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CN-122007345-A - Processing method of fracture-preventing piston skirt copper ring

CN122007345ACN 122007345 ACN122007345 ACN 122007345ACN-122007345-A

Abstract

The application discloses a processing method of a breakage-proof piston skirt copper ring, which aims at the problems of lead emission, segregation and assembly breakage of MB7 alloy used for a piston skirt copper ring of a marine diesel engine, adopts a composite casting mold of a copper ring molten steel jacket and a resin sand core, forms a sequential solidification temperature gradient by matching with bottom pouring, solves the defect of nonuniform solidification of a low-melting-point phase by combining with a circulating water continuous chilling process, refines copper matrix grains to improve ductility, prepares a casting mold, smelts a second alloy, sequentially solidifies and pours a third bottom pouring type, continuously chills a fourth circulating water, and post-processes and assembles the fourth circulating water.

Inventors

  • WANG TAO
  • HE JIANHUA
  • WEN GUOHUI

Assignees

  • 襄阳铁源有色金属有限公司

Dates

Publication Date
20260512
Application Date
20260227

Claims (10)

  1. 1. The processing method of the anti-fracture piston skirt copper ring is characterized by comprising the following steps of: preparing a casting mold, namely forming a composite casting mold by adopting a copper ring molten steel jacket and a resin sand core, wherein the inner wall of the molten steel jacket is provided with a circulating water channel, and the core is reserved with a bottom pouring gate; smelting an alloy, namely smelting MB7 alloy raw materials to 1150-1200 ℃, degassing, standing and preserving heat; step three, bottom pouring type sequential solidification pouring, wherein molten metal is poured from the bottom of the casting mould to form forward temperature gradients of the lower part, the upper part and the central part; Continuously chilling by using circulating water, wherein the cooling rate is controlled to be 10-20 ℃ per minute in the solidification stage, and the chilling time is 1.5-2.5 hours; And fifthly, post-processing and assembling, and embedding the copper ring into the piston skirt after machining.
  2. 2. The processing method according to claim 1, wherein the MB7 alloy has a composition similar to ZCuPb20Sn5, and comprises, by mass, 70% -78% of Cu, 18% -22% of Pb, 4% -6% of Sn, and 25% -35% of total lead and tin.
  3. 3. The method according to claim 1, wherein the outer jacket of molten steel is made of low-carbon steel, the wall thickness is 15-25mm, the normal-temperature compressive strength of the resin sand core is more than or equal to 3MPa, and the gas generation amount is less than or equal to 10mL/g.
  4. 4. The process according to claim 1, wherein the molten metal flow rate of the bottom pouring is 0.4 to 0.6m/s and the temperature gradient difference between the lower part and the upper part of the mold during the pouring is 50 to 80 ℃.
  5. 5. The process of claim 1, wherein the circulating water is chilled at a circulating water inlet temperature of 20-30 ℃ and a water flow rate of 1.2-1.8m/s, and the cooling time from 1000 ℃ to 300 ℃ is 40-60min.
  6. 6. The method of claim 1, wherein argon is used for degassing in the alloy smelting step, the flow rate of the argon is 0.8-1.2L/min, the degassing time is 10-15min, the heat preservation temperature is 1120-1160 ℃ and the heat preservation time is 20-30min.
  7. 7. The method according to claim 1, wherein the post-treatment step comprises turning, grinding and surface polishing, the outer diameter machining precision of the copper ring is IT6 grade, the surface roughness Ra is less than or equal to 0.8 μm, and the inner surface of the copper ring is coated with a molybdenum-based antifriction coating with a thickness of 5-10 μm before the embedding assembly.
  8. 8. The process according to any one of claims 1 to 7, wherein the piston skirt copper ring prepared by the process has a copper matrix grain size of 20 to 30 μm, a room temperature elongation of 15 to 18% and a Brinell hardness of HB80-HB95.
  9. 9. The processing method of claim 1, wherein the method is suitable for mass production of the piston skirt copper ring of the marine low-speed diesel engine with the cylinder diameter of 160-400 mm.
  10. 10. The processing method according to claim 1, wherein the circulating water channel of the molten steel jacket is of a spiral structure, the cross section of the circulating water channel is rectangular, the width is 8-12mm, the depth is 6-10mm, and the circulating water channel is of a detachable design, so that the casting mold is convenient to maintain and clean.

