CN109014470B - Semi-solid state pressure reaction brazing method - Google Patents
Semi-solid state pressure reaction brazing method Download PDFInfo
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- CN109014470B CN109014470B CN201710440231.8A CN201710440231A CN109014470B CN 109014470 B CN109014470 B CN 109014470B CN 201710440231 A CN201710440231 A CN 201710440231A CN 109014470 B CN109014470 B CN 109014470B
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
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- B—PERFORMING OPERATIONS; TRANSPORTING
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- B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
- B23K1/00—Soldering, e.g. brazing, or unsoldering
- B23K1/19—Soldering, e.g. brazing, or unsoldering taking account of the properties of the materials to be soldered
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Abstract
The invention relates to a semi-solid state pressurized reaction brazing method, which adopts powder metal material as brazing filler metal, heats a weldment and the brazing filler metal to the semi-solid state temperature of the brazing filler metal, simultaneously applies pressure, keeps warm, forms weld metal and connection of the weld metal and a base metal through liquid phase wetting, atomic diffusion and chemical reaction, and completes the pressurized liquid phase reaction sintering process of the powder brazing filler metal. The semi-solid state pressurized reaction brazing method generates beneficial chemical reaction products in the welding process, improves the interface bonding state, improves the wettability of the brazing filler metal on the surface of the base metal, avoids harmful chemical reaction products, improves the weld joint structure and improves the shearing strength of the joint.
Description
Technical Field
The invention relates to a semi-solid state pressure reaction brazing method, and belongs to the technical field of welding.
Background
In 70% SiCpIn the process of welding the/Al composite material, the volume fraction of the SiC ceramic particle reinforced phase in the composite material is as high as 70 percent, so that the application of methods such as arc welding, electron beam welding, friction stir welding and the like in connection is greatly limited, and the brazing and diffusion welding methods become connection methods with relative potential. In 70% SiCpThe semi-solid state pressure reaction brazing method related by the invention is created in the process of brazing and diffusion welding research of the/Al composite material, and the brazing and diffusion welding technology is the closest technology to the semi-solid state pressure reaction brazing related by the invention.
The brazing is a method for connecting weldment by adopting brazing filler metal with a melting temperature lower than that of a base metal, adopting a welding temperature lower than a solidus line of the base metal and higher than a liquidus line of the brazing filler metal, wetting the base metal by the molten liquid brazing filler metal, filling a joint gap and mutually diffusing the joint gap and the base metal. When brazing, the brazing filler metal melts into liquid state and the base material keeps solid state, and the liquid brazing filler metal wets, flows in a capillary way, and flows in a capillary way,Filling, spreading, interacting with the parent metal (dissolution, diffusion or metallurgical bonding), cooling and solidifying to form a firm joint. 70% SiCpThe fact that the/Al composite material contains a large amount of SiC ceramic, the brazing filler metal is extremely difficult to wet on the surface of the SiC ceramic, which necessarily causes great difficulty in the application of brazing in the connection of the composite material. (Rong Wang, Cheng Dongfeng, niu Ji Tai. high volume fraction SiCpVacuum pressure brazing [ J ] of reinforced 6063 Al-based composite]Mechanical engineering materials 2014,38(9):34-38.) herein filled with Al70-Cu22.3-Si6.1-Mg1.6 paste solder to SiC with volume fraction of 60%pThe/6063 Al composite material is subjected to vacuum brazing, the wettability of the brazing filler metal to a bulk SiC reinforcing phase is general, a small gap exists between the brazing filler metal and the bulk SiC reinforcing phase, and the shear strength of a joint is 71.6 MPa. 70% SiCpThe SiC ceramic volume fraction contained in the Al composite material is higher, the welding is more difficult, and the joint strength is lower.
