Surface crack is one of the common defects in the process of melting and casting. For example, if we ignore a detail in melting and casting, we will make mistakes, which will cause loss and waste. What are the causes of surface crack of aluminum alloy ingot? If there are cracks, what measures should be taken? Here is a detailed answer.
Causes of surface cracks on aluminum alloy slab
Casting surface crack of aluminum alloy slab is a common defect. Many factors should be considered for the surface crack of aluminum alloy during semi continuous casting
1. Mould taper;
2. Casting temperature;
3. Slag inclusion in casting process;
4. The melt is overheated;
5. The casting speed is too fast;
6. Cooling system;
7. Chemical composition of alloy;
8. Operation skills;
1、 The following problems should be considered in the process of zinc alloy die casting
1. Whether the liquid metal can flow cleanly and smoothly in the gating system without separation and eddy current.
2. Is there any sharp corner or dead area?
3. Is there any change in sectional area of gating system?
4. Is the position of vent and overflow tank correct? Is it big enough? Will it be blocked? Can the gas be discharged effectively and smoothly? The purpose of using computer to simulate filling process is to analyze the above phenomena and select reasonable process parameters.
2、 Analysis of gas produced by coating
Coating properties: if the gas evolution is large, it has a direct impact on the porosity of zinc alloy die casting.
Spraying process: excessive use, resulting in a large amount of gas volatilization, too much punch lubricant, or burnt, are the sources of gas.
1. The way to solve the blowhole of zinc alloy die casting
First analyze what causes the blowhole, and then take the corresponding measures.
(1) Dry and clean alloy.
(2) Control melting temperature, avoid overheating, degassing treatment
(3) Reasonable selection of die casting process parameters, especially injection speed. Adjust the starting point of high speed switching.
(4) Sequential filling is beneficial to cavity gas discharge, and the sprue and runner have enough length; 50 mm), so as to facilitate the smooth flow of the alloy liquid and the chance of gas discharge. The gate thickness and direction can be changed, and overflow groove and exhaust groove can be set at the position of forming air hole. The total cross-sectional area of overflow products should not be less than 60% of the total cross-sectional area of inner gate, otherwise the slag removal effect is poor.
(5) Select the coating with good performance and control the spraying amount.
3、 How to measure the furnace temperature?
Melting temperature control of zinc alloy die casting and its influence
Melting of zinc alloy is an important part of die casting process. Melting process is not only to obtain molten metal, but also to obtain the liquid metal whose chemical composition meets the requirements, which can make the zinc alloy die casting obtain good crystal structure and small gas and inclusion. In the melting process, the interaction between metal and gas and the interaction between liquid metal and crucible make the composition change, produce inclusions and gas suction. Therefore, the correct melting process is an important guarantee to obtain high quality castings.