CN111139429B - Method for carburizing hard alloy by utilizing carbon-containing gas cracked in sintering process - Google Patents
Method for carburizing hard alloy by utilizing carbon-containing gas cracked in sintering process Download PDFInfo
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- CN111139429B CN111139429B CN202010101400.7A CN202010101400A CN111139429B CN 111139429 B CN111139429 B CN 111139429B CN 202010101400 A CN202010101400 A CN 202010101400A CN 111139429 B CN111139429 B CN 111139429B
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- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C8/00—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals
- C23C8/06—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases
- C23C8/08—Solid state diffusion of only non-metal elements into metallic material surfaces; Chemical surface treatment of metallic material by reaction of the surface with a reactive gas, leaving reaction products of surface material in the coating, e.g. conversion coatings, passivation of metals using gases only one element being applied
- C23C8/20—Carburising
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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
- 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
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
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Abstract
The method for carburizing the hard alloy by utilizing the carbon-containing gas cracked in the sintering process comprises the steps of putting a hard alloy pressed blank prepared from the carbon unsaturated mixture into a closed container, and placing a cracked carburizing gas substance capable of cracking out the carburizing gas during sintering into the closed container; and then putting the closed container into a sintering furnace for sintering, cracking out carburizing gas through organic matters in the closed container during sintering to perform carburizing treatment on the hard alloy pressed compact in the closed container, and forming the gradient structure hard alloy with the surface carbon content higher than the core carbon content of the product through carburizing. According to the invention, the closed container is adopted, a proper amount of the cleavable carburizing gas substance is added into the closed container, and the cleavable carburizing gas substance is used for cracking the carburizing gas during sintering to perform carburizing strengthening treatment on the hard alloy, so that the carbon content of the surface of the hard alloy can be effectively increased.
Description
Technical Field
The invention relates to a method for changing the surface performance of hard alloy, in particular to a method for carburizing the hard alloy by utilizing carbon-containing gas cracked in the sintering process; the method for carburizing the hard alloy by utilizing the carbon-containing gas cracked in the sintering process can effectively form the surface gradient structure of the hard alloy; belongs to the technical field of hard alloy production.
Background
Strengthening the surface of cemented carbide by carburizing is an effective method for improving the surface performance of cemented carbide at present, and is gradually drawing great attention. Research results show that the surface carburization strengthening treatment process of the WC-Co hard alloy has the advantages that the performance of the WC-Co hard alloy after the surface carburization treatment is obviously improved, and a hardened layer with the thickness of more than 1 mm can be obtained after the WC-Co hard alloy tooth is subjected to the surface carburization treatment. The hard alloy tooth treated by the developed surface carburization process has obviously improved wear resistance, compression fatigue resistance and impact resistance. The hard alloy teeth subjected to surface carburization strengthening treatment are subjected to a drilling field test on a roller bit, and show better footage capability and higher drilling speed; therefore, the strengthening carburization treatment of the surface of the hard alloy is worth to carry out deep research.
Currently, in general, cemented carbide is carburized by burying a cemented carbide compact in a solid carburizing-containing material or by passing a carburizing gas through the sintering process. Patent CN104493161B describes a method for carburizing cemented carbide in a vacuum sintering furnace, comprising the following steps: a. putting a single piece of each hard alloy decarburization product into a sheath containing a carburizing mixture, coating the hard alloy decarburization product with the carburizing mixture, fastening the mouth of the sheath, and putting the sheath into a cold isostatic press for pressing through a pressing process to form a compact block; b. removing the sheath on the surface of the compact block, and then putting the compact block into a vacuum sintering furnace for carburizing and sintering; c. after the carburization and sintering are finished, removing the carburization mixture coating on the surface of the hard alloy decarburization product; d. after removing the coating of the carburization mixture on the surface of the hard alloy decarburization product, performing sand blasting treatment on the hard alloy decarburization product, and storing the removed carburization mixture after homogenization treatment. Patent 107142445B describes that a cemented carbide blank containing carbide-forming elements is prepared, then the Al2O 3-coated powder of the core/shell structure of TiH2 and graphene are mixed and uniformly