As a kind of austenitic stainless steel, 304 stainless steel is a stainless steel material with strong versatility, good corrosion resistance, heat resistance, and non-magnetic. Corrosion resistance is stronger than 200 series stainless steel materials. In terms of high temperature resistance, it has good weldability, low sensitivity to cold cracks and hot cracks, good hot workability such as stamping and bending, no heat, and can be as high as 1000-1200 degrees.
In recent years, stainless steel has a wider range of applications, and it is used more and more in aerospace, electronic devices, medical equipment, nuclear industry, mechanical instruments, etc. Therefore, the packaging and welding of ultra-thin stainless steel products has become very important. Traditional welding methods are difficult to ensure the welding quality of thin plates, while laser welding has incomparable advantages over traditional welding, and can effectively reduce welding defects. The research on welding technology of 304 stainless steel is produced under this background.
In the process of using stainless steel, a large part must be welded, because the welding quality directly affects the performance of stainless steel parts. Stainless steel welded joints consist of three parts: weld metal zone, heat-affected zone and base metal (base metal) zone.
Advantages of laser welding of stainless steel
Compared with traditional welding, low-power pulsed laser seam welding has the advantages of high power density, energy concentration, low heat input, narrow weld seam and small deformation, and a small spot can be obtained after the laser beam is focused. Precise positioning, these features make laser seam welding more suitable for welding small-sized workpieces than other welding methods. For laser welding of ultra-thin stainless steel materials, because the material is very thin, it is easy to vaporize and perforate, and it is necessary to obtain a continuous weld without burn-through. The key is precise control of the parameters.
Laser welding is to use the characteristics of the excellent directionality and high power density of the laser beam to work. The laser beam is focused in a very small area by the optical system, and a heat source area with high energy concentration is formed in the welded part in a very short time, so that the welded object is melted and a firm welding spot and seam are formed.
There are two commonly used laser welding methods: pulsed laser welding and continuous laser welding. The former is mainly used for welding of continuous and thin materials at a single point. The latter is mainly used for welding and cutting of large and thick pieces.
ONE, the characteristics of laser welding processing method:
1. Non-contact processing, no need to pressurize the workpiece and perform surface treatment.
2. Small solder joints, high energy density, suitable for high-speed processing.
3. Short-time welding has no thermal influence on the outside world, but also has a small thermal deformation and heat-affected zone of the material itself, especially suitable for processing high melting point, high hardness and special materials.
4. No filler metal, no vacuum environment (can be performed directly in the air), and no danger of X-rays being generated in the air like electron beams.
5. Compared with the contact welding process. No wear and tear of electrodes, tools, etc.
6. No processing noise, no pollution to the environment.
7. Small workpieces can also be processed. In addition, welding can be performed through walls of transparent material.
8. It can realize long-distance and difficult-to-reach parts by optical fiber, multi-channel simultaneous or time-sharing welding.
9. It is easy to change the focal length of the laser output and the position of the solder joint.
10. It is easy to be mounted on automata and robotic devices.
11. The conductors with insulating layers can be directly welded, and dissimilar metals with large differences in performance can also be welded.
TWO. The main parameters that affect the quality of laser welding are welding current, pulse width, pulse frequency, etc. The main effects are as follows:
1. As the current increases, the width of the weld increases, spatters gradually appear during the welding process, and the surface of the weld appears to be oxidized and rough.
2. As the pulse width increases, the width of the weld also increases. The change of pulse width has a very significant influence on the welding effect of stainless steel ultra-thin plate laser welding machine. Small increases in pulse width can cause the sample to oxidize and burn through.
3. With the increase of pulse frequency, the overlap rate of solder joints increases, and the width of solder joints increases first. remained basically unchanged. Observed under the microscope, the weld is getting smoother and more beautiful. However, when the pulse frequency increases to a certain value, the welding process spatters seriously, the welding seam becomes rough, and the upper and lower surfaces of the welded parts are oxidized.
4. The laser welding of ultra-thin plate materials is suitable for positive defocusing. Under the same defocusing amount, the weld surface obtained by positive defocusing laser welding is smoother and more beautiful than negative defocusing.
