A6 Tool Steel - Air-Hardening, Medium-Alloy, Cold-Work Steels

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations

Introduction

Steels of the type A2, A3, A4, A6, A7, A8, A9, and A10 are called air-hardening, medium alloy, cold work steels or group A steels. Sufficient amounts of manganese, molybdenum and chromium present in group A steels provide full hardness in sections comprising thickness of at least 100 mm (4 in.) in diameter when air cooled.

The carbon content group A steels range from 0.5 to 2%. These steels are provided with air hardening characteristics that allow minimum cracking and distortion on quenching.

The data below will provide an overview of A6 air-hardening, medium-alloy, cold-work tool steels.

Chemical Composition

The chemical composition of A6 tool steels is outlined in the following table.

Element Content (%)
C 0.65-0.75
Mn 1.80-2.50
Si 0.5
Cr 0.90-1.20
Ni 0.3
Mo 0.90-1.40
Cu 0.25
P 0.03
S 0.03

Physical Properties

The following table shows the physical properties of A6 tool steels.

Properties Metric Imperial
Density 8.03 g/cm3 0.290 lb/in3

Mechanical Properties

The mechanical properties of A6 tool steels are displayed in the following table.

Properties Metric Imperial
Hardness, Rockwell C (as air quenched from 845°C, tempered for 2 hours. 61-62 HRC at 95°C temper, 60-61 HRC at 150°C temper, 58-59 HRC at 205°C temper, 56-57 HRC at 260°C temper, 55-56 HRC at 315°C temper, 52-53 HRC at 425°C temper, 50-51 HRC at 480°C temper, 48-49 HRC at 540°C temper) 61.0-62.0 61.0-62.0
Bulk modulus (typical for steels) 140 GPa 20300 ksi
Machinability (based on carbon tool steel) 65% 65%
Shear modulus (estimated from elastic modulus) 77.0 GPa 11200 ksi
Poisson's ratio 0.27-0.30 0.27-0.30
Elastic modulus 190-210 GPa 27557-30457 ksi

Thermal Properties

The thermal properties of A6 tool steels are given in the following table.

Properties Conditions
T (°C) Treatment
Thermal expansion 11.5 x 10-6/ºC 20-100 -

Other Designations

Equivalent materials to A2 tool steels are:

  • ASTM A68i
  • FED QQ-T-570
  • UNS T30i06
  • ASTM A681 (A-6)
  • UNS T30106

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