SU1569069A1 - Method of heating dies for heat treatment - Google Patents

Abstract

The invention relates to the processing of metals by pressure and can be used in the manufacture of hammer dies, namely, by heating them before quenching. In order to reduce the duration of their heating and the reduction of energy consumption, a stepwise heating mode is carried out. The duration of the heating and holding stages is determined by the formulas Τ _n = 36S ² (4)

Τ _n = 60S (T _dressing / T _Pec) / √T _printed -T _dressings (4)

_In Τ = 3,6S ² √T _printed -T _dressings (4)

where Τ _p , Τ _n - stages of heating

Τ _in - shutter speed

S - stamp thickness, m

T _dressings -zadanna final die surface temperature, ° C

T _Pec - furnace temperature in the second heating step, ° C. In the first stage of heating, the furnace temperature varies linearly from 550-600 ° C to 700-800 ° C. In the second step T _{is printed} constant and T _dressings exceeds by at least 30 ° C, while the holding time T _{is printed} constant and T _dressings exceed 5 ° C. Raising the temperature of the dies at the first stage of heating retains the quality of dies during quenching, and the recommended duration of the stages of heating and holding makes it possible to increase productivity and reduce the specific energy consumption during heating for heat treatment. 1 tab.

Description

The invention relates to the processing of metals by pressure and of coins to be used in the manufacture of hammer dies, namely, when heated before quenching.

The purpose of the invention is to increase productivity by reducing the heating time and reducing the energy intensity of the process of heating dies while maintaining their quality.

The method is carried out as follows.

Stamps designed for heat treatment, loaded into the furnace with a temperature of 550-600 ° C, heated to a temperature above the point Acé, and held. Heating of the dies to a temperature above Ac is carried out in two stages, the first is carried out for a time equal to Г ЗбЗ2, h, with a linear change in the furnace temperature to 00-800 CC, the second is carried out during the time Cu

60S (tnoe / tne4) / (4t

the furnace

- t

posture

).

ate

c Ј o

Od sb

keeping the furnace temperature constant above the specified final heating temperature of the stamp by at least 30 ° C. Stamping is carried out for a period of time equal to

3,6S2 jt pets-t П06, h, when the furnace temperature exceeds the final set temperature of the stamp by 5 ° C, where t furnace is the furnace temperature at the second heating stage, ° C; tin is the given final heating temperature of the stamp, ° С; S - stamp thickness, m

The duration of the first heating stage (° n 36s2, h) and the linear temperature change of the furnace from 550-600 to 700-800 ° C are caused by the need to reduce the thermal stresses arising in the dies during heating, which leads to a high quality of the dies.

Heating the dies at a furnace temperature below 550 ° C or above 800 ° C over a specified time leads to deformation of the dies during quenching due to the presence of greater thermal stresses. (In a shorter time (less than 36s2) of the first stage of heating, the dies do not have time to heat up to the required temperature, the temperature difference across the cross section is large, the thermal stresses remain high, and the quality of dies deteriorates during quenching.

With an increase in the duration (more than 36s2) of the first heating stage, the total heating time increases, as a result of which the fuel costs increase, the furnace productivity decreases.

During the second stage of heating, the time of which is determined by the formula ЈЈ 60S (tnoB / tne4) / (tne4- t), h, to ensure intensive heating of the dies, maintain a constant temperature in the furnace that exceeds the final temperature of the stamp at least than 30 ° C. In this mode, the duration of heating dies is reduced.

Failure to comply with the condition of the furnace temperature leads to fuel over-consumption, and maintaining the furnace temperature above the specified final die temperature less than 30 ° C increases the duration of intensive heating, over-consumption of fuel and decreases the furnace performance. Reducing the duration of the second stage of heating (Ј and less than 60S (tnoe /

The / tne4) / (- jtne4- t turn), h, causes the die to underheat to the required quenching temperature, leading to a rejection of the die when quenched.

