The thermal expansion coefficient of carbide blade and steel (tool rod) is quite different, and the thermal conductivity of the alloy is worse than the material, if the welding process is improper, will result in virtual welding or stress too large, in the use of the blade will appear to fall off or cracking phenomenon, Carbide Inserts serious will appear welding or welding blades directly pull crack, affect the life of the tool. Therefore, the welding process is critical to the life of the blade. Carbide blade welding is the most commonly used mainly high-frequency welding and oxygen welding two processes. High-frequency welding because the temperature is easy to control, heating uniformity, high efficiency, welding quality and stability gradually become the main blade welding mode.
1. Carbide Blade Inspection
Before welding, the carbide blades should be inspected for defects such as carburizing, crack, bending or uneven. Brazing surface must be flat, Carbide Inserts if it is spherical or rectangular cemented carbide brazing surface should conform to a certain geometric shape, to ensure a good contact between the alloy and the substrate to ensure the quality of brazing. Carburizing serious (darker, shiny) blade, Carbide Inserts there will be virtual welding or welding phenomenon.
Carbide blade surface should be kept clean, no oxidation layer and oil. Generally on the blade surface sandblasting treatment, no sand blasting equipment, can be used hand holding cemented carbide, Carbide Inserts rotating green silicon carbide grinding wheel on the brazing surface of the oxide layer and black letter. Without removing the oxide layer on the brazing surface of cemented carbide, the brazing material is not easy to wet the cemented carbide. Experience has proved that if there is oxide layer or black grade letter on brazing surface, Carbide Inserts it should be sprayed sand treatment, otherwise the brazing material is not easy to wet the cemented carbide, there will still be obvious black letter in the brazing seam, so that the brazing area is reduced and the welding phenomenon occurs. The cemented carbide after sandblasting can be cleaned with petrol and alcohol to remove oil.
2. Knife Rod
The tool-rod material is generally selected with carbon-content 0.4~0.7% carbon structural steel, the ratio of shank height to blade thickness should not be less than 3:1.
3. Blade Groove
Groove and blade welding surface shape as far as possible, blade and groove contact surface to be flat, the depth of the blade groove is less than 0 of the blade thickness. 3~1mm. Carbide Inserts The shape of the knife groove is not consistent with the welding surface of the tool rod or the difference is larger, forming a closed or semi-closed groove, easily causing too much welding surface and welding layer too large, because the shrinkage after thermal expansion is inconsistent, but also easily in the blade welding place caused by excessive stress, formation cracking. Carbide Inserts Reduce the area of brazing surface as far as possible by satisfying the required weld strength. The knife groove should also be sprayed with sand and cleaned to remove oil. When cleaning quantity is large, alkaline solution can be used to boil 10~15min.
The key points of operation of cemented carbide blades and steel oxygen-acetylene brazing are as follows:
1. In order to prevent carbide blades in the brazing process decarburization or excessive burning, Carbide Inserts to choose a carbonized flame.
2. Brazing temperature of 1000 ℃ or so is advisable, that is, carbide blade heating bright red. If the blade is dark red or white color can not brazing, because the former temperature is too low, the latter temperature is too high, there has been a burning phenomenon.
3. Welding torch from left to right, from right to left, Carbide Inserts from up and down repeatedly to the knife body heating, so that the knife body and blade heat evenly consistent.
4. brazing Nozzle and knife rod spacing is about 50mm, solder nozzle and knife end tilt angle is 110º, which can ensure effective use of flame heat and heat balance. During brazing, the flame is always covered throughout the brazing area so that it is isolated from the air to prevent oxidation or the formation of stomata.
5. Soldering speed shall be determined by the size of the blade. Brazing 40 Steel and YT15 carbide tool should be completed in 1min, which can effectively prevent the carbide from burning or decarbonization.
6. After brazing, the flame will be required to heat the blade part and then slowly move the nozzle away so that the weldment cools slowly to prevent cracks.