CN108788436A - A kind of technique connecting fusion reactor material tungsten and steel using the diffusion of hydrogen metal is set - Google Patents

Abstract

The invention discloses a kind of using the technique for setting hydrogen metal diffusion connection fusion reactor material tungsten and steel, using the pure titanium for setting hydrogen in advance（Vanadium）And its alloy can both reduce welding temperature as buffer layer material, reduce the reaction product generated between transition zone and steel；Transition zone yield strength is reduced, is conducive to be sustained stress；Meet low activation requirement of the fusion reactor to material again, reduces intermediate layer material and generate brittleness reaction product reduction quality of connection with steel；Tungsten/steel Joining Technology method of intermediate layer material high temperature sustained release residual stress ability can be improved again.

Description

A process for joining fusion reactor materials tungsten and steel by hydrogen metal diffusion

technical field

The invention relates to a technique for joining fusion reactor materials tungsten and steel by using hydrogen-containing metal diffusion, belonging to the field of metal diffusion welding.

Background technique

The first wall components of the China Fusion Engineering Test Reactor (CFETR) and various foreign demonstration reactors (DEMO) are in a hydrogen isotope environment, and will withstand the 14MeV neutrons and other high-energy components generated by the reaction of deuterium (D) + tritium (T) Particles are irradiated, so the first wall components are mostly designed to connect plasma-facing materials (eg tungsten) and structural materials (eg low-activation ferritic/martensitic steels). However, tungsten and steel are two kinds of dissimilar metal materials with large differences in thermophysical properties. Not only the difference in linear expansion coefficient between the two is large, it will generate large thermal stress, and at the same time, it will also generate brittle reaction products that weaken the welding performance of joints.

In the current research status at home and abroad, the solid phase diffusion welding process with the addition of an intermediate transition layer is a relatively promising tungsten/steel connection technology. However, the choice of intermediate layer material is a big problem, because the intermediate layer should not only improve the welding performance of tungsten/steel, such as connection strength, interface reaction products, thermal stress release effect, etc., but also need to be able to adapt to the harsh future The service environment of the first wall material of the fusion reactor: (1) The D+T reaction produces 14MeV neutrons, requiring low activation of material elements to meet the standard of low-emission nuclear waste; (2) The hydrogen isotope environment inside the fusion reactor requires materials Brittle fracture does not occur in the atmosphere; (3) D, T impurity particle flow requires the material to have good thermal shock resistance under plasma irradiation conditions.

However, none of the intermediate layer materials currently used for tungsten/steel connections can meet the above requirements:

(1) The effective connection of tungsten/steel can be realized by using Ni, Cu and other metals. Ni and Cu have high thermal conductivity. Using Ni and Cu can even obtain high-quality tungsten/steel joints with small interfacial residual stress and no reaction products. However, both are highly active elements and are not suitable for low activation in future fusion reactors. Material needs.

(2) Ti, V and other low-activation metals can also realize the connection of tungsten/steel, but compared with Ni and Cu, pure metal Ti, V and steel are easy to form FeTi ₂ when welding at higher temperature (≥900℃), V ₂ C and other brittle reaction products weaken the joint performance.

Taking pure titanium as an example, the structure of pure titanium at room temperature is α-Ti structure, and the main elements in steel, such as Fe and Cr, have the same crystal structure as high-temperature phase β-Ti elements, so the solubility of Fe and Cr in β-Ti is relatively low. High, but low solubility in α-Ti. The transition temperature from α-Ti to β-Ti is about 880°C. If higher temperature welding is used, Ti and steel will easily form brittle reaction products. If lower temperature welding is used, the diffusion between Ti and steel will be weakened.

At the same time, the yield strength of the transition layer will affect the slow release of residual stress between tungsten and steel. Compared with Cu and Ni metals, the yield strength of Ti is relatively high, which is not conducive to the slow release of residual stress.

However, Ti and V elements meet the requirements of low-activation materials for fusion reactors. Therefore, it is of great significance to improve the performance of Ti or V metals and make them meet the welding requirements of tungsten and steel for the continuous operation of fusion reactors.

For a long time, it was believed that hydrogen would cause embrittlement of Ti metal, but research in recent years has shown that:

(1) From the Ti-H phase diagram, it can be seen that H is a strong β-Ti stabilizing element, which can significantly reduce the phase transition temperature of α-β Ti (from ~880°C to ~330°C), which has It is beneficial to reduce the connection temperature of tungsten/titanium/steel and reduce the appearance of brittle reaction products between Ti and steel. The formation of β-Ti can promote the diffusion between Ti and steel, improve the connection strength, and make up for the influence of lower welding temperature on diffusion to a certain extent.

