CN114472896B - Method for reinforcing hardness of brazing tool blank - Google Patents
Method for reinforcing hardness of brazing tool blank Download PDFInfo
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- CN114472896B CN114472896B CN202210064669.1A CN202210064669A CN114472896B CN 114472896 B CN114472896 B CN 114472896B CN 202210064669 A CN202210064669 A CN 202210064669A CN 114472896 B CN114472896 B CN 114472896B
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Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D1/00—General methods or devices for heat treatment, e.g. annealing, hardening, quenching or tempering
- C21D1/26—Methods of annealing
-
- C—CHEMISTRY; METALLURGY
- C21—METALLURGY OF IRON
- C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
- C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
- C21D9/0068—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for particular articles not mentioned below
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/10—Alloys containing non-metals
- C22C1/1036—Alloys containing non-metals starting from a melt
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C1/00—Making non-ferrous alloys
- C22C1/10—Alloys containing non-metals
- C22C1/1036—Alloys containing non-metals starting from a melt
- C22C1/1047—Alloys containing non-metals starting from a melt by mixing and casting liquid metal matrix composites
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/105—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding
- B22F2003/1054—Sintering only by using electric current other than for infrared radiant energy, laser radiation or plasma ; by ultrasonic bonding by microwave
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
- B22F2003/248—Thermal after-treatment
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
- B22F2005/002—Tools other than cutting tools
Abstract
The invention provides a method for reinforcing the hardness of a brazing tool blank, which comprises the following steps: s1: preparing a blank, namely adding 2.5wt% of metal carbide additive into molten materials, and preserving heat to S2: sintering the blank body, and S3: and (5) continuously annealing the blank. According to the invention, the metal carbide is added when the brazing tool blank is melted, so that the sintered brazing tool blank has excellent fire resistance, brinell hardness and toughness, the strength and fire resistance of the brazing tool blank can be enhanced by adding the metal carbide, the service life is longer, the brazing tool blank after continuous annealing is better in crystallization state, and the hardness is improved, therefore, the metal carbide is added into the brazing tool blank, and the brazing tool blank is continuously annealed in a continuous annealing mode, so that the strength and fire resistance of the brazing tool blank can be further improved, and the service life of the brazing tool blank is prolonged.
Description
Technical Field
The invention relates to the technical field of brazing tool processing, in particular to a method for reinforcing the hardness of a brazing tool blank.
Background
The brazing is a welding method that after brazing filler metal lower than the melting point of a weldment and the weldment are heated to the melting temperature of the brazing filler metal at the same time, gaps of solid workpieces are filled with liquid brazing filler metal to enable metals to be connected, firstly, an oxide film and greasy dirt on a contact surface of a base metal are removed, so that capillary tubes can play a role after the brazing filler metal is melted, wettability and capillary mobility of the brazing filler metal are improved, and brazing is divided into brazing and soldering according to the difference of the melting points of the brazing filler metal;
the brazing process is to use a flame gun to spray high-temperature flame to melt and fill the brazing filler metal into the object so as to achieve the aim of connecting or solidifying the object, wherein the gun head of the flame gun is a brazing tool and mainly made of a blank material of the brazing tool.
The prior art has the following defects: the brazing tool is often used in a high-temperature environment (400-500 ℃), in the preparation process of the blank of the existing brazing tool, the blank of the brazing tool is mainly formed by processing through steps of melting, forming, annealing and the like, the whole strength and the fire resistance of the formed blank of the brazing tool are poor, the blank of the brazing tool is easy to deform or damage in the long-term use process, and the service life is short.
Disclosure of Invention
The invention provides a method for reinforcing the hardness of a brazing tool blank body aiming at the defects of the prior art.
