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the following failure forms are more common.

• 01 The service surface of the formwork has uniform wear. When the lower part of the formwork has great wear, the size of the brickwork is out of tolerance or it is difficult to demolish the formwork, the formwork will fail. Such failure is a normal failure.
• 02 The lower part of the template brick forming part, the plate surface wear is not synchronized, resulting in the surface of different sizes, different shapes of pits. The surface of the brick is wrinkled and cracked after demolding, which is a common failure form.
• 03 the template plate first forms a pit, and then the pit in the scraping action of hard particles along the length direction of the plate continues to expand and grind out one or more channels of different depths, different width grooves, resulting in the template scrapped, this failure form is also more common.

The failure reasons of steel formwork mainly have the following aspects.

• 01 The template carburizing layer is shallow and the carbon concentration is not high. After annealing with high temperature anti-oxidation decarburizing coating, the depth of carburizing layer was determined by metallographic method, and the carbon content in the surface layer was estimated roughly. The depth of infiltration layer is only 1.4 ~ 2.0mm. The microstructure observation shows that the carbon content in the surface layer is not high, and only a small amount of discontinuous secondary cementite network appears in the most surface layer of the template. The carbon content in the surface layer is estimated to be about 0.8% ~ 0.9%. The formwork layer is shallow, and the depth of hardened layer after quenching is also shallow. Because the surface carbon concentration is not high, there is no secondary carbide in the quenching state, so the wear resistance of the template is not too high.
• 02 the template carburizing layer is shallow, the transition zone is narrow, and the inner layer hardness is low. The hardness test showed that the hardness decreased rapidly from the surface of the template to the heart, and the hardness gradient was very large. The hardness at some parts 1.5mm away from the surface had fallen below HRC30. Once the surface is worn, the wear resistance of the template will drop sharply.
• 03 the hardness of the template is extremely uneven, there are many soft spots. The hardness of the high hardness area is HRC62, and the hardness of the soft spot area is below HRC35. The area with high hardness has good wear resistance and is not easy to wear, while the soft spot area has poor wear resistance and is easy to wear and sag, that is, the uneven wear of each place causes the early pitting of the template.

These are the main causes of premature template failure. This is caused by improper selection of template materials and some problems in heat treatment process.

Our company has a mature technical scheme on the wear-resistant coating of the firebrick mould. After verification by many customers, the process of heat treatment and spraying tungsten carbide can improve the service life of the mould by more than 3 times. Generally, each set of mould can press about 10,000 ~ 20,000 pieces of firebrick.

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