Nov 20 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Thermal Properties
Processing Properties
Other Designations
Introduction
Cold-work tool steels are high carbon steels that are further classified into three subgroups such as oil-hardening steels, high-carbon, high-chromium steels, and air-hardening steels. Oil-hardening cold-work steels are also known as group O steels consisting of O1, O2, O6, and O7 types.
Type O7 oil-hardening cold-work steel consists of chromium and manganese, and has higher tungsten content than type O1. The O7 steel has the best wear resistance among the O series steels, however, it has relatively low hardenability. The following datasheet provides details about the O7 type.
Chemical Composition
The following table shows the chemical composition of O7 tools steels.
|
Element |
Content (%) |
|
Iron, Fe |
~95% |
|
Carbon, C |
1.10-1.30 |
|
Manganese, Mn |
1.00 |
|
Silicon, Si |
0.60 |
|
Chromium, Cr |
0.35-0.85 |
|
Nickel, Ni |
0.30 |
|
Molybdenum, Mo |
0.30 |
|
Tungsten, W |
1.00-2.00 |
|
Vanadium, V |
0.40 |
|
Copper, Cu |
0.25 |
|
Phosphorous, P |
0.03 |
|
Sulfur, S |
0.03 |
Physical Properties
The physical properties of O7 tool steels are outlined in the following table.
|
Properties |
Metric |
Imperial |
|
Density |
7.80 g/cm3 |
0.282 lb/in3 |
Mechanical Properties
The mechanical properties of O7 steels are tabulated below.
|
Properties |
Metric |
Imperial |
|
Hardness, Rockwell C |
58.0-64.0 |
58.0-64.0 |
|
Bulk modulus |
140 GPa |
20300 ksi |
|
Shear modulus |
80.0 GPa |
11600 ksi |
|
Machinability (based on 1% carbon water-hardening tool steel) |
85% |
85% |
|
Poisson's ratio (25°C) |
0.27-0.30 |
0.27-0.30 |
|
Elastic modulus (25°C) |
190-210 GPa |
27557-30458 ksi |
Thermal Properties
The table below shows the thermal properties of O7 tool steels.
|
Properties |
Metric |
Imperial |
|
CTE, linear |
11.2 mm/m°C |
6.22 min/in°F |
Processing Properties
The following table provides the processing properties of O7 tool steels.
|
Properties |
Metric |
Imperial |
|
Processing temperature (tempering) |
175-290°C |
347-554°F |
|
Processing temperature (hardening) |
790-885°C |
1450-1630°F |
|
Annealing temperature |
790-815°C |
1450-1500°F |
Other Designations
Other designations that are equivalent to AISI O7 tool steels include:
-
ASTM A681
-
FED QQ-T-570
-
UNS T31507