(2) Adding a small amount of hydrogen to titanium and its alloys can improve the processing performance and flow stress of Ti, and reduce the yield strength, which is conducive to the release of residual stress.

(3) As a temporary alloying element, the presence of hydrogen in titanium is reversible, and the dissolved hydrogen isotope in Ti can be removed by annealing.

Therefore, the use of hydrogen-absorbing titanium alloy as the transition layer material can well meet the low activation requirements of fusion reactors, and at the same time solve the problem of brittle reaction products between tungsten/titanium/steel and weak diffusion between titanium/steel. Larger yield strength is unfavorable for slow release of residual stress and other issues. Solid-phase diffusion welding of tungsten and steel using hydrogen-containing titanium (vanadium) alloy as the transition layer material is a potential method for connecting tungsten and steel, the first wall material of a fusion reactor.

Contents of the invention

The present invention aims to solve the problems that commonly used pure metal transition layers such as nickel and copper cannot be used in fusion reactor components as low activation materials in the prior art; titanium, vanadium, etc. are easy to form brittle reaction products with steel, and the yield strength of titanium metal is relatively high. . Provided is a new type of hydrogen-absorbing metal intermediate layer, which can not only meet the requirements of low activation of fusion reactor materials; reduce the generation of brittle reaction products with steel;

The present invention is achieved through the following technical solutions:

A process for connecting fusion reactor material tungsten and steel by hydrogen metal diffusion, characterized in that the process steps are:

1) Prepare the tungsten, steel and non-hydrogen transition layer materials required for solid phase diffusion welding, and grind and polish the surfaces to be welded of tungsten, steel and transition layer materials, so that the tungsten, steel and transition layer materials The surface roughness of the surface to be welded is lower than Ra≤3.2μm, cleaned after grinding and polished and vacuum packaged for use;

2) The transition layer material obtained above is preset into a hydrogen-absorbing alloy with a mass fraction of 0-1 wt% by a solid-state hydrogen-absorbing method;

3) Place the hydrogen-containing alloy in the middle of the tungsten sheet and the steel block to be superimposed on each other, and perform welding treatment by solid-phase diffusion welding methods such as vacuum hot pressing or hot isostatic pressing, to obtain welded workpieces;

4) The vacuum annealing method is used to dehydrogenate the welded workpiece to realize the connection of the fusion reactor material tungsten and steel.

The process for joining fusion reactor material tungsten and steel by hydrogen metal diffusion is characterized in that the steel is low-activation ferrite/martensitic (RAFM) steel or other low-activation steel.

The process for joining fusion reactor material tungsten and steel by hydrogen metal diffusion is characterized in that the transition layer material is titanium, vanadium, titanium alloy or vanadium alloy.

The process for connecting fusion reactor material tungsten and steel by hydrogenation metal diffusion is characterized in that: the solid-state hydrogenation method in step 2) is to place the transition layer material in a heating furnace, and the filling pressure is 200Pa-0.1 MPa of high-purity hydrogen, the temperature rises to accelerate the diffusion of hydrogen in the transition layer material, the holding temperature is 200°C-700°C, and the holding time is 1-10h to obtain a hydrogen-absorbing alloy.

A process for joining fusion reactor materials tungsten and steel by hydrogen metal diffusion, characterized in that: in step 3), the process parameters when using vacuum hot pressing are: vacuum degree ≤ 10 ^-2 Pa, welding temperature 600°C-1050°C , holding time 0.5-6h, welding pressure 5-20MPa.

The process for joining fusion reactor materials tungsten and steel by hydrogen metal diffusion is characterized in that: in step 3), when the hot isostatic solid-phase diffusion welding method is used, a machined sheath is required, and the sheath includes a box body and top cover; put the hydrogen-preserved alloy in the middle of the tungsten sheet and the steel block and put them into the package, and seal the box body and the top cover by electron beam or argon arc welding, Then put the obtained sheath as a whole into the hot isostatic pressing machine for hot isostatic pressing treatment, the heat preservation temperature is 600°C-1050°C, the welding pressure is 100-200MPa, and the heat preservation time is 0.5-6h; the sheath is removed after hot isostatic pressing , to obtain the welded workpiece.

The process for connecting tungsten and steel as the first wall material of a fusion reactor is characterized in that: in step 3), molybdenum sheets are placed on the outer surfaces of both the tungsten sheet and the steel block.

The process for joining fusion reactor material tungsten and steel by hydrogen metal diffusion is characterized in that: after the hydrogen removal treatment in step 4), the solid phase diffusion joint temperature is higher than the austenitization temperature of the steel. Post-weld heat treatment is also required.