Diffusion welding is a process in which the surfaces to be joined are closely adhered at a certain temperature and pressure, the physical connection of the surfaces to be joined is enlarged by causing local microscopic plastic deformation or by a microscopic liquid phase generated at the surfaces to be joined, and then the atoms of the bonding layers are interdiffused for a certain time to form a reliable connection of the bonding interface. Diffusion bonding can be classified according to various criteria, with transient liquid phase diffusion bonding (TLP) being most similar to semi-solid pressure reaction brazing in accordance with the present invention. Transient liquid phase diffusion welding refers to a diffusion bonding method in which a trace amount of liquid phase appears in a joint region for a short time during diffusion bonding. In the diffusion welding process, the intermediate layer and the base metal are subjected to eutectic reaction to form an extremely thin liquid-phase film, and the liquid film is subjected to isothermal solidification and uniform diffusion treatment after filling the whole joint gap, so that a uniform diffusion welding joint is obtained. 70% SiCpThe Al composite material contains a large amount of SiC ceramic particles, most of the surface of the SiC ceramic particles are covered by the SiC particles, less of the surface of the SiC ceramic particles are exposed Al alloy matrix, the Al alloy matrix can form a liquid phase with the middle layer, even if the formed liquid film fills the whole joint gap, the SiC is extremely difficult to wet by the liquid phase, so that only weak connection can be formed between the eutectic liquid phase and the SiC particles, and the existence of a large amount of weak connection in the joint can lead to the fact thatThe mechanical property of the joint is poor, and the application of diffusion welding in the composite material welding also meets great difficulty.
Disclosure of Invention
The invention aims to provide a semi-solid state pressure reaction brazing method.
In order to solve the technical problems, the technical scheme is as follows:
a semi-solid state pressure reaction brazing method comprises the following specific steps:
and 4, extracting vacuum, and setting welding parameters: welding temperature T, heat preservation time T and pressure P;
and 6, cooling along with the furnace, and taking out the sample.
Further, in step 1, the solder preparation and DSC test steps are:
step 1.1, preparing a metal powder raw material according to a formula of a brazing filler metal, wherein the granularity of the metal powder is 200-300 meshes;
step 1.2, weighing metal powder raw materials according to a formula proportion, and mixing and stirring the raw materials;
step 1.3, ball milling the stirred brazing filler metal at the speed of 250r/min for 4-6 h;
step 1.4, performing DSC melting characteristic test on the solder subjected to ball milling, and recording the initial generation of liquid phaseTemperature T1Temperature T of complete melting2。
Further, in step 2, the preparation steps before welding are as follows:
step 2.1, placing 240# water grinding sand paper on a water grinding machine, and performing coarse grinding on the surface of the base material by utilizing the automatic rotation of the water grinding machine;
2.2, accurately grinding the surface of the test sample after coarse grinding by using 280, 320, 400 and 600# metallographic abrasive paper in sequence;
and 2.3, putting the polished sample into acetone for ultrasonic cleaning, and drying by cold air for later use.
In step 3, the assembling steps are as follows:
step 3.1, adopting smooth ceramic as a substrate, and coating a paste solder resist on the surface of the substrate;
step 3.2, placing the sample to be welded on a substrate, enabling the surface to be welded to face upwards, and filling powder brazing filler metal in the center of the surface to be welded;
step 3.3, placing the sample to be welded on the brazing filler metal, and tightly attaching the surface to be welded to the brazing filler metal;
step 3.4, placing a ceramic pressing block on the sample to be welded, and flattening and pressing;
and 3.5, supporting the ceramic substrate, and slowly putting the assembled sample and the pressing block together into the center of an objective table in the vacuum furnace.
In step 4, the process of setting the welding temperature T is as follows:
step 4.1, setting the welding temperature in the beneficial compound generation temperature interval T according to the components of the base metal and the brazing filler metal3～T4Wherein the temperature is not lower than T3Can generate beneficial intermetallic compounds at a temperature exceeding T4Intermetallic compounds are brittle;
step 4.2, according to the melting point of the parent metal, the temperature of the semi-solid state pressure reaction brazing is lower than the melting point T of the low-melting-point component in the parent metal0Continuing to narrow the welding temperature range to T3～Min(T0,T4)；
Step 4.3, according to the melting characteristics of the brazing filler metal and DSC test results, the melting interval of the brazing filler metal is T1～T2Reducing the welding temperature range to Max (T)1,T3)～Min(T0,T2,T4)。
Further, in step 4, the holding time t is determined, and t is the critical value tcCritical value tcThe critical time for achieving relative balance of pore reducing effect and pore enlarging effect of the Cokendall effect caused by the sintering structure of the brazing filler metal in the heating process is reached.
Furthermore, in step 4, step 4.6, the welding pressure is set to 10-15Mpa to ensure that the base material is not deformed.
Further, the base material was 70% SiCpa/Al composite material.
Further, the brazing filler metal is Ti-containing aluminum-based brazing filler metal.
