JP4160520B2 - Low strain rapid water quenching equipment - Google Patents

Description

  In the heat treatment of steel and alloy parts, the present invention uses high-speed flowing water as a rapid cooling refrigerant after heating such as quenching, so that rapid and uniform cooling is achieved, and heat treatment strain combining cooling strain and transformation strain. It is related with the technology which aims at the reduction of cooling and improvement of cooling capacity.

In heat treatment of steel and alloy parts, mineral oil is widely used as a rapid cooling refrigerant after heating such as quenching. In recent years, it has been proposed by the inventors of the present invention (Reference 1) to uniformly cool by rapid flowing water to increase cooling capacity and reduce heat treatment distortion. In the range of this method, the strain after heat treatment cannot be said to be less than that of mineral oil.
In addition, it is assumed that the mineral oil refrigerant has a small amount of distortion after heat treatment, and it is cooled with a refrigerant that is pressurized (0.5 to 4.0 megapascals) with a neutral gas that does not cause a gas or liquid phase change during cooling. Therefore, it is also practiced to reduce distortion. In general, cooling by this gas has a lower cooling capacity than mineral oil, so it is necessary to improve the cooling capacity compared to conventional alloy steel, and the use of higher-priced steel with higher price is required. .
JP 2002-97520 A

  In quenching using commonly used mineral oils, “refrigerant mineral oil quality maintenance management” and “refrigerant mineral oil speed management” are bothersome to suppress distortion, and “refrigerant cost” and “removal of refrigerant after processing” The cost of processing is high, such as “costs for disaster prevention for buildings and the like because refrigerant is a dangerous substance”.

  Even when high pressure gas is used to reduce strain, these "high gas costs" and "high pressure gas safety costs", as well as the low cooling capacity of the gas, "make the material highly alloyed" For example, the material cost is high.

  Use water or an aqueous solution (hereinafter referred to as “water”) that does not pollute the environment even if it is discarded as the main component in the literature 1, and the flow rate is 1.0 m / second or more. This solves the problem of using mineral oil and high-pressure gas. However, the strain after heat treatment obtained there is close to that of mineral oil, which is far from the strain when high-pressure gas is used.

  The present invention has been made in view of the above circumstances, and in the case of quenching treatment of steel and alloy parts, in order to cool down more uniformly and reduce distortion and cracking, the processing strain is more aggressive in oil quenching and below. The purpose is to reduce the material cost and the processing cost by reducing to a low alloy steel by improving the quenching performance.

The invention according to claim 1 of the present invention is an aqueous solution that does not pollute the environment even when discarded with water or water as a main component as a coolant for rapid cooling after heating in heat treatment of steel and alloy parts. A quenching device that cools the treated product in running water, a quenching water tank that stores the refrigerant, a cooling chamber that is provided in the quenching water tank and places the treated product, and circulates the refrigerant to A flowing water pump that keeps the flow rate of the refrigerant in the cooling chamber at 3.0 m / second or more (hereinafter referred to as “specified flow rate”) , and the refrigerant flows into the cooling chamber before the processed product is placed in the cooling chamber. A cooling auxiliary device that allows a refrigerant having a specified flow rate to flow into the cooling chamber without touching the refrigerant having a flow rate lower than the specified flow rate before cooling the processed product after being placed in the cooling chamber. It is characterized by having.
Thus, by setting the speed of flowing water to 3.0 m / second or more, the entire surface of the treated product is cooled more uniformly and rapidly. As a result, the temperature drop near the surface and the slow speed of the transformation start time on the entire surface are made negligible in terms of strain generation. Further, a thicker and stronger hardened layer is created in the layer near the surface over the entire surface, and the amount of strain is reduced by suppressing expansion and contraction caused by cooling and transformation occurring later. Furthermore, by submerging into running water at a specified flow rate without touching flowing water at a specified flow rate before cooling, all processed products are uniformly cooled even when quenching thin-walled products or complex shaped products. The
The cooling auxiliary device can be switched between a state in which the inflow of the refrigerant into the cooling chamber is blocked and a state in which the cooling is not blocked by operating, and various shapes can be considered depending on the direction of the flow of the refrigerant with respect to the processed product. With such a configuration prevents the partially uneven cooling touching the running water loose speed cold却前occurs.

The invention according to claim 2 of the present invention has a water channel structure adjusted so that the flow velocity at an arbitrary position in the cross section perpendicular to the direction of the water flow is within ± 10% of the prescribed flow velocity in the cooling chamber. It is characterized by. By equalizing the flow velocity in this way, it is possible to prevent the cooling from being slowed by the installation position of the processed product in the cooling chamber and resulting in uneven cooling. As such a water channel structure, for example, it is conceivable to provide a flow velocity distribution adjustment guide for rectification in the flow channel.

