CN112090973A - Process for manufacturing high-performance seamless steel tube cold-drawing die by using low-carbon low-alloy steel - Google Patents
Process for manufacturing high-performance seamless steel tube cold-drawing die by using low-carbon low-alloy steel Download PDFInfo
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- CN112090973A CN112090973A CN202010935034.5A CN202010935034A CN112090973A CN 112090973 A CN112090973 A CN 112090973A CN 202010935034 A CN202010935034 A CN 202010935034A CN 112090973 A CN112090973 A CN 112090973A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C3/00—Profiling tools for metal drawing; Combinations of dies and mandrels
- B21C3/02—Dies; Selection of material therefor; Cleaning thereof
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C1/00—Manufacture of metal sheets, metal wire, metal rods, metal tubes by drawing
- B21C1/16—Metal drawing by machines or apparatus in which the drawing action is effected by other means than drums, e.g. by a longitudinally-moved carriage pulling or pushing the work or stock for making metal sheets, bars, or tubes
- B21C1/22—Metal drawing by machines or apparatus in which the drawing action is effected by other means than drums, e.g. by a longitudinally-moved carriage pulling or pushing the work or stock for making metal sheets, bars, or tubes specially adapted for making tubular articles
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
- B21C—MANUFACTURE OF METAL SHEETS, WIRE, RODS, TUBES OR PROFILES, OTHERWISE THAN BY ROLLING; AUXILIARY OPERATIONS USED IN CONNECTION WITH METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL
- B21C3/00—Profiling tools for metal drawing; Combinations of dies and mandrels
- B21C3/18—Making tools by operations not covered by a single other subclass; Repairing
Abstract
A process for manufacturing a high-performance seamless steel tube cold-drawing die by using low-carbon low-alloy steel comprises the steps of turning the cold-drawing die, and reserving 0.2mm of grinding amount; putting a stainless steel infiltration box filled with a solid carbonitriding agent and a cold-drawing die into a hearth of a heat treatment furnace, electrifying and heating until carbonitriding is carried out, taking out, air-cooling and normalizing to room temperature; then grinding according to the standard size and roughness requirement of the cold-drawing die to obtain a carbonitriding cold-drawing die; adding a vanadizing agent into a stainless steel crucible of an external heating salt bath furnace, forming a vanadizing salt bath at 900 ℃, hanging an internal cold-drawing die into the vanadizing salt bath, carrying out vanadizing at the constant temperature of 900 ℃ for 4 hours, carrying out water-cooling quenching, and returning in an electric furnace; cleaning and polishing to obtain the product. The advantages are that: the manufacturing material has low cost, the heat treatment process is simple and convenient to operate, the toughness and the surface wear resistance of the matrix can be obviously improved, the surface cracking and the matrix brittle failure of the cold-drawing die in service are reduced, and the service life of the seamless steel pipe cold-drawing die is prolonged.
Description
Technical Field
The invention belongs to the field of die production, and relates to a process which is simple and convenient to operate, easy to master and capable of effectively prolonging the service life of a seamless steel tube cold-drawing die, namely a process for manufacturing a seamless steel tube cold-drawing die with high toughness and high wear resistance by using low-carbon low-alloy steel. The cold drawing die for seamless steel tubes can be manufactured by using low-carbon low-alloy carburizing steel to replace high-carbon steel, high-carbon high-alloy steel or hard alloy through the surface strengthening combining medium-temperature carbonitriding and liquid vanadinizing on the surface of the low-carbon low-alloy carburizing steel, so that the cold drawing die has high surface wear resistance and good core toughness, and the service life of the cold drawing die for seamless steel tubes can be effectively prolonged.
Background
The seamless steel pipe is an important material used in a large amount in the fields of petroleum drilling and chemical production and many production fields, and the quality and the service life of cold drawing dies (an inner die and an outer die) are important factors influencing the product quality and the production efficiency in the production process of seamless steel pipes with various specifications. No matter the inner mold or the outer mold is used, in a severe cold drawing production environment, huge surface friction, radial compressive stress and axial impact force can be borne, particularly, under the severe conditions of poor steel pipe blank lubrication and insufficient mold surface hardness, abrasive wear and adhesive wear exist between the mold surface and the steel pipe surface, meanwhile, in the drawing process of drawing the steel pipe by a drawing machine, an impact phenomenon exists between the steel pipe and the mold, and the wear and brittle fracture of the mold surface are main failure and damage modes. Therefore, the cold-drawing die for seamless steel pipes must have a combination of high tensile strength and high core toughness and excellent surface wear resistance.
