Analysis Of Stainless Steels

The stainless steels are one of the most applicable engineering materials due to high strength, and are used where both the characteristics of ordinary steels and corrosion resistance are required in the automotive, marine and aerospace industries to reduce fuel consumption. Typical applications including automotive trim, aircrafts, home appliances, tanks, storage vessels and pipes for corrosive liquids, mining, chemical, cryogenic, food and beverage, and pharmaceutical equipment, and architecture field [1-4]. These steels don't generally corrode and stain with water compared to unprotected carbon steels which rust readily when expose to air and moisture. Stainless steels can be divided into three main groups for different environmental applications,

Among the austenitic Stainless steels, grade 304 is the most commonly used for sheet metal forming processes due to superior formability. Austenite in grade 304 is unstable and will transform to martensite during forming [6]. The deformation-induced martensitic transformation has unfavorable influences including increase in the forming force, decreasing in the corrosion-resistivity and formability, and the magnetization [7]. The annealing treatment or warm forming processes can overcome these

If the blank is heated, in spite of the increased formability, higher drawbility is restricted. Flow stress decreases by increasing of blank temperature, so the fracture possibility in the region in contact with the rP increases in the beginning of the process. So, if blank strength in this region (rP) increases, early fracture is prevented. To increase the strength in this region, isothermal warm deep drawing process can be replaced by gradient warm deep drawing process, in which the punch gets cooled. Many researches have compared isothermal warm deep drawing with gradient one [16-18], and have reported that gradient warm deep drawing has better results compared to uniform heating of whole die setup which is done in isothermal warm deep drawing