Stainless Steel 420

Stainless Steel 420 in CNC Machining

Stainless steel 420 comes in various grades, with the most common ones being 420A, 420B, and 420D. These versions differ in carbon content, affecting their hardness after heat treatment.

For instance, 420A or X20Cr13 has ~0.20% carbon and reaches 48-50 HRC hardness. 420B, or X30Cr13 with ~0.30% carbon, achieves 50-52 HRC. 420D or X46Cr13 with ~0.46% carbon, reaches 52-54 HRC. The carbon percentage is denoted in the EN norm (e.g., X20Cr13 means 0.20% carbon). Higher carbon increases hardness but reduces corrosion resistance; 420D has lower corrosion resistance than 420A due to its higher carbon content.

Stainless steel 420 has good machinability but tends to distort because of its high hardness, so we use coated carbide tools with a high cutting speed and low feed rate for turning, milling, and drilling operations. We use proper fixturing to minimize vibrations and maintain dimensional accuracy. We also use water-soluble cutting fluids to dissipate heat and prolong tool life. Heat treatment is applied to improve hardness and other mechanical properties. We use chip breakers and control the chip size to avoid chip nesting and tool wear. We do polishing or grinding for a smoother surface finish. We also do post-process annealing to relieve stresses and enhance corrosion resistance.

What is Stainless Steel 420?

Stainless Steel 420 is a type of strong and hard martensitic stainless steel with high durability. It is composed of around 0.15% to 0.40% carbon, 12% to 14% chromium, and small amounts of manganese, silicon, phosphorus, and sulfur.

This steel is also known for its excellent wear resistance and corrosion resistance, which is why it’s used in cutlery and surgical instruments. Its hardness can be adjusted through heat treatment.