CN109396631B - A hot isostatic pressing diffusion bonding method of tungsten/transition layer/stainless steel - Google Patents

Abstract

The invention discloses a hot isostatic pressure diffusion connecting method of tungsten/transition layer/stainless steel, which solves the problem that the tungsten and steel connecting parts used to face the plasma divertor module of the first wall of the fusion reactor in the prior art are easy to connect at the interface The problem of forming large thermal stress and microscopic defects. In the present invention, a hot isostatic pressing diffusion joining method of tungsten/transition layer/stainless steel takes pure tungsten, transition layer and stainless steel as raw materials, and is first subjected to wrapping treatment, followed by hot isostatic pressing treatment, stress relief annealing, and decompression treatment. The hot isostatic pressing diffusion joint can be obtained. The invention is simple to operate, can realize defect-free metallurgical bonding, and has excellent and stable joint performance.

Description

A hot isostatic pressing diffusion bonding method of tungsten/transition layer/stainless steel

technical field

The invention belongs to the technical field of metal material interface connection preparation, and particularly relates to a hot isostatic pressure diffusion connection method of tungsten/transition layer/stainless steel.

Background technique

Nuclear fusion energy is known as "artificial solar energy" because of its high efficiency, cleanliness, safety and rich raw material resources. one. The development of nuclear fusion energy has important strategic and economic significance for the sustainable development of our country.

At present, one of the key problems restricting the research of nuclear fusion reactor is the preparation of divertor. As the core component of a nuclear fusion reactor, the divertor is located in the transition zone between high-temperature plasma and ordinary solid materials. The main components include plasma-facing materials, heat sink materials and structural materials. Due to the different working environments of the various components of the divertor, the corresponding performance requirements for the materials are also different. Tungsten is considered to be the most promising plasma-oriented material due to its excellent properties such as high thermal conductivity, high temperature resistance, sputter-corrosion resistance, and low deuterium-tritium adsorption. Low activation steel is considered to be an ideal material for structural materials and heat sink materials because of its good resistance to radiation expansion, oxidation resistance, high temperature mechanical properties and economy. Therefore, it is the key to the preparation of divertor to successfully connect tungsten and steel together and make it have certain performance.

The key problem of diffusion connection of tungsten steel The melting point of tungsten and steel (Tw=3400℃, TS=～1500℃) is quite different, and the thermal expansion coefficient is quite different. The thermal expansion coefficient is 12×10-6·K-1), which leads to large residual stress at the joint interface, and it is difficult to connect them by traditional fusion welding. At present, the connection methods of tungsten and steel mainly include high temperature brazing connection and diffusion welding connection. High temperature brazing and diffusion welding connections are prone to large thermal stress and microscopic defects at the interface. To obtain better heat transport properties, tungsten steel joints must obtain defect-free metallurgical bonding interfaces.

The patent of CN106181015A, "Manufacturing process of the first wall part of the U-shaped flow channel containing tungsten attached to the cladding of fusion reactor", discloses a manufacturing process of the first wall part of the U-shaped containing flow channel with tungsten attached to the cladding of the fusion reactor. Method, using hot isostatic pressure diffusion welding technology to compound tungsten and U-shaped steel with runner, and then realize functionalization. But the patent only presents a conceptual idea for the combination of tungsten and steel. In the atmospheric environment, the welding surface will be oxidized due to the high temperature; in addition, the coating is a porous non-dense material, and the adsorbed air is still difficult to be completely desorbed during thermal degassing, and it will still oxidize or remain on the interface. Reduce performance. In addition, the soldering temperature of this document is obviously too low, so that the interdiffusion of interfacial elements is insufficient, and the connection strength is low.

Therefore, to provide a tungsten steel connection method, which is easy to operate, can achieve defect-free metallurgical bonding, and has excellent and stable joint performance, has become an urgent problem to be solved by those skilled in the art.

SUMMARY OF THE INVENTION

The technical problem solved by the present invention is: to provide a hot isostatic pressure diffusion connection method of tungsten/transition layer/stainless steel, so as to solve the connection between tungsten and steel in the prior art for facing the plasma divertor module of the first wall of the fusion reactor It is easy to form large thermal stress and microscopic defects at the interface.

