Abstract
A cold forging process for starting gear end face teeth, including cutting, annealing, billet making, surface lubrication, pre forging teeth, and precision forging teeth. Beneficial effects: The present invention compresses metal at room temperature, resulting in fine metal grains with a grain size grade of 6 or above. At the same time, production efficiency is greatly improved, and product quality is stable and reliable.
Description
Cold forging process for starting gear end face teeth
technical field
The present invention relates to a cold forging process for the end face teeth of a starting gear.
Background technology
At present, there are many types of starting gears on the market, which have been widely used on motorcycles, but the end face teeth are basically machined using traditional milling. The traditional process route is hot forging billet → turning outer circle and end face → milling end face teeth. Traditional processing methods have disadvantages such as low efficiency, excessive energy consumption, large equipment investment, and unstable product quality. Each shift can only produce about 150 blanks, and the investment in equipment and cutting tools is too large (a total of 1 milling cutter costs 10000 RMB, and 4 milling machines cost 80W RMB). In addition, there is serious waste of raw materials (about 0.15kg of a single blank is wasted), and due to the defects of the hot forging blank itself (such as inclusions, metal fibers not flowing smoothly, etc.), they cannot be compensated for through subsequent processing, which poses a hidden danger to product quality. The starting gear is a type of starting mechanism that requires high strength for the end face teeth and extremely high metallographic requirements for the product (with a grain size grade of 6). Traditional manufacturing methods are difficult to achieve.
Summary of the invention
Invention objective: The purpose of the present invention is to provide a cold forging process for the end face teeth of a starting gear with high production efficiency, stable quality, and high strength.
Technical solution: A cold forging process for starting gear end face teeth, comprising the following steps:
a) Cutting: CNC sawing machine is used for cutting, with a verticality of less than or equal to 0.3;
b) Annealing: A well type vacuum annealing furnace is used for vacuum extraction and nitrogen protection annealing. After annealing, the depth of oxidation decarburization on one side is less than or equal to 0.1 millimeters, and the hardness of the material after annealing is HB113-120;
c) Billet making: using an instrument lathe to make the billet, with a height error controlled within 0.3;
d) Surface lubrication: Perform degreasing, acid washing, water washing, phosphating, air cooling, and saponification treatment on the billet in step c;
e) Pre forged teeth: using a 2000KN hydraulic press for extrusion, with an extrusion force of 200T and a tooth equal division error within 0.05;
f) Precision forging teeth: using a 2000KN hydraulic press for extrusion, with an extrusion force of 200T, a tooth height error of less than 0.05 on the end face, a tooth surface roughness of 1.6, a hardness of HB150-180 after extrusion, and an extrusion speed of ≥ 8 pieces/min.
The annealing heating rate described in step b is less than 150 ℃/h, and the cooling rate is less than 50 ℃/h; Pre vacuum pumping, fill with nitrogen gas after each pumping, with a pressure greater than or equal to 0.01MPa; The annealed metallographic structure consists of F+P spheres, with grades ranging from 4 to 6.
The surface lubrication described in step d includes the following steps:
a) Chemical degreasing: Add 60-100g/L of sodium hydroxide to the billet 60-80g/L sodium carbonate 25-80g/L sodium phosphate and 10-15g/L sodium silicate solution, treatment temperature ≥ 85 ℃, treatment time 15-25 minutes;
b) Rinse with flowing water;
c) Acid washing: Put the billet into a solution of 120-180g/L sulfuric acid and 8-10g/L sodium chloride for acid washing. The acid washing temperature is 65-75 ℃ and the acid washing time is 5-10 minutes;
d) Flowing water washing: It is to prevent the acid washing solution adsorbed on the surface of the billet from being carried into the next phosphating solution, which affects the phosphating effect;
e) Hot water washing: preheating before phosphating;
f) Phosphating treatment: Put the raw material that has been acid washed and water washed into a 9g/L zinc oxide and 23mg/L phosphoric acid solution for phosphating treatment. The total acidity of the solution is 16-20 points, the free acidity is 2.5-4.5 points, the temperature is 85-90 ℃, and the treatment time is 30-40 minutes;
g) Air cooling;
h) Saponification: After melting the saponification solution, immerse the billet in the saponification solution and pull it up for air cooling, then immerse and pull it up again. Repeat this process 3-4 times before air cooling again.
