Are cracks allowed on the wear-resistant steel plate?

After observation, it will be found that there are many cracks on the surface of the wear-resistant composite steel plate. Is the crack on the wear-resistant steel plate a normal phenomenon? These cracks seem to be easy to worry about, fearing that the cracks of the wear-resistant composite steel plate will expand during use, or even break or fall off, which will affect the wear resistance.

Let's do a detailed analysis of the causes of cracks. According to relevant information, it can be understood that the production process of wear-resistant composite plate is made by metallurgical hardfacing. The welding current is generally 350-500A, the temperature of the welding arc reaches 1000-1500℃, and the instantaneous high temperature makes the welding wire and the mother board reach the melting point. The molten pool (the so-called weld bead), and the alloy powder added to the molten pool is melted to form a hardfacing layer.

During the hardfacing welding process, the temperature of the mother board adjacent to the molten pool will reach 600-800℃, or even higher. Since the mother board generally uses ordinary Q235 low carbon steel and the wear layer is high carbon and high chromium, during the surfacing welding process, The temperature difference of each part of the mother board is very large, resulting in extremely uneven expansion, contraction and deformation. Because the mother board is firmly fastened by the pressure plate around the mother board, it cannot be deformed freely, and the wear-resistant layer is a welding wire made of a large amount of alloy powder. Metallurgical surfacing is performed on the mother board to form a typical high-hardness and high wear-resistant material. Because the thermal expansion coefficient of the surfacing layer and the mother board is quite different, the mother board with good toughness can withstand greater thermal deformation, and The ability of the high-hardness surfacing layer to withstand thermal deformation is almost zero, so it generates a great thermal stress inside. If this stress is not released immediately, it will easily break, chip, and resist during the later processing (such as crimping). Problems such as shedding of the abrasive layer.

In the cooling process after thermal deformation, in order to release the welding stress existing in the surfacing composite steel plate, many cracks of different sizes will be generated on the surface of the surfacing layer perpendicular to the weld bead. This crack is the result of stress release. It does not affect the use of.

Through analysis, we can understand that this worry about cracks is unnecessary. The wear-resistant composite steel plate is produced by welding technology, which belongs to metallurgical bonding and has excellent bonding performance. Cracks will not fall off or break during use.

In terms of standards, you can refer to the relevant acceptance standards:

　　 1. The length of the crack cannot exceed 10mm.

　　2, Rockwell hardness (HRC60-65).

　　3, the thickness and size of the wear-resistant layer

　　4. The quality of surfacing welding: whether there is peeling, porosity, adhesion of the surfacing layer, flatness, etc.

　　 5. Metal composition of the wear-resistant layer, metallographic test data