Laser welding diamond circular saw blade transition layer material and its requirements

From a theoretical analysis, laser welding is easy to obtain high weld strength. However, in the production of diamond saw blades, due to the large difference between the material of the transition layer (welding layer) of the diamond blade and the base material of the saw blade, and the performance difference between the two is also large, the welding between them belongs to the welding of dissimilar materials and must be reasonable. Only by selecting welding process parameters and strictly controlling the process can high weld strength be obtained. The base material of the saw blade is generally determined. Usually 30CrMo/28CrMo, 50Mn2V, 65Mn and other steel materials. The design of the transition layer of the saw blade is the key to ensure the laser welding strength of the saw blade.

 

The material of the transition layer should not only have the welding performance as close as possible to the base material, but also must match the matrix of the working layer of the blade. Usually, the material of the base material and the material of the working layer of the cutter head are quite different, so it is very difficult to design the transition layer of the saw blade.

The characteristics of laser welding are: the focused laser beam energy density is high (105~107W/cm2), the heating rate is fast, the welding rate is fast, and the heat-affected zone is small, but the laser welding seam temperature is high and the temperature gradient is large.

Therefore, the basic requirements for the laser welding transition layer are:

(1) The boiling point of each element in the transition layer should be similar to prevent weld bubbles;

(2) The transition layer should have high strength (σmin≥6×108Pa) and good toughness to prevent the saw blade from losing teeth during work;

(3) The sintering performance of the transition layer and the working layer matrix should be similar, and under the same sintering conditions, it has good interfacial bonding strength after sintering (σmin≥6×108Pa);

(4) The thermal expansion coefficient of the transition layer and the working layer should be similar, and the thermal expansion coefficient of the transition layer should be slightly smaller to prevent cracks between the transition layer and the working layer during laser welding;

(5) The welding performance of the transition layer and the saw blade substrate should be as similar as possible;

(6) The range of sintering process is wide, which is convenient for industrial scale production.

Most of the transition layer formulas are composed of single element Co, Ni, dual element FeCo, FeNi, CoNi, FeCu, or FeCoNi three components, and the transition layer cannot contain low melting point metals, such as tin and other elements, because such elements It is easy to evaporate and gasify and produce pores; adding a small amount of Mn and Cr to the transition layer material can not only produce solid solution strengthening, increase wear resistance, but also effectively reduce welding pores. At present, some foreign companies such as Dr. Fritsch in Germany and Eurotungstone in France have carried out a series of work on the development of transition layer formula and powder preparation. Considering the transition layer formula from the matrix, cutter head, welding strength, surface quality, etc., the V 27-589, V6-790, NEXT series and other pre-alloyed powders.