Further, in step 3, the vacuum degree of the vacuum furnace reaches 3.3X 10-3-4.1×10-3Pa。
Compared with the prior art, the invention has the following remarkable advantages:
1. beneficial chemical reaction products are generated in the welding process, the interface bonding state is improved, and the wettability of the brazing filler metal on the surface of the base metal is improved.
2. Avoiding harmful chemical reaction products, improving the weld joint structure and improving the shearing strength of the joint.
3. The welding process is changed into a pressurized liquid phase reaction sintering process of the powder brazing filler metal, the requirement on the wettability of the brazing filler metal is reduced, and the method is particularly suitable for welding of the base metal difficult to wet.
4. Filling Ti-containing solder to 70% SiCpthe/Al composite material is subjected to semi-solid state pressure reaction brazing and can react on the surface of SiC particles to generate Ti7Al5Si12The compound improves the wettability of the brazing filler metal on the surface of the composite material and improves the interface bonding force; while avoiding TiAl3The generation of brittle compounds improves the weld structure and the joint strength. The shear strength of the joint reaches 90-140 MPa, which is about 6 times of that of the joint obtained during brazing.
Drawings
FIG. 1 is a micro-metallurgical process of a semi-solid pressure reaction brazing process; FIGS. 1a, 1b, and 1c show a first stage, a second stage, and a third stage, respectively;
FIG. 2 is a macro-metallurgical process of a semi-solid pressure reaction brazing process; FIGS. 2a, 2b, 2c, 2d show the stages of powder mixing, liquid phase formation and particle rearrangement, solid phase dissolution-precipitation, solid phase framework formation, respectively;
FIG. 3 is a solder melting characteristic curve with multiple solid-liquid phase temperature intervals;
FIG. 4 is 70% SiCpThe size and the assembly of a/Al composite material semi-solid state pressure reaction brazing sample are schematically shown;
FIG. 5 is 70% SiCpSEM microstructure diagram of/Al composite material semi-solid state pressure reaction soldered joint
FIG. 6 is a pictorial view of a 70% SiCp/Al composite diffusion bond.
Detailed Description
The invention provides a semi-solid state pressurized reaction brazing method, which adopts powder metal material as brazing filler metal, heats a weldment and the brazing filler metal to the semi-solid state temperature of the brazing filler metal, applies pressure at the same time, keeps the temperature, forms weld metal and connection between the weld metal and a base metal through liquid phase wetting, atomic diffusion and chemical reaction, and is essentially the pressurized liquid phase reaction sintering process of the powder brazing filler metal. Beneficial compounds are generated in the welding process, harmful compounds are avoided, the interface bonding state is improved, the weld joint structure is improved, and the joint shearing strength is improved.
The invention relates to semi-solid state pressurized reaction brazing, which is essentially a pressurized liquid phase reaction sintering process of powder brazing filler metal. The principle is as follows:
the semi-solid pressure reaction brazing according to the present invention can be microscopically divided into three stages, as shown in fig. 1.
The first stage is as follows: and (6) bonding. At the initial stage of the semi-solid state pressure reaction brazing, original contact points or surfaces among particles are converted into crystal combination under the action of pressure, and sintering necks are formed through atomic processes of nucleation, crystal growth and the like. At this stage, the grains within the granules are unchanged.
And a second stage: the sintering neck grows up, and liquid phase is formed and reacts with the chemical reaction. With the formation of the sintering necks in the first stage, a large number of atoms migrate to the grain junction surface to expand the sintering necks, and the inter-grain distances shrink to form a continuous network of pores. As the diffusion proceeds, chemical reactions take place where the components are appropriate to form a liquid phase; or a liquid phase is formed where the components are appropriate, and a chemical reaction occurs as atoms dissolve into the liquid phase. In summary, during this phase, the grains grow, the grain boundaries move across the pores, the pores disappear, the weld shrinks, the weld density and strength increase, and as the liquid phase forms and the chemical reaction progresses, the final chemical reaction product remains in the weld and forms a weld structure together with the base alloy.
And a third stage: closed cell spheroidisation and shrinkage. As the sintering progresses, most of the pores are completely separated quickly under the action of pressure, the number of closed pores is greatly increased, and the shape of the pores gradually tends to be spherical and is continuously reduced.
The semi-solid pressure reaction brazing according to the present invention can be macroscopically divided into several stages, as shown in fig. 2.
