Development and application review of vertical grinding roll hard surface overlay welding in building materials industry.Date: 2019-06-21 Views:
Vertical grinding is an important equipment in cement flour making system, but because of the high hardness and corrosion of working materials (such as steel slag, limestone, etc.), the workpiece such as grinding disk and roller is worn and impacted in the process of crushing and grinding. At the same time, the wear resistance of the workpiece itself is not strong, so the life of the workpiece is short, which seriously affects the normal production. Traditionally, domestic cement plants have adopted the way of replacing spare parts to ensure production, but it is bound to cause a waste of money and time.
In the middle of 1990s, Europe developed and popularized the off-line surfacing repair technology of vertical mill roller disc, which solved the disadvantages of serious wear and short life of grinding roller disc in vertical mill production at that time, which not only reduced the production cost, but also reduced the unnecessary grinding time.
Since 1998, the author has been looking for a reasonable and efficient way of maintenance. Since participating in the on-line surfacing repair of the first slag mill in China in 2001, the open arc surfacing repair technology of cement or slag vertical grinding roller and disc has been carried out in China, and the suitable special flux-cored wire has been selected. By August 2008, the author has directly and indirectly repaired at least 100 raw material mills and slag mills offline or online, and has participated in at least 160 pieces of Yubu, Kawasaki, heavy and extraordinary. The manufacture of new roller spare parts such as Laijie and Tianjin Academy is used to replace import. The practice shows that the relative casting parts are clear. Arc surfacing repair can double the life of cement or slag vertical grinding roller and grinding disk, and the cost of producing new products by composite manufacturing is about 1 × 2 of that of the original import, but the service life is the same as that of the original import. This paper reviews the situation and application effect of various types of vertical grinding surfacing involved by the author in the past.
Wear Mechanism of 2 Mill
The wear of the mill is mainly the three-body abrasive wear caused by the friction and loss of the material to the roller and the grinding disk. By means of electron microscope and metallographic analysis, it can be seen that with the increase of the content of impurities in the material (such as quartz and pyrite), the grinding groove formed on the surface of the roller increases and widens obviously. Therefore, the hardness of impurities in the material has an important influence on the wear of the grinding roller. The wear degree of different materials to the metal is different, and the life of the workpiece is also different. Therefore, the wear mode of the grinding roller is mainly caused by the grinding of the hard particles in the material, which causes the metal surface to be micromachined and carbide broken and peeled off. For example, slag vertical mill, do not need hard The total wear rate of surface surfacing is usually 10-12g/ ton.. However, the wear rate is determined by the content of free iron to a large extent. The results show that when the content of free iron increases by 0.1%, the wear rate increases by 10%. Because of the high wear rate, its service life is low.
Performance comparison between surfacing workpiece and casting workpiece
3.1 differences between cast and surfacing workpieces
Represented by a rolling disc and one to four rollers, it is driven by the internal grinding of the disc and roller. This kind of grinding mainly shatters limestone, limestone (cement raw material), coal block (for heating and drying), low impact, three-body wear.
For many years, the wear parts can only be replaced by new roller and disc castings. However, the castings rely on a hard material to enhance the wear resistance, while the casting process limits the content of this kind of alloy. Therefore, wear-resistant castings never achieve the maximum utility, which is due to the local excessive failure, resulting in low service life of the workpiece. The company adopts the method of open arc surfacing to repair the worn and scrapped workpiece, and also makes a large number of new products. All kinds of metals in flux-cored welding wire can be easily added, so that the performance of the workpiece after surfacing is much better than that of castings.
At present, there are two kinds of grinding roller and disc used in vertical mill, that is, casting parts and surfacing parts. The chemical composition of the wear resistant layer of the two components belongs to the series of high carbon and high chromium alloy cast iron. The casting parts contain a certain amount of Ni elements. The reason for the difference in wear resistance is due to the different microstructure distribution and properties of the two parts. On the one hand, the macro hardness of the two components is different due to the different microhardness in the microstructure (the hardness of the casting is HRC52--58, surfacing hardness HRC58--62). On the other hand, due to the difference of carbide distribution in the matrix, the casting parts are much lower than those of the surfacing parts. Running life. Therefore, the surfacing parts are superior to the castings in process, internal quality, repairable, economic and so on.