JP2007000883A - Method for manufacturing hot-forged hub product - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for keeping the hardness of a forged hub product at a constant value without any adjustment of the hardness by the costly normalizing process by maintaining and controlling the cooling rate of the hot-forged hub product of a parts for an automobile at an adequate value irrespective of the season, i.e., summer or autumn. <P>SOLUTION: A hot-forged hub product 8 of a parts for an automobile is taken out of a hot-forging press 1. Then, the forged hub product 8 conveyed by a conveyor 2 is transferred to a heat-insulated container 5 in a heat-insulated chamber 4 for slow cooling at 650-800°C, and stacked. The heat-insulated chamber 4 for slow cooling is covered with a slow cooling sheet cover 6 to perform the slow cooling from the temperature in a range of 650-800°C to the normal temperature. The hardness of a part of an upper surface 9 of a flange of the hot-forged hub product 8 is controlled in a range of the standard of HRC93-99. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a hub forged product that is an automobile part, and more particularly to a method for controlling the hardness of the flange upper surface of a hub forged product by hot forging to HRB93 to 99 of customer requirements.

  Conventionally, hub forgings, which are automotive parts, had to have an average hardness of any three locations on the flange top surface to meet customer requirements in order to meet customer requirements HRB93-99. Therefore, there was a case where the hardness of the flange upper surface did not satisfy HRB93 to 99 of the above standard.

  By the way, generally when manufacturing a hub forging by a hot forging press, if the cooling temperature after forging is not controlled, the cooling rate of the upper surface of the flange for hot forged hub forging is fast when the temperature is low. Therefore, the hardness of the upper surface of the flange of the obtained hub forged product sometimes exceeded HRB99 of the above-mentioned standard.

  When the hardness of the flange top surface exceeds the standard HRB99 as described above, the hub forging product, which is an automotive part, is subjected to a normalization process according to the customer's processing request and the average of any three points on the flange top surface of the hub forging product The hardness was sometimes adjusted to the standard HRB93 to 99.

  Conventionally, for example, when manufacturing a machine part of a predetermined shape by cold forging, for example, when manufacturing a part having a collar part and a shaft part, the outer diameter of the collar part is increased by the upsetting process and the extrusion process is performed at the same time. The length of the shaft is extended by By the way, in this method, a method of adjusting the punch height with respect to the die for cold forging has been developed so as to theoretically match the expansion of the outer diameter of the flange portion due to upsetting and the extension of the shaft portion due to extrusion. (For example, refer to Patent Document 1). However, this method is different from the hot forging in the cold forging, and it is not necessary to adjust the cooling rate so that the hardness of the product forged like the hot forged product falls within a certain range.

  On the other hand, in the hot forging method, the hardness and strain variation of the product are controlled by soaking the hot forged product with the mold set to a temperature higher than the temperature of the soaking chamber. A method has been developed (see, for example, Patent Document 2). However, in this method, since the mold is moved to the soaking chamber with the product attached to the product, a large number of molds are required on the production line, and thus there is a problem of requiring extra cost. .

  Furthermore, in hot forging molds that produce flash-out forged products, the life is further extended by changing the material of the build-up layer in accordance with the fluidity of the flash. A mold has been developed (see, for example, Patent Document 3). However, this method is also a method for extending the life of the mold, and is not intended to cool the product by adjusting the hardness of the obtained product within a certain range.

JP 2004-148359 A JP 2004-148375 A Japanese Patent Laid-Open No. 11-347678

  The problem to be solved by the present invention is not a method of improving the temperature maintenance function of a building in which hot forging of a hub forged product of an automobile part is installed by costly refurbishing a building in which a hot forging device is installed. By maintaining the cooling rate of the hot forged hub forged product at an appropriate cooling rate regardless of the temperature difference, it is possible to adjust the hardness after hot forging without adjusting the hardness by costly normalizing treatment. It is to provide a method for manufacturing a hub forged product by hot forging that maintains the hardness of the flange portion of the hub forged product within a certain range at all times by satisfying the standard by controlling the cooling temperature of the product. .

