Different materials of ball screw, due to its different composition, in hardness and corrosion resistance exhibited obvious differences. This is especially true when comparing the properties of two mainstream materials: alloy steel and stainless steel. Specific differences are as follows:
Steel Ball Screws (Common Materials: SUJ2 High-Carbon Chromium Bearing Steel, SCM440 Alloy Structural Steel)
1.Hardness
The surface hardness of alloy steel ball screws can reach HRC58-62 and core hardness is about HRC30-40 by quenching and tempering. This high surface hardness greatly improves the abrasion resistance of the raceways and sphere and reduces precision loss caused by friction during long drive. Therefore, it is especially suitable for machine tool cutting, heavy automation equipment and other high-load applications, to maintain long-term transmission stability.
2.Corrosion Resistance
Alloy steel is mainly composed of iron, carbon, chromium, molybdenum and other small alloying elements. The chromium content is generally less than 10% and lacks sufficient corrosion resistance. This makes them susceptible to oxidation and rust in humid and dusty environments or when exposed to mildly corrosive media such as workplace condensation, weak acids, and alkali mist, leading to ball jamming and reduced transmission efficiency. Therefore, alloy steel ball screws requires to take protective measures such as shield, anti-rust grease, more suitable for general automated production line, precision machine and other dry, clean indoor environment.
ii. Stainless Steel Ball Screws (Common Materials: SUS440C Martensitic Stainless Steel, SUS304 Austenitic Stainless Steel)
1.Hardness Characteristics
The hardness of stainless ball screws varies greatly according to the material:
After heat treatment surface hardness surface hardness SUS440C martensitic stainless steel can reach HRC55-58, which is close to the hardness of alloy steel. However, the toughness of the core is lower and the hardness uniformity is worse. This makes it suitable for applications requiring high hardness and corrosion resistance. SUS304 austenitic stainless steel does not require heat treatment and has a natural hardness of only HV150-200 (approx. HRC13-18), which is significantly lower than alloy steel and SUS440C martensitic stainless steel. This leads to poor abrasion resistance, working under high load for long periods of time, easy to lead to raceway wear and reduce accuracy.
2. Corrosion Resistance
Stainless steel's core advantage lies its excellent corrosion resistance. Its chromium content is not at least 12%, of which SUS304 austenitic stainless steel is 18-20% and SUS440C martensitic stainless steel 16-18%. This chromium element form a dense protective coating of chromium oxide on the surface of steel, which is effective against corrosion by water, steam, weak acids and alkali, such as organic acids common in food processing and salt haze in marine environment. As a result, stainless steel ball screws can be used for long periods of time in humid environments (such as cleaning equipment), outdoor settings (such as photovoltaic tracking systems), and working conditions with corrosive media (such as food processing workshops, mildly corroded chemical workshops). Without complex safeguards, the risk of rust is much lower than for alloy ball screws.
