JP2002097520A - Method for quick hardening with water and apparatus thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for using water as a medium for quickly cooling after heating such as hardening, etc., in a heat treatment and processing of parts of steel or the alloy, whereby a generation of a strain by non-uniform cooling can be reduced as that of a conventional method using fat. SOLUTION: The material to be treated is quickly cooled in flowing water having an average rate of 1.0 m/sec or above, using the water as the medium. Thereby, parts of the material are uniformly cooled and the strain by non- uniform cooling is reduced, to solve the problem of an environmental pollution and a cooling cost. And further, the treated material heated in atmosphere is quickly cooled with water without contacting with air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a cooling method using "water" as a refrigerant for rapid cooling after heating, such as quenching, in heat treatment of steel and alloy parts.

[0002]

2. Description of the Related Art In the heat treatment of steel and alloy parts,
As a refrigerant for rapid cooling after heating such as quenching, mineral oil is generally used. "Water" has been used for a long time, and some are still used today.However, it is difficult to control the vapor film stage during cooling, and in combination with the large cooling capacity, large cooling strain may lead to cracking. . For this reason, mineral oils having relatively small cooling capacity but capable of more uniform cooling are widely used.

[0003]

In the case of cooling with mineral oil, many factors such as oil composition, temperature, and agitation conditions for improving cooling performance and reducing cooling distortion are troublesome. In addition to the fact that the cooling oil itself is expensive,
The cost of degreasing after the treatment and the disposal of the remover and the removed oil are enormous. In addition, fats and oils are combustible materials, have a bad working environment, and have a large expense for disaster prevention equipment at a work place.

[0004] In terms of cooling uniformity alone, gaseous refrigerants have recently been used. Although the cooling is more uniform, in order to bring the cooling capacity closer to fats and oils, nitrogen, hydrogen, helium and the like are used as the gas species, and the pressure is used at a high pressure of 10 to 20 bar. These gases are expensive, and the use of high-pressure gas has a problem in terms of security, so that equipment and its maintenance and management are very expensive.

In the present invention, "water", which originally has excellent cooling capacity, is used as a refrigerant, and the reason why "water" is avoided is as follows.
Provided is a cooling method for reducing the occurrence of distortion due to uneven cooling to the level of current fats and oils. This solves the environmental problems of heat treatment, and at the same time improves the coolant and its processing cost. At the same time, by improving the cooling capacity, the material of the processed parts is a low cost material that is inferior to the current one in hardenability. Can be changed to

[0006]

According to the present invention, a "water" refrigerant has been used for the purpose of improving cost and environment while maintaining the same quality as that of a widely used oil and fat refrigerant. In the conventional method of cooling with "water", when the product heated to a high temperature is put into "water" under strong stirring, the surface of the processed product is initially covered with a "water" vapor film,
There is a vapor film stage with a low cooling rate. As the temperature of the processed product decreases, the power of forming the vapor film decreases, and the process enters a boiling stage in which the film is peeled off by a stream of water. The shift from the vapor film stage to the boiling stage causes a time lag depending on the part to be treated, and the cooling speed becomes non-uniform, which is a major cause of heat treatment distortion.

[0007] In the present invention, instead of simply stirring the "water" of the refrigerant, the vapor film generated on the surface of the processed product is immediately stripped off, and the entire surface is removed from the strong boiling stage without forming a vapor film stage. In order to cool the processing product, the processing product is thrown into flowing water in which the flow speed of “water” in the effective region where the processing product is thrown is adjusted to 1.0 m / sec or more and cooled.

In the present invention, when the treated product is charged into the "water", the treated product is charged so that the water vapor from the "water" does not contaminate the room filled with the protective atmosphere above the cooling water tank. The structure is such that the speed of the surface of the "water" flowing into the area can be adjusted, and the water vapor coming out of the "water" and the atmospheric gas near the surface of the "water" are caught in the running water and swept downstream.

[0009]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows an example of a water quenching apparatus according to the present invention. The water quenching apparatus has a cooling chamber 3 connected to the heating chamber 1. "Water" with high flow velocity at the bottom of the cooling chamber
Cooling devices 11 to 14 are provided. In order to obtain a large flow rate of "water" in the apparatus, a suction mechanism 9 of a propeller type or a suction mechanism of a "water" injection type (not shown) is provided. There is provided a mechanism for taking out the processed product after cooling through the door 14 or returning the processed product to the cooling chamber 3 and then out of the system. The cooling chamber 3 is separated from the heating chamber 1 and the water cooling chamber 11 by a door 2 and a door 10 having a structure capable of holding a gas tight even if one of the chambers becomes vacuum.

[0010] Cooling after heating will be described in order. The processed product 4, which has been heated in various atmospheres including vacuum, is moved to the position 5 by opening the door 2 to the cooling chamber 3 adjusted to the same atmosphere as the heating chamber in advance. After confirming that the door 2 was closed and the atmosphere in the cooling chamber 3 was at atmospheric pressure, the door 10 on the water cooling device side was opened, and 6 of the refrigerant flowing through the processing product at a high speed was opened.
Immerse in the position and cool. Inside the water cooling device 11, the coolant “water” flows at a speed of 1.0 m / sec or more by the suction mechanism 9, and the flow velocity of the surface of the “water” flowing into the water cooling device 11 is “water”. And the atmosphere of the cooling chamber 3 is controlled so as to be involved and flow out downstream along with the refrigerant. During the cooling, the cooling chamber 3 is maintained at the atmospheric pressure through the gas pressure regulating mechanism 15 so that the pressure of the cooling chamber 3 becomes negative due to the outflow of the atmosphere and the flow efficiency of “water” does not decrease.

