Brazing furnace for capillary brazing and brazing process thereof

Abstract

The invention discloses a capillary brazing process, which comprises the following steps: (1) ultrasonic cleaning and acid pickling activation are carried out on a joint part at the place where a header and the capillary are welded; (2) a nickel-based brazing material is uniformly plated on the wall surface of a header opening and around the hole on the outer surface of the header in an electroless nickel plating mode, and drying after water washing is carried out; (3) with alloy deposited on the plating layer as a brazing material, the capillary and the header are fixedly assembled and are then placed in a capillary brazing furnace; (4) vacuum pumping is carried out on the capillary brazing furnace and hydrogen is supplied; (5) a heating coil is electrified, continuous temperature measurement is carried out through a thermocouple, the furnace is slowly heated, the temperature rises to 750 DEG C, the temperature is continuously preserved for 30 min, slowing heating is then carried out,the brazing temperature is then 910 DEG C, and the temperature is preserved for 25 min; and (6) after heating, supply of the hydrogen is closed, vacuum cooling after vacuum pumping is carried out, and brazing is completed. According to the brazing process, the brazing material can be uniformly plated at the brazing element connection place, the problems of difficult placement and uniform coatingof the brazing material in capillary brazing can be solved, and the quality of the capillary brazing is improved.

Description

technical field [0001] The invention relates to the field of brazing, in particular to a capillary brazing furnace suitable for brazing small diameter capillary tubes and a brazing process thereof. Background technique [0002] When stainless steel capillary tubes are increasingly used in aerospace, precision instruments, and heat exchange equipment, they need to be connected to headers, flat plates or tube sheets. Since the diameter of the capillary is less than 2mm and the thickness is less than 0.5mm, the traditional strength expansion strength welding cannot be applied to the connection of the capillary, so the capillary and other components are mainly connected by brazing. However, the difference between the capillary and other pipe fittings is that the size is too small, and the placement of the solder is difficult. Especially when the header is connected, it is connected by brazing. The selection and use of brazing material has a great impact on the brazing quality o...

AI Technical Summary

Problems solved by technology

However, the difference between the capillary and other pipe fittings is that the size is too small, and the placement of the solder is difficult

Especially when connecting headers, the connection is done by brazing, the selection and use of brazing material has a great influence on the brazing quality of headers and capillary tubes, thus affecting the service life and safety of capillary tube equipment

For capillary brazing, manual welding will inevitably affect adjacent solder joints, resulting in welding defects

When using the traditional manual flame brazing technology to weld such workpieces, the skills of the welding personnel are very high. Therefore, the vacuum brazing process is mostly used at present, but the heating in the vacuum furnace will cause the problem of uneven heating.

[0003] To sum up, the diameter and thickness of the capillary are very small, and the connection hole with the header or the tube sheet is very small, and the tube spacing is often less than 3mm when the tube is arranged. Therefore, when using the traditional brazing process for brazing, there are the following problems: Disadvantages: 1. Soldering filler metals, including powdery solid or paste filler metals, cannot be accurately and uniformly placed on the surface of the hole in a small space, and it is very difficult to place the filler metal

When the solder is placed unevenly, it will cause various problems. For example, if the solder is placed too little, it will easily cause the brazing to not be filled; if the solder is placed too much, it will cause the capillary wall to be eroded and penetrated or welded.

2. The pipe joint requires good strength and corrosion resistance, and the wall thickness of the capillary is very thin. The use of ordinary solder is easy to corrode the pipe wall and cause the pipe wall to become thinner, which seriously affects its life.

3. Due to the characteristics of capillary and ultrafine tube bundles, when using traditional vacuum furnace or protective atmosphere furnace for brazing, it is easy to heat unevenly, and at the same time, a very small amount of oxygen will still affect the brazing quality

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