At present, domestic materials and process methods for manufacturing seamless steel pipe cold-drawing dies are various, such as an internal die which is made of high alloy steel (such as Cr12MoV steel and tungsten steel) through quenching and nitriding; an internal mold with hard chromium or vanadinizing surface is plated after high-carbon steel (such as T10) is quenched; an inner mold for carburizing medium carbon steel (such as 45 steel) first and then boriding; spraying a wear-resistant material inner mold on the surface of the medium carbon steel: cemented carbide inner molds, and the like. The cold-drawing internal dies of the types commonly solve the problem of surface wear resistance, but neglect how to improve the toughness of the core of the die and reduce the problems of surface cracking and brittle fracture of the matrix of the die in service, and simultaneously have the problems of overhigh cost of the used materials and the process, and the like.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a process for manufacturing a seamless steel pipe cold-drawing die with high toughness and high wear resistance by using low-carbon low-alloy steel, which has the advantages of low manufacturing material cost and simple and convenient operation of a heat treatment process, can obviously improve the toughness and the high wear resistance, reduces the surface cracking and the matrix brittle fracture of the cold-drawing die in service, and prolongs the service life of the seamless steel pipe cold-drawing die.
The technical solution of the invention is as follows:
the invention relates to a material selection and composite heat treatment process of a seamless steel pipe cold-drawing die, in particular to a carbon-nitrogen-vanadium composite cementation surface strengthening process of a low-carbon low-alloy steel cold-drawing die. The treated low-carbon low-alloy steel die can obtain a high-carbon vanadium-nitrogen surface gradient hardened layer, wherein the depth of a carbonitriding layer on the secondary surface is 0.8-1.2 mm, and the hardness is 60-62 HRC; the thickness of the continuous and uniform vanadium carbide layer formed on the outer surface is 10-15 mu m, and the hardness is as high as 2500HV0.1～2800HV0.1(ii) a Meanwhile, the hardness of the core matrix of the die is kept between 40 and 45 HRC.
A process for manufacturing a high-performance seamless steel pipe cold-drawing die by using low-carbon low-alloy steel comprises the following specific steps:
(1) material selection for cold-drawing dies
The method is characterized in that 20CrMnTi round steel is selected as a material for manufacturing a cold-drawing die, and the chemical composition requirements are as follows: 0.17 to 0.23 percent of C, 0.17 to 0.37 percent of Si, 0.80 to 1.10 percent of Mn, less than or equal to 0.035 percent of S, less than or equal to 0.035 percent of P, 1.00 to 1.30 percent of Cr, 0.04 to 0.10 percent of Ti, less than or equal to 0.030 percent of Ni and less than or equal to 0.030 percent of Cu;
the microstructure requirement is as follows: pearlite and ferrite structures having a banded structure grade of not more than 3;
(2) machining
When the cold-drawing die is an inner die, turning the inner die, and reserving the grinding amount of 0.2mm on the basis of the standard size of the diameter size of the outer circle of the inner die; when the cold-drawing die is an external die, turning the external die, and reserving 0.2mm grinding amount on the basis of the standard size of the inner diameter of the external die;
(3) solid carbonitriding agent ingredient
Preparing a solid carbonitriding agent, wherein the solid carbonitriding agent consists of 603 liquid carburizing agent powder and carbon nitride powder in a mass ratio of 7: 3;
(4) mould packing
Putting the cold-drawing die and the solid carbonitriding agent into a stainless steel plate infiltration box together, and sealing the box cover;
(5) carbonitriding
Firstly, heating a heat treatment furnace to 800 ℃, then placing a stainless steel infiltration box filled with a solid carbonitriding agent and a cold drawing die into a hearth of the heat treatment furnace, electrifying and heating to 880-900 ℃, carrying out constant-temperature diffusion for 1.75-2 hours, then taking out the infiltration box, opening a box cover, taking out the cold drawing die in the solid carbonitriding agent, placing the cold drawing die on the air, and carrying out air cooling and normalizing to room temperature;
(6) cylindrical grinding
Grinding the cold-drawing die after carbonitriding normalizing according to the standard size and roughness requirement of the cold-drawing die to obtain a carbonitriding cold-drawing die;
(7) preparation of vanadinizing salt bath
Vanadinizing agent according toThe weight percentage composition is as follows: aqueous borax powder (Na)2B4O7·10H280% of O), 10% of potassium chloride (KCl) and vanadium pentoxide (V)2O5)6 percent of aluminum powder and 4 percent of aluminum powder;
(8) vanadinizing quenching
Adding the prepared vanadinizing agent into a stainless steel crucible of an external heating salt bath furnace, forming a vanadinizing salt bath at 900 ℃, hanging an internal cold-drawing die into the vanadinizing salt bath, keeping the temperature at 900 ℃ for 4 hours, taking out the cold-drawing die from the vanadinizing salt bath, removing salt adhered to the cold-drawing die, cooling and quenching the cold-drawing die in water, immediately putting the cold-drawing die into an electric furnace at 200 ℃ for tempering for 1.5 hours after quenching;
(9) and (3) carrying out infiltration post-treatment:
and (3) putting the tempered cold-drawing die into a sodium hydroxide solution with the mass content of 10%, boiling, preserving the temperature for 1 hour, polishing the surface of the cold-drawing die, and coating oil after polishing to obtain the cold-drawing die with high toughness and high wear resistance.
