High temperature press-rolling joining of rotary cutters and planer cutters
Peelers and planers are mechanical blades that are spliced together. That is, the blade steel and the low-carbon steel blade body are heated to high temperature, and the blade steel and the blade body are welded together by a rolling mill. This is a solid phase welding method. The steel splicing process is divided into three methods: hot-rolled flux splicing, non-oxidation hot-rolled splicing, and non-oxidation plus flux hot-rolled splicing. Hot-rolled flux splicing is to fill a mixed powder of borax, sodium fluoride, and iron powder between the blade steel and the blade body. Borax and sodium fluoride are dissolved and diluted at high temperature to evenly adhere to the bonding surface. Borax is mainly used to prevent oxidation, and sodium fluoride is mainly used to chemically activate the surface atoms of steel, so that the contact surface is close under the pressure of the rolling mill to generate free electron exchange between atoms to form attraction. Iron powder is mainly used to fill the concave part of the contact surface. Non-oxidation hot-rolled splicing is to seal the blade steel and the blade body with melt welding. It will not continue to oxidize during high-temperature heating and hot rolling, and the blade body with good plasticity and the blade steel with poor plasticity will be deformed synchronously to reduce the relative sliding of the contact surface. The atomic attraction between the contact surfaces mainly depends on thermal activation. Non-oxidation hot rolling splicing requires a large rolling deformation to break the residual oxide film and increase the clean contact surface. Therefore, a high-power rolling mill is required. Since there is no residual flux inclusion on the bonding surface, its welding strength is also high. Non-oxidation hot rolling splicing with flux is a combination of the first two methods. It is mainly used for the splicing of high-alloy steel blade steel with poor high-temperature plasticity, which can reduce the hot rolling deformation of simple non-oxidation splicing. Because the contact surface with too large a difference in high-temperature plasticity not only hinders the continuity of each rolling welding, but also may produce internal cracks from the band-shaped defects in the middle of the blade steel.
The above-mentioned rolling splicing is carried out within the forging temperature range of the blade steel. Undoubtedly, increasing the heating temperature and increasing the rolling deformation are beneficial to the solid phase welding of the contact surface. However, too high a temperature will cause the workpiece surface to overheat or burn. Too large a single rolling reduction will pull apart the bonding surface formed by the previous rolling due to the difference in plasticity between the blade steel and the cutter body. Therefore, it is very important to strictly control the upper temperature limit and reasonably distribute the rolling reduction of each roller.