The technical scheme adopted in the present invention is as follows:

The hot isostatic pressing diffusion joining method of tungsten/transition layer/stainless steel according to the present invention uses pure tungsten, transition layer and stainless steel as raw materials, and then undergoes hot isostatic pressing treatment and stress relief annealing after wrapping treatment. , to remove the jacket, you can obtain the hot isostatic pressure diffusion connector.

Further, the following steps are included:

Step 1. Assembly: Put the pure tungsten, transition layer and stainless steel into the package in turn;

Step 2. Welding: Weld the package assembled in step 1 with the package cover with the exhaust pipe to form a package assembly;

Step 3. Leak detection: perform leak detection on the package assembly prepared in step 2;

Step 4. Thermal degassing: put the package components that have passed the leak detection in step 3 into the muffle furnace for thermal degassing;

Step 5. Sealing: heat and seal the air extraction pipe on the package assembly completed in Step 4;

Step 6. Hot isostatic pressing connection: place the sheathing assembly processed in step 5 in a hot isostatic pressing machine, and perform diffusion bonding on the tungsten steel sealed in the sheathing;

Step 7. Stress relief annealing: stress relief annealing in a hot isostatic press;

Step 8. De-encapsulation: The encapsulation component annealed in step 7 is turned to remove the encapsulation material, and the hot isostatic pressure diffusion joint can be obtained.

Further, before assembling, it also includes a surface treatment step: grinding and polishing the surfaces to be joined of pure tungsten, transition layer and stainless steel to a mirror surface with sandpaper; after grinding and polishing, ultrasonically clean with alcohol and acetone for 10-30 minutes.

Further, the pure tungsten is tungsten with a mass percentage greater than 99.5%; the transition layer is selected from a single transition layer of copper foil, nickel foil, and titanium foil, or a composite transition layer of copper foil+nickel foil, and The mass percentage of the transition layer is greater than 99.8%, and the thickness is 0.1mm-0.5mm.

Further, the material of the wrapping, wrapping cover, and air extraction pipe is selected from any one of 08F iron sheet, 1Cr18Ni9Ti steel, and 316L stainless steel.

Further, the welding in the step 2 is argon arc welding in a low-oxygen and low-humidity argon protected glove box; or electron beam welding in a high-vacuum chamber.

Further, when the step 2 is argon arc welding, the H ₂ O content and the O content in the protective glove box are both lower than 10 ppm; when the step 2 is electron beam welding, the vacuum degree in the high vacuum chamber is greater than 4 ppm. ×10 ^-3 Pa.

Further, in the step 6, the hot isostatic pressure diffusion connection is specifically as follows: the method of first pressurizing and then heating up is adopted, and the initial pressure is pressurized to 50MPa～60MPa and then the temperature rises; the holding time is 30min～120min, and the hot isostatic pressing The pressure is 130MPa to 160MPa.

Further, when the transition layer is copper foil, the hot isostatic pressing temperature in the step 6 is 1000°C to 1050°C;

When the transition layer is nickel foil, the hot isostatic pressing temperature in step 6 is 1300°C to 1350°C;

When the transition layer is a titanium foil, the hot isostatic pressing temperature in the step 6 is 1250°C to 1350°C;

When the transition layer is a copper foil+nickel foil composite layer, the hot isostatic pressing temperature in the step 6 is 950°C to 1050°C.

Further, in the step 7, when the temperature of the workpiece in the hot isostatic pressing machine drops to 500° C. to 600° C., the gas is returned to uniform pressure to normal pressure, and then the temperature is kept for 30 minutes for stress relief annealing.

The pure tungsten in the step 1 is a pure tungsten block, and the stainless steel is a stainless steel block.

Compared with the prior art, the present invention has the following beneficial effects:

The invention is scientific in design and simple in operation, promotes atomic diffusion of connecting interface materials through the combined action of high temperature and high pressure, adopts appropriate transition layer and process to avoid brittle phase, and uses stress relief annealing to effectively relieve interface residual stress and effectively solve interface problems. Contamination, residual stress, brittle phase, micro-defects and other technical problems, the obtained joint elements diffuse evenly, and a defect-free metallurgical bond is realized. The joint performance is excellent and stable, and it has positive engineering use value.