According to the apparatus of the present invention, in the quenching treatment of steel and alloy parts, if the flow rate of the water quenching refrigerant is set to 3.0 m / second or more, the total amount of strain after quenching is generally used with mineral oil. It was possible to make it smaller than the previous device . In particular, it was found that the strain can be further reduced by setting the flow rate to 5.0 m / sec or more. This greatly reduces post-processing due to “strain”, which is the biggest problem in heat treatment of steel parts.

According to the apparatus of the present invention, quenching and cooling ability is improved as compared with the conventional apparatus , and steel parts with high hardness and high strength can be obtained with inexpensive simple carbon steel. Compared to material costs. Since no mineral oil is used as the refrigerant, the cost of the quenching oil itself, the cost required for degreasing after the treatment, and the disaster prevention equipment and building costs required by using the mineral oil can be reduced. By using a low alloy material, forging pressure and cutting become easy, and the processing costs before and after can be reduced. Further, low strain can be realized without cooling with an expensive and dangerous high-pressure gas that is expected to further reduce strain.

According to the apparatus of the present invention, since fats and oils such as mineral oil are not used as a refrigerant, the fats and fats and a solvent for degreasing are not required, which greatly contributes to reduction of carbon dioxide and ozone layer depleting substances. In addition, the use of dangerous materials (oils and fats) and high-pressure gas can improve work safety and the environment.

Embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows an example of a rapid water quenching apparatus. This apparatus has a quenching water tank 1 for storing refrigerant, a flowing water duct 2 for defining the flow direction of the refrigerant, and a cooling chamber 4 for placing a processed product, and a heating furnace zone above the cooling chamber 4. 9 is directly connected. In order to prevent outside air from entering the cooling chamber 4, a tank atmosphere blocking wall 8 is provided. In this apparatus, the processed product that has been heated in the heating furnace zone 9 is installed in the cooling chamber 4 so as not to come into contact with a loose water flow or the like that causes non-uniform cooling (processed product carry-in path 11), and before cooling. Cooling with running water at a specified flow rate from the beginning without touching the refrigerant below the specified flow rate.

  The speed of water flowing into the cooling chamber 4 is 3.0 m / sec or more, and the speed is obtained by the pump 7 and the pump power 6 in the same water channel. The water discharged from the pump 7 circulates after discharging the introduced bubbles, enters the cooling chamber 4 again, and is used for cooling (cooling flowing water flow direction 13). The pump 7 is for ensuring the flow rate of water, and may be a propeller type or any other type.

Here, the example of the method of installing a processed product in the cooling chamber 4 without touching a loose water flow etc. is shown in FIGS.
FIG. 2 shows a case where the refrigerant flows downward with respect to the processed product. Before starting cooling, the processed product guide 3 is substantially cylindrical and is substantially cylindrical and is in close contact with the outer periphery of the processed product guide 3. However, the flow of the refrigerant into the cooling chamber 4 is blocked by the variable stretchable product guide (cooling auxiliary device) 10 whose upper end protrudes from the liquid level of the refrigerant. At the time of cooling, the expansion / contraction variable processing product guide 10 moves downward together with the flowing water flowing outside the cooling chamber 4, so that a refrigerant having a specified flow rate flows into the cooling chamber 4 from above, and the processed product has a specified flow rate from the beginning. It is cooled by touching the refrigerant. The bottom surface on which the processed product is placed has a saw-like shape and does not hinder the flow of the refrigerant. However, before the start of cooling, the refrigerant is sucked from below, so that the refrigerant does not flow into the cooling chamber 4.
FIG. 3 shows a case where the refrigerant flows upward with respect to the processed product, and before starting cooling, the flowing water blocking damper (cooling auxiliary device) 12 installed below the processed product is closed. Inflow of the refrigerant into the cooling chamber 4 is blocked and flows outside the cooling chamber 4. At the time of cooling, the flowing water blocking damper 12 is opened, the refrigerant flows into the cooling chamber 4 from below, and the processed product is cooled by touching the refrigerant at a prescribed flow rate from the beginning.
FIG. 4 shows a case where the refrigerant flows laterally with respect to the processed product. Before the cooling starts, the flowing water blocking dampers 12 installed on the upstream side and the downstream side of the processed product are closed, so that the refrigerant Is blocked from flowing into the cooling chamber 4 and flows outside the cooling chamber 4. At the time of cooling, the two running water shut-off dampers 12 are simultaneously opened, the refrigerant flows into the cooling chamber 4 from the upstream side, and the processed product is cooled by touching the refrigerant having a prescribed flow rate from the beginning.

  Moreover, it is an essential condition for uniform cooling of the processed product that the velocity of the water flowing in the cooling chamber 4 is uniform in a cross section perpendicular to the flowing direction. In the present invention, the flow velocity distribution adjusting guide 5 is attached so that the water flow velocity of each part in the cooling chamber 4 is within ± 10% of the prescribed flow velocity. If it exceeds ± 20%, the strain may be remarkably increased.

