The following eight measures can be taken to prevent the square tube from hot cracking:

（1） According to the pipe structure, size, length, width, thickness, etc., design the correct and reasonable gating system structure and location. In the process of condensation line shrinkage, ensure the temperature difference is balanced, and then solidify in order to make the square tube shrink normally and freely.

（2） According to the mud core structure, the core bone structure shall be manufactured with corresponding rigidity and corresponding sand consumption. The sand consumption of core bone in ordinary mud core is 20-30mm. If the diameter of mud core is Φ 400mm, core diameter: Φ 340-360mm。 The sand consumption of the larger mud core is 50-80mm. After the mud core is prepared, insert long iron nails for reinforcement.

（3） Improve the mechanical properties of the square tube, weigh the burden in proportion, strictly control the chemical composition in molten iron, and try to reduce the content of harmful elements, such as sulfur and phosphorus.

（4） According to the square tube structure, design a reasonable sand box structure and stiffness to ensure a corresponding sand intake. After the sand box is placed on the wood mold, the sand consumption around the box should be equal, and the box stop should not be close to the flange or convex parts, but should have some distance. When necessary, after pouring, the molding sand at the flange or convex part and the gating and riser can be dug out to make the casting shrink freely.

（5） Batch seams are not allowed on the parting surface of the cavity, but corresponding batch seams are allowed on the edge of the cavity, and the cavity will collapse if there is no batch sewing box. The batch seam is determined according to the casting structure and size. The common repair and scraping batch seam is 0.5-1 mm or 2-3mm, and the large parts shall not exceed 5mm.

（6） If the structural design is found unreasonable in the preparation process, it shall be corrected in time to prevent the square tube from cracking and other defects.

（7） Pipe fittings shall not be unpacked prematurely or cleaned at high temperature without watering.

（8） Generally, 3% - 4% of sawdust, 3% - 5% of old coal powder, 2% - 3% of bentonite and other clays are involved in the mud core sand, which has good yielding and sanding properties.