Cold Forming
Stainless steel supplied in the annealing condition (No.1, HRA, 2D, 2B or Bright Annealing) can be cold formed by any of the conventional processes. These processes include blanking, bending, piercing, roll forming, coining, embossing, pressing, spinning, flow forming and deep drawing. In general the equipment such as presses, press brakes, guillotines, etc. used for carbon steel can be used for stainless steel.
However, as more power is required to work stainless steel, the capacity of the equipment is effectively reduced, eg. Guillotines and press brakes that are rated up to 6mm thickness for carbon steel are restricted to 4mm for stainless steel. In operations where austenitic grades are cold worked, eg. Pressing and deep drawing the capacity of the equipment can be effectively reduced by up to 60% due to rapid work hardening characteristics of these materials.
In addition to the extra power requirements to from stainless steel, greater demands are made on the form tooling. Stainless steel not only have greater strength than carbon steel but work harden more, cause more wear, are susceptible to pressure welding, exhibit more springback and have lower heat conductivity. As a result of this, tool material must be harder, smoother and better designed than tooling for carbon steel.
Higher grade tool steel are required and frequently tungsten carbide or aluminium bronze are utilized. However, in the case of the latter these metals can be used as "inserts" in critical areas rather than the complete tool. In many cases tools designed for carbon steel are used for stainless steel, in such cases one must expect to make changes in "setting", use higher quality lubricants, have more frequent maintenance and reduced life.
As a result of the above, lubrication requirements are critical and high quality products are essential. Heavy duty pastes and emulsions, sulphurised or sulphurchlorinated oils, chlorinated oils or waxes are used depending on the forming operation. Mineral oils, soap solutions and general purpose soluble oils are not usually used. Ease of removal after forming is also a consideration since all traces of lubricant must be removed prior to subsequent heat treatment or before putting into service. Surface contamination can increase finishing coasts and adversely affect corrosion resistance. In some cases, especially pressing or deep drawing of ferritic grades, material is PVC or PE coated prior to forming. This not only acts as a very effective lubricant, but increases the formability, prevents galling and/or pressure welding and minimises damage to the surface finish.
Cold Forming - Blanking and Piercing | Press Breaking and Roll Forming | Spinning and Flow Forming | Coining and Embossing | Press Forming | Deep Drawing
Cutting - Sawing | Hand Hacksawing | Shearing | Abrasive Cutting | Thermal Cutting
Hot Rolling - Hot Rolling Process | Hot Rolling Application | Types of Hot Rolling Mill | Hot Rolled Steel Tube | History
Cold Rolling - Physical metallurgy | Degree of cold work | Cold Rolling Stainless Steel | Manufacturing Process
Foil rolling | Rolling Mill | Steel Mill | Production methods | Recycling of Steel | Modern Steelmaking | Contemporary Steel
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