With an increase in the time of the second stage of heating (n more than 60S (tnoe / tne4) /

50

5 n

five

/ (- Jtnew t noe h) the specific fuel consumption increases, the total duration of the heating process, the furnace productivity decreases.

At the end of the second heating stage, the temperature of the die surface reaches the quenching temperature, but the temperature difference remains. To equalize the temperature over the die section, the exposure is carried out, the duration of which is determined by the formula Јb 3, b52l 4 t oven & h, at the oven temperature exceeding the specified final heating temperature of the die by 5 ° C.

With a decrease in the exposure time (less than 3.6s2 - | tne4- tn06), temperature unevenness over the die section remains, which degrades the quality of the stamp during quenching. An increase in the duration of exposure (Јv more than 3.6s2 tnoe) leads to excessive fuel consumption, a decrease in the productivity of the furnace 44 and an increase in the total time of the heating process.

Setting the furnace temperature exceeding the final target temperature of the die surface by more than 5 ° C leads to an undesirable rise in the final temperature of the die surface, i.e. overheating, which is accompanied by a deterioration in the quality of dies during quenching, maintaining the furnace temperature above the end temperature of the die less than 5 ° C, increases the duration of exposure, as well as fuel consumption and total heating time.

Example. Heating was conducted in a fiery furnace. The stamps were heated from 20 to 860 ° C. The furnace temperature at the time of loading is 600 ° C. The thickness of the dies is 0.3 m. The stamps were placed on the hearth in one layer.

During Јn 36s2, 30S2 and 40S2, the furnace temperature was raised from 600 to 650-850 ° С (the first heating stage). After the specified time expires, as quickly as possible (approximately in 0.5 h and less), the furnace temperature was raised in one case to 890 С, which exceeded the final heating temperature of the stamp by 30 ° С, and in another case - up to 910 е С (t. e. tpov + 50 ° C). The furnace temperatures indicated (890 and 9 ° C) were kept constant for a time determined by the formula he 60S (tffoe / / t, e4) / (tfie4) (second heating stage) In addition, heating was carried out while maintaining the indicated oven temperatures constant over a period of time that was more or less than that proposed. of time

Ј8 3.6S -J7

the furnace

- t

eat

- tnM- SPOB, Јv 4, OS2

3.0S

- t

noe

(h), at the furnace temperature,

ten

15

exceeding the final heating temperature of the dies by 5 ° C, less than 5 ° C or more, meme by 5 ° C, which corresponded to the values of 865, 860 and.

The duration of heating was controlled, starting from the moment of loading the dies into the furnace and ending with the issuance of heated dies from the furnace, using a clock mechanism. At the end of the heating process, the dies were removed from the furnace and cooled in oil.

Heating was also carried out from 20 to 860 ° C dies with a thickness of 0.3 m by a known method. The initial temperature of the furnace (at the time of loading the dies) is 600 ° C. The heating time was determined 25 according to the formula Јц S / 0.025, (h), and the duration of the exposure to Ce was 0.2GN, h. Heating and holding were carried out at a furnace temperature of 860 °. The stamps were placed in a single layer on the bottom.

Technological parameters and test results of the proposed and known methods are presented in the table.

Studies show that in examples 2-4, corresponding to the proposed parameters of the method, high results were obtained (reduction of the heating time by 40% compared with the known).

When the proposed method parameters are exceeded, both downwards (Example 1) and upwards (Example 5), the dies are underheated to the specified final temperature in the first case and the total heating time increases (taking into account the shutter speed) in the second case. .

Keeping beyond the proposed limits. Keeping the furnace temperature outside the suggested limits leads to underheating of the dies to the specified final temperature at the furnace temperature below the specified one (examples 8 and 16) with a simultaneous deterioration of the quality of the dies, or to an increase in the total heating time (example 12) with a decrease in the productivity of the furnace, the deterioration of the quality of the stamp (examples 9 and 17).

When heated by a known method (Example 18) of the RRR, it took 2 times more time to achieve the same temperature of this final temperature (860 ° C), the meme when heated by the proposed method, and 1.3 times more when held.

