Strengthening by cold rolling is accompanied by decreased ductUity. A softening heat treatment is needed when ductUity is lowered to below levels required by subsequent processing. Annealing treatments are done interchangeably as batch or continuous operations. 

Shafts are made of material ranging from medium carbon to low alloy steel and are usually heat treated. Shafts were originally made of forgings for the compressors in process service. But because of the availability ot high quality material, hot rolled bar stock has been used for shafts up to S inches in diameter. Bar stock shafts are given the same heat treatment and quality control as forgings. Many of the process users prefer a low alloy, chrome-moly-nickel material for shafting, particularly for compressors in critical service. 

Before steel strip or rod can be cold rolled, tinned, galvanised, or enamelled, etc. any scale formed on it by previous heat treatment must be removed. This can be done by mechanical and other special methods, but if a perfectly clean surface is to be produced, acid pickling is preferred, either alone or in conjunction with other pretreatment processes. 

Cladding of steel sheets with aluminum has been a commercial process for more than three decades and is of particular use in several corrosive environments. Work by Cooke and Levy [124] has demonstrated the importance of surface pretreatment, pressure, and heat treatment. For example, the required bonding temperature was found to be an inverse function of pressure (e.g., the same bonding strength could be attained at either 13.8 MPa/400°C or 20.7 MPa/345°C) subsequent annealing could double the bond strength. The sheets are preroughened by rotary wire brushes, rolled at... 

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