Description

Processing method of fracture-preventing piston skirt copper ring Technical Field The invention relates to the technical field of manufacturing of key parts of marine diesel engines, in particular to a machining method of an anti-fracture piston skirt copper ring suitable for MB7 lead-tin bronze alloy. Background The piston is one of key parts of an engine, the piston skirt mainly plays a role in guiding and transferring heat to the piston and bears side thrust from a crank connecting rod mechanism, the piston skirt copper ring is a copper annular fitting arranged on the piston skirt of the internal combustion engine, belongs to an auxiliary wear-resistant heat dissipation structure of the piston, has the core effects of optimizing friction characteristics between the piston and a cylinder wall and improving heat dissipation efficiency of the piston, is inlaid in a special annular groove of the piston skirt, is generally of a thin-wall annular structure, is made of bronze, is made of Finnish standard MB7, is similar to domestic ZCuPb20Sn5 alloy in composition, has excellent antifriction performance, can greatly improve the service life of the piston skirt, but has obvious defects in the traditional casting process, has high casting defects, and low-melting-point element lead and tin are easy to sweat and lead-like and ingredient segregation during casting, so that the product rejection rate is high. On the basis, the application number CN201310722770.2 relates to a piston skirt remanufacturing method and a piston, wherein the method comprises a substrate pretreatment step for removing grease and dust on the surface of a substrate, a fixture mounting step for only exposing the piston skirt to be sprayed, one or more spraying steps for preparing a coating on the surface of the piston skirt, a coating post-processing step for enabling the piston skirt to meet the requirements of process specifications through grinding, and a supersonic plasma spraying technology for preparing a nickel-aluminum composite coating on the surface of the piston skirt. The method for processing the piston skirt copper ring has the defects that the conventional processing method is high in embedded assembly fracture risk and insufficient in ductility of a copper ring matrix, fine cracks are easily generated due to circumferential pressure when the piston skirt is embedded and assembled, fracture is finally caused, assembly quality and equipment operation safety are seriously affected, the conventional casting process mostly adopts a top injection casting and static cooling mode, the problems of uneven solidification of low-melting-point alloy and unsmooth feeding channel cannot be solved, and the requirement of a marine diesel engine on high reliability of the piston skirt copper ring is difficult to meet. To solve the above problems, a method for processing a piston skirt copper ring is provided. Disclosure of Invention The invention aims to provide a method for processing a piston skirt copper ring capable of preventing breakage, which adopts the device to work, so that the problems that the conventional processing method in the background art is high in embedded assembly breakage risk, insufficient in ductility of a copper ring matrix, easy to generate fine cracks due to hoop pressure when the piston skirt is embedded and assembled, and finally broken, and seriously affecting the assembly quality and the equipment operation safety are solved. In order to achieve the purpose, the invention provides the following technical scheme that the processing method of the piston skirt copper ring capable of preventing breakage is characterized by comprising the following steps of: preparing a casting mold, namely forming a composite casting mold by adopting a copper ring molten steel jacket and a resin sand core, wherein the inner wall of the molten steel jacket is provided with a circulating water channel, and the core is reserved with a bottom pouring gate; smelting an alloy, namely smelting MB7 alloy raw materials to 1150-1200 ℃, degassing, standing and preserving heat; step three, bottom pouring type sequential solidification pouring, wherein molten metal is poured from the bottom of the casting mould to form forward temperature gradients of the lower part, the upper part and the central part; Continuously chilling by using circulating water, wherein the cooling rate is controlled to be 10-20 ℃ per minute in the solidification stage, and the chilling time is 1.5-2.5 hours; And fifthly, post-processing and assembling, and embedding the copper ring into the piston skirt after machining. Preferably, the MB7 alloy has a composition similar to ZCUPb20Sn5, and contains 70-78% of Cu, 18-22% of Pb, 4-6% of Sn and 25-35% of lead-tin by mass percent. The design is characterized in that Cu is used as a matrix element, the content range of 70% -78% can ensure the overall structural strength of the copper ring, the defect that the bearing capacity of