The invention solves the technical problems by the following technical means: a method of reinforcing the hardness of a brazing tool blank, the method comprising the steps of:
s1: preparation of green body
Adding 12wt% of Cr, 0.5wt% of Ti, 2.5wt% of W and 0.05wt% of V into a high-temperature furnace for melt mixing, adding 2.5wt% of metal carbide additive into the molten material for heat preservation, and pouring the molten material into a mold for cooling to obtain a brazing tool blank;
preferably, the metal carbide comprises VC, cr 3 C 2 TaC and NbC;
preferably, wherein VC, cr 3 C 2 Is a common hard phase grain growth inhibitor, and is added with a small amount of Cr 3 C 2 The strength and high-temperature oxidation resistance of the brazing tool blank can be improved, 2wt% of VC is added into the brazing tool blank synthesized in situ, and then sintering is carried out, so that WC grains in the brazing tool blank sintered body can be inhibited from growing, the brazing tool blank with the hard phase granularity of 65nm is prepared, and the WC/VC coherent phase interface is formed by adding VC, so that the migration of WC grain boundaries and the merging growth among WC grains are inhibited;
preferably, cr 3 C 2 Carbon black and VC powder are used as raw materials, a metal carbide is prepared by adopting an in-situ reduction carbonization method, then the metal carbide is sintered by discharge plasma, and finally the average grain size of a brazing tool blank is 101nm, so that the brazing tool blank has high hardness and good toughness;
preferably, cr 3 C 2 The corrosion resistance of the brazing tool blank is improved most obviously, the effect of VC is inferior, and Cr is added 3 C 2 The brazing tool blank after WC-Co sintering is subjected to the action of VC and rare earth La to form a large number of plate-shaped WC grains with uniform size, and the brazing tool blank has good mechanical properties, but VC and Cr are added 3 C 2 The refractory properties of the post braze tool blank are reduced.
Preferably, the TaC is a cubic crystal with density lower than WC, has the characteristics of high melting point, high hardness and better wettability with Co, the high-temperature property of a brazing tool blank added with the TaC is obviously improved, the microhardness of the TaC at 400-1000 ℃ is higher than that of WC, and the high-temperature hardness of the brazing tool blank can be improved by adding the TaC into the brazing tool blank;
preferably, the wear resistance of the brazing tool blank added with 2wt% of TaC is obviously improved, the hard phase crystal grains are finest, the hardness and the strength are highest when the amount of 2.5wt% of TaC is added, the TaC content is further increased, the hard phase crystal grains are not refined any more, the WC crystal grains in the brazing tool blank can be effectively prevented from growing excessively by adding the TaC into the brazing tool blank, the bending strength of the brazing tool blank is high when the temperature of the brazing tool blank is higher than 800 ℃ after the TaC is added, and the toughness of the brazing tool blank is reduced after the TaC is added.
Preferably, nb and Ta belong to the same group in the periodic table of elements, so that NbC has the characteristics of similar performance to TaC, high melting point, high hardness, small density compared with TaC and good wetting effect compared with a binding phase, and NbC is added to prepare a brazing tool blank, so that the hardness and bending strength of the brazing tool blank are obviously improved, and the fire resistance and hardness of the hard alloy prepared by sintering through a PECS method are improved while the high toughness is maintained.
Preferably, by comparison of VC, cr 3 C 2 Experimental study of TaC and NbC, we found that when VC and Cr are added 3 C 2 After that, the overall strength and corrosion resistance of the brazing tool blank are increased, but the overall fire resistance of the brazing tool blank is poor, after TaC is added, the overall strength and fire resistance of the brazing tool blank are increased, but the toughness is poor and is easy to break, after NbC is added, the overall strength and fire resistance of the brazing tool blank are improvedSince the fire performance is increased and the toughness is moderate, nbC is preferably added as a metal carbide to the molten material in this embodiment.