Illustrating an example was carried out in cold 却装 location of the present invention. In order to investigate the relationship between the cooling water speed and the cooling capacity, for each of the steel types S25C, S35C, and S45C, which are high hardenability high carbon chromium bearing steel SUJ2 and simple carbon steel, φ20 mm, φ40 mm, and φ60 mm. After austenitizing heating, cooling with conventional oil cooling, still water, running water of 1.0 m / second, running water of 3.0 m / second was performed, and the surface hardness and the hardness of the central part were compared. Table 1 shows the respective cooling conditions and the hardness after quenching.

The cooling capacity in the cooling device of the present invention increases as the flow rate of water increases. In cooling with flowing water at a flow rate of 3.0 m / sec, the hardness of the surface of a simple carbon steel with a material having a size of φ20 mm is close to the maximum hardness of the carbon steel. The larger the flow rate, the greater the cooling capacity can be without distortion or defects.

The specimen shown in FIG. 5 was used to investigate quenching strain reduction, which is the main effect of the present invention. After this specimen was austenitized and heated at 850 ° C., conventional oil cooling, static water, 1.3 m / second flowing water, 2.0 m / second flowing water, 2.9 m / second flowing water, 4.8 m / second flowing water And quenching distortion was measured. The measurement position and method are shown in FIG. Table 2 shows the variation and average value of the amount of strain after cooling.

  The amount of distortion of the treated specimen decreased as the flow rate of the refrigerant increased. In the specimen used for the test, when the flow rate of water exceeds 3.0 m / sec, the amount of strain is smaller than that of cooling by mineral oil which is generally performed. It can be said that the strain after heat treatment of steel parts decreases as the flow rate of cooling water increases. In small steel parts, rapid water quenching at a refrigerant flow rate of 3.0 m / sec or more can increase quenching hardness and reduce post-quenching distortion as compared with oil cooling. If the flow rate is 5.0 m / sec or more, the strain can be further reduced.

  If the flow rate of the refrigerant on the surface of the processed product increases, the entire surface will be cooled more uniformly, and the internal surface will be delayed in order to harden (cool, transform) deeply under the surface in a short time. This is thought to be due to the fact that the volume change and stress to be contained are contained to prevent external strain generation. If the objective is simply to reduce quenching distortion, it is possible to use not only “water”, which has no environmental impact, but also an aqueous solution of inorganic salts with a higher heat transfer coefficient after taking environmental measures. Conceivable.

The whole schematic diagram during processing goods cooling in the low distortion rapid water quenching apparatus of the present invention. Example of processed product guide when flowing water flows from top to bottom After the processed product is installed at a fixed position, the guide is contracted and flowing water at a specified flow rate is introduced from above. Example of treated product guide when running water flows upward from below After the treated product is installed at a fixed position, open the lower damper and enter the running water at the specified flow rate from below. Example of treated product guide when flowing water flows from the lateral direction After the treated product is installed at a fixed position, open the upstream and downstream dampers at the same time, and supply the flowing water at the specified flow rate from the upstream. It is the shape size and material of the specimen used for the quenching strain measurement. This is the position and method for measuring the distortion of the quenched specimen. All the distortions were arc-shaped bends with the groove portions convex.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Quenching water tank 2 Flowing water duct 3 Processed product guide 4 Cooling chamber 5 Flow velocity distribution adjustment guide 6 Pump power 7 Pump 8 Tank atmosphere blockage wall 9 Heating furnace zone 10 Expansion / contraction variable processed product guide (cooling auxiliary device)
11 Processed goods delivery route 12 Flowing water cutoff damper (cooling auxiliary device)
13 Flow direction of cooling water

Claims (2)

In heat treatment of steel and alloy parts, water or an aqueous solution that does not pollute the environment even when discarded is used as a cooling agent for rapid cooling after heating, and the treated product is cooled in running water. A quenching water tank for storing a refrigerant, a cooling chamber provided in the quenching water tank for placing a processed product, and circulating the refrigerant to increase a flow rate of the refrigerant in the cooling chamber to 3.0 m / A flowing water pump that maintains a flow rate of more than 1 second (hereinafter referred to as “specified flow velocity”) , and prevents the refrigerant from flowing into the cooling chamber before the processed product is placed in the cooling chamber. And a cooling auxiliary device that allows a coolant having a specified flow rate to flow into the cooling chamber without contacting the processed product with a coolant having a flow rate lower than the specified flow rate before cooling. apparatus. 2. The low flow path structure according to claim 1 , further comprising: a water channel structure adjusted so that a flow velocity at an arbitrary position of a cross section perpendicular to the direction of the water flow in the cooling chamber is within ± 10% of a predetermined flow velocity. Strain rapid water quenching equipment.

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