Influencing factors of induction brazing quality

1. Stability and accuracy of induction power supply equipment

1) Power control accuracy of the equipment

  Usually, the induction heating power supply is output and controlled by the way of current and power. The output precision of the induction heating power supply directly affects the stability of induction heating.

2) Cooling water temperature

  The cooling water temperature here refers to the cooling water temperature that is used to cool the IGBT control board or main board of the induction power supply through the water cooling structure inside the induction power supply. The rise of the water temperature will cause some internal components of the induction power supply to work abnormally, resulting in the increase of power output fluctuation, which will affect the brazing heating effect. Usually, this water temperature should not exceed 35℃.

Influencing factors of induction brazing quality (6)

 

2. Stability of input power supply

  Input power supply stability mainly refers to the input voltage and frequency voltage stability. Induction heating power supply, each has its design allows the working voltage or frequency range, when the input voltage or frequency exceeds the range of induction power supply design value, the power supply itself may appear output volatility, abnormal work and equipment impact damage, such as fault, therefore in the induction brazing, quantitatively monitoring at the input voltage and frequency, prevent abnormal.

 

3. Induction coil design and structure

  The induction coil is the core component to realize the heating of welder parts. To a certain extent, the induction coil is the most important factor related to the temperature uniformity of workpiece induction heating and filler metal flow filling in the gap. Therefore, special caution must be taken when designing and structuring the induction coil.

1) Induction coil structure

  It is necessary to design a special inductor according to the structure and shape of the heated workpiece and the size of the joint and to design and manufacture the heating structure of the inductor structure especially, so as to obtain the best temperature uniformity and the best heating effect.

2) Size of induction ring

  The size of the induction coil includes copper tube material used for coil winding, pitch, and inner diameter. The basic principles of inductor design are as follows:

Heat occurs only in the vicinity of the sensor, the sensor should only surround the part of the workpiece that needs heating;

  The closer the induction ring is to the workpiece surface, the heating is pleasant. So changing the coupling can adjust the heating rate. No contact between inductor and workpiece;

  In order to obtain a uniform heating range in the multi-turn induction coil, the distance between turns (pitch) should be minimum, but they are not allowed to contact each other;

  The induction coil should have the most turns in harmony with the workpiece shape size and should be able to obtain the required heat distribution range.

Influencing factors of induction brazing quality (1)

 

4. Consistency of incoming size of the workpiece

1) It involves the consistency of welding joint clearance processing size

  The brazing joint clearance is the most important size of the brazing joint, which is directly related to the flow of filler metal and the formation of the weld when brazing. Because the induction brazing is usually automatic welding, the solder is added by quantitative addition of welding ring, filamentation, flake, or paste.

If the joint clearance increases, the following problems may exist during brazing:

The capillary force decreases, and the flow caulking capacity of the solder decreases;

  The gap increases, which is not conducive to heat conduction or heat transmission between the two base metals, and is not conducive to uniform heating;

When the gap increases, the filler metal cannot fill the gap completely, which is easy to form the appearance of virtual welding defects;

  Increase the possibility of contact between the base metal and air, resulting in serious oxidation problems.

  If the joint clearance is reduced, the following problems may exist during brazing:

The brazing agent can not completely fill the joint gap and can not form high quality joint;

  Reduction of clearance may lead to assembly difficulties and low production efficiency;

  If the clearance is reduced, it may cause the appearance of the weld to be bulky.

Therefore, when high-frequency welding, welding clearance must be strictly controlled (especially for automatic brazing), joint clearance deviation should not exceed ±0.03mm, which can meet the requirements of batch induction brazing.

2) Consistency of workpiece thickness and size

The thickness of the workpiece is directly related to the heating efficiency of the workpiece, and the thickness deviation of the workpiece heating part should not exceed ±0.3mm as far as possible.

 

5. The material and composition of the welder are consistent

  For welding workpieces of resistivity changes with the composition of different, in the case of workpiece shape and size is consistent, such as severe fluctuation of the composition of the workpiece, can lead to artifacts resistivity volatility, and the induction heating depends on the metal itself resistance brazing fever heat, the higher the resistance, the higher the heating efficiency, the faster the heating rate, the child is lower, The fluctuation of the composition will lead to the fluctuation of the metal resistance, which will directly affect the control of the induction heating parameters and process, especially for the automatic induction brazing process and quality control is very unfavorable, so it should ensure the consistency of the material composition of the welder, to avoid the occurrence of large fluctuation of the composition.

Influencing factors of induction brazing quality (4)

 

6. Solder brazing agent

1) Composition grade of brazing agent

  The composition and grade of solder brazing agent selected, directly related to filler and joint performance, different matrix metals have the best solder brazing agent, can obtain the best brazing effect and quality, about this part of the content can refer to the public number of solder brazing agent selection related article reference.

2) Solder flux form (liquid, powder, paste)

  Induction brazing, the first choice of liquid brazing agent, because liquid brazing agent can be more evenly added in the metal matrix and joint clearance inside, can better and more evenly cover the matrix metal surface, add location is more guaranteed, get the best effect of brazing agent.

  For the solder, the solder form suitable for automatic addition (such as paste) is preferred to ensure the relative position consistency between the solder and the base metal workpiece.

3) adding method of brazing agent

  The automatic addition of a brazing agent is preferred to ensure that brazing quality meets the requirements.

 

7. Brazing parameters

1) Parameter setting mode

  The corresponding parameters should be set according to the properties, operating temperature, and special requirements of the joint of the base metal and brazing agent.

2) Parameters of different manufacturers

  There are many suppliers for most companies, the same workpiece, used by each supplier for raw materials and processing technology and so on are different, workpiece material, composition and performance differences, induction heating, the heating workpiece is different, different manufacturers, therefore, induction heating parameters of the workpiece is different, need to set different parameters for different manufacturers, therefore, workpiece, Verification must be performed based on specific artifacts.

Influencing factors of induction brazing quality (3)

 

8. Workpiece welding before processing

  Before welding process of the workpiece, before welding process is the same with another brazing method, its purpose is to eliminate the matrix metal affect flow filling solder wetting the surface of the debris, such as oxide impurities, rust, oil, and reduce the surface tension of the metal substrate, the substrate metal surface conducive to the rapid flow of the molten solder.

 

9. Fixture

1) Repeated positioning accuracy of fixture

  The main purpose of the fixture is to ensure the relative position of the workpiece heating part and sensor is stable and workpiece assembly is centered and the clearance is even. The workpiece heating temperature and heating speed are greatly related to the distance between the workpiece and the sensor. The closer the distance is, the faster the heating speed will be. The farther the distance is, the slower the heating speed will be. Therefore, the repeated positioning accuracy of positioning tools has a great impact on the uniformity of workpiece induction heating. Usually, the repeated positioning accuracy of positioning tools is higher than ±0.5mm, which can avoid the impact on heating.

2) Reliability of fixture

  Due to the induction heating, when the sensor heats the workpiece, it will heat the fixture synchronously. Therefore, when designing the fixture, the influence of induction heating on the fixture should be considered in advance to prevent the fixture from deformation or failure, resulting in the decrease of fixture positioning accuracy and failure.

3) The influence of fixtures on induction heating

Positioning fixture material

Distance between positioning tool and sensor

The temperature of cooling equipment

Influencing factors of induction brazing quality (2)

 

10. Site operation

  Operators should master the basic knowledge of induction brazing and be familiar with the factors that affect the quality of workpiece induction brazing. During brazing operations, operators must operate according to the quality of brazing to ensure the quality of brazing.

Influencing factors of induction brazing quality (5)

 

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