Detailed ways

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention, but not to limit the present invention.

The leak detection in the present invention is to connect the helium mass spectrometer leak detector with the air extraction conduit on the end cap of the package to perform leak detection.

Example 1

The present embodiment provides the preparation method of the present invention, specifically:

The φ25×20mm pure tungsten with a purity of 99.5wt%, the φ25×0.25mm copper foil with a purity of 99.9wt%, and the 316L steel with a φ25×20 were passed through 200-mesh, 400-mesh, 600-mesh, 1000-mesh, and 2000-mesh sandpaper respectively. Grinding, and then water-polished diamond particles with a particle size of (2-5) μm to a mirror state, and then ultrasonically cleaned with alcohol and acetone for 30 minutes respectively.

Put the cleaned pure tungsten, copper foil and 316L stainless steel into the 1Cr18Ni9Ti envelope in turn, and cover the envelope and the envelope with the air extraction tube in a low-oxygen, low-humidity argon gas with H ₂ O content and O content below 10ppm. In the atmosphere glove box, argon arc welding is used to weld the package components, in which the exhaust pipe and the package cover are made of 1Cr18Ni9Ti material. After the welding is completed, the leakage of the package shall be checked, and the leakage rate shall be ≤3×10 ^-9 Pa·m ³ /s.

Place the package assembly that has passed the leak detection in the muffle furnace, connect the air extraction pipe on the package cover to the high vacuum air extraction system, and use the muffle furnace to heat and degas the package assembly as a whole at 700°C. For 1 hour of degassing, the vacuum degree during the process should be better than 3×10 ^-3 Pa. The air extraction tube on the envelope cover is heated and sealed three times in sequence from near to far from the envelope assembly.

The packaged components after heating and sealing were placed in a hot isostatic pressing machine for diffusion connection. The hot isostatic pressing temperature was 1050° C., the pressure was 152 MPa, and the time was 30 minutes.

When the temperature of the workpiece in the hot isostatic pressing machine drops to 600 ℃, return the air to uniform pressure to normal pressure and then keep it for 30 minutes to remove the stress.

Finally, machining to remove the jacket results in a HIP diffusion joint.

The interface of the HIP diffusion connector prepared in this example is tightly bonded, has no microscopic defects, and has a tensile strength of 480 MPa.

Example 2

The present embodiment provides the preparation method of the present invention, specifically:

The φ25×20mm pure tungsten with a purity of 99.5wt%, the φ25×0.25mm nickel foil with a purity of 99.9wt%, and the 316L steel with a φ25×20 were respectively washed with 200-mesh, 400-mesh, 600-mesh, 1000-mesh, and 2000-mesh sandpaper. Grinding, and then water-polished diamond particles with a particle size of (2-5) μm to a mirror state, and then ultrasonically cleaned with alcohol and acetone for 15 minutes respectively.

Put the cleaned pure tungsten, nickel foil and 316L stainless steel into the 316L stainless steel sleeve in turn, and cover the sleeve and the sleeve with the air extraction tube in the low oxygen and low humidity argon gas with H ₂ O content and O content less than 10ppm. In the atmosphere glove box, argon arc welding is used to weld the package components, and the exhaust pipe and the package cover are made of 316L stainless steel. After the welding is completed, the leakage of the package shall be checked, and the leakage rate shall be ≤4×10 ^-9 Pa·m ³ /s.

Place the package assembly that has passed the leak detection in the muffle furnace, connect the air extraction pipe on the package cover to the high-vacuum air extraction system, and use the muffle furnace to heat and degas the package assembly at 550°C as a whole. For 3 hours of degassing, the vacuum degree during the process should be better than 3×10 ^-3 Pa. The air extraction tube on the envelope cover is heated and sealed three times in sequence from near to far from the envelope assembly.

Diffusion connection was carried out on the heating and sandwiching of the sheathing components in a hot isostatic pressing machine, the temperature of the hot isostatic pressing was 1350° C., the pressure was 150 MPa, and the time was 90 minutes.

When the temperature of the workpiece in the hot isostatic pressing machine drops to 500 ℃, return the gas to the normal pressure and keep it for 30 minutes to remove the stress.