The fusion reactor material tungsten, steel and transition layer materials all need to meet the requirements of low activation materials, the steel material is low activation ferrite/martensitic (RAFM) steel or other low activation steel, and the transition layer material is titanium ( vanadium) and its alloys. The hydrogen-inserting metal is a metal containing a certain amount of hydrogen obtained by putting hydrogen into the metal as a temporary alloying element.

The material of the transition layer is preset into a hydrogen storage alloy with a certain mass fraction (0-1 wt%) by solid or liquid hydrogen storage method, and the hydrogen storage process varies with the transition layer material.

The vacuum annealing method is used to dehydrogenate the joined tungsten/hydrogen-absorbing metal/steel workpiece, and the dehydrogenation process is related to the selected hydrogen-absorbing metal.

For workpieces whose solid phase diffusion bonding temperature is higher than the austenitizing temperature of the steel, post-weld heat treatment is required to restore the structure and properties of the steel after dehydrogenation.

The beneficial effects of the present invention are:

The use of pre-hydrogenated pure titanium (vanadium) and its alloys as the transition layer material can not only reduce the welding temperature, reduce the reaction products between the transition layer and steel; reduce the yield strength of the transition layer, which is conducive to the slow release of stress; and meet Fusion reactors have low activation requirements for materials. Therefore, it can well solve the difficulties existing in the prior art, and it is a very potential method for connecting fusion reactor materials tungsten and steel.

Description of drawings

Fig. 1 is a structural schematic diagram of the middle layer structure of the present invention.

Fig. 2 is a schematic diagram of assembly when vacuum hot pressing is used in the present invention.

Fig. 3 is a schematic diagram of the hot isostatic pressing jacket in the present invention.

Detailed ways

Taking the China Fusion Engineering Test Reactor (CFETR) water-cooled ceramic cladding (WCCB) first wall (FW), tungsten and low-activation steel vacuum thermocompression welding as an example for further explanation.

As shown in Figure 1 and Figure 2, a manufacturing process suitable for the connection between tungsten and steel of the first wall part of the fusion reactor, the process steps are:

1) Machining the tungsten sheet 1 required for vacuum thermocompression welding, the steel block 2 and the transition layer metal pure titanium sheet 3 to be hydrogenated, as shown in FIG. 1 . The surface roughness of the surface to be welded was finely ground to ≤ Ra 0.8 μm, and the sample was placed in an acetone solution at 35°C for 30 minutes to remove surface grease and dirt. After taking it out, it was vacuum-packed for use.

2) The processed titanium sheet 3 is subjected to vacuum annealing treatment, the vacuum degree is ≤10 ⁻⁴ Pa, the annealing temperature is 700° C., and the annealing time is 5 hours to remove water, hydrogen and other gases in the titanium sheet 3 .

3) Before hydrogenation, the titanium sheet 3 is weighed with a precision balance with an accuracy of 10 ⁻⁵ g, and after weighing, the annealed titanium sheet 3 is placed in a vacuum furnace by a solid-state hydrogenation method. First fill in a certain pressure of high-purity hydrogen 200Pa-0.1MPa, then increase the temperature to accelerate the diffusion of hydrogen in titanium metal, the holding temperature is 200°C-700°C, and the holding time is 1-10h. Control the content of hydrogen in the metal (0-1 wt%) by changing the gas pressure, holding temperature, holding time, etc.

4) The titanium sheet 3 after hydrogenation is weighed again to measure the content of hydrogen in the titanium metal.

5) Combining the titanium sheet 3 with a certain hydrogen content, the tungsten sheet 1 and the steel block 2 into a vacuum hot press machine for hot pressing. The vacuum degree of vacuum hot pressing needs to be ≤10 ^-2 Pa, the holding temperature is 600°C-1050°C, and the welding pressure is 5-20MPa. In order to prevent the pressure head of the hot press from sticking to the tungsten sheet 1 and the steel block 2, a piece of molybdenum sheet 4 is placed on the tungsten sheet 1 and below the steel block 2, as shown in Fig. 2 .

6) Put the welded workpiece into a vacuum annealing furnace for dehydrogenation treatment, and the dehydrogenation standard process needs to be formulated for the titanium material used.

7) If the welding temperature is higher than ~760 °C, post-weld heat treatment is required for the welded parts, and the heat treatment parameters are the same as the heat treatment system of the low-activation steel used.

8) If the hot isostatic welding method is adopted, the process steps 1)-4) are similar to the vacuum hot pressing method. In addition to preparing the workpiece, it is also necessary to prepare a sheath, which is used to fix the workpiece and prevent oxidation. Tooling, as shown in Figure 3.

