Forging process of gearbox body

Abstract

The invention belongs to the technical field of forging, and particularly relates to a forging process of a gearbox body, which specifically comprises the following steps: blanking, heating, upsetting, finish forging, punching and trimming, heat treatment, shot blasting, flaw detection and inspection and warehousing. The steel billet raw material is in a round bar shape, the diameter of the steel billet raw material is 145-155 mm, and the weight of the steel billet raw material is 25 In the heating procedure, the temperature of the blank is controlled to be 1170-1230 DEG C; in the upsetting process, the obtained steel billet is placed above a forging die and is punched and stretched by a punch, so that the whole die is filled with the blank to form a blank piece, and the upsetting height is 60-65 mm; in the finish forging procedure, the temperature after forging is controlled to be 800 DEG C or above, and the striking energy of the first four machines is controlled to be 30%; in the heat treatment procedure, Rm is 650-800 N / mm, the hardness HB is 205-245, and the metallographic grade is 1-4, the forming process of the gearbox body is changed from extrusion to stretching through the forging technology, the problem of clamping marks on the gearbox body is thoroughly solved, the product rejection rate is greatly reduced, and the production cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of forging industry, and in particular relates to a forging process for a gearbox body. Background Art

[0002] The gearbox is one of the important components of the automobile transmission system, and the gearbox body is the basic part of the gearbox assembly. It is used to ensure the correct position of each part in the gearbox and bear the load during operation. Therefore, there are strict requirements on its quality and performance. Some minor defects may cause it to be damaged and cause serious consequences.

[0003] For this type of gyratory forgings, the process route usually adopted is: blanking - heating - upsetting - final forging - punching and trimming - heat treatment - shot blasting - flaw detection - inspection - storage. During forging, the blank is placed in the forging die. Figure 6 , the upsetting height is about 160mm, and then it is extruded forged. After executing this process, it is found that the forging is at the position shown in the figure. Figure 7 , there will be a thin and long pinch mark, which is visible to the naked eye, and if the pinch mark is very deep, it is completely impossible to rework and repair, and the whole thing has to be scrapped, causing huge losses. Publication No. CN107470527A discloses a forging process for a gearbox case, which solves the problem of improving vehicle performance by reducing the weight of the vehicle gearbox. However, during forging, a cylindrical ingot is placed in the forging die, and the ingot is punched with a punch so that the billet fills the entire die to form a rectangular blank. Although the weight and performance problems are solved, the above-mentioned problems still exist during the forging process. After many tests and research and discussion by various departments, it was found that this pinch mark was caused by the special structure of the gearbox case itself. When the metal is squeezed to fill the outer ring of the outer gearbox case, a small part of the inner wall is still not filled, resulting in metal reflux and eventually generating a pinch mark.

[0004] Therefore, the above problems are issues that should be considered and solved during the forging process of the gearbox body. Summary of the invention

[0005] In view of the above problems, the purpose of the present invention is to provide a forging process for a gearbox body, which can completely solve the problem of pinch marks on the gearbox body.

[0006] In order to solve the above technical problems, the technical solution adopted by the present invention is a forging process for a gearbox body, which specifically includes the following steps: blanking--heating--upsetting--final forging--punching and trimming--heat treatment--shot blasting--flaw detection--inspection and warehousing. In the blanking process, carbon structural steel billets are selected as raw materials, and the steel billet raw materials are round rods with a diameter of 145-155mm and a weight of 25-26kg; in the heating process, the billet temperature is controlled at 1170-1230℃; in the upsetting process, the obtained steel billet is placed above the forging die and punched and stretched with a punch so that the billet fills the entire die to form a blank, and the upsetting height is 60-65mm; in the final forging process, the post-forging temperature is controlled at above 800℃, and the first four machine strike energy is controlled at 30%; in the heat treatment process, Rm: 650-800N / mm², hardness HB205-245, metallographic grade 1-4.

[0007] A further improvement of the present invention is that in the heating process, the obtained blank is added into a medium frequency induction heating furnace for heating.

[0008] A further improvement of the present invention is that in the heat treatment process, the forging is first heated to 300°C-400°C for preheating for 3 hours, then heated to 570°C for insulation for 2 hours, placed in oil and cooled to 50°C-70°C, then air-cooled, and then quickly subjected to 150°C low-temperature tempering treatment.

