On 2018-08-08 14:48:54
Centrifugal casting process rules
Centrifugal casting is our factory manufacture bimetallic bearing casting method, it is to put the nonferrous metals or alloys in a steel body, and then heated to a certain temperature, the steel body is still a solid, non-ferrous metal or alloy melt into liquid, and then in the high speed rotating under the condition of cooling down, in order to get the outer for steel shell, the inner layer for non-ferrous metal or alloy workpiece. The workpiece has good strength and rigidity, good wear resistance and ideal hardness, suitable for sliding bearings, so centrifugal casting process has become one of the important methods of manufacturing bearings.
(1) bimetallic materials
The steel body should be 15# or 20#, the non-ferrous metal is cast bronze alloy, the steel body must meet the requirements of the process drawings, the outer surface and both ends should have machining allowance, the inner surface should reach the smoothness above ∆5, the copper material should be die-cast, there should be no loose pores and slag inclusion, the copper bar should be according to the size of the car.
(2) prepare blank
1. Welding bottom: the steel body blank through the hole shall be soldered first. Do not let the solder into the inner hole and the inner surface of the cover when welding the bottom. The weld shall be dense and shall not leak copper during heating.
2. Cleaning: heat the steel body and the top cover in the mixed solution of 70-80 g/l sodium carbonate 6-8 g/l water glass to 85-95℃ for 10-15 minutes to remove the surface grease of the workpiece. For the workpiece with more grease, the cleaning time can be appropriately extended until it is cleaned.
3. Washing: wash the lye off the workpiece surface with cold water.
4. Rust removal: place the steel body and cover in industrial hydrochloric acid containing 30% for 3-5 minutes to remove rust spots.
5. Cleaning: rinse off the surface acid with cold water.
6. Neutralization: place the steel body in a solution containing 2-3% sodium carbonate to neutralize the surface acid.
7. Drying: keep the steel body in a 200-300℃ oven for half an hour and dry it.
8. Borax coating: apply the saturated borax solution with a brush on the inner surface of the hot steel body that has been dried. The thickness should be within 0.05-0.10mm, and it should be uniform.
9. Copper loading: clean up the dirty material and put it into the steel body. Check whether it meets the requirements of the drawing when loading.
10. Loading accessories: add about 50 grams of anhydrous borax and 10 grams of wood toner into the steel body with copper material to prevent oxidation.
11. Welding top cover: cover the top cover with holes on the steel body and weld it well. The solder shall not enter into the steel body.
Chamfering: chamfering the steel body according to the requirements of the drawing, shall not seriously cut the weld, resulting in copper leakage in the heating process.
(3), centrifugal casting, centrifugal casting is divided into preheating, heating, and cooling process, respectively in preheating furnace, heating furnace and the centrifugal casting machine, before work should check whether the equipment is in good condition, especially should check before the centrifugal casting machine, hydraulic water cooling system is sensitive and good, otherwise the correction immediately, and choose the right holder.
1. The preheating
A) equipment: rjx-45-9
B) preheating temperature: 750-800℃
C) preheating time: 60-90 minutes
A) equipment: rjx-50-13
B) heating temperature 1200±10℃
C) heating time: 15-45 minutes
3. The cooling
A) clamping: take the workpiece out of the furnace and clamp it on the head without obvious vibration. The movement should be rapid to prevent the temperature of the workpiece from dropping too much.
B) start the switch to make the workpiece rotate at a speed of 1100 RPM, so that the linear speed on the surface of the steel body is not less than 3 m/s. The oxide skin on the surface of the workpiece should be removed during the rotation.
C) cooling: air cooling for 35-90 seconds; Water cooling for 35-90 seconds; Take the water pressure of 1-1.2kg/cm 2-- 1.2-2.5kg/cm 2, take the upper limit of cooling time and water pressure of the larger workpiece, and take the lower limit on the contrary.
D) air cooling: stop the machine to rotate and take down the workpiece. At this time, the workpiece is about 750-800℃, and it is cooled to room temperature in the static hollow, and then the machine is ready for inspection.
(4) reverse repair: for unqualified parts, such as parts with pores, slag inclusion, loose, crack, shucking, etc., need to reverse repair in addition to the shucking need to car to remove the copper layer, re-cleaning, and other circumstances other than rust only need to add the right amount of copper material to re-operation, but can only reverse repair once.