S2 Tool Steel - Shock-Resisting Steel (UNS T41902)

Topics Covered

Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Other Designations
Fabrication and Heat Treatment
     Machinability
     Forming
     Welding
     Heat Treatment
     Forging
     Cold Working
     Annealing
     Tempering
Applications

Introduction

Shock-resisting tool steels are designated as group S steels according to the AISI classification system. These steels include S1, S2, S5, S6, and S7 types. The hardenability of group S steels can be controlled by varying thier composition rather than adjusting the melting methods and grain size. They can obtain optimum hardness at higher austenitizing temperatures. The tempering resistance of group S steels can be enhanced by the addition of silicon, which also forms a microstructure to resist distortion in tempered conditions.

The following section will give an overview of S2 shock-resisting tool steels.

Chemical Composition

The following table shows the chemical composition of S2 tool steels.

Element
Content (%)
Iron, Fe
97.0
Silicon
1.05
Carbon, C
0.4-0.55
Molybdenum, Mo
0.4
Manganese, Mn
0.4
Vanadium, V
≤0.5
Phosphorus, P
≤0.03
Sulfur, S
≤0.03

Physical Properties

The physical properties of S2 tool steels are given in the following table.

Properties Metric Imperial
Density 7.79 g/cc 0.281 lb/in3
Melting point 1421°C 2590°F

Mechanical Properties

The mechanical properties of S2 tool steels are tabulated below.

Properties Conditions
T (°C) Treatment
Poisson's ratio 0.27-0.30 25 -
Elastic modulus 190-210 GPa 25 -

Thermal Properties

The following table shows the thermal properties of S2 tool steels.

Properties Conditions
T (°C) Treatment
Thermal expansion 10.9 x 10-6/ºC 20-100 -

Other Designations

Other designations that are equivalent to S2 tool steels include:

  • ASTM A681
  • FED QQ-T-570
  • SAE J437
  • SAE J438
  • UNS T41902

Fabrication and Heat Treatment

Machinability

The machinability rating of S2 tool steels is 85% of that of the W group steels.

Forming

S2 tool steels are formed using conventional procedures under annealed conditions.

Welding

S2 tool steels are readily weldable using standard methods.

Heat Treatment

S2 tool steels are slowly preheated to 649ºC (1200ºF) and then directly heated by increasing the temperature to 871ºC (1600ºF). This is followed by holding the steels for 10 to 20 mins and quenching in brine or water.

Forging

Forging is carried out in S2 tool steels at temperatures ranging from 899 to 1093ºC (1650 to 2000ºF). Forging below 871ºC (1600ºF) is not preferred.

Cold Working

S2 tool steels can be cold worked under annealed conditions.

Annealing

Annealing is performed on S2 tool steels at 788ºC (1450ºF) followed by cooling in the furnace at a rate of not more than 4ºC per hour.

Tempering

S2 tool steels are tempered at 177 to 427ºC (350 to 800ºF) to obtain Rockwell C hardness of 60 to 50.

Applications

The following are the major applications of S2 tool steels:

  • Chisels
  • Hammers

Date Added: Jul 25, 2012 | Updated: Jun 11, 2013
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