301L stainless steel is a steady-state austenitic stainless steel. After solution heat treatment, it exhibits a single-phase austenite structure at room temperature. The stainless steel with single-phase austenite structure itself has high toughness and plasticity, and has good cold workability. However, its yield strength and tensile strength are not high, which cannot meet the requirements of most of the load-bearing skeleton structures on the car body. It is necessary to improve its strength by means of deformation strengthening, that is, through multiple cold rolling processes, so that a certain amount of material is produced. Deformation of martensite to increase strength.
The N content of 301L stainless steel is high, which increases the stability of austenite, and has good plasticity and certain subsequent forming ability. It has a large calendering rate, and can obtain five strength grades of materials such as LT, DLT, ST, MT, and HT by controlling the size of the calendering rate (0% to 23%).
In the process of deformation strengthening and subsequent cold working, austenite is continuously transformed into martensite. Since martensite is hard and brittle, the increase in its content will increase the strength of the steel and reduce its plasticity. This phenomenon will increase the possibility of product cracking, so that the total deformation rate of stainless steel plate processing is limited within a certain range. The higher the strength level of the steel plate, the higher the cold rolling rate during the deformation strengthening process, and the cold working deformation rate within the safe range will be reduced accordingly in the subsequent cold bending, bending and other processes. Therefore, when selecting 301L stainless steel sheet, in addition to the lower limit of yield strength and tensile strength specified in the standard, the upper limit should be specified separately. The lower limit is specified to ensure that the required strength and stiffness are achieved, and the upper limit is specified to set a maximum strength to obtain suitable subsequent cold working properties.