Case

Hand-held (HHP) Induction Brazing Carbide turning tool

June 12, 2020

 HHP Induction Brazing Carbide turning tool

 

Brazing is a method of connecting welding pieces by using a metal material with a lower melting point than the parent material, heating the solder and the solder to a temperature higher than the melting point of the parent material but lower than the melting point of the parent material, using a liquid solder to infiltrate the parent material, filling the joint gap, and diffusing with the parent material.

 

Brazing is a traditional and widely used cemented carbide welding method. Its technology is mature and reliable. Induction heating brazing is also one of the widely used methods.

 

Induction heating brazing has the advantages of rapid heating, short liquefaction process of the filler metal, and being able to be carried out in a variety of atmosphere (air, shielding gas, vacuum), which can reduce the overheat and oxidation of cemented carbide and improve the welding quality.The disadvantages of this method are that the equipment is more complex and the one-time investment is large, followed by the skin effect of induction current. When brazing large and thick workpieces, the heating temperature is not uniform, so it is difficult to ensure the brazing quality, and the efficiency is also low. Therefore, it is generally only applicable to small size brazing pieces with simple structure (preferably with shaft type thin and long type).

 

The technological parameters of induction heating brazing generally include such factors as brazing gap, heating speed, cooling speed, shape and size of induction ring, and addition mode of brazing agent.These factors must have an appropriate matching range, the fluctuation of factors will have a negative impact on the quality of the weld, especially in the cemented carbide has a greater welding stress.

 

Weld clearance is an important parameter to ensure the quality of brazing.Generally speaking, the smaller the brazing joint is, the greater the welding stress is, and vice versa.When the bit gap is too small, there will be "squeeze death" and "bit impenetrability", which will decrease the joint strength and increase the welding stress.But the clearance is too big, the capillary action is weakened, also can cause "the bit is not permeable", causes the joint strength to decline.Therefore, the moderate size of brazing gap has a great effect on reducing welding stress and enhancing weld fastness.

 

The heating and cooling speed have great influence on the quality of brazing joint.Heating speed is too fast, the alloy will produce greater stress;If the heating is too slow, the residence time at high temperature will be long. Although this can improve the wetting and diffusion of liquid solder, it will cause the oxidation and burning loss of the alloy.Generally, heating should not exceed 100℃/ s.If the cooling rate is too fast, great shrinkage stress will occur in the alloy.The cooling speed is too slow, although it can reduce the welding stress, it is not good for the hardening of steel body material, so 60℃/s is generally appropriate.

 

Induction coil is an important component of induction heating equipment. The energy of AC power supply is transferred to welding parts through it to realize heating. Therefore, whether the structure of induction coil is reasonable has a great impact on brazing quality and production efficiency.The principle of correct design and selection of the induction ring is: the induction ring should have a shape suitable for the welding piece, and the useless gap between the induction ring itself and the welding piece should be reduced as far as possible. The gap should be no more than 2 ~ 3 mm, so as to improve the heating efficiency.In order to make the heating of welding piece smooth and uniform and prevent local overheating at the sharp corner of welding piece, the parameters such as the turns of induction coil and the alternating frequency of induction current should be selected reasonably


TAG:  Induction brazing