CN103480846B - Connecting method for sintering/welding titanium-steel dissimilar metal - Google Patents

Abstract

The invention discloses a connecting method for sintering/welding titanium-steel dissimilar metal. The differences of physical properties of the titanium and the steel which are dissimilar metal are large, and the titanium and the steel are hard to connect through conventional methods. According to the connecting method, firstly, the titanium or titanium alloy, V-Cu gradient alloy powder C1, C2 and C3 and stainless steel are placed in a die one by one to be pressed in advance, and secondly, the die is placed in a sintering device to be sintered in a spark plasma mode, wherein the V-Cu gradient alloy powder C1, C2 and C3 are composed of mixed powder which is formed by mixing a plurality of kinds of metal powder according to different proportions, and the expansion factor gradient of the V-Cu gradient alloy powder C1, the expansion factor gradient of the V-Cu gradient alloy powder C2 and the expansion factor gradient of the V-Cu gradient alloy powder C3 are matched with one another. The titanium or the titanium alloy and the stainless steel are directly connected and formed at a time in a sintering mode, the method of spark plasma sintering is particularly suitable for sintering molding of V-Cu gradient connectors of the titanium and the stainless steel, and a titanium-steel dissimilar metal sintering/welding connector can have a high mechanical property.

Description

A kind of connection method of titanium-steel dissimilar metal sintering/welding

technical field

The invention belongs to the field of metal processing, and in particular relates to a sintering/welding connection method of titanium-steel dissimilar metals.

Background technique

The difference in physical and chemical properties between titanium alloy and stainless steel is very large, and it is very difficult to obtain a good connection joint. At present, electron beam or laser beam and intermediate metal foil transition layer are mostly used at home and abroad for titanium alloy-stainless steel fusion welding connection, but it is still difficult to avoid the generation of brittle intermetallic compounds and stress in the joint, and the joint strength is still difficult to reach 0.7 of the base metal strength. times; at home and abroad, titanium alloy-stainless steel solid-phase welding (diffusion welding, friction welding, explosive welding, hot isostatic pressure diffusion welding) with a single or composite metal foil as the intermediate layer is also widely used. These welding methods have generally achieved good results. Some progress has been made, but the overall welding effect is not very satisfactory, and there are a series of technical issues that need further research.

Spark plasma sintering (Spark Plasma Sintering or SPS), also known as plasma activated sintering (Plasma Activated Sintering or PAS), is a new technology developed in recent years, which can realize rapid sintering of dense materials at lower temperatures and can be used to prepare nano-blocks Bulk materials, amorphous bulk materials, composite materials, gradient materials, etc. Since the composition of the gradient material changes gradually and the sintering temperature of each layer is different, it is difficult to sinter in one time by using the traditional sintering method. Gradient blanks with different composition ratios can be sintered into gradient materials at one time in the temperature gradient field. The sintering time is generally only a few minutes. Gradient materials that have achieved good sintering effects are: stainless steel/ZrO2 gradient materials; PSZ/Ti gradient materials, etc.

At present, no one at home and abroad has applied spark plasma sintering technology to the welding connection of dissimilar metals. Besides the discharge plasma technology, there is currently no welding or sintering technology that can realize the one-time welding and sintering of titanium-steel dissimilar metals plus gradient joints, and the gradient transition of the obtained gradient joints is not uniform enough, and the gradient layer interface is small in size. Layers are difficult to control.

Contents of the invention

The object of the present invention is to provide a titanium-steel dissimilar metal sintering/welding connection method and a gradient joint suitable for titanium-steel dissimilar metal connection to solve the problems existing in the prior art.