Further, when the liquid vanadinizing agent is prepared, firstly, the water-containing borax powder is put into a stainless steel crucible of a salt bath furnace, then the temperature is set, the electric heating is carried out to 800 ℃, after the borax is completely melted, the vanadium pentoxide is added, then the aluminum powder is added and continuously stirred uniformly, finally, the temperature is raised to the vanadinizing process temperature of 900 ℃, the potassium chloride is added, and after the borax is completely melted, the salt bath melt is stirred uniformly for standby application.
Further, when the molds are boxed, a solid carbonitriding agent with the thickness of 2cm is paved at the bottom of the infiltration box, then a layer of cold-drawing mold is placed on the surface of the solid carbonitriding agent, the distance between the cold-drawing mold and the box wall is not less than 1cm, the sum distance between two adjacent cold-drawing molds is not less than 1cm, then the solid carbonitriding agent is buried and tamped, then a second layer of cold-drawing mold and the solid carbonitriding agent are placed, the distance between two adjacent layers of cold-drawing molds is not less than 1cm, the solid carbonitriding agent with the thickness of not less than 4cm is buried and tamped above the last layer of cold-drawing mold, then a box cover is added, and the gap between the box cover and the box wall is sealed by refractory sealing.
Further, the high-toughness and high-wear-resistance cold-drawing die is subjected to carbonitridingThe depth of the hardened layer is 0.8 mm-1.2 mm, the structure of the hardened layer is fine needle-shaped tempered martensite and granular carbon and nitrogen compounds distributed in a dispersion way, and the hardness of the hardened layer is 60 HRC-62 HRC; the outermost layer is coated with a white and bright vanadized hardened layer with a hardness of 2500HV0.1～2800HV01; the core structure of the die is fine lath-shaped tempered martensite, and the hardness of the die is 40 HRC-45 HRC. The vanadium-impregnated layer on the surface is a compact vanadium carbide layer, and the main structures of the vanadium-impregnated layer are VC type and V type8C7A type carbide.
Fundamental principles and performance of the invention
The cold-drawing die (particularly the inner die) for the seamless steel tube is a key component for drawing production of the seamless steel tube, bears huge drawing stress, surface friction force and core impact force in the whole drawing production process, and often causes failure failures such as severe abrasion (both adhesive abrasion and abrasive wear) of an excircle bearing belt of the die, axial waist collapse deformation, surface layer collapse, integral fracture and the like, so that the die must have higher integral tensile strength, fatigue strength, surface abrasion resistance and seizure resistance and must also have higher integral impact toughness. In order to obtain the above properties, the toughness of the core should be improved while the surface wear resistance of the die is effectively improved. At present, the materials used in the manufacture of seamless steel pipe dies in China are basically medium and high carbon steel and alloy steel, even hard alloy, and the heat treatment method and the heat treatment process are mostly used for improving the surface wear resistance, but the consideration on the overall toughness of the die is less. The method for improving the service life of the seamless steel pipe drawing inner die mainly starts from three aspects, and one of the three aspects is to effectively improve the strength, the abrasion resistance and the seizure resistance of the surface of the die; secondly, the overall toughness of the die material is effectively improved, and thirdly, the problems of low cost and easy operation of die production are also considered. The invention considers the problems of improving the surface performance and the core performance, selects low-carbon low-alloy steel as the die material, applies surface carbon nitrogen vanadium composite infiltration and then carries out quenching and tempering, and uses the low-carbon alloy steel as the base material of the cold-drawing inner die to solve the brittleness problem of the die in service; by using a carbonitriding and vanadinizing combined surface chemical heat treatment strengthening method, a high hardness gradient is formed in a certain depth of the surface of the inner die, so that the problem of abrasion resistance of the surface of the inner die can be effectively solved; thereby not only effectively improving the toughness of the matrix of the die, but also effectively improving the surface abrasion resistance of the die, and further prolonging the service life of the cold-drawing die.
