Selection of die materials when forming bevel gears by “two forging in one heat”, the die is in contact with high-temperature blank, the die cavity is usually heated to 500-600 ° C, the metal flow is violent, the surface of the die cavity is very easy to wear, and the die also works under the condition of continuous and repeated heating and cooling, which often leads to failure in the form of work part collapse, thermal wear, thermal fatigue and fracture. Therefore, the die material shall have the following properties:
(1) High strength and sufficient toughness;
(2) High high temperature strength;
(3) Good tempering stability;
(4) Good cold and hot fatigue performance;
(5) Good oxidation resistance and hot melt property;
(6) High hardenability;
(7) Good cold and hot processing performance.
The die materials and hardness of each part of the die structure for precision forging bevel gear by friction press are listed in the table.
| Forging die part | Forging die material | Hardness (HB) |
| Punch | 5CrMnMo | 390-490 |
| Female die | H13, 3Cr2W8V | 390-440 |
| Die sleeve | 40Cr, 45 Steel | 349-390 |
| Upper and lower pressing ring | 45 Steel, 40 Steel | 349-390 |
| Upper and lower base plates | T7 Steel, T8 Steel | 369-422 |
| Upper and lower ejector rods | T7 Steel, T8 Steel | 369-422 |
| Guide post and guide sleeve | T7 Steel, T8 Steel | HRC 56-58 |
Improving the bearing capacity of the bevel gear die material itself is a very important method to prolong the service life of the bevel gear die. At present, there are two main ways to improve the comprehensive performance of the bevel gear die material: one is to optimize the heat treatment process of the existing bevel gear die material, improve its high temperature performance, and give full play to the potential of the bevel gear die material, such as by increasing the quenching heating temperature of 3gr2w8v, Improve its high-temperature strength and thermal stability: second, research and develop new bevel gear die materials with better high-temperature performance, such as SKD61 steel, 5cr4w4movnbre steel and 4Cr3Mo2NiVNb steel, which have been newly developed in recent years. They all have good comprehensive properties.