[0009] A further improvement of the present invention is that after the heat treatment process, the forging is subjected to a sulfurizing treatment, the forging is placed in a salt bath for an electrolytic sulfurizing treatment, and the wear resistance of the forging surface is improved.

[0010] A further improvement of the present invention is that a pretreatment step is included before the unloading process, in which impurities on the surface of the steel billet are polished by a polishing device to remove impurities and defects on the surface of the steel billet, and then the polished steel billet is cleaned multiple times, dried, and set aside.

[0011] A further improvement of the present invention is that in the shot blasting step, the forging is sequentially ground and shot peened, the grinding includes circular grinding and chamfering grinding, and the shot blasting is to place the forging in a shot blasting machine to remove burrs and oxide scales, and then perform surface phosphorus saponification treatment to obtain a precisely forged forging product workpiece before entering the next process.

[0012] A further improvement of the present invention is that in the flaw detection process, the magnetic suspension is sprayed first, and then the flaw detector is used to perform magnetic detection, which is repeated twice, and finally the finished product is demagnetized and inspected.

[0013] The further improvement of the present invention is that in the flaw detection process, each surface of the forging is required to be 100% free of cracks and folds. If there are cracks, they are marked with chalk and placed in the waiting area. After polishing, the flaw detection is repeated. The qualified workpieces are tested for the corresponding specification parameters, and those that meet the standards are sent to the warehouse. Compared with the prior art, The present invention can achieve the following technical effects: the forging process changes the forming process of the gearbox body from extrusion to stretching, which completely solves the problem of pinch marks on the gearbox body, greatly reduces the product scrap rate, reduces production costs, effectively improves product quality and pass rate, and avoids later repairs; and the gearbox body obtained by this method is light in weight, improves vehicle performance, has high structural strength, and can meet the mechanical properties of the vehicle gearbox. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The drawings described herein are used to provide a further understanding of the present invention and constitute a part of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the drawings: Figure 1 It is a schematic diagram of blank placement of the present invention; Figure 2 , 3 , 4, and 5 are schematic diagrams of the billet forging simulation process in the present invention; Figure 6 This is a schematic diagram of the placement of the blanks in the original forging process; Figure 7 It is the schematic diagram of the metal flow of the original forging process and the schematic diagram of the clamping position; Among them, 1-blank, 2-clamping position. DETAILED DESCRIPTION

[0015] The following will describe the implementation methods of the present invention in detail with reference to the accompanying drawings and embodiments, so that the implementation process of how the present invention applies technical means to solve technical problems and achieve technical effects can be fully understood and implemented accordingly.

[0016] The forging process of a gearbox body provided in this embodiment specifically includes the following steps: (1) Cutting: Carbon structural steel billets are selected as raw materials. First, the impurities on the surface of the billets are ground through a grinding device to remove impurities and defects on the surface of the billets. Then, the ground billets are cleaned several times, dried, and set aside for cutting. The billet raw material is a round bar with a diameter of 150 mm and a weight of 25.5 kg. (2) Heating: The blank is placed in a medium frequency induction heating furnace for heating, and the blank temperature is controlled at 1200°C; (3) Upsetting: Place the obtained steel billet on top of the forging die, such as Figure 1The blank is punched and stretched with a punch so that the blank fills the entire die to form a blank. The upsetting height is 62mm. (4) Final forging: The forging equipment is a 6T program-controlled electro-hydraulic hammer, the temperature after forging is controlled above 800°C, and the striking energy of the first four machines is controlled at 30%; (5) Punching and trimming: Check the size and pay attention to trimming residue and mold misalignment; (6) Heat treatment: In the heat treatment process, the forging is first heated to 350°C for preheating for 3 hours, then heated to 570°C for 2 hours, placed in oil and cooled to 60°C, then air-cooled, and then quickly tempered at 150°C, where Rm: 650-800N / mm², hardness HB205-245, metallographic grade 1-4, and then the forging is sulfurized, and the forging is placed in a salt bath for electrolytic sulfurization to improve the wear resistance of the forging surface; (7) Shot blasting: The forgings are subjected to grinding and shot blasting in sequence. The grinding includes circular grinding and chamfering. The shot blasting is to place the forgings in a shot blasting machine to remove burrs and oxide scales, and then perform surface phosphorus saponification treatment to obtain the accurately forged forging product workpiece and enter the next process; (8) Flaw detection: First spray the magnetic suspension, then use the flaw detector to detect the magnetic field, and repeat twice. Finally, demagnetize the finished product and inspect it. It is required that all surfaces of the forgings are 100% free of cracks and folds. If there are cracks, mark them with chalk, place them in the waiting area, and inspect them again after polishing. (9) Inspection and warehousing: The workpieces that have passed the flaw detection are inspected for the corresponding specification parameters in accordance with GB2828.1-2003 (according to the normal level II inspection AQL=2.5), and those that meet the standards are sent to the warehouse.