  The means of the present invention for solving the above-mentioned problems is that, in the invention of claim 1, in the production of a hub forged product of an automotive part by hot forging, it is taken out from the hot forging press and conveyed by a conveyor 650. The hub forgings at a high temperature of 800 ° C. are transferred from the conveyor to a heat insulating container in the adjacent annealing chamber and accumulated at a high temperature, and the annealing chamber is covered with an annealing cover to 650 to 720 to 800 ° C. This is a method for manufacturing a hub forged product by hot forging in which the hardness of the flange upper surface portion of the hub forged product is controlled in the range of HRC 93 to 99 by slowly cooling to 500 ° C. from the range.

  Explaining this action, the means of the method of the present invention is to further dissipate heat by accumulating hub forgings, which are hot forgings, in a high temperature state, and covering the annealing chamber with a cooling cover. Is reduced. As a result, even in winter, it can be cooled to room temperature by slow cooling for the purpose of slow cooling, and the hardness of the obtained hub forged product can be maintained within the range of HRC 93 to 99 standards. The reason for the slow cooling from 650 to 800 ° C. in the means of the present invention will be explained. In the carbon steel generally used as a hub forging, the amount of ferrite is further increased by slowly cooling from 650 to 800 ° C. to around 500 ° C. There is a tendency that the lamellar spacing of pearlite tends to be widened, and it is considered that the hardness does not exceed the upper limit of the standard as compared with the case where this temperature range is not slowly cooled.

  In the cooling process after hot forging into the product shape, the hub forged product for automobile parts according to the manufacturing method of the present invention is provided in a warming room for slow cooling in which a hot forged hub forged product is covered with a slow cooling cover. By accumulating in the heat insulation container and slowly cooling from the range of 650 to 800 ° C, the hardness of the flange top surface of the hub forging product can be controlled by the customer without controlling the temperature of the factory building by controlling the start of accumulation. It can be controlled within the required range of HRB 93 to 99, and there are excellent effects such as eliminating the need for rework by heat treatment such as normalization and reducing costs.

  The best mode for carrying out the present invention will be described with reference to the drawings. First, a steel material for a hub forged product of an automobile part, for example, a steel material made of high cleanliness steel of carbon steel for mechanical structure such as S53C defined in JIS G4051, is sheared and used as a raw material. The forging temperature is heated to a hot forging temperature in an induction heating furnace, and the hub forging 8 having a desired shape is forged by the hot forging press 1. The hot forged hub forged product 8 is taken out from the hot forging press 1 onto the conveyor 2, and the hot forged hub forged product 8 is naturally cooled in the factory building while being conveyed by the conveyor 2. The hub forged product 8 is transferred from the conveyor 2 to the heat-retaining container 5 of the slow-cooling warming chamber 4 in the building at ℃, and accumulated. Next, the slow cooling greenhouse 4 is covered with a warming cover 6 so that heat is not rapidly escaped from the slow cooling greenhouse 4 due to the atmospheric temperature in the factory building. In this state, the hub forged product 8 at 650 to 800 ° C. is held in the heat retaining container 6 of the thermal storage chamber 4, so that the hub forged product 8 is slowly cooled and cooled to 500 ° C. and then allowed to cool.

  Further, the annealing chamber 4 for slow cooling in the present invention will be described. As shown in FIG. 3 (a), the annealing chamber 4 is formed of a metal frame 4a, and rails 4b are laid on the floor surface in the left and right longitudinal directions of the annealing chamber 4. . On this rail 4b, for example, two heat insulating containers 5 made of a metal frame are placed so as to be movable left and right. As shown in (b) of FIG. 3, the periphery and the ceiling of the metal frame 4 a of the annealing chamber 4 are covered with a heat-insulating annealing sheet cover 6. The slow cooling seat cover 6 is capable of turning the cover lid portion 6a up and out of the hub forged product 8. A broken line on the right side of the rail 4b in FIG. On the other hand, as shown in FIG. 1, a conveyor 2 a is laid as the conveyor 2 at the outlet of the 3000-ton hot forging press 1. A chute 2 f that reaches the slow cooling warming chamber 4 from the end of the conveyor 2 d that is being transported is provided on the heat retaining container 5, and the hub forging 8 that cools gradually in the heat retaining container 5 can be accumulated.

