Introduction
Tools steels are mainly used for manufacturing tools used in machining plastics, metals and woods. However, tool steels must be fabricated into the desired shape before they are able to be used. They have good toughness, wear resistance, machinability and resistance to decarburization.
AISI T4 tool steel is a high speed, tungsten type tool steel. It is a deep hardening alloy capable of Rockwell C 64 hardness.
The following datasheet will provide an overview of grade T4 tool steels.
Chemical Composition
The chemical composition of T4 tool steels is outlined in the following table.
| Element | Content (%) |
|---|---|
| Tungsten, W | 17.5 – 19 |
| Cobalt, Co | 4.25 – 5.75 |
| Chromium, Cr | 3.75 – 4.5 |
| Vanadium, V | 0.8 – 1.2 |
| Carbon, C | 0.7 – 0.8 |
| Molybdenum, Mo | 0.4 – 1 |
| Silicon, Si | 0.2 – 0.4 |
| Manganese, Mn | 0.1 – 0.4 |
| Phosphorus, P | 0.03 max |
| Sulfur, S | 0.03 max |
| Iron, Fe | Balance |
Physical Properties
The following table shows the physical properties of T4 tool steels.
| Properties | Metric | Imperial |
|---|---|---|
| Density | 8.68 g/cm3 | 0.313 lb/in3 |
| Melting point | 1432°C | 2610°F |
Mechanical Properties
The mechanical properties of T4 tool steels are displayed in the following table.
| Properties | Metric | Imperial |
|---|---|---|
| Modulus of elasticity | 190-210 GPa | 27557-30458 ksi |
| Poisson’s ratio | 0.27-0.30 | 0.27-0.30 |
Thermal Properties
The thermal properties of T4 tool steels are given in the following table
| Properties | Metric | Imperial |
|---|---|---|
| Thermal expansion co-efficient | 11.9 µm/m°C | 6.6 µin/in°F |
Fabrication and Heat treatment
Machinability
The machinability of T4 tool steel is 55%.
Forming
T4 tool steel has good ductility in annealed condition and can be formed by conventional methods.
Heat Treatment
T4 tool steel is pre-heated to 843°C (1550°F) and rapidly heated to 1274°C (2325°F). It is then quenched in oil, air or salt bath.
Forging
Forging of T4 tool steel can be carried out from 968 to 1149°C (1775 to 2100°F).
Cold Working
T4 tool steel can be cold worked in the annealed condition using conventional method.
Annealing
Annealing of T4 steel is performed at 885°C (1625°F) followed by slow cooling.
Tempering
T4 tool steel is tempered at 538 to 593°C (1000 to 1100°F) to obtain Rockwell C hardness of 66 to 62.
Applications
The following are the list of applications of T4 tool steels:
- Cutting tools
- Cold extrusion punches
- Broaches