Sep 20 2012
Topics Covered
Introduction
Chemical Composition
Physical Properties
Mechanical Properties
Other Designations
Introduction
Mold steels are designated as group P steels according to the AISI
classification system. These steels include one medium carbon steel and
all low-carbon P-series tool steels such as P2, P3, P4, P5, P6, P20,
and P21 type steels. Nickel and chromium are the two major elements
present in the mold steels. Except P4 and P21, all the other P-series
steels have low softening resistance at high temperatures, whereas P21
and P4 have medium softening resistance. These low-carbon mold steels
are subjected to deep hardening.
The following section will give an overview of the P4 low-carbon
mold steel, which can be carburized and air-cooled to achieve full
hardness.
Chemical Composition
The following table shows the chemical composition of P4 tool steels.
| Element |
Content
(%) |
Fe
|
92
|
| C |
0.12 |
| Mn |
0.20-0.60 |
| Si |
0.10-0.40 |
| Cr |
4.00-5.25 |
| Mo |
0.40-1.00 |
| Cu |
0.25 |
| P |
0.03 |
| S |
0.03 |
Physical Properties
The physical properties of P4 tool steels are given in the following
table.
| Properties |
Metric |
Imperial |
| Density |
7.85 g/cm3 |
0.284 lb/in3 |
Mechanical Properties
The mechanical properties of P4 tool steels are tabulated below.
| Properties |
Metric |
Imperial |
| Hardness, Knoop (converted from Rockwell C
hardness) |
426 |
426 |
| Hardness, Rockwell C |
42 |
42 |
| Hardness, Vickers |
410 |
410 |
| Tensile strength, ultimate |
1290 MPa |
187000 psi |
| Tensile strength, yield |
1035 MPa |
150100 psi |
| Elongation at break (in 50 mm) |
15.80% |
15.80% |
| Bulk modulus (typical for steel) |
140 GPa |
20300 ksi |
| Charpy impact (V-notch) |
43.0 J |
31.7 ft-lb |
| Poisson's ratio |
0.27-0.30 |
0.27-0.30 |
| Elastic modulus |
190-210 GPa |
27557-30458 ksi |
Other Designations
Other designations that are equivalent to P4 tool steels include:
- DIN 1.2341
- ASTM A681
- UNS T51604