When the cooling of the processed product 6 is completed, the door 10 is closed, the operation of the suction mechanism 9 is stopped, and the door 14 in the water cooling device is closed.
Is opened, the processed product is moved to the position 7 and taken out of the system to end the cooling process.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the cooling method of the present invention will be described.
Heated to 850 ° C. in a non-oxidizing atmosphere. S45C and SC
For a method of cooling a φ12 × 45 mm bolt and a φ12 × 120 mm round bar made of two steel grades of M435 using a cooling device similar to FIG. 1, the average flow rate of “water” was 1.0 m / sec and 1.5 m. / Sec (water temperature 25 ° C.). For comparison, the conventional oil cooling (oil temperature 80 ° C.) and strong stirring water (H = 1.6 to 2.0, temperature 25 ° C.) were also tried. For bolts, hardness and tensile strength were examined, and for round bars, deflection at the center in the Nagasawa direction was investigated. The tensile strength of S45C material is about HRC27.2,
The CM435 material was investigated by adjusting the hardness by tempering to about HRC 31.5.

Table 1 shows the results in the examples.
In the "water" cooling in the method of the present invention, the cooling capacity is higher than that of strongly stirred water, and a high quenching hardness can be obtained, but the amount of bending due to uneven cooling is almost the same as that of oil cooling. . In strong stirring water cooling, due to non-uniform cooling, all in carbon steel,
60% of the alloy steel was cracked. The tensile strength of the round bar adjusted to the same hardness in the tempering treatment did not differ between oil cooling and cooling by the present method. In order to check the contamination of the cooling chamber due to the vapor of “water” in the apparatus of the present invention, the dew point of the atmosphere of the cooling chamber was maintained at −4 ° C.
The dew point meter installed on the ceiling of the cooling chamber 3 did not show any change even when the partitioning door 10 was opened by adjusting the flow velocity at the outermost surface to the extent that the atmosphere gas was involved. Next, when the flow of “water” in the water cooling device is stopped while the door 10 is opened, the dew point rapidly increases by + 5 ° C. by the dew point meter installed on the ceiling of the cooling chamber 3.
Up. Subsequently, when the flow of “water” in the water cooling device was started again, the dew point returned to the original -4 ° C. in about 20 minutes.

[0014]

According to the method of the present invention, there is no time when the surface of the treated product is covered with the vapor film, and all the parts are simultaneously in the boiling stage and are cooled rapidly and uniformly, so that the heat distortion is small. Cooling was done. The higher the velocity of the "water", the more
It was recognized that the cooling of each part of the processed product became uniform and the distortion became smaller.

According to the method of the present invention, the refrigerant is inexpensive "water" and there is no need to use fats and oils. Therefore, the cost of the fat and oil itself, the cost of removing the fat and oil, and the cost of disposing of the fat and oil and the degreasing agent are not required. In addition, since expensive gas such as pressurized gas cooling is not used, expensive security equipment for high-pressure gas is required. In addition, the working environment was improved and environmental pollution was completely prevented.

By using the apparatus of the present invention, the ambient atmosphere gas and the water vapor of the refrigerant do not contaminate the atmosphere in the cooling chamber. Non-oxidative cooling was achieved.

By using the apparatus of the present invention, if the advantage of high cooling ability is utilized, the high-cost alloy steel used for improving hardenability is changed to less expensive alloy steel or carbon steel. It is also expected to be effective in reducing material costs.

[Brief description of the drawings]

FIG. 1 is an overall sectional schematic view of a water quenching apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Heating room 2 Heating room door 3 Cooling room 4-7 Processed goods 8 Water tank 9 Cooling water suction mechanism 10 Cooling room door 11-14 Water cooling mechanism 15 Atmospheric pressure adjustment equipment

Claims (3)

[Claims] (1) In a heat treatment process for steel and alloy parts, water or an aqueous solution which does not have a fear of polluting the environment even if it is disposed of as a cooling medium for rapid cooling after heating such as quenching. (Hereinafter referred to as "water"). By cooling the treated product in flowing water with an average speed of the refrigerant of 1.0 m / sec or more at the time of cooling, each part is uniformly cooled without forming a vapor film by "water", and heat treatment distortion due to uneven cooling. And a rapid water quenching method for reducing the cooling transformation effect. 2. The method and the apparatus according to claim 1, wherein the heating is performed in an atmosphere other than the reduced pressure or the atmosphere, and the treated product is introduced into the refrigerant in the non-oxidizing furnace in which the treated product is introduced into the refrigerant without contacting the atmosphere. A water quenching apparatus having a structure in which the atmosphere on the surface of the refrigerant is always entrained in flowing water together with the water vapor so that water vapor from the refrigerant does not contaminate the protective atmosphere of the cooling chamber. 3. A door according to claim 2, wherein the atmosphere is completely shut off between the cooling chamber filled with the protective atmosphere and the water tank in which the coolant "water" is flowing except when cooling the treated product. A water quenching device having an adjusting device for preventing the atmospheric pressure of the cooling chamber from being taken out together with the "water" during the cooling, thereby preventing the cooling chamber from becoming negative pressure.