mixed during planetary ball milling to form a hydrogen-containing carburizing medium, then the porous green compact is placed into the carburizing medium and compacted, and finally, the cemented carbide surface carburization is realized during liquid phase sintering. In the two methods, because the hard alloy pressed compact and the carburizing medium are in solid contact, particularly after the pressed compact shrinks at high temperature, the contact between different parts of the product and the carburizing medium is microscopically uneven, so that the carburizing effect of different parts of the pressed compact is possibly uneven, and meanwhile, if high-pressure gas is introduced into a furnace for pressure sintering in the later sintering stage, the pressure sintering effect is influenced because the solid carburizing substance on the outer layer loses loss when transmitting pressure. Patent No. CN 108149183 a describes: putting the hard alloy into a low-pressure sintering furnace with graphite as a heating body, introducing mixed gas of reducing gas, carburizing gas and inert gas, heating to 1000 ℃ at room temperature at the heating rate of 2-10 ℃/min, heating to 1300-1400 ℃ at the heating rate of 2-5 ℃/min, preserving heat for 30-180 min for carburizing treatment, then cooling for diffusion treatment, and finally cooling to room temperature to obtain the hard alloy with the surface layer hardness in gradient distribution. Patent No. CN 107267837B describes a preparation method of gradient hard alloy, which comprises preparing WC-Co powder; adjusting the carbon content of the WC-Co powder, and calculating the upper limit and the lower limit of the carbon content in a sub-stoichiometric manner; adding a forming agent; pressing into a blank; removing the forming agent; vacuum sintering; performing carburizing heat treatment, namely heating to 900-1200 ℃, performing carburizing heat treatment on the vacuum sintered body, and introducing gas in a pulse mode; heating to 1275-1325 ℃, and carrying out Co phase migration treatment; heating to 1380-1450 ℃, introducing Ar gas, and keeping the pressure at 10-20 mbar; pressure sintering; rapidly cooling to 1270 ℃; then cooling the alloy to room temperature from 1270 ℃, and discharging the alloy to obtain the gradient hard alloy. In the methods described in the two patents, carburizing gas is introduced into a hearth, and because products with different sizes have different surface areas and different reaction speeds with the gas, the carburizing degree of the products with different sizes cannot be controlled; meanwhile, when the hearth is large, the gas concentration difference of each part in the hearth is large, and the carburization degree of the same furnace product cannot be accurately controlled.
Therefore, how to perform uniform carburization on different sizes of products in batches and how to perform precise control on the carburization degree are still problems faced by vast hard alloy enterprises. There is therefore a great need for improvement.
Disclosure of Invention
The invention aims to provide a novel method for carburizing hard alloy by utilizing carbon-containing gas cracked in the sintering process, aiming at solving the problems in the existing hard alloy carburizing modification.
In order to achieve the purpose, the invention provides a method for carburizing hard alloy by utilizing carbon-containing gas cracked in the sintering process, which comprises the steps of putting a hard alloy pressed blank to be sintered into a closed container, and placing a substance which can crack out carburizing gas in the sintering process in the closed container; and then putting the closed container into a sintering furnace for sintering, cracking carburizing gas out through a cracking carburizing gas substance in the closed container during sintering, carburizing the hard alloy pressed compact in the closed container, and carburizing to form the hard alloy with the gradient structure, wherein the carbon content of the surface layer is higher than that of the core part of the product.
Further, the step of placing the hard alloy pressed compact to be sintered into a closed container is to place the hard alloy pressed compact to be sintered into the closed container with the cover, place a proper amount of cleavable carburizing gas substance into the closed container with the cover, and seal the closed container after placing the hard alloy pressed compact and the cleavable carburizing gas substance into the closed container, so that the hard alloy pressed compact and the cleavable carburizing gas substance are in a closed state in the closed container.
Furthermore, the closed container is made of high-temperature-resistant materials, and the high-temperature-resistant materials do not react or are mutually soluble with any component in the hard alloy at the sintering temperature, and other harmful impurities cannot be volatilized; the high-temperature resistant material comprises graphite, dense white corundum or mullite.
Furthermore, the closed container is an ink box with a cover stone made of graphite materials.
Furthermore, a movable valve is additionally arranged on the stone ink box, and the valve is in a closed state and is difficult to escape when carburizing gas is cracked out in the box in the sintering process through the movable valve; however, in the pressure sintering stage, when high-pressure gas is filled into the furnace, the high-pressure gas can open the valve and smoothly enter the graphite box to pressurize the hard alloy pressed compact without damaging the container.