S2: sintering the green body
Sintering the formed brazing tool blank structure, and constructing a sintered blank through three stages of heating, heat preservation and cooling;
preferably, the structural sintering comprises solid phase sintering and subsequent HIP treatment method, liquid phase sintering method, hot pressing method, microwave sintering method, electric spark sintering method and the like;
preferably, the solid phase sintering and the subsequent HIP treatment are used for pressing and forming a pressed compact with a composition gradient or a hard phase granularity gradient, and the pressed compact is subjected to hot isostatic pressing after the solid phase sintering;
preferably, however, the method has complex process and low production efficiency, is not beneficial to realizing large-scale industrial production, and is easy to generate homogenization due to atomic diffusion between adjacent layers of the pressing block in the sintering process, so that gradient characteristics are weakened or even disappear.
Preferably, the liquid phase sintering method heats the pressed compact with component gradient or grain size gradient to a high enough temperature to make the liquid phase appear in the precast block, keeps the temperature for a short time, and reduces the temperature to below the liquid phase point before homogenizing the tissue components to finish sintering;
preferably, the liquid phase sintering process is simplified compared with the solid phase sintering+subsequent HIP treatment process, but the presence of the liquid phase makes the alloy more easily homogenized during sintering, and the sintering characteristics are different due to different chemical compositions between different gradient layers in the compact, and internal stress is generated during sintering to cause deformation of the whole material.
Preferably, the pressed blank is subjected to hot pressing sintering by a hot pressing method, and a brazing tool blank with a gradient structure and higher density can be prepared in one step;
preferably, the hot press sintering process is simplified and can be performed at a relatively low temperature, so that the homogenization process of the alloy during sintering is performed slowly and is easier to control, but the hot press method cannot produce a member having a complicated shape.
Preferably, the microwave sintering method comprises the steps of firstly pressing a pressed blank with gradient components by a cold isostatic pressing method, and then preparing a brazing tool blank with gradient structure by microwave sintering in a pure Ar environment;
preferably, the microwave sintering is easy to control, safe, pollution-free, rapid in heating speed and short in sintering time, new materials and new structures can be obtained in a selective heating mode, and in addition, the metallurgical and mechanical properties of the hard alloy are enhanced by the thermal activation and local heating of the WC crystal grains by microwaves.
Preferably, the electric spark sintering method is to load metal powder into a graphite mold, the upper die punch and the lower die punch of the mold are used as power-on electrodes, pressure and pulse voltage are simultaneously applied to the powder, the graphite mold with a gradient structure can form a temperature gradient in a sintering body to realize gradient sintering, and a brazing tool blank with a gradient structure is prepared through spark plasma activation, resistance heating and thermoplastic deformation.
Preferably, the internal stress caused by different densities of different parts and sintering densification speeds in the gradient material can be effectively eliminated, but similar to the hot press sintering method, the method cannot prepare a member with a complex shape.
Preferably, in order to further improve the density, strength and fire resistance of the brazing tool blank itself, the microwave sintering method is preferred as the structural sintering treatment of the brazing tool blank in this embodiment.
