SU1765210A1 - Method for heat-treating of hammer dies - Google Patents

Abstract

The invention relates to heat treatment processes for dies, which is carried out in pull-hearth furnaces. The essence of the method is as follows: the furnace, in which the tempering is carried out, is heated to the quenching temperature, after which it is held without heating with the machine pulled out during the time the die is in the quenching tank. Then the furnace is closed and the die is heated without switching on the heaters to 400 ° C. 1 tab.

Description

The invention relates to the field of heat treatment of tool steels and can be used in the process of strengthening hammer dies.

There is a method of heat treatment of dies from steel 5HNM (and others like them), including heating for quenching, quenching in a tank, installing dies in a tempering furnace heated to a temperature not higher than 400 ° C, heating with a furnace to 400 ° C, subsequent heating to the tempering temperature and holding at tempering, and for heating for quenching and tempering, separate electric or gas furnaces with a sliding hearth or with balls on the hearth, along which pallets with stamps are moved, are used (A.A. Shmykov, The Handbook of Thermist M., 1961 , p. 315-316).

The disadvantage of this method is the long duration of the process, in particular at the stage of heating for tempering, due to the following reasons. The furnace is heated to 400 ° C for prevention of cracking, after being placed in

her tempered stamp for a long time does not go to a given mode (400 ° C). In addition, since the heating of the hearth is superficial and the heat from it is quickly selected by the punch, the shank is heated only in the initial period, after 4 the heat outflow begins in the sub.

The goal of H3o6pefeHHfl is a reduction in the duration of 4 percent e s sa due to uniform heating of the strain

The goal is to be fused by the fact that in the method of heat treatment of hammer dies, predominantly by heating in pull-hearth furnaces, including heating for quenching, tank hardening, installing dies in a furnace heated to a temperature less than or equal to 400 ° C, heating for tempering by heating the die to 400 ° C and subsequent heating to the temperature from start-up and tempering, according to the invention, heating for quenching and tempering is carried out in the same furnace, the dies are set to under the shank, the furnace temperature is less than or equal to 400 ° C, is provided by means of living

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it with the carter extended from the temperature of heating under the mirror and heating the stamp to 400 ° C is carried out in a closed furnace without turning on the heaters.

The method is carried out as follows.

Molotovy dies of steel 5HNM with dimensions in height from 250 to 630 mm in electric furnaces with a sliding hearth were subjected to heat treatment:

1.From 250 to 300 mm - in the oven

with dimensions of 1600x650 mm

2. From 350 to 400 mm - 1800x950 mm

3. From 450 to 630 mm - 2800x1400 mm Heated together with the furnace to the quenching temperature, the stamp is placed in a quenching tank, where it is maintained for a specified time, determined by the size of the stamp.

During the entire period of cooling the die in the tank, the quenching furnace remains with the bottom advanced and with the flap open. Due to the accumulation of heat by laying in the furnace chamber, an optimal mode is created for heating the die for tempering: the air temperature is about 400 ° C during the whole heating period (practically without a drop in temperature), the die shank has a constant heat supply, somewhat more intense than from the workspace.

After cooling in the tank, the stamp is installed by the shank on the under-forced quenching furnace and held without heating up the heaters for the estimated heating time to 400 ° C.

PRI me R 1. Molotovy stamp with a height of 250 mm and hardness HB 388-444 heated in the following modes: heated to a temperature of 400 ° C for 0.75 hours (not less), heated to 420 ° C and the shutter speed less than 1.5 hours. Total duration of the process is 3 hours.

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PRI mme R 2. Molotovy stamp with a height of 350 mm and hardness HB 321-375 heated in the following modes: heated to 400 ° C for 1.25 hours (not less), heated to 520 ° C, holding at least 2.5 hours. The total duration of the process is 5 hours.

PRI me R 3. Molotovy stamp with a height of 550 mm and hardness HB 277-311 heated in the following modes: heated to 400 ° C for 2.25 hours (at least), heated to 600 ° C, holding at least 4.5 hours The total duration of the process is 9 hours.

The table shows the comparative data on the duration of heating for tempering according to the known and proposed methods for the main sizes of stamps.

As can be seen from the table, the proposed method makes it possible to shorten the duration of the tempering process by 3.1 ... 3.8 times. In addition, the use of a heated tempering furnace for heating under tempering will reduce energy costs.

Claims (1)

The invention of the method of heat treatment of molotovy dies mainly with heating in furnaces with a sliding hearth, including heating for quenching, quenching in the tank, installing dies in a furnace heated to a temperature less than or equal to 400 ° C, heated for tempering by heating the stamp to 400 ° C and subsequent heating to the tempering temperature and tempering, characterized in that, in order to reduce the process time due to uniform heating, heating for quenching and tempering is carried out in one furnace, the punches are set on the shank, the temperature is Heat exchangers less than or equal to 400 ° C are provided by pressing it with the hearth extended from the heating temperature for quenching, and the stamp is heated to 400 ° C in a closed furnace without turning on the heaters. Note: the duration of the process for a known method is increased by 20% with regard to heating in electric furnaces.