Furthermore, the carburizing treatment of the hard alloy pressed compact in the closed container is carried out by cracking the carburizing gas out through the organic matters in the closed container in the sintering process, namely, in the sintering process, the cracking carburizing gas in the stone ink box cracks the carburizing gas out, and the carburizing gas further cracks carbon out on the surface of the hard alloy pressed compact, so that the carbon content of the surface layer of the hard alloy pressed compact is higher than that of the core part of the hard alloy pressed compact.
Further, the sintering refers to liquid phase sintering of the hard alloy, and as the time and the amount of the liquid phase are related to the carbon content, the higher the carbon content is, the earlier the liquid phase appears, and the more the amount of the liquid phase is; in the sintering process, the carbon content of the surface layer of the hard alloy pressed compact is increased under the action of carburizing gas, and when a liquid phase appears in the hard alloy pressed compact, the liquid phase of the surface layer of the hard alloy pressed compact will appear first and flow to the core part of the hard alloy pressed compact; after sintering, a gradient hard alloy structure with low cobalt content on the surface layer and high cobalt content in the core part is formed in the hard alloy pressed compact.
Furthermore, the hard alloy compact is made of a carbon unsaturated mixture, and alloy components are in a carbon-poor area in a phase diagram.
Further, the hard alloy mixture takes one or a combination of more of cobalt, nickel and iron as a binding phase, and the hard phase is one or more of tungsten, titanium, tantalum, niobium, vanadium, chromium and other refractory metal carbides, wherein the most common hard alloy is tungsten-cobalt hard alloy and tungsten-titanium-cobalt hard alloy.
Further, the cleavable carburizing gas substance is an organic material block, and comprises a rubber block, a paraffin block or a rubber and paraffin composition.
The invention has the advantages that:
because the cemented carbide is liquid phase sintered, the time and amount of liquid phase occurrence during sintering is related to the carbon content, and the higher the carbon content is, the earlier the liquid phase occurrence time is, and the more the amount of liquid phase is. According to the invention, the hard alloy green compact is filled in the closed container, a proper amount of the cleavable carburizing gas substance is added in the closed container, and the cleavable carburizing gas substance is used for cracking the carburizing gas during sintering to perform carburizing strengthening treatment on the hard alloy, so that the carbon content of the surface of the hard alloy can be effectively improved, the performance of the hard alloy can be changed by improving the carbon content of the surface of the hard alloy, and the bending strength of the hard alloy is improved.
Drawings
FIG. 1 is a schematic structural view of a cemented carbide carburizing containment vessel according to one embodiment of the invention;
FIG. 2 is a schematic view of the opening structure of a movable valve of a cemented carbide carburizing sealed container box according to one embodiment of the invention;
FIG. 3 is a schematic view of a detection site and a direction of a cemented carbide sample according to an embodiment of the present invention;
FIG. 4 is a schematic illustration of a cobalt content profile according to an embodiment of the present invention;
FIG. 5 is a schematic view of a cobalt content distribution according to another embodiment of the present invention;
FIG. 6 is a schematic view of a cobalt content distribution according to another embodiment of the present invention;
FIG. 7 is a schematic diagram of a cobalt content distribution according to another embodiment of the present invention.
Detailed Description
The invention is further illustrated with reference to the following figures and specific examples.
