Precautions for pouring machine tool castings
Pouring machine tool castings is a key link in the casting process, which directly affects the quality, performance and yield of castings. The following are the main matters that need to be paid attention to during the pouring process:
Preparation before pouring
Personnel protection: Pouring personnel must wear work clothes and protective glasses as required to ensure personal safety.
Equipment inspection: Ladles, pouring tools, etc. should be dried before use, and their integrity should be checked to prevent pouring accidents caused by equipment problems.
Site cleaning: The work site should be kept clean and free of obstacles to ensure a smooth pouring process.
Control of the pouring process
Pouring temperature: Too low temperature will lead to cold shut and insufficient pouring; too high temperature will easily cause sticky sand and coarse grains. It needs to be adjusted according to different materials.
Temperature monitoring: Use an infrared thermometer to monitor the temperature of molten iron in real time to avoid fluctuations.
Pouring speed: The pouring speed should follow the principle of slow, fast, and slow. It is better to start slowly to facilitate the alignment of the gate, reduce the impact of molten metal on the sand mold, and facilitate gas discharge; the intermediate stage can be appropriately accelerated to improve production efficiency; when it is almost full, the speed should be slowed down to prevent overflow. Avoid interruption, prevent cold shut or stratification defects, especially large castings need to be poured at one time.
Slag removal and slag blocking: The molten iron in the ladle needs to be fully still, and the slag should be removed before pouring. Use a teapot bag or filter to block the slag.
Gas treatment: During the pouring process, the gas emitted from the mold should be ignited in time to prevent the gas from being entrained in the casting to produce pores, and at the same time avoid the pollution of harmful gases to human health and the environment.
Casting quality control
Shrinkage compensation: For machine tool castings with large liquid shrinkage and solidification shrinkage, such as medium and large castings, after pouring, it should be replenished from the gate or riser in time to ensure the integrity of the casting.
Cooling and insulation: After the mold is full, the riser should be covered with dry sand, straw ash or other insulation to prevent radiant light and heat and to keep warm. For thick castings, when the surface of the riser begins to solidify, a preheated iron rod can be inserted and shaken to improve the shrinkage compensation effect.
Avoid defects: Through reasonable casting process and mold design, avoid shrinkage holes, shrinkage, cracks, slag inclusions and other defects. For example, adopt measures such as grain refinement, improving the yield of molding sand, and setting anti-crack ribs to prevent hot cracking; reduce shrinkage by adjusting the chemical composition of castings and improving the chilling ability of castings.
Safe operation
Equipment safety: Ensure that the pouring equipment is safe and reliable to prevent safety accidents caused by equipment failure.
Site safety: Safety warning signs should be set up at the pouring site to prohibit non-operating personnel from entering. At the same time, keep the site well ventilated to prevent the accumulation of harmful gases.
Emergency treatment: Develop emergency plans so that emergency situations such as pouring accidents or fires can be dealt with quickly and effectively.
The casting of machine tool castings requires attention to many aspects, such as pre-pouring preparation, pouring process control, casting quality control and safe operation. Only by considering and strictly implementing these points in many aspects can we ensure that the quality and performance of the castings meet the requirements.