The technical solution to realize the purpose of the present invention is: a gradient joint suitable for the connection of titanium-steel dissimilar metals, using a V-Cu-based gradient alloy as the gradient joint for titanium-steel dissimilar metal connections, wherein the V-Cu-based gradient alloy C1 , C2, and C3 are composed of mixed powders with gradient matching expansion coefficients obtained by mixing various metal powders in different proportions. The contents of vanadium powder in C1, C2, and C3 are 50% to 60%, 25% to 30%, and 10% respectively. %~20%; the content of copper powder in C1, C2, and C3 is 25%~35%, 50%~60%, and 65%~75% respectively; the content of nickel, aluminum, and chromium metal powder in C1, C2, and C3 Both are 3%~10%, and the expansion coefficients of C1, C2, and C3 are: 9.5~10.5X10 ^-6 .K ^-1 , 11.5~12.5X10 ^-6 .K ^-1 , 13.5~14.3X10 ^-6 .K ^-1 .

The titanium connected with the V-Cu-based gradient alloy powder in the present invention is titanium or its alloy; the steel connected with the V-Cu-based gradient alloy powder is stainless steel.

A titanium-steel dissimilar metal connection sintering/welding method. Firstly, titanium and its alloys are placed in a mold and pre-pressurized, and then V-Cu-based gradient alloy powders C1, C2, and C3 are placed in the mold one by one and pre-pressurized. Press, then put the stainless steel in the mold and pre-pressurize, and finally put the mold in the sintering equipment for spark plasma sintering.

In the discharge plasma sintering process of the present invention, the sintering temperature is 825°C-950°C, the sintering pressure is 40-50MPa, and the holding time is 10-15min.

The titanium or its alloys and stainless steel described in the present invention are bulk or powder.

The particle size of the titanium or its alloy powder, V-Cu-based gradient alloy powder and stainless steel powder in the present invention is between 300 mesh and 500 mesh.

The titanium or its alloy powder and the stainless steel powder described in the present invention are all processed by ball milling, the mass ratio of ball to material is 10:1, the rotating speed is 200r/min, and the ball milling time is 6h.

In the V-Cu-based gradient alloy powder described in the present invention, all the metal powders except the low-melting point metal powder are ball-milled, the ball-to-material mass ratio is 10:1, the rotating speed is 200r/min, and the ball-milling time is 6h.

The mold of the present invention adopts the hollow cylindrical shape processed by ISO-63 graphite rod.

Compared with the prior art, the present invention has the following remarkable advantages: First, the sintering temperature is low and the sintering time is short by adopting the spark plasma sintering technology (SPS for short), which can obtain a fine and uniform structure, and can effectively control the connection interface diffusion layer Thickness, to achieve gradient uniformity of the sintered body. In addition, using this technology, the connection conditions are well controllable, the process is simple, and the heat consumption is small; second, in the present invention, the sintered metal powder does not need a binder for bonding, and the powder is directly loaded into the sintered powder in sequence according to the gradient relationship. The mold is sufficient, and only one sintering is required to obtain a sintered body. Third, the use of mixed powder with a gradient transition in composition and linear expansion coefficient as the intermediate layer can effectively prevent problems such as brittle phase cracking caused by thermal stress and phase transformation stress caused by sudden changes in composition and large differences in expansion coefficient when titanium and steel are directly connected. Thereby solving the problems of poor connectability between titanium and titanium alloys and stainless steel, low joint strength, low thermal fatigue life, difficult welding process, and poor joint reliability. Fourth, add mixed powder to connect titanium and titanium alloys with stainless steel. By adjusting the powder composition and distribution, the isolation of titanium and iron elements can be achieved, the formation of brittle phases can be reduced, and the distribution of brittle phases can be optimized. The addition of alloying elements improves the plastic toughness of the brittle phase. Therefore, the use of this technology for the connection of titanium-steel combines the advantages of solid-phase welding and powder composition adjustment, which not only avoids the combination of excessive titanium and iron elements and the growth of grains under fusion welding conditions, but also can pass the powder The role of alloying elements in the alloy can inhibit the interdiffusion between brittle phase-forming elements, improve the plasticity and toughness of brittle phases, minimize the segregation of alloy components, and eliminate coarse and uneven casting structures.