The first stage is as follows: liquid phase formation and particle rearrangement. When the temperature in the vacuum furnace rises to the eutectic temperature, a small amount of liquid phase is formed in the brazing filler metal, capillary force formed by the liquid phase in pores among the particles and pressure applied from the outside enable the liquid phase to generate viscous flow, so that the particles are adjusted in position and redistributed to achieve the tightest arrangement. At this stage, the density of the sintered body is increased more, and at the same time, some other atoms are diffused and dissolved into the liquid phase.
And a second stage: secondary liquid phase formation and pore filling. When the temperature is continuously increased to a new eutectic temperature, more eutectic liquid phases are formed in the areas where the fluctuation of the components in the brazing filler metal meets the eutectic requirement, the liquid phases fill the pores between the sintering necks under the action of pressure and capillary force, and the weld density is further increased. The secondary liquid phase forming and pore filling stages are not phenomena which can occur in all semi-solid pressurizing reaction brazing processes, and if the brazing filler metal is not formed with the second liquid phase in the whole thermal process, the semi-solid pressurizing reaction brazing does not have the secondary liquid phase flowing and pore filling stages; if the brazing filler metal forms a second, third or even more kinds of liquid phases at different temperatures, the semi-solid pressure reaction brazing at this time has two, three or even more liquid phase forming and pore filling stages.
And a third stage: solid phase dissolution-reprecipitation. The solid phase has a certain solubility in the liquid phase and diffusion transfer is a necessary condition for dissolution-reprecipitation. This process is generally characterized by a coarsening of the microstructure, otherwise known as Ostwald ripening. The solubility of the solid phase in the liquid phase varies with temperature and the shape and size of the particles. The solubility of small particles is higher than that of large particles, so that small particles dissolve preferentially, and corners and convex portions (having a larger curvature) of the particle surface also dissolve preferentially. In this case, the small particles tend to be reduced, and the particle surface tends to be flat and smooth; in contrast, a portion of the supersaturated atoms in the solution precipitate out on the surface of the macroparticle, tending to grow the macroparticle. This is the process of solid phase dissolution and precipitation, i.e. the migration of substances through the liquid phase. As a result of the dissolution and precipitation processes, the particles gradually tend to be spherical in shape, small particles gradually shrink or disappear, large particles grow larger, the particles are closer together in the process, and the whole sintered body shrinks.
A fourth stage: and (3) forming a solid-phase framework. After the action of the previous stages, the particles are mutually close, contacted and adhered to form a continuous framework, and the liquid phase is filled in the gaps of the framework. At this stage, the rigidity of the solid-phase skeleton prevents further rearrangement of the particles, so that the densification speed of the sintered body is significantly slowed. And the skeleton has more pores, even under the action of pressure, the pores can be reduced to a certain extent, and are difficult to completely disappear, and especially when the liquid phase is insufficient or cannot penetrate through tiny pores among particles for infiltration filling under the action of capillary force and external pressure, the pores can be further reduced only through atomic diffusion, and the effect is very small.
The semi-solid state is a generalized semi-solid state, brazing filler metal solid-liquid phase coexists during welding, and one of two modes can be selected to achieve the effect of the coexistence of the solid and the liquid phases. These two modes are: a) the brazing filler metal has a wider liquid phase generation interval, when the temperature is below a solidus line, the brazing filler metal is in a solid state, when the temperature is above a liquidus line, the brazing filler metal is in a liquid state, and the welding temperature is set between the solidus and liquidus temperatures; b) different from the middle-semisolid meaning of the common semisolid processing concept, the brazing filler metal has a plurality of liquid phase generation intervals, as shown in fig. 3, wherein 1, 2, 3, 4 and 5 respectively represent different solid-liquid phase temperature intervals, when the welding temperature is lower than the lowest temperature of the interval 1, no liquid phase appears in the whole welding process, when the welding temperature is higher than the liquidus temperature of the interval 5, the brazing filler metal is in a liquid state in the welding process, and when the welding temperature is between the solidus of the interval 1 and the liquidus of the interval 5, the brazing filler metal is in a solid-liquid coexisting state, namely semisolid state in the welding process. No matter which mode of semi-solid state is selected, a liquid phase and a solid phase exist in a welding seam in the welding process, and the purpose of the existence of the liquid phase is mainly to improve the atomic diffusion speed in the welding process, promote the particle rearrangement and promote the metallurgical bonding of the powder brazing filler metal.
