1. Characteristics of vacuum diffusion welding

(1) The joint strength is high. It is especially suitable for the welding of materials that are prone to cracks by fusion welding. Since the properties of the base metal are not changed, the chemical composition and microstructure of the joint are the same or close to those of the base metal, and the joint strength is high.

(2) There are many types of weldable materials. Diffusion welding can weld a variety of similar metals and alloys, and can also weld many dissimilar materials. If vacuum diffusion welding with a transition alloy layer is used, it is also possible to weld dissimilar or homogeneous materials with great differences in physical and chemical properties and easy to form brittle compounds at high temperatures.

(3) It can be used in the manufacture of components that require large-area bonding, laminated components, hollow components, porous components or components with complex internal passages, closed internal joints, and other components with poor accessibility by welding methods.

(4) Diffusion welding is integral heating, with small component deformation and high dimensional accuracy

2. Main applications of vacuum diffusion welding

Diffusion welding is mainly used for welding, welding and brazing of small, precise and complex weldments that are difficult to meet quality requirements. In recent years, diffusion welding has solved the welding problems of various special materials in technical fields such as atomic energy and aerospace missiles. For example, in the connection of important parts such as wings, hatches, fuselage bulkheads, engine rotor blades, guide vanes, turbine disks, nozzle fairings, fan blades, etc. of advanced aircraft; thrust chambers and tail nozzles of rocket engines; aerospace Aircraft laminate injectors, aerospace aircraft honeycomb panels and other key components. Diffusion welding is also widely used in the machinery manufacturing industry, such as inlaying carbide (or carbide) blades onto heavy tools.

3. Main configurations of vacuum diffusion welding equipment

· Working area size: 600mm (length) × 600mm (width) × 500mm (height)

· Maximum temperature: 1100℃

· Temperature uniformity: ±3℃

· Temperature control accuracy ≤±1℃

· Working vacuum ≤4×10-3Pa

· Master cylinder pressure 500KN, pressure head stroke 400mm

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1. Vacuum brazing characteristics

(1) During the whole brazing process, no flux is used, and the parts to be brazed are under vacuum conditions, so there will be no oxidation, carburization, decarburization, pollution and deterioration, and the brazing seam is beautifully formed.

(2) When brazing, the entire part is heated evenly and the thermal stress is small. The amount of deformation can be controlled to a minimum, and no margin processing and precision brazing can be achieved.

(3) Multiple adjacent brazing seams can be brazed at one time, or multiple components can be brazed in the same furnace according to the capacity of the furnace to improve brazing efficiency.

(4) There are many types of basic metals that can be brazed, especially suitable for brazing aluminum alloys, titanium alloys, stainless steel, high-temperature alloys, etc. It is also suitable for composite materials, ceramics, graphite, glass, diamond and other materials.

(5) The product design approach has been broadened, and components with narrow grooves, extremely small transition tables, blind holes, closed containers, and components with complex shapes can be used, without considering corrosion, cleaning, etc. caused by flux, etc. Destruction and other issues.

2. The main application of vacuum brazing:

Vacuum brazing technology has become a promising welding technology since its inception in the 1940s. At present, the vacuum brazing process has been promoted and popularized in aviation, aerospace, atomic energy, electrical instrumentation, petrochemicals, automobiles, tools and other fields. In terms of aero-engine applications, the JT9D engine honeycomb sealing ring of the Pratt & Whitney Company of the United States is made by vacuum brazing of rings and honeycomb sandwich cores; the engine fuel manifold and stainless steel heat exchanger are composed of vacuum brazing; JTBD engine 12 , 13-stage compressor stator ring is made of inner and outer rings and dozens of blades by vacuum brazing. The engine casing of GE in the United States is also made of more than 240 0.25-0.7~ thick Inconel alloy parts that are vacuum-brazed in three steps. Domestically, Shenyang Liming Engine Company and Chengdu Engine Company respectively apply vacuum brazing to aero-engines with some components. In recent years, with the development of science and technology, especially the high-speed development of the home appliance industry (especially the refrigeration industry, including refrigeration equipment, such as refrigerators, air conditioners and their three-way, four-way valves and other accessories), the automobile industry, and the electronics industry, The application of brazing technology is also becoming more and more extensive.

3. Main configuration of vacuum brazing equipment

· Working area size: 800mm (height) x 800mm (width) x 1500mm (length)

· Maximum temperature: 800℃

· Temperature uniformity: ±3℃

· Temperature control accuracy ≤±1℃

· Number of temperature control zones: 10 zones

· Working vacuum: 2×10-3Pa

· Furnace loading capacity: 1000kg

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1. Quenching principle:

Vacuum quenching refers to a heat treatment method that heats and maintains the workpiece to be processed in a vacuum state, and then rapidly cools it in high-pressure cooling gas to harden it. The operation process is usually as follows: put the workpiece into the furnace, evacuate, and start heating when the vacuum reaches 1-10-2Pa. It usually requires preheating to make the workpiece temperature the same as the temperature. When the solid solution temperature is reached, keep it warm. , after the heat preservation is completed, fill the furnace with inert gas at a pressure of 2-10 bar, and use a fan to circulate the cooling gas between the workpiece and the heat exchanger to meet the requirement of rapid cooling from the solid solution temperature, thereby achieving the hardening of the workpiece being processed. Since vacuum high-pressure gas quenching has the advantages of high cooling rate, no surface oxidation or carbonization, good quenching uniformity, small deformation of the workpiece, high production efficiency, low cost, and no environmental pollution, its application is increasing day by day and it has developed quite rapidly. It has become the most eye-catching vacuum heat treatment technology at home and abroad.

2. Quenching characteristics

The best effect of vacuum gas quenching is to obtain the best mechanical properties of the treated parts, which requires both high cooling rate and good cooling properties. A low cooling rate can ensure the hardness of the processed parts, and good cooling uniformity can ensure minimal deformation. Since the vacuum heat treatment of metals and alloys is carried out under negative pressure, it is easy to obtain treatment effects that are difficult to obtain in general atmosphere heat treatment, so that the workpiece has excellent performance.

(1) No oxidation and no decarburization.

(2) Surface purification effect, the surface brightness of the workpiece is good.

(3) Less deformation during heat treatment.

(4) Improve service life.

3. Main application

Mainly used for tools, molds, cutting tools and mechanical parts with relatively high technical requirements and complex shapes. The materials processed include W18Cr4V, W6Mo5Cr4VZ, Cr12, Cr12MOV, gCrsi, CrWMn, 3CrZWS, GCr15, 40Cr, 9Cr13, 3Cr13, 50CrV, 60512, 17-4PH, 15-7MOPH, ICr13NigTs, QBeZ and other materials. At the same time, machined or welded aluminum alloys, titanium alloys, etc. with complex shapes and high dimensional accuracy requirements also have the advantage of maintaining dimensional stability that other heat treatments cannot match.

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