S3: annealing of blanks
Preferably, the annealing process is recrystallization annealing, the brazing tool blank is heated to a temperature higher than the recrystallization temperature, and is cooled after heat preservation for a certain time, so that the brazing tool blank is recrystallized, deformed grains are recrystallized into uniform equiaxed grains, and the purpose of the annealing process is to eliminate deformation strengthening and residual stress;
preferably, the microstructure of the metal is refined through recovery and recrystallization in the annealing process until the microstructure becomes fine and uniform equiaxed grains, metal work hardening is removed, the plasticity and deformation capacity of the brazing tool blank are recovered, the annealing process is a process for determining the comprehensive mechanical properties of the brazing tool blank, and the annealing temperature and the heat preservation time are the most important process parameters in the annealing process, and have the greatest influence on the subsequent structure and the performance of the brazing tool blank;
preferably, the annealing temperature and the heat preservation time of the brazing tool blank are taken as important research directions, namely the structure and the performance of the brazing tool blank are changed under different annealing temperatures and heat preservation times, so that a change rule is summarized, and the annealing process of the brazing tool blank is better formulated; under different annealing processes, the recrystallization conditions of the brazing tool blank are different, and the recrystallization process of the brazing tool blank often has important influence on the structure and performance of the annealed brazing tool blank;
preferably, the recrystallization annealing includes cap annealing and continuous annealing;
preferably, the hood type annealing is to place the brazing tool blank in a hood type furnace in a stacking mode for annealing, wherein the heating mode is divided into flame direct heating and radiant tube indirect heating, the hood type furnace adopts two internal cooling modes of split flow or full flow, and forced external cooling adopts a cooling hood;
preferably, the continuous annealing is that the brazing tool blank is annealed by an annealing furnace without a closed port, and the brazing tool blank is not stopped in the middle;
preferably, under the hood-type annealing process, the crystal grains are firstly in a cake shape in the recrystallization process, and then gradually change from cake-shaped crystal grains to equiaxed crystal grains, and the deformed crystal grains are changed into uniform equiaxed crystal grains by continuous annealing, meanwhile, the continuous annealing can remove work hardening and residual internal stress generated in the deformation process, and recover the structure and performance of the brazing tool blank to a state before cold deformation, and the continuous annealing has the characteristics of less equipment investment, uniform product quality, short production period, small occupied area and the like, so the continuous annealing mode is preferred to anneal the brazing tool blank in the embodiment;
preferably, in the continuous annealing process, the brazing tool blank is placed into a high-temperature furnace, heated to 600 ℃ for continuous annealing for 30min, heated to 800 ℃ at 80 ℃/h, and then subjected to water cooling to finish annealing treatment.
The invention has the beneficial effects that:
according to the invention, the metal carbide is added when the brazing tool blank is melted, so that the sintered brazing tool blank has excellent fire resistance, brinell hardness and toughness, the strength and fire resistance of the brazing tool blank can be enhanced by adding the metal carbide, the service life is longer, the brazing tool blank after continuous annealing is better in crystallization state, and the hardness is improved, therefore, the metal carbide is added into the brazing tool blank, and the brazing tool blank is continuously annealed in a continuous annealing mode, so that the strength and fire resistance of the brazing tool blank can be further improved, and the service life of the brazing tool blank is prolonged.
Drawings
FIG. 1 is a workflow diagram of the present invention;
FIG. 2 is a microstructure view of a braze tool blank of the present invention after annealing.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention, and it is apparent that the described embodiments are some embodiments of the present invention, but not all embodiments of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
It will be understood that when an element is referred to as being "fixed to" another element, it can be directly on the other element or intervening elements may also be present. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or intervening elements may also be present.
Example 1
Referring to fig. 1, the method for reinforcing the hardness of a blank of a brazing tool according to this embodiment includes the steps of:
s1: preparation of green body
Adding 12wt% of Cr, 0.5wt% of Ti, 2.5wt% of W and 0.05wt% of V into a high-temperature furnace for melt mixing, adding 2.5wt% of metal carbide additive into the molten material for heat preservation, and pouring the molten material into a mold for cooling to obtain a brazing tool blank;
the metal carbide comprises VC, cr 3 C 2 TaC and NbC;
wherein VC, cr 3 C 2 Is a common hard phase grain growth inhibitor, and is added with a small amount of Cr 3 C 2 The strength and high-temperature oxidation resistance of the brazing tool blank can be improved, 2wt% of VC is added into the brazing tool blank synthesized in situ, and then sintering is carried out, so that WC grains in the brazing tool blank sintered body can be inhibited from growing, the brazing tool blank with the hard phase granularity of 65nm is prepared, and the WC/VC coherent phase interface is formed by adding VC, so that the migration of WC grain boundaries and the merging growth among WC grains are inhibited;
by Cr 3 C 2 Carbon black and VC powder are used as raw materials, a metal carbide is prepared by adopting an in-situ reduction carbonization method, then the metal carbide is sintered by discharge plasma, and finally the average grain size of a brazing tool blank is 101nm, so that the brazing tool blank has high hardness and good toughness;
Cr 3 C 2 the corrosion resistance of the brazing tool blank is improved most obviously, the effect of VC is inferior, and Cr is added 3 C 2 The brazing tool blank after WC-Co sintering is subjected to the action of VC and rare earth La to form a large number of plate-shaped WC grains with uniform size, and the brazing tool blank has good mechanical properties, but VC and Cr are added 3 C 2 The refractory properties of the post braze tool blank are reduced.