The invention relates to a semi-solid state pressure reaction brazing method, which comprises the following specific steps:
and 4, extracting vacuum, and setting welding parameters: welding temperature T, heat preservation time T and pressure P;
and 6, cooling along with the furnace, and taking out the sample.
In step 4, the welding process parameters are set as follows:
step 4.1, the temperature interval for the formation of the beneficial compound is taken into account. The beneficial compound A is expected to be generated in the welding process, the brittle intermetallic compound B is avoided to be generated, and the temperature is not lower than T3When the temperature exceeds T, compound A can be generated4Compound B is formed, so the welding temperature is T3～T4Within the range;
and 4.2, considering the melting point of the parent metal. In general, the temperature of the semi-solid pressure reaction brazing should be lower than the melting point T of the low-melting-point component in the parent metal in order not to affect the properties of the parent metal0Therefore, the temperature range of the semi-solid state pressure reaction brazing can be continuously reduced to T3～Min(T0,T4)；
And 4.3, considering the melting characteristic of the brazing filler metal. According to DSC test results, the melting interval of the brazing filler metal is T1～T2If the welding temperature is lower than the solidus, no liquid phase exists in the welding line, the diffusion of elements is slow, the compactness of the welding line structure is low, and the strength of a joint is low. If the temperature is higher than the liquidus line, the welding seam is all in a liquid phase, the liquid phase brazing filler metal can be extruded out under the action of pressure, the connection mainly depends on the wetting of the brazing filler metal to a base metal, and the joint strength is low due to poor wetting property. Only when the welding temperature is in the melting interval of the brazing filler metal, the solid phase and the liquid phase in the welding seam coexist, and the welding seam structure is mainly formed by the pressurized liquid phase reaction sintering process of the powder brazing filler metal, so that the requirement on the wettability of the brazing filler metal is reduced, and the obtained welding seam structure is compact and has high joint strength. Therefore, the selectable range of the semi-solid state pressure reaction brazing temperature can be reduced to Max (T)1,T3)～Min(T0,T2,T4)
Step 4.4, the joint strength is considered. At Max (T)1,T3)～Min(T0,T2,T4) The semi-solid state pressure reaction brazing is carried out at a temperature of 10 ℃ every other for testing, and the optimal welding temperature is selected through testing the mechanical property of the joint.
And 4.5, designing heat preservation time. Because the welding process mainly depends on the pressurized liquid phase reaction sintering of the solder powderTherefore, the welding time is longer than that of the common brazing so as to obtain a compact weld joint structure, but when the holding time reaches a critical value hcThen, the influence of the continuous heat preservation time on the densification of the sintered body is reduced, and simultaneously, the function of the Kerkdall effect is highlighted, so that the density of the weld joint structure is reduced, and although the density of the weld joint is continuously improved after the heat preservation time is further prolonged, huge time and energy waste is caused, so that the optimal heat preservation time is hc。
And 4.6, designing welding pressure. Generally, increasing the welding pressure is beneficial to improving the mechanical property of the joint, so that the higher welding pressure is selected as much as possible, and the upper limit is that the base metal after welding does not deform greatly.
The present invention will be described in further detail with reference to examples. The technical method of the invention is not limited to the specific embodiments listed below, but also includes welding of any other material, and is particularly suitable for welding of materials difficult to wet.
Example 1
Preparing Al-Si1.9-Mg0.1-Ti35-Cu15-In20 powder solder, testing the melting characteristic of the solder, and filling 70% SiC In the solderpthe/Al composite material is subjected to semi-solid state pressurization reaction brazing, the welding temperature is 600 ℃, the heat preservation time is 1.5h, and the welding pressure is 6 MPa.