Finally, machining to remove the jacket results in a HIP diffusion joint.

The interface of the HIP diffusion connector prepared in this example is tightly bonded, has no microscopic defects, and has a tensile strength of 426 MPa.

Example 3

The present embodiment provides the preparation method of the present invention, specifically:

The φ25×20mm pure tungsten with a purity of 99.5wt%, a φ25×0.25mm copper foil with a purity of 99.9wt%, a φ30×0.25mm nickel foil with a purity of 99.9wt% and a φ25×20 316L steel were respectively subjected to 200 Mesh, 400-mesh, 600-mesh, 1000-mesh, 2000-mesh sandpaper, and then water-polished with (2-5) μm diamond particles to a mirror-like state, and then ultrasonically cleaned with alcohol and acetone for 20 minutes.

Put the cleaned pure tungsten, copper foil, nickel foil, and 316L stainless steel into a 304 stainless steel envelope in turn, and use electron beams in a high vacuum chamber to weld the envelope and the envelope cover with an air extraction tube to form a envelope assembly. The degree of vacuum is better than 4×10 ^-3 Pa. Among them, the exhaust pipe and the cover are made of 304 stainless steel. After the welding is completed, the leakage of the package shall be checked, and the leakage rate shall be ≤3×10 ^-9 Pa·m ³ /s.

Place the package assembly that has passed the leak detection in the muffle furnace, connect the air extraction pipe on the package cover to the high vacuum air extraction system, and use the muffle furnace to heat and degas the package assembly at 600°C as a whole. For 2 hours of degassing, the vacuum degree during the process should be better than 3×10 ^-3 Pa. The air extraction tube on the envelope cover is heated and sealed three times in sequence from near to far from the envelope assembly.

Diffusion connection was carried out in a hot isostatic pressing machine after being heated and sandwiched. The hot isostatic pressing temperature was 1050° C., the pressure was 155 MPa, and the time was 60 min.

When the temperature of the workpiece in the hot isostatic pressing machine drops to 550 °C, return the air to uniform pressure to normal pressure and then keep it for 30 minutes to remove stress.

Finally, machining to remove the jacket results in a HIP diffusion joint.

The interface of the HIP diffusion connector prepared in this example is tightly bonded, has no microscopic defects, and has a tensile strength of 470 MPa.

Example 4

This example is a comparative example

纯钨、

的316L钢依次分别经200目、400目、600目、1000目、2000目砂纸打磨，然后经粒度(2～5)μm金刚石颗粒水抛光到镜面状态，然后依次分别经酒精、丙酮超声清洗20分钟。will be 99.5wt% pure

pure tungsten,

The 316L steel was polished with 200-mesh, 400-mesh, 600-mesh, 1000-mesh, and 2000-mesh sandpaper in turn, and then water-polished with (2-5) μm diamond particles to a mirror state, and then ultrasonically cleaned with alcohol and acetone for 20 minutes. minute.

The surface to be welded of pure tungsten block is coated with Ni transition layer of 200 μm by physical vapor deposition method. Then, the cleaned pure tungsten+Ni transition layer and 316L stainless steel are sequentially put into a 304 stainless steel jacket, and the whole is sealed and welded.

Place the package assembly that has passed the leak detection in the muffle furnace, connect the air extraction pipe on the package cover to the high vacuum air extraction system, and use the muffle furnace to heat and degas the package assembly at 600°C as a whole. After degassing for 2 hours, the vacuum degree during the process should be better than 3×10-3Pa. The air extraction tube on the envelope cover is heated and sealed three times in sequence from near to far from the envelope assembly.

Diffusion connection was carried out in a hot isostatic pressing machine after being heated and sandwiched. The hot isostatic pressing temperature was 850° C., the pressure was 130 MPa, and the time was 3 hours.

After the workpiece in the hot isostatic pressing machine is at room temperature, the jacket is removed to obtain a hot isostatic pressing diffusion connector, and the tensile strength of the connector is 80 MPa.

The interface of the HIP diffusion connector prepared in this example has been oxidized, mainly because the temperature to be welded has been oxidized due to the high temperature during the overall sealing and welding of the envelope; It is still difficult to desorb completely.

