Generally speaking, austenite is non-magnetic or weakly magnetic, while martensite or ferrite is magnetic. Due to the composition segregation or improper heat treatment during smelting or forging, a small amount of martensite or ferrite can be found in austenitic stainless steel. In this way, the austenitic stainless steel will have a weak magnetic In addition, the microstructure of austenitic stainless steel will also transform to martensite after cold working. The greater the cold working deformation, the more martensitic transformation, the greater the magnetic properties of the steel. Like the same batch of steel strip, the steel pipe with a diameter of 6cm has no obvious magnetic induction. For the steel pipe with the diameter of 2cm, the magnetic induction is more obvious due to the large cold bending deformation. The deformation of square rectangular pipe is more intense than that of round pipe, especially the corner part, and the magnetic property is more obvious. The same principle, the original non-magnetic 304 stainless steel plate is used in the cold drawing process of making water tank Magnetic production, reflected in the water tank more obvious position is the corner, that is, the largest deformation.
The general stainless steel bearing material has the following several kinds;
一、SUS420（3Cr13）
420 stainless steel is a kind of martensitic stainless steel, with certain wear resistance and corrosion resistance, high hardness, suitable for all kinds of bearings, precision machinery, electrical, equipment,
instruments, instruments, transportation tools, household appliances, etc. It is widely used in the field of bearing.
二、SUS440（9Cr18） 、SUS440C（9Cr18Mo）
Martensitic stainless steel has higher carbon content than Cr13 steel, so its strength and hardness are higher than that of Cr13 steel, and other properties are similar to Cr13 steel, but its weldability is poor,
corrosion resistance and toughness are very strong, so it is widely used in the field of micro and small bearings and high speed bearings.
三、Sus630 stainless steel
630 stainless steel is martensitic precipitation hardening stainless steel. 630 stainless steel has good attenuation performance, corrosion fatigue resistance and water drop resistance. It is suitable for food
industry, offshore platform, papermaking industry, medical equipment, water washing equipment, environmental cleaning machinery, chemical machinery, and widely used in industries with high requirements for
prevention.
四、SUS304(06Cr19Ni10/0Cr18Ni9)
304 austenitic stainless steel has good corrosion resistance, heat resistance, low temperature strength and mechanical properties. It has good hot workability such as stamping and bending, and has no thermal
hardening phenomenon. Non magnetic 304 (weak magnetic after processing) stainless steel is widely used in the production of equipment and parts with corrosion resistance and formability because of its good
heat resistance. At present, 304 stainless steel bearings are widely used in food processing machinery, chemical machinery, marine equipment, medical equipment, water washing equipment, environmental
protection cleaning machinery, and widely used in anti rust industries.
四、SUS316（0Cr17Ni12Mo2）
316 austenitic stainless steel has good plasticity, toughness, cold denaturation, good welding process performance, good appearance gloss of cold-rolled products; due to the addition of Mo (2-3%), the corrosion
resistance and especially pitting corrosion resistance are particularly excellent, so it is used for bearings with strong acid-base environment requirements.