TaC is a cubic crystal with density lower than WC, has the characteristics of high melting point, high hardness and better wettability with Co, the high-temperature property of a brazing tool blank body added with TaC is obviously improved, the microhardness of TaC at 400-1000 ℃ is higher than that of WC, and the high-temperature hardness of the brazing tool blank body can be improved by adding TaC into the brazing tool blank body;
the abrasion resistance of the brazing tool blank added with 2wt% of TaC is obviously improved, the grains of the hard phase are the finest, the hardness and the strength are the highest when the amount of 2.5wt% of TaC is added, the grains of the hard phase are not refined any more, the addition of TaC in the brazing tool blank can effectively prevent the WC grains in the brazing tool blank from growing excessively, and the bending strength of the brazing tool blank is high when the temperature of the brazing tool blank is higher than 800 ℃ after the TaC is added, but the toughness of the brazing tool blank is reduced after the TaC is added.
Nb and Ta belong to the same group in the periodic table of elements, so that the NbC has the characteristics of similar performance to TaC, high melting point, high hardness, small density compared with the TaC, and good wetting effect compared with a binding phase, and the NbC is added to prepare a brazing tool blank, so that the hardness and the bending strength of the brazing tool blank are obviously improved, and the fire resistance and the hardness of the hard alloy prepared by sintering through a PECS method are improved while the high toughness is maintained.
By the method for VC, cr 3 C 2 Experimental study of TaC and NbC, we found that when VC and Cr are added 3 C 2 After that, the overall strength and corrosion resistance of the brazing tool blank are increased, but the overall fire resistance of the brazing tool blank is poor, and after TaC is added, the overall strength and fire resistance of the brazing tool blank are increased, but the toughness is poor, and after NbC is added, the overall strength and fire resistance of the brazing tool blank are increased, and the toughness is moderate, so that NbC is preferably added as a metal carbide to the molten material for use in the present embodiment.
S2: sintering the green body
Sintering the formed brazing tool blank structure, and constructing a sintered blank through three stages of heating, heat preservation and cooling;
the structural sintering comprises a solid phase sintering and a subsequent HIP treatment method, a liquid phase sintering method, a hot pressing method, a microwave sintering method, an electric spark sintering method and the like;
wherein, the solid phase sintering and the subsequent HIP treatment are used for pressing and forming the pressed compact with the composition gradient or the hard phase granularity gradient, and the pressed compact is treated by hot isostatic pressing after the solid phase sintering;
however, the method has complex process and lower production efficiency, is not beneficial to realizing large-scale industrialized production, and can easily generate homogenization between adjacent layers of the pressing block due to atomic diffusion in the sintering process, so that gradient characteristics are weakened or even disappear.
The liquid phase sintering method heats the pressed compact with component gradient or grain size gradient to a high enough temperature to make the liquid phase appear in the precast block, keeps the temperature for a short time, and reduces the temperature to below the liquid phase point before homogenizing the tissue components to finish sintering;
compared with the solid phase sintering and the subsequent HIP treatment, the liquid phase sintering method has simplified preparation process, but the alloy is more easily homogenized in the sintering process due to the presence of the liquid phase, and the sintering characteristics are different due to different chemical compositions among different gradient layers in the pressed compact, so that internal stress is generated during sintering to cause deformation of the whole material.