The 20CrMnTi steel is low-carbon low-alloy carburizing steel, has good hardenability during heat treatment and small grain growth tendency, and obtains fine high-carbon acicular martensite and granular alloy carbonitride on the surface after carbonitriding quenching, and the center of the steel is fine low-carbon lath martensite. The core of the material has good comprehensive mechanical property and low-temperature impact toughness, and the surface of the material has good wear resistance. If carbonitriding is carried out and then surface vanadizing and quenching heat treatment are carried out, a layer of white and bright carbon-vanadium compound layer can be formed on the high carbonitrided layer, and although the carbon-vanadium compound layer is very thin, the adhesion force of the carbon-vanadium compound layer is excellent and the carbon-vanadium compound layer is not easy to peel off. The vanadium carbide layer has extremely high hardness (2500-2800 HV), and is compounded with the carbonitriding hardened layer of the substrate to form a reasonable surface hardness gradient, so that the surface of the cold-drawing die has excellent wear resistance, seizure resistance and a lower friction coefficient. Because the 20CrMnTi steel belongs to low-carbon steel, and the inner die has good integral toughness when the core part of the steel obtains fine low-carbon lath martensite after the carbon-nitrogen-vanadium composite infiltration and quenching, the cold-drawn inner die made of the 20CrMnTi steel has longer service life after the carbon-nitrogen-vanadium composite strengthening treatment by a solid-liquid method.
The invention has the beneficial effects that:
the low-carbon low-alloy steel cold-drawing die is subjected to surface strengthening treatment by carbon nitrogen vanadium composite infiltration through a solid-liquid method, is converted into a novel seamless steel pipe cold-drawing die with a carbon nitrogen vanadium surface gradient hardened layer with the depth of 0.8-1.2 mm on the surface and lath martensite at the core, has excellent surface wear resistance and core toughness, and can effectively prolong the service life of the die in the cold-drawing process of seamless steel pipes. The seamless steel pipe cold-drawing die obtains good use effect through batch production trial. The heat treatment process for the surface composite infiltration strengthening of the carbon-nitrogen-vanadium by the solid-liquid method has the advantages of simple method, convenient operation and low production cost, and is easy for steel pipe production enterprises to automatically solve the problem of die manufacturing and processing.
Drawings
FIG. 1 is a graph of a heat treatment process of carbonitriding by a solid-liquid method for cold-drawing a mold according to the present invention;
FIG. 2 is a picture (500X) of the metallographic structure of the surface layer of a 20CrMnTi steel test piece obtained by the invention through solid-liquid carbonitriding + normalizing;
FIG. 3 is a photograph showing the metallographic structure of the surface layer of a 20CrMnTi steel specimen subjected to solid-liquid carbonitriding + quenching in accordance with the present invention (corresponding to example 1);
FIG. 4 is a scanning electron microscope structural photograph of a surface layer of a 20CrMnTi steel test piece of the present invention (corresponding to example 1) after solid-liquid carbonitriding quenching;
FIG. 5 is a graph showing the energy spectrum analysis of a surface vanadium layer of a 20CrMnTi steel specimen subjected to solid-liquid carbonitriding of the steel specimen of the present invention (corresponding to example 1);
FIG. 6 is a cross-sectional microscopic Vickers hardness gradient distribution graph of 20CrMnTi steel test piece quenched and tempered after solid-liquid carbonitriding in accordance with the present invention (corresponding to example 1).