Detailed ways

Below in conjunction with embodiment the present invention is described in further detail.

Example 1

The gradient joint is a V-Cu-based gradient alloy, in which vanadium metal and copper metal are the main components. Titanium or its alloy adopts TC4 titanium alloy block, stainless steel adopts 316L stainless steel block, and the expansion coefficient of TC4 titanium alloy block, 316L stainless steel block and V-Cu-based gradient alloy is matched in a gradient change. In order to make the two ends of the V-Cu-based gradient alloy have good connection with the TC4 titanium alloy block and the 316L stainless steel block, the V-Cu-based gradient alloy is mixed with a variety of metal powders in different proportions to form a mixed powder with a gradient matching expansion coefficient The composition is set according to the following gradient: C1+C2+C3, wherein the C1 mixed powder is connected to one side of the TC4 titanium alloy block, the C3 mixed powder is connected to the side of the 316L stainless steel block, and the composition of the C1 mixed powder is: nickel 5%, Vanadium 53.0%, copper 32.0%, aluminum 5%, chromium 5%; C2 mixed powder composition: nickel 5%, vanadium 28.0%, copper 57.0%, aluminum 5%, chromium 5%; C3 mixed powder composition: nickel 5% %, vanadium 13.0%, copper 72.0%, aluminum 5%, chromium 5%.

The above-mentioned calculation of the gradient matching of the expansion coefficient of the mixed powder adopts the empirical equation for calculating the average linear expansion coefficient of polycrystalline, multi-phase or composite materials proposed by Turner after model analysis. According to the calculation, the theoretical linear expansion coefficient at 20℃—100℃ is C1: 11.51X10 ^-6 .K ^-1 , C2: 13.0X10 ^-6 .K ^-1 , C3: 14.7X10 ^-6 .K ^-1 , TC420℃— The coefficient of linear expansion at 100°C is 7.89X10 ^-6 .K ^-1 , and that of 316L at 20°C—100°C is 16X10 ^-6 .K ^-1 .

The TC4 titanium alloy block and the 316L stainless steel block are mechanically polished, derusted and decontaminated.

The gradient powders C1, C2, and C3 of the mixed powder are first ball milled. The steps are: firstly, other gradient powders except low melting point metal aluminum are ball milled and mixed. The ball milling time is 6 hours; secondly, low-melting-point metal aluminum is added to each gradient powder and mixed mechanically and uniformly.

The TC4 titanium alloy block, the mixed powder, and the 316L stainless steel block are sequentially loaded into the hollow cylindrical mold processed by the ISO-63 graphite rod according to the gradient relationship. The shape and size are matched, and the end surface is flat. When the powder is loaded into the mold, the TC4 titanium alloy block is first loaded, and then the C1 mixed powder, C2 mixed powder, and C3 mixed powder are added in sequence, and each time the mixed powder is added, a pre-pressurization is required. , and finally add a 316L stainless steel block, pre-pressurize and cover the indenter, and conduct spark plasma sintering to prepare samples. The sintering temperature is 900 ° C, the sintering pressure is 45 MPa, and the holding time is 15 minutes. The resulting sintered sample has a density of not less than 90% and a strength of not less than 450MPa.

Example 2

The gradient joint is a V-Cu-based gradient alloy, in which vanadium metal and copper metal are the main components. Ti metal powder is used for titanium or its alloy, and 316L stainless steel powder is used for stainless steel. The expansion coefficient of Ti metal powder, 316L stainless steel powder and V-Cu-based gradient alloy is matched in a gradient change. In order to make the two ends of the V-Cu-based gradient alloy have good connection with Ti metal powder and 316L stainless steel powder, the V-Cu-based gradient alloy is composed of a mixed powder with a gradient matching expansion coefficient obtained by mixing various metal powders in different proportions. The following gradient setting is: C1+C2+C3, where C1 mixed powder is connected to one side of Ti metal powder, C3 mixed powder is connected to one side of 316L stainless steel powder, and the composition of C1 mixed powder is: nickel 5%, vanadium 60%, copper 25 %, aluminum 5%, chromium 5%; C2 mixed powder composition is: nickel 5%, vanadium 35%, copper 50%, aluminum 5%, chromium 5%; C3 mixed powder composition is: nickel 5%, vanadium 20%, Copper 65%, Aluminum 5%, Chromium 5%.

