High Strength Grinded / Black H21 Hot Work Tool Steel ASTM A681 AISI

ASTM A681 AISI H21 Hot Work Tool Steel Round Bar for Hot Extrusion Dies , Lower Dies

Description:

◆ Equivalence

◆ Chemical Composition (%)

◆ Dimensions

◆ Delivery Condition

EAF+(ESR) or EAF+LF+VD+(ESR), Hot rolled or Forged, Annealed, Hardness≤235HB,

Black surface or Machined surface (Peeld, Turned, Grinded), UT 100% Passed

◆ Characteristics

Hot work tool steel for oil or air hardening to develop high hot strength, retention of hardness, and heat checking resistance.

◆ Applications

1. Highly stressed hot work tools, such as mandrels, dies and containers for metal tube and rod extrusion; hot extrusion tools;

2. Tools for the manufacture of hollows, screws, rivets, nuts and bolts.

3. Die casting tools, forming dies, die inserts, hot shear blades.

◆ Forging Technique

◆ Heat Treatment

750 to 800°C (1382 to 1472°F)

Slow controlled cooling in furnace at a rate of 10 to 20°C/hr (50 to 68°F/hr) down to

approx. 600°C (1112°F), further cooling in air.

Hardness after annealing: max. 235 HB.

600 to 650°C (1112 to 1202°F)

Slow cooling in furnace; intended to relieve stresses set up by extensive machining,

or in complex shapes.

After through heating, hold in neutral atmosphere for 1 - 2 hours.

1070 to 1150°C (1958 to 2102°F)

Oil, salt bath (500 - 550°C / 932-1022°F), air

Holding time after temperature equalization: 15 to 30 minutes.

Obtainable hardness:

48 - 52 HRC in oil or salt bath,

44 - 48 HRC in air.

Slow heating to tempering temperature immediately after hardening / time in furnace

1 hour for each 20 mm of work piece thickness, but at least 2 hours / cooling in air.

It is recommended to temper at least twice.

A third tempering cycle for the purpose of stress relieving may be advantageous.

1st tempering approx. 30°C (86°F) above maximum secondary hardness.

2nd tempe