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What preventable problems may be encountered by copper casting manufacturers when making copper cast

  • By Wanhe Copper
  • 2020-11-02
  • click:218

   Copper castings are metal moldings obtained by various casting methods, that is, the tempered liquid metal is poured into a pre-prepared mold by pouring, injection, inhalation or other casting methods, and after cooling, it will be shaken out and finished. And post-processing, etc., to obtain objects with certain shapes, scales and functions.

What preventable problems may be encountered by copper casting manufacturers when making copper cast(图1)

   Copper castings have the following characteristics:


   High hardness, excellent wear resistance, not easy to cause seizure, good casting function and cutting processing function, good corrosion resistance in the atmosphere and fresh water.


   can be used for high load (below 20Mpa) and high sliding speed (8m/s) wear-resistant parts, such as connecting rods, bushings, bearings, gears, worm gears.


   has good mechanical function, corrosion resistance in the atmosphere, fresh water and sea water, good casting function, fineness, good air tightness, good wear resistance, and can be welded.


   Corrosion-resistant, wear-resistant parts, large castings with simple shapes, pipe fittings operating below 250°C and castings that require airtightness, such as gas seals in turbochargers.


What preventable problems may be encountered by copper casting manufacturers when making copper castings? (figure 1)


   What can prevent problems that may be encountered in copper castings?


   1. Stomas (bubbles, choking holes, air pockets), which are holes that exist on the surface or inside of the casting, are round, oval or irregular. Sometimes multiple pores form an air mass, generally pear-shaped under the skin. The shape of the choking hole is irregular and the surface is rough. The air pocket is a recess on the surface of the casting, and the surface is smooth. The visible holes can be found by visual inspection, and the subcutaneous pores can only be found after machining.


   is formed due to:


   The mold preheating temperature is too low, and the liquid metal cools too fast when passing through the pouring system.


  The mold exhaust design is poor, and the gas cannot be discharged smoothly.


   The paint is not good, the exhaust gas is not good, and even volatilizes or decomposes gas.


   There are holes and pits on the surface of the mold cavity. After the liquid metal is injected into the holes and pits, the gas rapidly expands and compresses the liquid metal, forming choking holes.


   The surface of the mold cavity is corroded and not cleaned.


   Prevention methods are:


  The mold should be fully preheated, the particle size of the coating (graphite) should not be too fine, and the air permeability should be good.


   Use inclined pouring method for pouring.


  ③The raw materials should be stored in a ventilated and dry place and preheated before use.


  2. Shrinkage cavity (shrinkage porosity). Shrinkage cavity is a kind of rough surface existing on the surface or inside of the casting. Slight shrinkage cavity is a lot of scattered small shrinkage holes, that is, shrinkage cavity, shrinkage cavity or coarse grain at the shrinkage porosity. It often occurs near the runner in the casting, the root of the riser, the thick part, the wall thickness transition and the thick and thin parts with large planes.


   is formed due to:


  The mold working temperature control does not meet the requirements of directional solidification.


   Improper paint selection, poor control of the thickness of the paint layer at different parts.


  The position of the copper casting in the mold is not designed properly.


   Prevention methods are:


   Increase the temperature of the abrasive tool.


  Adjust the thickness of the coating layer. The spraying of the coating should be even, and the coating should not be accumulated when the coating is peeled off and recoated.


   Partially heat the mold or use heat-insulating material to keep it warm.


  Inlaid copper blocks at the hot spots to chill the parts.


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