The pressed blank is subjected to hot pressing sintering by a hot pressing method, and a brazing tool blank with a gradient structure and higher density can be prepared in one step;
the hot press sintering process is simplified and can be performed at a relatively low temperature, so that the homogenization process of the alloy in the sintering process is slower and easier to control, but the hot press method cannot prepare a component with a complex shape.
The microwave sintering method comprises the steps of firstly pressing a pressed blank with gradient components by a cold isostatic pressing method, and then preparing a brazing tool blank with gradient structure by microwave sintering in a pure Ar environment;
the microwave sintering is easy to control, safe, pollution-free, high in heating speed and short in sintering time, new materials and new structures can be obtained in a selective heating mode, and in addition, the metallurgical and mechanical properties of the hard alloy are enhanced by the thermal activation and local heating of WC crystal grains by microwaves.
The electric spark sintering method is to load metal powder into graphite mold, to apply pressure and pulse voltage to the powder simultaneously, to form temperature gradient inside the sintered body to realize gradient sintering, to activate spark plasma, to heat resistance and to heat thermoplastic deformation to prepare the brazing tool blank.
Internal stress caused by different part densities and sintering densification speeds in the gradient material can be effectively eliminated, but similar to the hot press sintering method, the method cannot prepare a component with a complex shape.
In summary, in order to further improve the density, strength, and fire resistance of the brazing tool blank itself, the microwave sintering method is preferred as the structural sintering treatment of the brazing tool blank in this embodiment.
S3: annealing of blanks
The annealing process adopted in the embodiment is recrystallization annealing, the brazing tool blank is heated to a temperature higher than the recrystallization temperature, and is cooled after heat preservation for a certain time, so that the brazing tool blank is recrystallized, deformed grains are recrystallized into uniform equiaxed grains, and the purpose of the annealing process is to eliminate deformation strengthening and residual stress;
refining a metal microstructure through recovery and recrystallization in the annealing process until the microstructure becomes fine and uniform equiaxial grains, removing metal work hardening, and recovering plasticity and deformability of a brazing tool blank, wherein an annealing process is a process for determining comprehensive mechanical properties of the brazing tool blank, and an annealing temperature and a heat preservation time are the most important process parameters in the annealing process, and have the greatest influence on subsequent structure and performance of the brazing tool blank;
therefore, the annealing temperature and the heat preservation time of the brazing tool blank are taken as important research directions, namely the structure and the performance of the brazing tool blank are changed under different annealing temperatures and heat preservation times, so that a change rule is summarized, and the annealing process of the brazing tool blank is better formulated; under different annealing processes, the recrystallization conditions of the brazing tool blank are different, and the recrystallization process of the brazing tool blank often has important influence on the structure and performance of the annealed brazing tool blank;
the recrystallization annealing includes cap annealing and continuous annealing;
wherein, the hood type annealing is to place the brazing tool blank in a hood type furnace in a stacking mode for annealing, the heating mode is divided into flame direct heating and radiant tube indirect heating, the hood type furnace uses two internal cooling modes of split flow or full flow, and forced external cooling adopts a cooling hood;
the continuous annealing is that the brazing tool blank passes through an annealing furnace without a closed port to be annealed, and the brazing tool blank is not stopped in the middle;
under the hood-type annealing process, the crystal grains are firstly in a cake shape in the recrystallization process, then gradually change from cake-shaped crystal grains to equiaxed crystal grains, and the deformed crystal grains are changed into uniform equiaxed crystal grains by continuous annealing, meanwhile, the continuous annealing can remove work hardening and residual internal stress generated in the deformation process, and recover the structure and performance of the brazing tool blank to a state before cold deformation, and the continuous annealing has the characteristics of less equipment investment, uniform product quality, short production period, small occupied area and the like, so the brazing tool blank is annealed by the continuous annealing mode in the embodiment;
in the continuous annealing process, the brazing tool blank is placed into a high-temperature furnace, the temperature is increased to 600 ℃ for continuous annealing for 30min, the temperature is increased to 800 ℃ at 80 ℃/h, the heat preservation is carried out for 2h, the water cooling is carried out, the annealing treatment is finished, and the tissue morphology of the brazing tool blank is observed through a scanning electron microscope after the annealing, and is shown in the figure 2.