If the soldering temperature is too low, the interdiffusion of interface elements is insufficient, and the connection strength is low.

The above-mentioned embodiment is only one of the preferred embodiments of the present invention, and should not be used to limit the protection scope of the present invention. If the technical problem is still consistent with the present invention, it should be included within the protection scope of the present invention.

Claims (8)

1. A hot isostatic pressing diffusion connection method of tungsten/transition layer/stainless steel is characterized in that pure tungsten, the transition layer and stainless steel are used as raw materials, and hot isostatic pressing treatment, stress relief annealing and de-wrapping are carried out after wrapping treatment, so that a hot isostatic pressing diffusion connection piece can be obtained; the method comprises the following steps:

step 1, assembling: sequentially filling pure tungsten, the transition layer and the stainless steel into a sheath;

step 2, welding: welding the sheath assembled in the step 1 with a sheath cover with an exhaust tube to manufacture a sheath assembly;

and step 3, leak detection: detecting leakage of the sheath assembly prepared in the step 2;

step 4, thermal degassing: placing the sheath assembly qualified in the leak detection in the step 3 into a muffle furnace for thermal degassing;

and step 5, sealing: heating and clamping the exhaust pipe on the sheath assembly after the step 4;

step 6, hot isostatic pressing connection: placing the sheath assembly processed in the step 5 in a hot isostatic pressing machine, and performing diffusion connection on tungsten steel sealed in the sheath;

step 7, stress relief annealing: when the temperature of the workpiece in the hot isostatic pressing machine is reduced to 500-600 ℃, the return gas is uniformly pressurized to normal pressure, and then the heat is preserved and the stress is removed for annealing;

step 8, removing the sheath: turning the sheath assembly annealed in the step 7 to remove sheath materials to obtain the hot isostatic pressing diffusion connecting piece;

the transition layer is selected from one of single transition layers of copper foil, nickel foil and titanium foil, or is a composite transition layer of copper foil and nickel foil;

when the transition layer is a copper foil, the hot isostatic pressing temperature in the step 6 is 1000-1050 ℃;

when the transition layer is a nickel foil, the hot isostatic pressing temperature in the step 6 is 1300-1350 ℃;

when the transition layer is a titanium foil, the hot isostatic pressing temperature in the step 6 is 1250-1350 ℃;

when the transition layer is a copper foil and nickel foil composite layer, the hot isostatic pressing temperature in the step 6 is 950-1050 ℃.

2. The method of hot isostatic pressing diffusion bonding of tungsten/transition layer/stainless steel according to claim 1, further comprising, before assembly, a surface treatment step: grinding and polishing the surfaces to be connected of the pure tungsten, the transition layer and the stainless steel to a mirror surface by using abrasive paper; and after polishing, ultrasonic cleaning is carried out for 10-30 minutes by alcohol and acetone in sequence.

3. The method of claim 1, wherein the pure tungsten is greater than 99.5% by mass tungsten, and the transition layer is greater than 99.8% by mass and has a thickness of 0.1mm to 0.5 mm.

4. The hip diffusion bonding method of W/T/stainless steel as claimed in claim 1, wherein the material of the sheath, sheath cover and exhaust tube is selected from any one of 08F iron sheet, 1Cr18Ni9Ti steel and 316L stainless steel.

5. The method of claim 1, wherein the welding in step 2 is argon arc welding in a low oxygen and low humidity argon shielded glove box; or electron beam welding in a high vacuum chamber.

6. The HIP method of claim 5, wherein step 2 is protection of H inside a glove box during argon arc welding₂Both the O content and the O content are lower than 10 ppm; step 2 is that when the electron beam welding is carried out, the vacuum degree in the high vacuum chamber is more than 4 multiplied by 10^-3Pa。

7. The method of claim 1, wherein the step of increasing the temperature is performed after the initial pressure is increased to 50MPa to 60 MPa; the heat preservation time is 30min to 120min, and the hot isostatic pressure is 130MPa to 160 MPa.

8. The method of claim 1, wherein in step 7, the annealing for stress relief is performed by holding the temperature for 30min after the return gas is pressurized to normal pressure.