The above calculation of the gradient matching of the expansion coefficient of the mixed powder adopts the empirical equation for calculating the average linear expansion coefficient of polycrystalline, multiphase or composite materials proposed by Turner after model analysis. According to the calculation, the theoretical linear expansion coefficient at 20°C-100°C is C1: 9.8X10 ^-6 .K ^-1 , C2: 11.7X10 ^-6 .K ^-1 , C3: 13.5X10 ^-6 .K ^-1 , Ti20°C— The coefficient of linear expansion at 100°C is 7.89X10 ^-6 .K ^-1 , and that of 316L at 20°C—100°C is 16X10 ^-6 .K ^-1 .

The Ti metal powder and 316L stainless steel powder were ball milled in advance, the mass ratio of the ball to material was 10:1, and the ball milling time was 6h at a rotational speed of 200r/min.

The gradient powders C1, C2, and C3 of the mixed powder are first ball milled. The steps are: firstly, other gradient powders except low melting point metal aluminum are ball milled and mixed. The ball milling time is 6 hours; secondly, the low-melting-point metal aluminum is added to each gradient powder and mixed mechanically and uniformly.

Put Ti metal powder, mixed powder, and 316L stainless steel powder into the hollow cylindrical mold processed by ISO-63 graphite rod in sequence according to the gradient relationship. Matching, and the end surface is flat. When the powder is loaded into the mold, the Ti metal powder is first loaded, and then the C1 mixed powder, C2 mixed powder, and C3 mixed powder are added in sequence, and each time the mixed powder is added, a pre-pressurization is required, and finally 316L stainless steel is added. The block powder is pre-pressurized and covered with a pressure head, and the sample is prepared by spark plasma sintering. The sintering temperature is 850°C, the sintering pressure is 40MPa, and the holding time is 12min. . The resulting sintered sample has a density of not less than 85% and a strength of not less than 250MPa.

Example 3

The gradient joint is a V-Cu-based gradient alloy, in which vanadium metal and copper metal are the main components. Titanium or its alloy adopts TC4 titanium alloy block, stainless steel adopts 304SS stainless steel block, and the expansion coefficient of TC4 titanium alloy block, 304SS stainless steel block and V-Cu-based gradient alloy is gradiently matched. In order to make the two ends of the V-Cu-based gradient alloy have good connection with the TC4 titanium alloy block and the 304SS stainless steel block, the V-Cu-based gradient alloy is mixed with a variety of metal powders in different proportions to form a mixed powder with a gradient matching expansion coefficient The composition is set according to the following gradient: C1+C2+C3, wherein the C1 mixed powder is connected to one side of the TC4 titanium alloy block, the C3 mixed powder is connected to the side of the 316L stainless steel block, and the composition of the C1 mixed powder is: nickel 5%, Vanadium 53.0%, copper 32.0%, aluminum 5%, chromium 5%; C2 mixed powder composition: nickel 5%, vanadium 28.0%, copper 57.0%, aluminum 5%, chromium 5%; C3 mixed powder composition: nickel 5% %, vanadium 13.0%, copper 72.0%, aluminum 5%, chromium 5%.

The above-mentioned calculation of the gradient matching of the expansion coefficient of the mixed powder adopts the empirical equation for calculating the average linear expansion coefficient of polycrystalline, multi-phase or composite materials proposed by Turner after model analysis. According to the calculation, the theoretical linear expansion coefficient at 20℃—100℃ is C1: 11.51X10 ^-6 .K ^-1 , C2: 13.0X10 ^-6 .K ^-1 , C3: 14.7X10 ^-6 .K ^-1 , TC420℃— The coefficient of linear expansion at 100°C is 7.89X10 ^-6 .K ^-1 , and that of 316L at 20°C—100°C is 16X10 ^-6 .K ^-1 .