Beneficial effects: The present invention compresses metal at room temperature, resulting in fine metal grains with a grain size grade of 6 or above. At the same time, production efficiency is greatly improved, and product quality is stable and reliable.
Specific implementation method
The present invention will be further explained in conjunction with the embodiments.
Invention process route: cutting → annealing → surface lubrication → pre forging teeth → precision forging teeth
The production efficiency of this production method has been greatly improved, with each shift capable of producing about 5000 blanks. The equipment and tooling investment is relatively low (only one 18WRMB press machine, two sets of 2WRMB molds, and some auxiliary supporting facilities totaling 20WRMB are required). In addition, a single blank can save about 0.1kg of raw materials. Moreover, during the cold extrusion process, the metal undergoes severe deformation, resulting in cold work hardening, and the metal fibers are intact, greatly improving the technical strength index and compensating for the possible defects of the hot-rolled bar material itself, ensuring production quality.
Cutting: CNC band sawing machine is used for cutting, with perpendicularity ≤ 0.3.
Annealing: A well type vacuum annealing furnace is used to evacuate and protect annealing with nitrogen gas. After annealing, the oxidation decarburization on one side is ≤ 0.1 mm, and the material hardness after annealing is HB113-120.
Requirement: 1. Heating rate<150 ℃/h, cooling rate<50 ℃/h;
2. Pre vacuum pumping, fill with nitrogen gas after each pumping, with a pressure of ≥ 0.01Mpa;
3. The annealed metallographic structure consists of F+P spheres, with grades ranging from 4 to 6
Billet making: Made using an instrument lathe, with a height error controlled within 0.3.
Surface lubrication:
a) Chemical degreasing: Add 60-100g/L of sodium hydroxide to the billet 60-80g/L sodium carbonate 25-80g/L sodium phosphate and 10-15g/L sodium silicate solution, treatment temperature ≥ 85 ℃, treatment time 15-25 minutes;
b) Rinse with flowing water;
c) Acid washing: Put the billet into a solution of 120-180g/L sulfuric acid and 8-10g/L sodium chloride for acid washing. The acid washing temperature is 65-75 ℃ and the acid washing time is 5-10 minutes;
d) Flowing water washing: It is to prevent the acid washing solution adsorbed on the surface of the billet from being carried into the next phosphating solution, which affects the phosphating effect;
e) Hot water washing: preheating before phosphating;
f) Phosphating treatment: Put the raw material that has been acid washed and water washed into a 9g/L zinc oxide and 23mg/L phosphoric acid solution for phosphating treatment. The total acidity of the solution is 16-20 points, the free acidity is 2.5-4.5 points, the temperature is 85-90 ℃, and the treatment time is 30-40 minutes;
g) Air cooling;
h) Saponification: After melting the saponification solution, immerse the billet in the saponification solution and pull it up for air cooling, then immerse and pull it up again. Repeat this process 3-4 times before air cooling again.
Pre forged teeth: using a 2000KN hydraulic press for extrusion, with an extrusion force of P=200T and a tooth equal division error within 0.05.
Precision forging teeth: using a 2000KN hydraulic press for extrusion, with an extrusion force of P=200T, a tooth height error of less than 0.05 on the end face, a tooth surface roughness of 1.6, a hardness of HB150-180 after extrusion, and an extrusion speed of ≥ 8 pieces/min. After testing, the metal grains after extrusion have changed, causing the originally nearly spherical grains to be elongated due to deformation and arranged in an orderly manner. The grain orientation is in an ordered state, which improves the deformation resistance and also makes the mechanical properties anisotropic.
Practice has proven that the main technical characteristics of the end face teeth of the starting gear after extrusion are:
1. Grain size better than level 6
2. Mechanical properties: σb≥1300MPa σs≥900MPa
3. Cooperation level: Level 9
4. Mechanical durability: ≥ 1 million cycles
In summary, the quality and performance of the starting shaft produced by cold forging are reliable, the production efficiency is greatly improved, and the cost is significantly reduced, which can meet the needs of customers.
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