How is the surface crack in the aluminum alloy flat ingot produced? How to prevent it?
In actual production, the surface temperature distribution in the width direction of the ingot is not uniform, so that the temperature distribution is uneven, as long as it is willing: Fi..........
In actual production, the surface temperature distribution in the width direction of the ingot is not uniform, so that the temperature distribution is uneven, as long as it is willing: First, the crystallizer with a small noodle strip is used to greatly increase the width and the upper end of the ingot. Partial temperature difference; second, the shrinkage value of the thickness of each point on the wide surface of the ingot associated with the liquid flow supply mode and the cross-sectional shape of the crystallizer is different, resulting in a different gap value between the ingot and the mold wall, The temperature non-uniformity of the outlet thermometer on the surface of the ingot is improved. Third, the uneven water supply in the cooling system causes local unevenness of the surface temperature. Due to the different temperatures of the above factors, when the water position is not at the same horizontal line, the cooling rate is not the same. The shrinkage and shrinkage rates are also different, which restrict each other, so that a larger tensile stress is formed at a portion where the temperature is higher, resulting in cracks. Once cracks are generated, they tend to become places of stress concentration, and they are expected to develop in length and depth. However, the depth of crack development is limited, because the central part of the flat ingot is subjected to stress and can automatically suppress the development of cracks.
The fundamental way to prevent surface cracks:
One is to control the chemical composition of the alloy and improve the plasticity of the alloy at temperature and low temperature, that is, the ability to resist hot cracks and cold cracks;
The second is to eliminate stress concentration sources, including a summary of slag inclusions, funnel low junctions, layering, cracking and crystal microcracks. In operation, the focus should be on increasing the uniformity of the temperature distribution in the width direction of the ingot and reducing the temperature of the ingot at the exit of the mold. To do this, the following should be done:
1 Properly reduce the water pressure on the surface and reduce the casting speed and casting temperature;
2 appropriately reduce the taper of the inner surface of the crystallization tank, and appropriately reduce the metal page in the crystallizer;
3 Ensure that the water on both sides of the large surface is evenly cooled (the crystallizer is flat, and the metal pages in the crystallizer are reduced on both sides);
4 Evenly distribute the liquid flow to prevent the funnel from skewing;
5 Special care to prevent surface slag and cracking;
Keywords: alloy aluminum plate, imported aluminum alloy Source: American Airlines Metal www.bombgroup17.com