How to ensure the consistency of stainless steel welding quality

Update: 16-09-2019

Welding is a process in which a material is permanently […]

Welding is a process in which a material is permanently joined by melting at a high temperature generated and becomes a processing technique having a set functional structure. In recent years, almost all electronic products, such as computers, televisions, mobile phones, digital cameras, and many electronic components, have applied welding techniques to varying degrees in manufacturing. Welding has penetrated into all areas of manufacturing, directly affecting the quality, reliability and longevity of the product as well as the cost, efficiency and market response speed of the production. In the process of mass production of welding, how to ensure the consistency of welding quality of products is a very important issue in the production management process.
In general, the factors affecting the welding effect can be summarized as the following three options: 1 selection of welding materials 2 selection of welding machine 3 selection of processing table.
First, the choice of welding materials:
The welding effect is related to the optical, physical and mechanical properties of the material being processed. Optical properties: including material reflectivity, absorptivity, transmittance, etc.; physical properties: including thermal conductivity, thermal diffusivity, density, specific heat, heat capacity, melt viscosity, vaporization temperature, etc.; mechanical properties: mechanical processing Accuracy, stress strength, material weldability, workpiece cleanliness, etc.
First of all, when determining the processing materials, especially two or more different materials for welding, it is necessary to refer to the relevant literature to determine whether the materials can be reliably welded. In addition, the reflectivity of different materials for different wavelengths is also different, and the reflectivity is higher. High, the harder the welding.
In addition, the physical and mechanical properties of different materials can have a crucial impact on the welding effect. In general, in spot welding, the higher the thermal conductivity, the better the welding effect; on the contrary, in the seam welding, the smaller the thermal conductivity, the better the welding effect. Users need to make reasonable choices according to different application requirements.
Sometimes, even the same material, such as aluminum, due to the purity of the aluminum and the doping of the elements, sometimes the material type is different, the resulting welding effect is different, even the same type of material, different batches, welding The effect is not the same; in this case, the user needs to adjust the power waveform of the welding machine according to different situations to improve.
Second, the choice of welding machine
When choosing a welding machine, the following factors generally need to be considered:
1. Optical characteristics: spot size (rod diameter, fiber diameter and type, exit head parameters), focal plane height, depth of field, spot position, spot incidence angle;
2. Control characteristics: feedback control mode and power waveform selection.
The optical properties of the welding machine can be determined at the time of proofing. The user can intuitively determine the welding effect when the product is initially tested. Therefore, the details of the control that affect the welding consistency will be highlighted.
The welding machines currently on the market are mainly divided into two categories from the control characteristics: current negative feedback and power negative feedback.
Current negative feedback is a control that controls the pumping xenon current to keep the xenon current constant each time. However, the output power is not linearly proportional to the current of the pump xenon lamp, and as the pump xenon lamp is used for a prolonged period of time, the electro-optical conversion efficiency is significantly reduced, which reduces the output energy and affects the consistency of the soldering effect.
Power negative feedback is a control method that adds a photodetector to the output of the cavity to compare the detected power with the required power to control the pumping current of the xenon lamp.
Power negative feedback is divided into real-time negative feedback and non-real-time negative feedback. Real-time negative feedback is a control method that compares the detected power with the required power in a power pulse to control the pumping current of the xenon lamp. The non-real-time negative feedback is a method of comparing the power waveform detected by the previous pulse with the set waveform, and then determining the current of the next pulse pumping xenon lamp current.
Compared with the current negative feedback control, the power negative feedback can greatly improve the control accuracy of the output energy, especially suitable for mass production.
Under the same output power condition, the energy instability under current negative feedback is greater than 8%, while the output energy instability under power negative feedback is less than 3%. Moreover, with the prolonged use time of the pumping xenon lamp of the welding machine, the electro-optical conversion efficiency of the pump xenon lamp is further reduced, and the output energy is gradually reduced under the negative current feedback state, and the quality control personnel often need to detect the output energy, thereby increasing the production cost. When power negative feedback is used, the system automatically compares the magnitude of the output energy and adjusts the current of the pumping xenon lamp in real time, thus ensuring that the output energy is always within a relatively stable range.
In addition, the welding machine with power negative feedback control can easily realize the power waveform control. In fact, different power waveforms can be used for different materials, which can make the welding effect more beautiful. Sometimes even materials that cannot be welded by traditional methods can be used. A better soldering effect is obtained by changing the power waveform.
When selecting the power waveform, generally speaking, under the premise of outputting the same energy, the wider the pulse width, the larger the solder spot; the higher the peak power of the power waveform, the deeper the solder spot. At present, there is no complete set of power waveform setting methods, users can gradually explore the power waveform suitable for their products during the use process.
The choice of welding machine is very important for the batch processing yield; therefore, the user can use the power real-time negative feedback welding machine to improve the excellent rate of the product under the premise of the condition permit.
Third, the choice of processing workbench:
In high-volume production, automatic workbench is often required to increase production efficiency, so the difference in the workbench will also have a great impact on the welding effect. The specific choice of the workbench is theoretically speaking, the higher the accuracy, the better; but the higher the precision, the higher the production cost of the workbench, so it is necessary to select the appropriate workbench. In addition, whether or not to use a shielding gas or to select a different shielding gas will also have a great influence on the actual welding effect. Workbench-related features mainly consider the following aspects:
Movement characteristics: movement accuracy, repeatability, movement speed.
Fixture characteristics: fixture accuracy, heat dissipation, clamping force, and convenience.
Auxiliary gases: shape, pore size, gas type, flow rate, pressure, angle, distance.
Fourth, summary
In the actual welding production, there will be various problems. How to determine the cause of the problem and how to solve these problems is also a very important part of the production process management process.
In general, there is continuous welding failure in the same part of the welded product. It is very likely that the workbench and the clamp have problems. In this case, it is necessary to solve the problem from the fixture and the workbench; if the incoming batch is different, it is caused. Poor welding processing, may be a problem of incoming materials, need to check the replacement of incoming materials or change the welding machine waveform to set the process conditions to solve; if there are occasional welding and soldering, you can check the energy stability of the welding machine or the table and fixture Is there a problem?
In short, the quality assurance of welding products is a very complicated system engineering, and each small link will affect the excellent rate of the product. This requires the user to summarize according to different situations and find out the welding quality control method suitable for the characteristics of their respective products.