The wall thickness of the copper casting will change with its shape. There are many reasons for this, such as poor mold, wear of the locating pin sleeve, movement of the mold on the copper casting, errors in other parts of the mold, the mold or the mud box, etc.
It is also possible that the sand box is not suitable; the clay core is deformed during the production, baking and transportation; in order to prevent the change of wall thickness of the copper casting, the damage of the mold and the sand box should be repaired immediately to deflect the copper casting;
Check whether the locating pins are moved or damaged, and check that the locating pins and pin holes on the sand box and template are not worn or deformed.
In addition, the gap between cores needs to be strictly controlled. When forming the template, locating pins should be used to ensure that the appearance of the copper castings of the high and low boxes is different; tenons can be used to prevent tilting;
The deformation of copper castings is caused by forging stress, and the appearance and size of copper castings do not match the type, and the resulting temperature difference is also large.
Because the beams are adjacent from top to bottom, the thickness of the beams is not only shortened because of the temperature drop, but also shortened by the tightening and thinning. Conversely, there is larger collapse of thickness.
Qualified copper casting is widely used in various machines, and attention should be paid to their performance when using them. If you look at it closely, it can be seen that it is a precision part with a brush-plated transition layer on the outer surface.
The transition layer of copper castings is also called primer or pre-coating. Electric brush plating can achieve good bonding without a transition layer, but a transition layer can improve the adhesion. Generally, there is no need to pre-plate the transition layer for anti-corrosion coating. After the transition layer is plated, the working layer can be directly plated.
Sometimes, according to the requirements of the copper casting surface, after plating a layer of nickel or copper on the transition layer, it is also covered with a thin layer of bright nickel or nickel-tungsten alloy or iron alloy.
At this time, the working layer is bright nickel, nickel-tungsten alloy or iron alloy, and the transition layer of the copper casting can also play a role of isolation, which can prevent the diffusion between the coating and the base material.
When the plating solution corrodes the base material, or a displacement reaction occurs between the plating solution and the base metal, a transition layer can be pre-plated, which can prevent poor bonding of the displacement coating or corrosion of the plating solution to the base metal.
Various metal coatings have their own safe thicknesses. The thicker the coating, the longer the coating time, the greater the current, the coarser the crystal and stress of the coating, and the quality of the coating cannot be guaranteed.
Once the plating thickness of copper castings exceeds the safe thickness, cracks on the surface of the coating will increase, and the adhesion between the coating of copper for casting of copper castings and the base metal will decrease.
Before electroplating, the coating structure should be designed and appropriate measures should be taken. Although the brush plated transition layer of copper castings is relatively thin, it can protect the castings well, and at the same time play a great role in anti-corrosion and polishing. When using it, be careful not to remove this brush plated transition layer.