Introduction

420 Stainless Tool Steel is a martensitic stainless steel with 12% Chromium which is sufficient to give good corrosive resistance properties. It’s best corrosive resistance is when hardened and surface is ground or polished.It has good ductility in the annealed condition but can be hardened up to 500HB (highest of the chromium grades). Martensitic Grades are known for high hardness and allowances must be
made for poor weldability and usually allowances for a final harden and temper treatment. Steel is magnetic and welding is not recommended.

Applications

Moulds for corrosive plastic materials such as PVC, recycled polymers etc., moulds for chemically aggressive plastics and plastics containing abrasive fillers, mould inserts, dies and gauges for PVC extrusions, screws and barrels for extruders, moulds for automotive, food, medical and optical industry such as spectacles, compact discs, lenses.

Quality Standard:

 ASTM A176 1999 Standard Specification for Stainless and Heat-Resisting Chromium Steel Plate, Sheet,and Strip

All Grades Comparison

ASTM A176:420

Werstoff:1.2083

ASSAB:S316

JIS:SUS420J2

Mechanical Properties (Q+T)

Tensile Strength (Mpa):850-1000

Yield Strength (Mpa):600min

Elongation (%):12min

Hardness (HB):280min

HEAT TREATMENT

Forging: P20 plastic mould steel are forged at 1093°C (2000°F) down to 899°C (1650°F). Forging below 871°C (1600°F) is not recommended for these steels.

Annealing: For maximum softness, heat uniformly to 1500 – 1650°F (816 – 899°C) and cool slowly in the furnace.

Stress Relieving: Heat at 300 – 800°F (149 – 427°C) for 1 to 3 hours, cool in air
or quench in oil or water.

Hardening: Preheat, then heat to 1800 -1950°F (982 – 1066°C), soak at temperature
and air cool or quench in warm oil.

Welding: The martensitic class of stainless steels has limited weldability due to its
hardenability. Special consideration is required to avoid cold cracking by preheating to 550°F (260°C). Post-weld heat treatment should be considered to achieve required properties. This particular alloy is generally considered to have poorer weldability than the most common alloy of this stainless class, Type
410. A major difference is higher carbon content for this alloy which requires both preheat and post-weld heat treatment. When a weld filler is needed, AWS E/ER 420, 410 NiMo and 309L are most often specified. Type 420 is well known in reference literature and more information can be obtained in this way.

Forming: If annealed for maximum softness, Type 420 can be moderately drawn and
formed.

Mill′s test certificate

EN 10204/3.1 with all relevant data reg. chem. composition, mech. properties and results of testing.