The method comprises the following specific steps: preparing brazing filler metal from pure metal powder of Al, Si, Mg, Ti, Cu and In according to the proportion of Al-Si1.9-Mg0.1-Ti35-Cu15-In20, and preparing the brazing filler metal for later use after stirring, ball milling and drying; melting property test of the prepared solder is carried out by a Differential Scanning Calorimetry (DSC), and the result is shown in figure 3; placing No. 240 abrasive paper on a water mill, roughly grinding the surface of the composite material to be welded by utilizing the automatic rotation of the water mill, then accurately grinding the surface of the to-be-welded sample which is roughly ground by sequentially adopting No. 280, 320, 400 and 600 abrasive paper, and drying the ground sample by cold air for later use; according to the assembly mode shown in FIG. 4, prepared powder solder is filled between the surfaces to be welded of the samples, and the samples are placed into a vacuum furnace for reasonable assembly; closing the furnace door, extracting vacuum, setting parameters when the vacuum degree reaches 3.9 multiplied by 10-3After Pa, heating was started at a rate of 10 ℃/min,and (3) starting heat preservation after heating to 600 ℃, preserving heat for 1.5h, simultaneously applying 6MPa pressure, unloading after heat preservation, and cooling along with the furnace.
70％SiCpThe shear strength of the/Al composite material semi-solid state pressure reaction soldered joint is 90.2 MPa.
Example 2
Preparing B-Al89 SiMg-6% Ti powder solder, testing the melting characteristics of the solder, and filling 70% SiC in the solderpthe/Al composite material is subjected to semi-solid state pressurization reaction brazing, the welding temperature is 600 ℃, the heat preservation time is 1.5h, and the welding pressure is 10 MPa.
The method comprises the following specific steps: preparing a brazing filler metal by using B-Al89SiMg powder brazing filler metal and pure metal Ti powder according to the proportion of B-Al89SiMg to 6 percent of Ti, and preparing the brazing filler metal for later use after stirring, ball milling and drying; testing the melting characteristic of the prepared brazing filler metal by adopting a Differential Scanning Calorimetry (DSC), wherein the melting interval is 565-612 ℃; placing No. 240 abrasive paper on a water mill, roughly grinding the surface of the composite material to be welded by utilizing the automatic rotation of the water mill, then accurately grinding the surface of the to-be-welded sample which is roughly ground by sequentially adopting No. 280, 320, 400 and 600 abrasive paper, and drying the ground sample by cold air for later use; according to the assembly mode shown in FIG. 4, prepared powder solder is filled between the surfaces to be welded of the samples, and the samples are placed into a vacuum furnace for reasonable assembly; closing the furnace door, extracting vacuum, setting parameters when the vacuum degree reaches 3.9 multiplied by 10-3And after Pa, starting heating at the speed of 10 ℃/min, starting heat preservation after heating to 600 ℃, keeping the temperature for 1.5h, simultaneously applying 10MPa pressure, unloading after heat preservation, and cooling along with the furnace.
70％SiCpThe shear strength of the/Al composite material semi-solid state pressure reaction brazed joint is 98.5 MPa.
Example 3
Preparing B-Al89 SiMg-6% Ti powder solder, testing the melting characteristics of the solder, and filling the solder with 70% SiC treated by titanizingpthe/Al composite material is subjected to semi-solid state pressurization reaction brazing, the welding temperature is 600 ℃, the heat preservation time is 1.5h, and the welding pressure is 10 MPa.
The method comprises the following specific steps: B-Al89SiMg powder solder and pure metal Ti powder are adoptedB-Al89 SiMg-6% Ti, stirring, ball milling, and oven drying to obtain solder; testing the melting characteristic of the prepared brazing filler metal by adopting a Differential Scanning Calorimetry (DSC), wherein the melting interval is 565-612 ℃; placing No. 240 abrasive paper on a water mill, roughly grinding the surface of the composite material to be welded by utilizing the automatic rotation of the water mill, then accurately grinding the surface of the to-be-welded sample which is roughly ground by sequentially adopting No. 280, 320, 400 and 600 abrasive paper, and drying the ground sample by cold air for later use; adding a small amount of alcohol into Ti powder, adjusting the Ti powder into a viscous state, coating the viscous state on the surface to be welded of the polished composite material, putting the coated sample into a vacuum furnace, keeping the surface to be welded upward, keeping the temperature of the sample at 600 ℃ for 2h for titanizing treatment, cooling, taking out the sample, newly polishing and cleaning the surface of the sample, and drying the sample by cold air for later use; according to the assembly mode shown in FIG. 4, prepared powder solder is filled between the surfaces to be welded of the samples, and the samples are placed into a vacuum furnace for reasonable assembly; closing the furnace door, extracting vacuum, setting parameters when the vacuum degree reaches 3.9 multiplied by 10-3And after Pa, starting heating at the speed of 10 ℃/min, starting heat preservation after heating to 600 ℃, keeping the temperature for 1.5h, simultaneously applying 10MPa pressure, unloading after heat preservation, and cooling along with the furnace.