Example one
A method for carburizing hard alloy by utilizing carbon-containing gas cracked in the sintering process comprises the steps of preparing a mixture from WC powder and Co powder according to the proportion of WC-6wt% of Co, controlling the carbon content of the mixture to be 5.67%, pressing the mixture into a hard alloy button green compact 12 with the diameter of 14mm, respectively filling the hard alloy button green compact 12 into a graphite box 1 with a cover and a movable valve (shown in figure 1), and putting 1.5g of rubber blocks into the graphite box 1; and then, after each graphite box 1 is sealed by a graphite box cover plate 3, the graphite box is simultaneously placed into the same sintering furnace for dewaxing and sintering, the bottom 4 of the graphite box is supported by graphite columns at intervals so as to prevent the graphite box 1 from being directly pressed on the movable valve 6, high-pressure gas can be ensured to push the movable valve 6 from the bottom to enter the graphite box 1, the graphite box cover plate 3 is opened after sintering is completed, and the hard alloy spherical teeth 12 are taken out of the graphite box 1. The sample was cut from the cross-section (as shown in fig. 3) by sampling the cemented carbide button 12 product removed and the cobalt content was measured at different locations using energy spectroscopy (as shown in fig. 4). From fig. 4, it can be seen that the distribution of cobalt content is shown, and fig. 4 shows that the cobalt content closer to the surface of the cemented carbide is lower, and the cobalt content after reaching the center is highest and tends to be stable, and experiments show that the cobalt content of each layer of the cemented carbide can be changed by carburizing the surface, and after sintering is completed, a gradient cemented carbide structure with low cobalt content in the surface layer and high cobalt content in the core is formed in the cemented carbide button 12, so that the performance of the cemented carbide can be effectively changed, and the bending strength can be improved.
The test shows that the invention uses the carbon-containing gas cracked in the sintering process to carburize the hard alloy button, the hard alloy button pressed compact 12 to be sintered is put into a closed graphite box, and a rubber block 13 which can crack the carburizing gas in the sintering process is placed in the closed graphite box 1, and also can be small organic blocks such as paraffin and the like which can release the equal amount of carburizing gas; and then the closed stone ink box 1 is placed into a sintering furnace for sintering, carburizing gas is cracked out through a rubber block 13 in the closed stone ink box 1 during sintering to carry out carburizing treatment on the hard alloy button pressed compact in the closed stone ink box 1, and the hard alloy button with the gradient structure, the carbon content of the surface layer of which is higher than that of the core part of the product, is formed through carburizing.
Wherein:
the hard alloy button pressed compact 12 blank to be sintered is placed into a closed stone ink box 1, the hard alloy button pressed compact 12 made by mixing WC powder and Co powder to be sintered is placed into the stone ink box 1 with a cover and a movable valve, 1.5g of rubber block 13 is placed into the stone ink box 1, after the hard alloy button pressed compact 12 and the rubber block 13 are placed into the stone ink box 1, the whole graphite box 1 is sealed, and the hard alloy button pressed compact 12 and the rubber block 13 are in a closed state in the stone ink box 1.
The graphite box 1 is made of high-temperature-resistant graphite materials, and the box materials are guaranteed not to react or be mutually soluble with any component in the hard alloy button pressed compact 12 at the sintering temperature, and other harmful impurities cannot be volatilized.
The stone ink box 1 is a sealed box (shown in figure 1) with a cover and a movable valve, the stone ink box 1 comprises an open box body 2, the upper end face of the open box body 2 is covered with a box cover 3, and the box cover 3 is screwed on the open box body 2 through a screw buckle; a movable valve 5 is arranged at the bottom 4 of the open box body 2, and hard alloy button pressed compacts 12 are uniformly placed in a closed inner cavity of the graphite box 1.
The movable valve 5 is an internal and external pressure balance valve arranged at the bottom of the stone ink box, and the movable valve 5 ensures that high-pressure gas can smoothly enter the graphite box to pressurize the hard alloy pressed compact without damaging the stone ink box in the pressure sintering process. The movable valve 5 comprises a movable valve core 6, and the movable valve core 6 is in an I shape; one end of the movable valve core 6 is a movable end 7 of a movable detachable structure, and the other end is a fixed end 9 connected with the middle part 8; the middle part 8 of the movable valve core 6 is sleeved in a movable valve hole 10 at the bottom of the stone ink box in a penetrating manner, after the middle part 8 of the movable valve core 6 passes through the movable valve hole 10 at the bottom of the stone ink box, the movable end 7 of the movable valve core is connected with the middle part 8 to form an I-shaped movable valve core, and a vent groove 11 is arranged at the middle part of the movable valve core; when the atmospheric pressure of stone ink horn 1 is higher than outside atmospheric pressure, block up the graphite box bottom through the one end shutoff of the movable valve element 6 of arranging in stone ink horn 1 in, when outside atmospheric pressure is higher than the inside atmospheric pressure of graphite box 1, will upwards promote movable valve element 6 upward movement through the pressure differential that is located the outside one end of stone ink horn 1 and inner face one end, the air channel 11 of mid portion 8 will communicate the inside and outside (as shown in figure 2) of stone ink horn 1 for outside high-pressure gas gets into the inside of stone ink horn 1, guarantee the inside and outside atmospheric pressure balance of stone ink horn 1, avoid damaging stone ink horn 1.