The TC4 titanium alloy block and the 304SS stainless steel block are mechanically polished, derusted and decontaminated.

The gradient powders C1, C2, and C3 of the mixed powder are first ball milled. The steps are: firstly, other gradient powders except low melting point metal aluminum are ball milled and mixed. The ball milling time is 6 hours; secondly, low-melting-point metal aluminum is added to each gradient powder and mixed mechanically and uniformly.

The TC4 titanium alloy block, the mixed powder, and the 304SS stainless steel block are sequentially loaded into the hollow cylindrical mold processed by the ISO-63 graphite rod according to the gradient relationship. The shape and size are matched, and the end surface is flat. When the powder is loaded into the mold, the TC4 titanium alloy block is first loaded, and then the C1 mixed powder, C2 mixed powder, and C3 mixed powder are added in sequence, and each time the mixed powder is added, a pre-pressurization is required. , and finally add a 304SS stainless steel block, pre-pressurize and cover the indenter, and carry out spark plasma sintering for sample preparation. The sintering temperature is 950°C, the sintering pressure is 45MPa, and the holding time is 15min. The density of the obtained sintered sample is not lower than 98%, and the strength is not lower than 300MPa.

Claims (7)

1. A connection method for titanium-steel dissimilar metal sintering/welding, characterized in that first titanium or its alloys are placed in the mold and pre-pressurized, followed by V-Cu base gradient alloy powder C1, C2, C3 one by one Put it in the mold and pre-pressurize it, then put the stainless steel in the mold and pre-press it, and finally put the mold in the sintering equipment for spark plasma sintering, wherein the contents of vanadium powder in the mixed powders of C1, C2 and C3 are respectively 50%～60%, 25%～30%, 10%～20%; the contents of copper powder in C1, C2 and C3 are respectively 25%～35%, 50%～60%, 65%～75%; C1, The contents of nickel, aluminum and chromium metal powder in C2 and C3 are all 3% to 10%, and the expansion coefficients of C1, C2 and C3 are respectively: 9.5 to 10.5X10 ^-6 .K ^-1 , 11.5 to 12.5X10 ^-6 .K ^-1 、13.5～14.3X10 ^-6 .K ^-1 . 2. The connection method of titanium-steel dissimilar metal sintering/welding according to claim 1, characterized in that in the spark plasma sintering process, the sintering temperature is 825°C-950°C, the sintering pressure is 40-50MPa, and the holding time 10-15min. 3. The sintering/welding joining method of titanium-steel dissimilar metals according to claim 1, characterized in that said titanium or its alloys and stainless steel are blocks or powders. 4. The connection method of titanium-steel dissimilar metals sintering/welding according to claim 1 or 3, characterized in that the particle size of said titanium or its alloys, V-Cu-based gradient alloy powder and stainless steel powder is between 300 mesh and 500 mesh between the eyes. 5. The connection method of titanium-steel dissimilar metals sintering/welding according to claim 1 or 3, characterized in that said titanium or its alloy and stainless steel powder are all processed by ball milling, and the mass ratio of ball to material is 10:1, The rotating speed is 200r/min, and the ball milling time is 6h. 6. The connection method of titanium-steel dissimilar metals sintering/welding according to claim 1, characterized in that in the described V-Cu base gradient alloy powder, other metal powders are all processed by ball milling except the low melting point metal powder aluminum , the mass ratio of ball to material is 10:1, the speed is 200r/min, and the ball milling time is 6h. 7. The sintering/welding joining method of titanium-steel dissimilar metals according to claim 1, characterized in that the mold is a hollow cylinder processed from ISO-63 graphite rods.