Titanized 70% SiCpThe shear strength of the/Al composite material semi-solid state pressure reaction brazed joint is 131.3 MPa.
Comparative example 1
Filling ER4047 foil-shaped brazing filler metal pair with 70% SiCpAnd brazing the/Al composite material, wherein the melting range of the brazing filler metal is 573-585 ℃, the brazing temperature is 600 ℃, the heat preservation time is 15min, and the welding pressure is 3 MPa.
The method comprises the following specific steps: placing No. 240 abrasive paper on a water mill, roughly grinding the surface of the composite material to be welded by utilizing the automatic rotation of the water mill, then accurately grinding the surface of the to-be-welded test sample and the surface of the brazing filler metal which are roughly ground by sequentially adopting No. 280, 320, 400 and 600 abrasive paper, and drying the ground test sample by cold air for later use; according to the assembly mode of figure 4, filling brazing filler metal between surfaces to be welded of the sample, and placing the sample into a vacuum furnace for reasonable assembly; closing the furnace door, extracting vacuum, setting parameters, and when the vacuum degree reaches3.9×10-3And after Pa, starting heating at the speed of 10 ℃/min, starting heat preservation after heating to 600 ℃, keeping the temperature for 15min, simultaneously applying the pressure of 3MPa, unloading after heat preservation is finished, and cooling along with the furnace.
70％SiCpThe shear strength of the/Al composite material soldered joint is 22.9 MPa.
Comparative example 2
For 70% SiCpThe intermediate-layer-free diffusion welding is carried out on the/Al composite material, the welding temperature is 550 ℃, the heat preservation time is 2 hours, and the welding pressure is 6 MPa.
The method comprises the following specific steps: placing No. 240 abrasive paper on a water mill, roughly grinding the surface of the composite material to be welded by utilizing the automatic rotation of the water mill, then accurately grinding the surface of the to-be-welded sample which is roughly ground by sequentially adopting No. 280, 320, 400 and 600 abrasive paper, and drying the ground sample by cold air for later use; according to the assembly mode of FIG. 4, the sample is put into a vacuum furnace for reasonable assembly; closing the furnace door, extracting vacuum, setting parameters when the vacuum degree reaches 3.9 multiplied by 10-3And after Pa, starting heating at the speed of 10 ℃/min, starting heat preservation after heating to 550 ℃, keeping the temperature for 2h, simultaneously applying the pressure of 6MPa, unloading after heat preservation is finished, and cooling along with the furnace.
70％SiCpthe/Al composite diffusion welded joint was unwelded as shown in fig. 6.
The semi-solid state pressure reaction brazing and the brazing method have obvious difference, brazing filler metal is in a liquid phase and a base material is in a solid phase in the brazing process, the connection process is mainly carried out by wetting the liquid phase brazing filler metal on the surface of the base material, the brazing filler metal is always in a semi-solid state in the semi-solid state pressure reaction brazing process, and the connection process is a comprehensive effect of wetting, diffusion, reaction and sintering processes. The semi-solid state pressure reaction brazing and the transient liquid phase diffusion brazing related to the invention are also obviously different, and the most prominent difference is that the sintering process is the main process of powder brazing alloy metallurgical bonding in the semi-solid state pressure reaction brazing process, the most prominent difference is that the powder brazing alloy is in the pressure liquid phase reaction sintering, and no matter which kind of diffusion welding is related to the process, the diffusion welding and the semi-solid state pressure reaction brazing are essentially different.
TABLE 1 differentiation of semi-solid state pressure reaction brazing from transient liquid phase diffusion welding
70 percent SiC is brazed by adopting the semi-solid state pressure reaction brazing methodpthe/Al composite material is welded, and a welded joint with high shear strength can be obtained.