The hard alloy pressure in the closed graphite box is carburized by cracking carburizing gas out through a rubber block in the graphite box in the sintering process, namely the hard alloy pressure blank and the cracking carburizing gas are put into the graphite box to be sealed, and then the sealed graphite box is sent into a sintering furnace to be sintered; in the sintering process, the rubber block in the graphite box cracks out carburizing gas, and the carburizing gas further cracks out carbon on the surface of the hard alloy pressed compact, so that the carbon content of the surface layer of the hard alloy pressed compact is higher than that of the core of the hard alloy pressed compact.
The sintering refers to hard alloy liquid phase sintering, and as the time and the amount of the liquid phase are related to the carbon content, the higher the carbon content is, the earlier the time of the liquid phase is, and the more the amount of the liquid phase is; in the sintering process, the carbon content of the surface layer of the hard alloy pressed compact is increased under the action of carburizing gas, and when a liquid phase appears in the hard alloy pressed compact, the liquid phase of the surface layer of the hard alloy pressed compact will appear first and flow to the core part of the hard alloy pressed compact; after sintering, a gradient hard alloy structure with low cobalt content on the surface layer and high cobalt content in the core part is formed in the hard alloy pressed compact.
The hard alloy pressed compact is a hard alloy ball tooth pressed compact prepared by mixing WC powder and Co powder with unsaturated carbon according to the proportion of WC-6wt% Co, and controlling the carbon content in the mixture to be 5.67%
Example two
The second embodiment has the same basic principle as the first embodiment, but the adopted materials and products are different, namely a method for carburizing the hard alloy teeth of the roller bit by utilizing the carbon-containing gas cracked in the sintering process is characterized in that WC and Co powder (or tungsten-titanium-cobalt powder) with the carbon content lower than the stoichiometric carbon content and a proper amount of pure W powder are prepared into a mixed raw material with the carbon content controlled at 5.42 percent, the mixed raw material is pressed into a hard alloy tooth pressed compact of the roller bit, the hard alloy tooth pressed compacts of the roller bit are respectively placed into closed boxes made of different mullite materials, 1.0g of paraffin block and rubber block mixture are placed into the closed boxes made of the mullite materials, the closed boxes made of the mullite materials are sealed and sent into a hard alloy sintering furnace for sintering, the pressed compacts of the hard alloy are carburized by utilizing the carbon-containing gas cracked from the paraffin blocks in the sintering process, and forming the hard alloy ball gear with the gradient structure, wherein the carbon content of the surface layer is higher than that of the core part of the hard alloy ball gear through carburizing. Wherein: the bottom of the sealed box made of the mullite material is provided with a movable valve and is supported by graphite columns at intervals, so that the mullite box is prevented from being directly pressed on the movable valve, and high-pressure gas can jack the movable valve from the bottom and enter the stone ink box; after sintering, respectively sampling products in a closed box made of mullite material, cutting the samples from the cross section, and detecting the cobalt content at different positions by using an energy spectrum. In the distribution of cobalt content in the sample of fig. 5, it can be seen from the figure that the cobalt content closer to the surface of the cemented carbide is lower, and the cobalt content after reaching the center is the highest and tends to be stable, and experiments show that the cobalt content of each layer of the cemented carbide can be changed by carburizing the surface, and after sintering is completed, a gradient cemented carbide structure with low cobalt content in the surface layer and high cobalt content in the core is formed in the cemented carbide button, so that the performance of the cemented carbide can be effectively changed, and the bending strength can be improved.
The structure of the closed box made of the mullite material is similar to that of the embodiment.