Using the method of heating dies before quenching provides, in comparison with the known method, the temperature of dies in the first heating stage depends on the thickness of dies,

It reduces the thermal stresses in the die, preserving their quality during quenching. The recommended duration of the heating and holding stages makes it possible to reduce the total time of the heating of the dies, increase the productivity of the furnace equipment, reduce the specific fuel consumption, and streamline the heating.

35

Claims (1)

Invention Formula 40 The method of heating dies for heat treatment, including loading dies into a furnace with a temperature of 550-600 ° C, heating dies to temperatures above d5 points Al-s and holding, characterized in that, in order to increase productivity by reducing the heating time and reducing the energy intensity of the process of heating the strain of at least one of the parameters of the presets while maintaining their quality, heating the lat (method) (examples 6–17) of the stamps to a temperature above Asz does not achieve the set goal. Thus, with a reduction in the duration of the heating stages (examples 6 and 10) and holding (example 14), the final temperature of the stamp does not reach the specified value, and therefore its quality during quenching is impaired. The increase in the duration of heating (examples 7 and 55 is carried out in two stages, with the first stage being carried out for a time equal to Јn ZbZ2, h, with an increase in the furnace temperature to 700-800 ° C at a constant speed, after which the furnace temperature is increased to a value exceeding the final heating temperature of the stamp by at least 30 ° C, 9069 ten 15 25 11) and shutter speeds (example 15) are accompanied by (an increase in the total time of the heating process (including shutter speed), with a decrease in furnace productivity). Maintaining the temperature of the furnace beyond the proposed limits leads to underheating of the dies to the specified final temperature at the furnace temperature below specified (examples 8 and 16) with a simultaneous deterioration in the quality of the dies, or to an increase in the total heating time (example 12) with a decrease in performance furnace, the deterioration of the quality of the stamp (examples 9 and 17). When heated by a known method (Example 18) of the RRR, it took 2 times more time to achieve the same temperature of this final temperature (860 ° C), the meme when heated by the proposed method, and 1.3 times more when held. Using the method of heating dies before quenching provides, in comparison with the known method, the temperature of dies in the first heating stage depends on the thickness of dies, It reduces the thermal stresses in the die, preserving their quality during quenching. The recommended duration of the heating and holding stages makes it possible to reduce the total time of the heating of the dies, increase the productivity of the furnace equipment, reduce the specific fuel consumption, and streamline the heating. 35 Invention Formula The method of heating dies for heat treatment, including loading dies into a furnace with a temperature of 550-600 ° C, heating dies to a temperature above the Al-3 point and holding, characterized in that, in order to increase productivity by shortening the heating time and reducing energy intensity of the process of heating the stamps, while maintaining their quality, the heating of the stamps to a temperature above Asz is carried out in two stages, with the first stage being carried out for a time equal to Јn ZbZ2, h, with an increase in the furnace temperature to 700-800 ° C at a constant speed, after which the furnace temperature is increased to a value energy intensity of the process of heating the stamps, while maintaining their quality, heat the stamps to a temperature above Asz exceeding the final heating temperature of the stamp by at least 30 ° C, and keep it constant during heating of the die, which is determined by the dependence keep the stamp at this temperature and for a time equal to St 3, tnoe pech 60n 60S (tw B / tnew) / (- itITe4- tnOB), h 5 then reduce the temperature of the furnace to a value exceeding the final temperature of the stamp by 5 C, and you - JQ Editor L. Zaitseva Compiled by S. Malay Tehred L. Serdyukoav Order Circulation A95 VNIIPI State Committee for Inventions and Discoveries at the State Committee on Science and Technology of the USSR 113035, Moscow, Zh-35, Raushsk nab., T./5 Production and Publishing Combine Patent, Uzhgorod, st. Gagarin, P1 t pepper - the temperature of the furnace in the second heating stage, ° C; t oov is the given final temperature of the stamp, C; S - stamp thickness, m Corrector 0. Ciple Subscription