Localized variations in chemistry can cause slight changes in ultimate tensile strength when drawing to fine wire. The pdf file at the bottom of the page (Typical Chemistry) will elaborate on this further.
Stainless Steel 302 Physical Properties
Modulus of Elasticity.......28.0 psi x 106
Electrical Resistivity........720 µohms-mm
Thermal Conductivity......16.3 W/m K (100°C)
Stainless Steel 302 Thermal Treatment
In wire form, cold worked Stainless Steel 302 will gain tensile strength when stress relieved at 350 - 427°C for 4 - 6 hours. A reducing atmosphere is preferred, but inert gas can be used. Stainless Steel 302 will fully anneal at 1010 - 1121°C in just a few minutes. There is a carbide precipitation phenomenon that occurs between 427 and 899°C that reduces the corrosion resistance of the alloy. American Society for Testing Materials (ASTM) has described a test method to ensure the alloy has not been damaged.
Stainless Steel 302 Applications
Stainless Steel 302 alloy is the same as Stainless Steel 304 alloy except for the .12% carbon maximum. In Stainless Steel 304 the maximum carbon is .08%. Technically, all Stainless Steel 304 alloy meets the requirements of Stainless Steel 302 alloy, but not all Stainless Steel 302 can meet Stainless Steel 304 chemistry. Practically, this means in general Stainless Steel 302 is harder than Stainless Steel 304 with the same amount of cold work. End uses for Stainless Steel 302 include: stylets, catheters, guide wires, spring and needles.
Stainless Steel 302 Surface Conditions
Stainless steels develop a highly polished appearance as they are drawn to fine diameters. Surface roughness can be less than 5 RMS when processed using SCND* dies and measured with a profilometer. Diameters over .040" will not have as smooth a finish because of polycrystaline dies. Diameters over .100" have an even rougher surface because they are drawn with carbide dies. Additional finish treatments can enhance the surface of the wire.