EXAMPLE III
The basic principle of the third embodiment is the same as that of the first embodiment, namely a method for carburizing hard alloy by utilizing carbon-containing gas cracked in the sintering process, WC and Co powder are mixed into a mixture according to the proportion of WC-6wt% Co and WC-11wt% Co, wherein the carbon content of the WC-6wt% Co mixture is controlled to be 5.67%, the carbon content of the WC-11wt% Co mixture is controlled to be 5.32%, the WC-6wt% Co mixture is pressed into a spherical tooth pressed blank with the diameter of 12, the WC-11wt% Co mixture is pressed into a spherical tooth pressed blank with the diameter of 16, a plurality of spherical tooth pressed blanks of the two spherical tooth pressed blanks are respectively placed into different compact white corundum boxes, paraffin blocks with different quantities are placed into the compact white corundum boxes, the compact white corundum boxes are sealed, the compact white corundum boxes provided with the spherical tooth pressed blank and the paraffin blocks are placed into a hard alloy sintering furnace together for sintering, and (3) carburizing the hard alloy button pressed compact by using carbon-containing gas cracked by a paraffin block in the sintering process, and forming the hard alloy button with the gradient structure, wherein the carbon content of the surface layer is higher than that of the core part of the hard alloy button, through carburizing. The method comprises the steps of putting 1.0g of paraffin blocks into a compact white corundum box with WC-6wt% of spherical teeth, putting 2.0g of paraffin blocks into a compact white corundum box with WC-11wt% of Co spherical teeth, covering the two compact white corundum boxes, putting the two compact white corundum boxes into the same sintering furnace for dewaxing and sintering, supporting the bottom of the compact white corundum box by using graphite columns at intervals to prevent the compact white corundum box from being directly pressed on a movable valve, simultaneously ensuring that high-pressure gas can push the movable valve open from the bottom to enter the compact white corundum box, respectively sampling products in the two compact white corundum boxes after sintering is finished, cutting the samples from cross sections, and detecting the cobalt content in different positions by using an energy spectrum. FIGS. 6 and 7 show the distribution of cobalt content in two samples, WC-11wt% Co and WC-6wt% Co, respectively, and it can be seen from the graphs that the thickness of the low-cobalt (lower than the average cobalt content) layer of both samples is 1.8-2.0mm, and experiments show that the preparation of the gradient structure cemented carbide button tooth with the same thickness can be realized in the same furnace according to different product sizes.
The structure of the compact white corundum box is similar to that of the embodiment.
The above listed embodiments are only for clear and complete description of the technical solution of the present invention with reference to the accompanying drawings; it should be understood that the embodiments described are only a part of the embodiments of the present invention, and not all embodiments, and the terms such as "upper", "lower", "front", "back", "middle", etc. used in this specification are for clarity of description only, and are not intended to limit the scope of the invention, which can be implemented, and the changes or modifications of the relative relationship thereof are also regarded as the scope of the invention without substantial technical changes. Meanwhile, the structures, the proportions, the sizes, and the like shown in the drawings are only used for matching with the contents disclosed in the specification, so as to be understood and read by those skilled in the art, and are not used for limiting the conditions under which the present invention can be implemented, so that the present invention has no technical essence, and any structural modification, changes in proportion relation, or adjustments of the sizes, can still fall within the range covered by the technical contents disclosed in the present invention without affecting the effects and the achievable purposes of the present invention. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
The invention has the advantages that:
because the cemented carbide is liquid phase sintered, the time and amount of liquid phase occurrence during sintering is related to the carbon content, and the higher the carbon content is, the earlier the liquid phase occurrence time is, and the more the amount of liquid phase is. The invention adopts a closed container to contain hard alloy pressed blanks, and a proper amount of rubber blocks are added into the closed container; in the sintering process, through the piece of rubber of putting in airtight container schizolysis carburizing gas when the sintering, carburizing gas can further split out carbon on the carbide surface, carry out carburization strengthening treatment to the carbide, thereby make product top layer carbon content be higher than the product core, after appearing the liquid phase in the product, the product top layer is because carbon content is high, the liquid phase appears earlier and flows to the product core, after the sintering is accomplished, the carbide will form the gradient structure that top layer cobalt content is low, core cobalt content is high, thereby improve carbide's bending strength. This has some advantages as follows:
1. when the rubber block and products with the same specification are relatively and uniformly placed in the closed container, the carburizing gas cracked from the rubber block can uniformly react with the products in the closed container, so that gradient structures formed by the products at different positions in the closed container are the same, and the consistency of the products is ensured.