Claims (9)
1. A semi-solid state pressure reaction brazing method is characterized by comprising the following specific steps:
step 1, preparing powder solder, carrying out DSC melting characteristic test on the powder solder, and measuring the lowest temperature T of the generated liquid phase1The temperature of complete melting is T2；
Step 2, preparing a base material to be welded before welding;
step 3, filling the prepared powder brazing filler metal between the surfaces to be welded of the sample, and putting the sample into a vacuum furnace for reasonable assembly;
and 4, extracting vacuum, and setting welding parameters: welding temperature T, heat preservation time T and pressure P;
in step 4, the process of setting the welding temperature T is as follows:
step 4.1, setting the welding temperature in the beneficial compound generation temperature interval T according to the components of the base metal and the brazing filler metal3～T4Wherein the temperature is not lower than T3Can generate beneficial intermetallic compounds at a temperature exceeding T4Intermetallic compounds are brittle;
step 4.2, according to the melting point of the parent metal, the temperature of the semi-solid state pressure reaction brazing is lower than the melting point T of the low-melting-point component in the parent metal0Continuing to narrow the welding temperature range to T3～Min(T0,T4)；
Step 4.3, according to the melting characteristics of the brazing filler metal and DSC test results, the melting interval of the brazing filler metal is T1～T2Reducing the welding temperature range to Max (T)1,T3)～Min(T0,T2,T4)；
Step 5, starting welding; heating at a heating rate of 8-12 ℃/min, keeping the temperature for 25-35min after the temperature reaches 300-400 ℃, continuing heating at a heating rate of 8-12 ℃/min, starting a pressurizing device for loading after the temperature reaches T-50 ℃, wherein the loading time is 5-10min, the loading is finished when the temperature reaches T, entering a heat preservation and pressure maintaining state, stopping heating and unloading after T hours, and the unloading time is 5-10 min;
and 6, cooling along with the furnace, and taking out the sample.
2. The semi-solid pressure reaction brazing method according to claim 1, wherein in the step 1, the brazing filler metal preparation and DSC test steps are as follows:
step 1.1, preparing a metal powder raw material according to a brazing filler metal formula, wherein the granularity of the metal powder is 200-300 meshes;
step 1.2, weighing metal powder raw materials according to a formula proportion, and mixing and stirring the raw materials;
step 1.3, ball milling the stirred brazing filler metal at the speed of 250r/min for 4-6 h;
step 1.4, performing DSC melting characteristic test on the solder subjected to ball milling, and recording the temperature T generated at the beginning of liquid phase1Temperature T of complete melting2。
3. A semi-solid pressure reaction brazing method according to claim 1, wherein in step 2, the pre-weld preparation step is:
step 2.1, placing 240# water grinding sand paper on a water grinding machine, and performing coarse grinding on the surface of the base material by utilizing the automatic rotation of the water grinding machine;
2.2, accurately grinding the surface of the test sample after coarse grinding by using 280, 320, 400 and 600# metallographic abrasive paper in sequence;
and 2.3, putting the polished sample into acetone for ultrasonic cleaning, and drying by cold air for later use.
4. A semi-solid pressure reaction brazing method according to claim 1, wherein in step 3, the assembling step is:
step 3.1, adopting smooth ceramic as a substrate, and coating a paste solder resist on the surface of the substrate;
step 3.2, placing the sample to be welded on a substrate, enabling the surface to be welded to face upwards, and filling powder brazing filler metal in the center of the surface to be welded;
step 3.3, placing the sample to be welded on the brazing filler metal, and tightly attaching the surface to be welded to the brazing filler metal;
step 3.4, placing a ceramic pressing block on the sample to be welded, and flattening and pressing;
and 3.5, supporting the ceramic substrate, and slowly putting the assembled sample and the pressing block together into the center of an objective table in the vacuum furnace.
5. A semi-solid pressure reaction brazing method according to claim 1, wherein in step 4, the holding time t is determined, wherein t is a critical value tcCritical value tcThe critical time for achieving relative balance of pore reducing effect and pore enlarging effect of the Cokendall effect caused by the sintering structure of the brazing filler metal in the heating process is reached.
6. The semi-solid pressure reaction brazing method according to claim 1, wherein in the step 4, the welding pressure is set to 10 to 15Mpa to ensure that the base material is not deformed.
7. A semi-solid state pressure reaction brazing method according to claim 1 or 3, wherein the matrix material is 70% SiCpa/Al composite material.
8. A semi-solid state pressure reaction brazing method according to claim 1, 2, 4 or 6, wherein the brazing filler metal is a Ti aluminum based brazing filler metal.
9. The semi-solid pressure reaction brazing method according to claim 1, wherein in the step 3, the vacuum degree of the vacuum furnace reaches 3.3 x 10-3-4.1×10-3Pa。
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