|How to solve common problems in the polishing of wire drawing dies
|1. Excessive polishing
The biggest problem encountered in the daily polishing process is "over polishing", which means that the longer the polishing time, the worse the quality of the mold surface. There are two phenomena of excessive polishing: "orange peel" and "pitting". Excessive polishing often occurs in mechanical polishing.
2. Causes of "orange peel" on the workpiece
The irregular and rough surface is called "orange peel". There are many reasons for "orange peel". The most common reason is caused by overheating or excessive carburizing of the mold surface. Excessive polishing pressure and polishing time are caused by The main reason for "orange peel". For example: polishing wheel polishing, the heat generated by the polishing wheel can easily cause "orange peel". Harder steels can withstand higher polishing pressures, and relatively soft steels are prone to over-polishing. Studies have shown that the time to produce over-polishing varies with the hardness of the steel.
3. Measures to eliminate "orange peel" of workpieces
When the surface quality is found to be poor, many people will increase the polishing pressure and prolong the polishing time, which often makes the surface quality worse.
The following methods can be used to remedy:
(1) Remove the defective surface. The grinding size is slightly coarser than the previous sand number, and then the grinding is performed. The polishing strength is lower than the previous.
(2) Perform stress relief at a temperature lower than the tempering temperature of 25 กใ C. Before grinding, use the finest sand number for grinding until a satisfactory result is achieved, and finally polish with a lighter intensity.
4. Causes of "pitting" on the workpiece surface
Due to some non-metallic impurities in the steel, usually hard and brittle oxides, they are pulled from the surface of the steel during the polishing process to form micropits or pitting corrosion. The main factors that cause "pitting corrosion" are the following:
(1) The polishing pressure is too high and the polishing time is too long.
(2) The purity of the steel is insufficient and the content of hard impurities is high.
(3) The surface of the mold is rusted.
(4) The black leather is not removed.
5. Measures to eliminate pitting of workpieces
(1) Carefully re-grind the surface. The grain size of the sand is slightly coarser than the grain size used before. The soft and sharpened whetstone is used for the final step of grinding before the polishing process.
(2) Avoid using the softest polishing tools when the grit size is less than 1 mm.
(3) Use the shortest possible polishing time and minimum polishing intensity.