2. When the number of the rubber blocks put into the box is different, the concentration of the carburizing gas cracked from the rubber blocks in the sintering process is different, so that the carbon amount reacted with the surface layer of the product is also different. Aiming at the condition that the surface layers of products with different specifications and sizes have different volumes, the gradient layers with the same thickness can be generated by adjusting the number of the rubber blocks in the closed container.
3. When the quantity of the products in the closed container is different or the gradient thickness of the products needs to be changed, the quantity of the rubber blocks placed in the closed container can be adjusted to realize the purpose. When different products are put into different closed containers and are put into a sintering furnace together, the production of the products with different specifications and different gradient layer thickness requirements can be realized simultaneously.
Claims (8)
1. The method for carburizing the hard alloy by utilizing the carbon-containing gas cracked in the sintering process is characterized by comprising the following steps: putting the hard alloy pressed compact to be sintered into different closed containers, and placing a cleavable carburizing gas substance which can crack out carburizing gas during sintering in the closed containers; in the sintering process, each closed container is a mutually independent carburizing processing unit in the sintering furnace, the carburizing degree of the hard alloy pressed compact in each closed container can be independently adjusted, the cleavable carburizing gas substance in each closed container cracks carburizing gas in the sintering process, and the carburizing gas can further crack carbon on the surface of the hard alloy pressed compact, so that the carbon content of the surface layer of the hard alloy pressed compact is higher than that of the core of the hard alloy pressed compact; the hard alloy pressed compact to be sintered is placed into a closed container with a cover, a proper amount of cleavable carburizing gas substances are placed into the closed container with the cover while the hard alloy pressed compact is placed into the closed container with the cover, and the closed container is sealed completely after the hard alloy pressed compact and the cleavable carburizing gas substances are placed into the closed container simultaneously, so that the hard alloy pressed compact and the cleavable carburizing gas substances are in a closed state in the closed container.
2. The method of carburizing cemented carbide with carbon-containing gas cracked during sintering as set forth in claim 1, wherein: the closed container is made of high-temperature-resistant materials, and the high-temperature-resistant materials do not react or are mutually soluble with any component in the hard alloy at the sintering temperature and do not volatilize harmful impurities.
3. The method of carburizing cemented carbide with carbon-containing gas cracked during sintering as set forth in claim 1, wherein: the closed container is an ink box with a cover made of graphite materials.
4. A method as claimed in claim 3 for carburizing cemented carbide using carbon-containing gas cracked during sintering, characterized in that: the movable valve is additionally arranged on the stone ink box, and ensures that the valve is in a closed state and the carburizing gas is not easy to escape when the carburizing gas is cracked out from the box in the sintering process; however, in the pressure sintering stage, when high-pressure gas is filled into the furnace, the high-pressure gas can open the valve and smoothly enter the graphite box to pressurize the hard alloy pressed compact without damaging the container.
5. The method of carburizing cemented carbide with carbon-containing gas cracked during sintering as claimed in claim 1, wherein: the sintering refers to hard alloy liquid phase sintering, and as the time and the amount of the liquid phase are related to the carbon content, the higher the carbon content is, the earlier the time of the liquid phase is, and the more the amount of the liquid phase is; in the sintering process, the carbon content of the surface layer of the hard alloy pressed compact is increased under the action of carburizing gas, and when a liquid phase appears in the hard alloy pressed compact, the liquid phase of the surface layer of the hard alloy pressed compact will appear first and flow to the core part of the hard alloy pressed compact; after sintering, a gradient hard alloy structure with low cobalt content on the surface layer and high cobalt content in the core part is formed in the hard alloy pressed compact.
6. The method of carburizing cemented carbide with carbon-containing gas cracked during sintering as set forth in claim 1, wherein: the hard alloy pressed compact is made of carbon unsaturated mixture, and alloy components are in a carbon-poor area in a phase diagram.
7. The method of carburizing cemented carbide with carbon-containing gas cracked during sintering as claimed in claim 6, wherein: the hard alloy mixture takes one or more of cobalt, nickel and iron as a binding phase, and the hard phase is one or more of tungsten, titanium, tantalum, niobium, vanadium and chromium refractory metal carbides.
8. The method of carburizing cemented carbide with carbon-containing gas cracked during sintering as claimed in claim 1, wherein: the fissionable carburizing gas substance is an organic material block.
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