Estudo sobre tratamento térmico de matriz de forjamento a quente de engrenagem de aço 5CrNiMo

Study on heat treatment of 5CrNiMo steel gear hot forging die

1. Preamble

5CrNiMo steel hot forging die has high cost and large consumption, so it has important economic value to improve its service life.

There are many factors that affect mold life, the most important of which are the quality of mold heat treatment and mold material selection.

This article analyzes and summarizes the relevant factors affecting the heat treatment quality of molds, designs and formulates the mold production organization scheme to meet the production organization needs of an enterprise, scientifically and reasonably determines the selection of mold material and heat treatment process parameters. of molds, so as to meet comprehensive mechanical property requirements.

Related reading: Effects of heat treatment

2. Matrix material selection and failure cause analysis

2.1 Part material and performance requirements

A company plans to produce a small batch of constant mesh idler gears.

In order to improve production efficiency and ensure product quality, it formulated a production plan using hot forging press equipment and 5CrNiMo steel to make molds (see Fig. 1).

The height of the designed forging die is 336mm, the surface hardness of the die is 38HRC, the hardness of the tail is 32HRC, and the weight of the forging die is 3t.

Fig. 2 Curve of the Heat Treatment Process of 5CrNiMo Steel

3.3 Mold dovetail tempering

In order to increase the service life of the forging die, especially to avoid wear of the hammer head and breakage of the hammer shank, it is specified that the dovetail hardness of the forging die should be lower than the hardness of the forging die. forging. work profile, then the plan needs to backfire.

The salt bath furnace is heated for quenching.

After the forging die is quenched and tempered, its dovetail is tempered in the low-temperature salt bath furnace.

For large and medium molds, the dovetail needs to be heated to 620 ~ 650 ℃, and the hardness reaches 286 ~ 321HBW (30.5 ~ 35HRC).

As for the heating time, it is generally determined by the tempering color of the working surface of the forging die.

When the color of the work surface is bluish gray or even gray (at this time, the work surface has reached about 400 ℃), the heating stops.

The dovetail can be oil cooled after heating. To reduce thermal stress, air cooling is proposed after the oil is cooled to about 100℃.

After dovetail treatment, a uniform sorbite structure can be obtained.

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