In the foundry industry, the quality of casting products is undoubtedly the top priority. In addition to the various performances of castings, the appearance quality is also an important indicator for customer acceptance. Whether the appearance of the casting is smooth and flat is also of certain value for practical applications. Generally speaking, improving the surface quality of cast iron parts is a comprehensive process involving control and optimization in many aspects. We usually conduct quality control in six aspects to improve the surface quality of castings.
1. Choose a suitable casting process
Process type: Common casting processes include sand casting, lost wax casting, die casting, etc. Different casting processes have different effects on the quality of the surface of cast iron parts. It is necessary to select a suitable process according to the specific requirements and conditions of the specific castings in order to reduce the probability of problems in the intermediate process.
Process optimization: In the casting process, by optimizing casting parameters such as pouring temperature, pouring speed, cooling speed, etc., the surface quality of cast iron parts can be effectively improved. This is a difficult link in the casting process, which tests the technical ability and practical experience of the casting personnel. At the same time, pay attention to adjusting the gate and exhaust system to avoid defects such as shrinkage holes and bubbles during casting. These defects will first destroy the quality of the casting surface, and then have a great impact on the overall performance.
2. Choose high-quality casting materials
Material selection: High-quality casting raw materials should be used first to reduce defects and impurities on the casting surface. Poor quality materials will affect the appearance and performance of castings. Sometimes even if all links are perfectly executed, bad materials will still cause problems with castings. Choose qualified raw materials as much as possible to reduce a point prone to problems from the source.
Material inspection: Strictly inspect and control casting materials to ensure that their chemical composition, physical properties and surface quality meet the requirements. Before the casting materials are used, some inspection methods can be used to check whether the quality of the materials meets the requirements. If there are any problems, try to solve them before casting production.
3. Strengthen the maintenance and management of casting equipment
Equipment maintenance: Regularly clean and maintain casting equipment, replace wearing parts, and ensure the normal operation and accuracy of the equipment.
Fault handling: For equipment that fails, repair and replace it in time to avoid affecting the quality of the casting.
Apart from the uncertainty of raw materials, casting equipment is also a point that is easily overlooked. Big problems with equipment are easy to be discovered, but small problems are easy to be overlooked. Check the condition of the equipment regularly to avoid any faults that have a negative impact on the performance and appearance of the castings.
4. Surface treatment
Mechanical polishing: Use polishing tools and abrasive particles to modify the surface of the casting to make it smoother and more uniform. Mechanical polishing generally goes through steps such as rough polishing, semi-finishing polishing, and fine polishing. It is necessary to select appropriate polishing tools and process parameters.
Chemical polishing: Use chemical agents to polish the castings, and the metal reacts with the chemical components in the reagents to dissolve the rough parts of the casting surface. Chemical polishing has the advantages of high work efficiency and large processing capacity, but it is necessary to pay attention to the ratio of chemical reagents and the control of polishing time.
Most of the time, there will be some small flaws in the surface appearance of casting products. Chemical reagents or mechanical equipment are usually used to optimize the surface, and the use time and degree can be controlled.
5. Rust-proof treatment
Blackening treatment at room temperature: After pre-treatment (degreasing, rust removal and activation), cast iron parts are subjected to blackening treatment at room temperature, which can form a dense black oxide film on the surface of the castings, improving the rust-proof ability and appearance quality of the castings.
Other rust-proof treatments: According to the working conditions and requirements of the castings, phosphating treatment, black nickel plating and other rust-proof treatment methods can also be selected to improve the corrosion resistance and decorativeness of the castings.
The preservation of castings also needs attention. If there are appearance problems during the storage stage, it will affect the final delivery.
6. Quality control and testing
Process control: During the casting process, strengthen quality control and testing, discover and correct problems in time, and ensure that the surface quality of castings meets the requirements.
Finished product testing: Perform multi-angle testing and evaluation of finished castings, including surface quality, dimensional accuracy, internal quality, etc., to ensure that the quality of castings meets the standards.
To improve the surface quality of cast iron parts, the concept of “prevention first, comprehensive management” should be implemented throughout, and surface defects should be systematically reduced through improving material purity, refining process parameters, equipment status maintenance and strict process monitoring. For specific problems (such as air holes, sand sticking, and cold shut), it is necessary to combine the defect characteristics and causes, give priority to solving the main contradictions, and gradually optimize the whole process control.
