EN

420

420 is a typical high-carbon martensitic stainless steel. It can achieve ultra-high hardness through quenching and tempering heat treatment, balancing moderate corrosion resistance and excellent wear resistance.

Typical Chemical Composition

  • Chromium (Cr): 12.0%–14.0% – Provides basic anti-rust and oxidation resistance
  • Carbon (C): 0.15%–0.40% – High carbon content is the key to high hardness after quenching
  • Trace elements: Mn, Si, P, S (strictly controlled)
  • Balance: Iron

Core Material Properties

  1. Ultra-high Hardness After Heat Treatment Fully quenched 420 can reach 50–58 HRC, with outstanding wear resistance, suitable for cutting, sliding and friction parts.
  2. Medium Corrosion Resistance Corrosion resistance is better than carbon steel and low-alloy steel, but inferior to 304/316 austenitic stainless steel. It resists air, fresh water and weak organic media, yet prone to rust in salt spray and acidic environments.
  3. Heat-Treatable Hardening Soft in annealed state for forming and machining; quenching followed by low-temperature tempering drastically boosts hardness and tensile strength.
  4. Magnetic Property Ferromagnetic under all heat treatment conditions, not suitable for magnetic-sensitive electronic assemblies.
  5. Forming Limitation High carbon content leads to poor ductility. It is prone to cracking during deep drawing or complex cold forming, so MIM sintering parameters need precise control.
  6. Temperature Performance Long-term service temperature should not exceed 250°C; high temperature will cause hardness decline.

Machining & MIM Process Adaptability

  1. Metal Injection Molding (MIM) 420 powder can form complex tiny structural parts via MIM. Strict control of carbon content and sintering atmosphere is required to avoid decarburization or carburization defects. Ideal for small cutting inserts, precision sliding parts and miniature tool components.
  2. Compatible Surface Treatments Supports polishing, sandblasting, passivation, PVD coating; polishing can achieve mirror finish for decorative & functional dual-purpose parts.
  3. Standard Heat Treatment Flow Annealing (softening) → quenching (high-temperature heating + rapid cooling) → low-temperature tempering to relieve internal stress and retain high hardness.

Advantages & Disadvantages

Advantages

  • Attainable ultra-high hardness and superior wear resistance after quenching
  • Lower material cost than 17-4PH precipitation hardening stainless steel
  • Good polishability for bright decorative surfaces
  • High surface hardness, ideal for long-term friction and cutting components

Disadvantages

  • Limited corrosion resistance, cannot be used in salt, acid or coastal humid environments
  • High carbon causes poor ductility, easy to crack during forming and sintering
  • Fully magnetic, incompatible with magnetic interference-sensitive equipment
  • Risk of decarburization during high-temperature sintering, requiring precise atmosphere control

Typical Applications

  1. Precision Tools & Medical Hardware: Small scalpels, miniature cutting forceps, low-corrosion surgical tool heads
  2. Consumer Hardware: Watch case inner structural sliding parts, miniature cutting blades
  3. Industrial Fittings: Low-corrosion wear-resistant shafts, small sliding valve cores
  4. Daily Precision Parts: High-hardness decorative trimming parts with light friction