Differences Between 304 Stainless Steel Deep Groove Ball Bearings and 420 Stainless Steel Bearing

I. Material Differences 

1. Basic Type and Composition

304 (Austenitic Stainless Steel)

•   Composition: Cr 18–20%, Ni 8–11%, C ≤0.08%
•   Structure: Austenite, non-magnetic (or weakly magnetic)
•   Hardness: HB ≤200 (HRC ≤28), soft with good toughness
•   Heat Treatment: Cannot be hardened by quenching, only slightly increased in hardness through cold working

420 (Martensitic Stainless Steel, Cutting Tool Grade)

•  Composition: Cr 12–14%, Ni ≤0.75%, C 0.16–0.25%
•  Structure: Martensite, magnetic
•  Hardness: HRC 50–55, hard and wear-resistant after quenching
•  Heat Treatment: Quenchable + temperable, significantly improving hardness and strength

2. Performance Comparison

II. Application Differences (How to Choose)

1. 304 Stainless Steel Deep Groove Ball Bearings: Scenarios Requiring Strong Corrosion Resistance, Sanitation and Non-Magnetism

• Food and Beverage Machinery: Filling machines, mixers, baking equipment (water-resistant, detergent-resistant, food-grade)
• Medical/Pharmaceutical Equipment: Centrifuges, surgical instruments, sterile production lines (non-magnetic, corrosion-resistant, high-temperature sterilizable)
• Chemical/Humid Environments: Water pumps, valves, marine equipment (resistant to weak acids, weak alkalis and salt spray)
• Electronics/Precision Instruments: Optical equipment, sensors (non-magnetic, no interference with magnetic fields)
• Limitations: Not suitable for heavy loads or high speeds, prone to wear and short service life

2. 420 Stainless Steel Deep Groove Ball Bearings: Scenarios with General Corrosion, Requiring Wear Resistance and Medium Load

• General Mechanical Equipment: Motors, pumps, fans, gearboxes (low cost, wear-resistant, general rust prevention)
• Daily Use/Home Appliances: Washing machines, air conditioners, small household appliance bearings
• Light-Load Food Components: Low-load food machinery (cost-sensitive, mild rust prevention)
• Precision Instruments/Tools: Measuring tools, cutting tools, small machine tools (requiring a certain degree of hardness and rust prevention)
• Limitations: Corrosion resistance is inferior to 304, not suitable for strong acids, strong alkalis or seawater; magnetic, cannot be used in non-magnetic equipment

III. Quick Selection Suggestions

• For humid/acid-alkali/salt spray environments, or requiring sanitation and non-magnetism → Choose 304 Stainless Steel Deep Groove Ball Bearing
• For general environments, requiring wear resistance, medium load and cost control → Choose 420 Stainless Steel Deep Groove Ball Bearing
• For heavy load/high speed/high wear resistance → Consider 440C Stainless Steel Deep Groove Ball Bearing (hardness HRC 58–62, medium corrosion resistance)