[0017] In the forging process, there are two key parameters: the heating temperature of the billet and the impact energy of the first few blows of the forging equipment, which need to be strictly controlled to avoid metal fracture due to excessive deformation during the forging process. After the auxiliary verification of the metal plasticity analysis software, this process is feasible. After actual verification, the problem of clamping has indeed been completely solved, and the product qualification rate has been greatly improved. The above description shows and describes several preferred embodiments of the present invention, but as mentioned above, it should be understood that the present invention is not limited to the form disclosed herein, and should not be regarded as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the invention concept described herein through the above teachings or the technology or knowledge of the relevant field. Changes and variations made by those skilled in the art do not depart from the spirit and scope of the present invention, and should be within the scope of protection of the claims attached to the present invention.

Claims

1. A forging process for a gearbox body, specifically comprising the following steps: blanking - heating - upsetting - final forging - punching and trimming - heat treatment - shot blasting - flaw detection - inspection and warehousing, characterized in that: In the blanking process, carbon structural steel billet is selected as the raw material, and the steel billet raw material is in the shape of a round bar with a diameter of 145-155mm and a weight of 25-26kg; in the heating process, the billet temperature is controlled at 1170-1230℃; in the upsetting process, the obtained steel billet is placed above the forging die and punched and stretched with a punch so that the billet fills the entire die to form a blank, and the upsetting height is 60-65mm; in the final forging process, the post-forging temperature is controlled at above 800℃, and the first four machine strike energy is controlled at 30%; in the heat treatment process, Rm: 650-800N / mm², hardness HB205-245, metallographic grade 1-4.

2. The forging process of a gearbox body according to claim 1, characterized in that: In the heating process, the obtained blank is added into a medium frequency induction heating furnace for heating.

3. The forging process of a gearbox body according to claim 1, characterized in that: In the heat treatment process, the forging is first heated to 300°C-400°C for preheating for 3 hours, then heated to 570°C for insulation for 2 hours, placed in oil and cooled to 50°C-70°C, then air-cooled, and then quickly subjected to 150°C low-temperature tempering treatment.

4. The forging process of a gearbox body according to claim 3, characterized in that: After the heat treatment process, the forgings are subjected to sulfurization treatment. The forgings are placed in a salt bath for electrolytic sulfurization treatment to improve the wear resistance of the forging surface.

5. The forging process of a gearbox body according to claim 1, characterized in that: Before the unloading process, a pretreatment step is also included, in which impurities on the surface of the steel billet are polished by a polishing device to remove impurities and defects on the surface of the steel billet, and then the polished steel billet is cleaned multiple times and dried for standby use.

6. The forging process of a gearbox body according to claim 1, characterized in that: In the shot blasting step, the forging is polished and shot blasted in sequence. The polishing includes circular polishing and chamfer polishing. The shot blasting is to put the forging into a shot blasting machine to remove burrs and oxide scales, and then perform surface phosphorus saponification treatment to obtain a precisely forged forging product workpiece and enter the next process.

7. The forging process of a gearbox body according to claim 1, characterized in that: In the flaw detection process, the magnetic suspension is sprayed first, and then the magnetic detection is performed by a flaw detector, and this is repeated twice. Finally, the finished product is demagnetized and inspected.

8. The forging process of a gearbox body according to claim 1, characterized in that: In the flaw detection process, it is required that each surface of the forging is 100% free of cracks and folds. If there are cracks, they will be marked with chalk, placed in the waiting area, and then polished and flaw-detected again. The qualified workpieces will be inspected for the corresponding specification parameters, and those that meet the standards will be sent to the warehouse.

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