  The layout of the factory building is shown in FIG. In this case, the hub forged product 8 is taken out from the 3000-ton hot forging press 1 and transported by placing it on the conveyor 2a. Further, the direction is changed from the conveyor 2a to the conveyor 2d, and the hub forgings 8 are conveyed while being naturally cooled. In FIG. 1, each of the conveyors 2b, 2c, and 2e is a conveyor for transporting the poultry that has been punched out by the hot forging press 1, and includes a terminal end of the conveyor 2c and a terminal end of the conveyor 2e. Is provided with a container 3 for pouring waste. The hub forged product 8 cooled in the annealing chamber 4 is taken out and accommodated in a rack 7.

  The hub forged product 8 being transported by the conveyor 2 is taken out at various temperatures in the cooling process (indicated by its high temperature part) and slowly cooled with a slow cooling vessel. The average hardness of the measurement positions 10, 11, and 12 at arbitrary three points shown in FIG. 5 on the flange upper surface 9 is shown in the graph of FIG. As a result, it was taken out near 760 ° C. and gradually cooled, and the hardness of the flange upper surface portion 9 was HRB 96.26. 5A is a plan view of the hub forged product 8, FIG. 5B is a longitudinal sectional view thereof, and arbitrary measurement positions 10, 11, and 12 are indicated by x.

  In order to know that the hardness of the hub forged product 8 gradually cooled according to the present invention is appropriate, the hardness is measured by setting the number N of hub forged products 8 to be measured in the annealing chamber 4 under the following measurement conditions. did. Table 1 shows the contents of the measurement items, changes in hardness, and evaluations thereof. From Table 1, it can be seen that the high-temperature accumulated No. 1 in the method of the present invention was obtained. In the case of No. 1, the hardness decreased by 1.29 HRB as compared with that manufactured in the winter in the conventional method. When the conveyor speed of No. 2 was increased, the hardness decreased by 0.74 HRB. No. 3 of the present invention combining these, the hardness is reduced by 0.54 HRB. In 4, the hardness decreased by 1.31 HRB, and the change in hardness was improved.

  As shown in Table 1, by installing an annealing chamber 4 at the end of the conveyor 2d in FIG. 1 and covering the annealing chamber 4 with an annealing sheet cover 6, the temperature in summer and winter It has been found that the average hardness of any three points on the flange upper surface 9 of the hub forged product 8 can be guaranteed to the hardness standards of HRB93 to 99 without being affected by the change in HRB93.

It is a figure which shows typically the factory layout in this invention. It is a graph which shows the correlation of the temperature and hardness of a hub forging product. BRIEF DESCRIPTION OF THE DRAWINGS It is a perspective view which shows the outline of the thermal storage chamber for slow cooling of this invention which has a thermal insulation container, (a) is the figure which removed the slow cooling sheet cover, (b) is the figure coat | covered with the slow cooling sheet cover. It is a top view which shows arrangement | positioning of a conveyer, a chute | shoot, and the annealing cool storage room. It is a figure which shows arbitrary measurement positions with the top view and longitudinal cross-sectional view of a hub forged product.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Hot forging press 2 Conveyor 2a Conveyor 2b Conveyor 2c Conveyor 2d Conveyor 2f Chute 3 Ponka container 4 Slow cooler 4a Metal frame 4b Rail 5 Insulated container 6 Slowly cooled sheet cover 6a Cover lid 7 Rack 8 Forged hub 9 Upper surface of flange 10 Measurement position 11 Measurement position 12 Measurement position

Claims (1)

  In manufacturing a hub forged product for automobile parts by hot forging, the hub forged product at a high temperature of 650 to 800 ° C. taken out from the hot forging device and conveyed by the conveyor is kept warm from the conveyor in the warming room for slow cooling. After transferring to a container and accumulating in a high temperature state, covering the annealing chamber with a cover, slowly cooling the forged hub forging from the range of 650 to 800 ° C. to room temperature, the flange upper surface of the hub forging A method for producing a hub forged product by hot forging, wherein the hardness is controlled within a range of HRB 93 to 99.

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