9) After machining the sheath, put the workpiece into the sheath according to the method shown in Figure 1, and weld the package with electron beam or argon arc welding. The package includes a box body 5 and a top cover 6; the hydrogenated alloy after hydrogenation is placed in the middle of the tungsten sheet and the steel block and then put into the package, and the box body is welded by electron beam or argon arc welding. After being packaged with the top cover, the obtained package is sent as a whole into a hot isostatic pressing machine for hot isostatic pressing treatment by the action of the pressure head 7 .

10) Send it into a hot isostatic pressing machine for hot isostatic pressing, the system is similar to vacuum hot pressing step 5), and the pressure is 100-200MPa.

11) After hot isostatic pressing, the sheath needs to be removed and processed according to steps 6) and 7) of vacuum hot pressing.

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the art should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description are only the principles of the present invention. Variations and improvements, which fall within the scope of the claimed invention. The scope of protection required by the present invention is defined by the appended claims and their equivalents.

Claims (8)

1. a kind of using the technique for setting hydrogen metal diffusion connection fusion reactor material tungsten and steel, which is characterized in that processing step is：

Tungsten, steel and the buffer layer material for not setting hydrogen needed for solid-state diffusion welding are prepared, and to tungsten, steel and buffer layer material Surface to be welded carry out grinding and polishing processing, make the surface to be welded of tungsten, steel and buffer layer material surface roughness be less than Ra≤3.2 μm, simultaneously Vacuum Package is for use for cleaning after grinding and polishing；

It is that 0-1 wt% set hydrogen alloy that buffer layer material obtained above is set hydrogen methods to preset to mass fraction with solid-state；

The centre for setting hydrogen alloy and being placed in leaf and bloom is superimposed with each other, using solids control equipments such as vacuum hotpressing or hot isostatic pressings It connects method and carries out soldering, the workpiece after being welded；

Dehydrogenation is carried out to the workpiece after welding using vacuum annealing method, realizes the connection of fusion reactor material tungsten and steel.

2. it is according to claim 1 a kind of using the technique for setting hydrogen metal diffusion connection fusion reactor material tungsten and steel, it is special Sign is：The steel is low activation ferrite/martensite（RAFM）Steel or other low activation steels.

3. it is according to claim 1 a kind of using the technique for setting hydrogen metal diffusion connection fusion reactor material tungsten and steel, it is special Sign is：The buffer layer material is titanium, vanadium, titanium alloy or vanadium alloy.

4. it is according to claim 1 a kind of using the technique for setting hydrogen metal diffusion connection fusion reactor material tungsten and steel, it is special Sign is：Step 2）It is that buffer layer material is placed in heating furnace that middle solid-state, which sets hydrogen method, and it is 200Pa-0.1MPa's to be filled with pressure High-purity hydrogen, diffusion of the heating acceleration hydrogen in buffer layer material, 200 DEG C -700 DEG C, soaking time 1-10h of holding temperature, It obtains setting hydrogen alloy.

5. it is according to claim 1 a kind of using the technique for setting hydrogen metal diffusion connection fusion reactor material tungsten and steel, it is special Sign is：Step 3）It is middle to use technological parameter when vacuum hotpressing for vacuum degree≤10^-2Pa, 600 DEG C -1050 DEG C of welding temperature, Soaking time 0.5-6h, welding pressure 5-20MPa.

6. it is according to claim 1 a kind of using the technique for setting hydrogen metal diffusion connection fusion reactor material tungsten and steel, it is special Sign is：Step 3）In, it needs to machine jacket when welding method using hot isostatic pressing solid-state diffusion, jacket includes box body and top Lid；By set after hydrogen set hydrogen alloy be placed in leaf and bloom centre be superimposed with each other after be put into jacket, and pass through electron beam Or after argon arc welding encapsulates box body and head cover, then obtained jacket is integrally sent into hot isostatic press and is carried out at hot isostatic pressing Reason, 600 DEG C -1050 DEG C, welding pressure 100-200MPa, soaking time 0.5-6h of holding temperature；Hot isostatic pressing removes packet later Set, the workpiece after being welded.

7. a kind of fusion reactor plasma facing material tungsten according to claim 1 and steel Joining Technology, it is characterised in that：Step 3） In, it is placed with molybdenum sheet in leaf and bloom lateral surface.

8. it is according to claim 1 a kind of using the technique for setting hydrogen metal diffusion connection fusion reactor material tungsten and steel, it is special Sign is：Step 4）It, need to also be into higher than the workpiece of the austenitizing temperature of steel to diffusion welding temperature after middle dehydrogenation Row post weld heat treatment.