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Vacuum Heat Treatment Furnace

Vacuum Sintering Furnace

Vacuum Brazing Furnace

Vacuum Furnace Brazing and Diffusion Bonding Services

1 vacuum brazing material

Nowadays, compared with oxygen-free copper, stainless steel is gradually widely used in the home appliance water heater industry due to its advantages of environmental protection, long life, corrosion resistance, and low cost. The requirements are high, so the same industry has been constantly exploring the technology of stainless steel vacuum brazing. According to the demand of the market, a detailed investigation has been carried out, and the vacuum brazing of stainless steel products is the future development trend.

2 The principle and characteristics of vacuum brazing

1) Principle of vacuum brazing

The principle of vacuum brazing is to use the solder suitable for the base metal. At high temperature, after the solder reaches the melting point, it will fill the weld seam of the base metal by its own capillary action, and finally solidify after passing through the sharply cold and hot ambient temperature. process.

The process of vacuum brazing is that the solder melts, but the base metal does not melt. The range of the weld seam is 0~0.05mm, which is the best welding requirement. The wettability of the solder will affect the welding pass rate and welding quality.

2) Features of vacuum brazing

Stainless steel vacuum brazing has the following three characteristics:

(1) Multiple welds can be welded at the same time, with high production efficiency;

(2) There are no strict requirements on the thickness of the base metal of the part;

(3) Since the base metal does not melt, the strength of the product after vacuum brazing is low, and the price of the solder is high;

The main influencing factors of vacuum brazing are as follows:

(1) The smoothness of the surface of the part;

(2) Fitting dimensions of parts assembly;

(3) Vacuum brazing temperature is the state where the solder is melted.

3 Vacuum brazing process flow

1) Preparation for vacuum brazing

Before the parts are assembled, it is required to use specific ultrasonic equipment to clean the oil and dirt on the surface of the parts, and it is necessary to add the specified cleaning agent for stainless steel parts. After several processes, it is dried to ensure the stainless steel parts before assembly. Surface finish, which is a prerequisite for vacuum brazing of stainless steel.

After the cleaning of the parts is completed, the assembly starts. According to the size requirements of the drawing, the multiple parts are assembled together by using specific fixtures and non-standard equipment for positioning, and then the solder is filled. The filling of the solder must be uniform. After repeated At present, the most suitable brazing filler metal for stainless steel vacuum brazing is nickel-based brazing filler metal. Ensure that the brazing filler metal is completely coated to the position of the weld seam. As shown in Figure 1, the weld seam gap should be controlled at 0~0.05 mm. The assembly process needs to wear dust-free protective gloves to ensure the cleanliness of the weld.

2) Start vacuum brazing

After the product is assembled, use a customized vacuum brazing furnace. After the furnace temperature rises to the set welding temperature, put the product into the furnace to melt the solder, and finally pass through the cooling section to solidify the weld to complete the stainless steel product. vacuum brazing.

4 Inspection after vacuum brazing and comparative analysis of defects

1) Post-weld inspection

After the welding is completed, the inspection is divided into two parts: air tightness inspection and pressure resistance inspection. CCD imaging technology is used to perform air tightness inspection on the welded products, and the compressed air pressure is 1.5 MPa.

Then carry out withstand voltage test, the test result is

P_A5.7=1.12×1.33=1. 49 MPa

P_wcp=0.93×1.50= 1.40 MPa

After 10 minutes of pressure holding time, if there is no leakage at the weld, it means that the welding is qualified.

2) Defect analysis and repair

The products completed by vacuum brazing under different welding parameters were compared and analyzed, and the welding seam was cut and dissected by wire cutting equipment, and the filling state of the solder was observed under a high-power microscope, as shown in Figure 2, Figure 2(a) It is a qualified state (the solder fills the weld), and Figure 2(b) is an unqualified state of leakage. After comparative analysis, the unqualified reason is that the solder failed to fill the weld seam, and the fluidity of the nail material did not reach the best melting state. It is necessary to readjust the welding parameters, and then conduct an anatomical analysis. The solder filling is shown in Figure 2 (a ), it is the best qualified state.

5 vacuum furnace options

Stainless steel vacuum brazing is a difficult type of welding in the industry. Through the introduction of the production process of stainless steel tube and plate vacuum brazing, we can understand the key points that need to be controlled in the production process, which is conducive to overcoming stainless steel in similar projects. Product vacuum brazing operation provides technical reference.

The vacuum heat treatment furnace produced by SIMUWU is a high-quality product for vacuum heat treatment process. Good temperature control accuracy and temperature control uniformity ensure the effective progress of vacuum heat treatment process. The equipment is easy to manage and maintain, greatly reducing maintenance costs. SIMUWU company focuses on the manufacture of vacuum furnaces, has more than ten years of relevant experience, and has a good reputation in the field of vacuum furnace manufacturing. The product line includes vacuum air quenching furnace, vacuum oil quenching furnace, vacuum brazing furnace, etc., which are widely sold in developed and developing countries.