Comparative example 1
The present comparative example is different from example 1 in that no metal carbide was added.
Comparative example 2
The difference between this comparative example and example 1 is that a hood-type annealing process is used for the blank annealing.
Example 2
In this example, the brazing tool blanks of example 1, comparative example 1 and comparative example 2 were each tested for fire resistance, brinell hardness and toughness, and the test results are shown in table 1:
TABLE 1
As can be seen from the table, according to the embodiment of the invention, by adding the metal carbide when the brazing tool blank is melted, the sintered brazing tool blank has excellent fire resistance, brinell hardness and toughness, compared with the brazing tool blank without adding the metal carbide in the comparative example 1, the brazing tool blank sintered by adding the metal carbide can enhance the strength and fire resistance of the brazing tool blank, has longer service life, and compared with the annealing process of the blank of the comparative example 2, the brazing tool blank after continuous annealing has better crystallization state and higher hardness, so that the metal carbide is added into the brazing tool blank, and the brazing tool blank is continuously annealed in a continuous annealing mode, so that the strength and fire resistance of the brazing tool blank can be further improved, and the service life of the brazing tool blank is prolonged.
It is noted that relational terms such as first and second, and the like, if any, are used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Moreover, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.
The above embodiments are only for illustrating the technical solution of the present invention, and are not limiting; although the invention has been described in detail with reference to the foregoing embodiments, it will be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention.
Claims (6)
1. The method for reinforcing the hardness of the brazing tool blank is characterized by comprising the following steps of: the reinforcing method comprises the following steps:
s1: preparation of green body
Adding raw materials into a high-temperature furnace for melt mixing, adding a metal carbide additive into the molten materials for heat preservation, and then pouring the molten materials into a mold for cooling to obtain a brazing tool blank;
s2: sintering the green body
Sintering the formed brazing tool blank structure, and constructing a sintered blank through three stages of heating, heat preservation and cooling;
s3: annealing of blanks
Continuously annealing the sintered brazing tool blank by a high-temperature furnace; in the step S1, the metal carbide comprises VC and Cr 3 C 2 TaC and NbC; after TaC and NbC are added, WC crystal grains in the brazing tool blank are inhibited from growing, and the bonding phase of NbC and the brazing tool blank is wetted; in the step S1, the addition amount of the metal carbide is 2.5-3wt%.
2. The brazing tool blank hardness reinforcing method according to claim 1, wherein: the VC, cr 3 C 2 Inhibiting WC crystal grain growth in the sintered body of the brazing tool blank after the addition, wherein the Cr 3 C 2 After addition, a large number of plate-shaped WC grains with uniform size are formed on the brazing tool blank.
3. The brazing tool blank hardness reinforcing method according to claim 1, wherein: in the step S1, the raw materials comprise 12-14wt% of Cr, 0.5-0.8wt% of Ti, 2.5-3wt% of W and 0.05-0.08wt% of V.
4. The brazing tool blank hardness reinforcing method according to claim 1, wherein: in the step S2, the structural sintering includes solid phase sintering+subsequent HIP treatment method, liquid phase sintering method, hot pressing method, microwave sintering method, and spark sintering method.
5. The brazing tool blank hardness reinforcing method according to claim 4, wherein: the microwave sintering method comprises the steps of firstly pressing a pressed blank with gradient components by a cold isostatic pressing method, and then preparing a brazing tool blank with gradient structure by microwave sintering in a pure Ar environment.
6. The brazing tool blank hardness reinforcing method according to claim 1, wherein: in the step S3, during continuous annealing, the temperature is raised to 600 ℃ for 30min, the temperature is raised to 800 ℃ at 80 ℃/h, and the annealing treatment is completed by water cooling after heat preservation for 2 h.
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