Detailed Description
Based on the research results of the seamless steel pipe cold-drawing die with high matrix toughness and high surface wear resistance, the invention is further detailed by combining the examples:
the chemical composition requirements of the steel 20CrMnTi used in the following examples are shown in Table 1:
TABLE 1 chemical composition requirement table (%) for steel materials (GB3077-2015)
| Material brand | C | Si | Mn | S | P | Cr | Ti | Ni | Cu |
| 20CrMnTi | 0.17-0.23 | 0.17-0.37 | 0.80-1.10 | ≤0.035 | ≤0.035 | 1.00-1.30 | 0.04-0.10 | ≤0.030 | ≤0.030 |
The microstructure requirement is as follows: pearlite and ferrite structures having a banded structure grade of not more than 3;
example 1 phi 76mm drawing inner die
(1) Phi 76mm drawing inner die and test piece material preparation
The inner mold is machined by round steel with the diameter of 80mm, turning (reserving allowance on the outer circle) is carried out according to the requirements of a drawing to form the inner mold, the diameter size of the outer circle is reserved with 0.2mm grinding amount on the basis of the standard size, and the requirements of the chemical components of steel materials meet the requirements of GB3077-2015 (Table 1); the test piece is made of the same material as the drawing inner die with the diameter of phi 76mm, and the size of the test piece is phi 25 multiplied by 6 mm;
(2) solid carbonitriding agent ingredient
Preparing a solid carbonitriding agent: 350kg of '603' liquid carburizing agent powder and 150kg of agricultural urea particles are uniformly mixed;
(3) mould packing
Paving a solid carbonitriding agent with the thickness of 2cm at the bottom of a infiltration box, then placing a layer of workpiece (phi 76mm drawing inner die or test piece) on the surface of the solid carbonitriding agent, wherein the distance between the workpiece and the box wall is more than or equal to 1cm, the sum distance between two adjacent workpieces is more than or equal to 1cm, then filling and tamping the solid carbonitriding agent, then placing a second layer of workpiece and the solid carbonitriding agent, wherein the distance between two adjacent layers of workpieces is more than or equal to 1cm, filling and tamping the solid carbonitriding agent with the thickness of more than or equal to 4cm above the last layer of workpiece, then adding a box cover, and sealing the gap between the box cover and the box wall by using refractory sealing mud;
(4) carbonitriding
Firstly, heating a heat treatment furnace to 800 ℃, then placing a stainless steel infiltration box filled with a solid carbonitriding agent and a workpiece into a hearth of the heat treatment furnace, electrifying and heating to 880 ℃, carrying out constant-temperature diffusion for 2 hours, then taking out the infiltration box, opening a box cover, taking out a phi 76mm drawing inner die and a test piece in the solid carbonitriding agent, placing the drawing inner die and the test piece on the air, and carrying out air cooling and normalizing to room temperature;
(5) cylindrical grinding
Grinding the phi 76mm drawing inner die subjected to carbonitriding normalizing according to the standard size and roughness requirements of the phi 76mm drawing inner die to obtain the carbonitriding phi 76mm drawing inner die; the treatment mode of the test piece is the same as that of the drawing inner die with the diameter phi of 76 mm;
(6) preparation of vanadinizing salt bath
Aqueous borax powder (Na)2B4O7·10H280kg of O), 10kg of potassium chloride (KCl) and vanadium pentoxide (V)2O5)6kg of aluminum powder and 4kg of aluminum powder;
(7) vanadinizing quenching
Putting water-containing borax powder into a stainless steel crucible of a salt bath furnace, then setting the temperature, electrifying and heating to 800 ℃, adding vanadium pentoxide after the water-containing borax powder is completely melted, then adding aluminum powder and continuously stirring uniformly, finally heating to the process temperature of vanadinizing 900 ℃, adding potassium chloride, stirring salt bath melt uniformly after the water-containing borax powder is completely melted to form a vanadinizing salt bath, hanging an inner phi 76mm drawing inner die and a test piece into the vanadinizing salt bath, keeping the temperature at 900 ℃ for 4 hours, then taking out the phi 76mm drawing inner die and the test piece from the vanadinizing salt bath, removing salt adhered to the phi 76mm drawing inner die and the test piece, then cooling and quenching the phi 76mm drawing inner die and the test piece in water, immediately putting into an electric furnace at 200 ℃ after quenching, and tempering for 1.5 hours;
(8) and (3) carrying out infiltration post-treatment:
placing the tempered drawing inner die with the diameter of 76mm and the test piece into a sodium hydroxide solution with the mass content of 10%, boiling, and keeping the temperature for 1 hour to remove the residual vanadinizing agent on the surfaces of the drawing inner die with the diameter of 76mm and the test piece; and then polishing the phi 76mm drawing inner die and the surface of the test piece, and oiling the polished phi 76mm drawing inner die to obtain the phi 76mm drawing inner die with high toughness and high wear resistance, wherein the test piece is used for performance inspection.
Heat treatment process
The structure and performance of the workpiece treated in the embodiment 1 of the invention are tested
1) Preparing a metallographic test piece by simultaneously processing the test piece and the drawing inner die with the diameter of 76 mm;
2) and (3) metallographic examination: metallographic microscope is adopted to carry out metallographic examination on the edge and the center of the test piece, as shown in figure 2, the metallographic structure (500 x) of the surface layer of the 20CrMnTi steel after the carbon nitrogen vanadium composite infiltration normalizing is carried out, and the white bright layer on the left side in figure 2 is a continuous and uniform vanadium carbide hardened layer; the right side is a fine pearlite structure after normalizing in the surface high carbon region. FIG. 3 is a metallographic structure (500X) of a surface layer of 20CrMnTi steel after the carbonitriding quenching, and a left white bright layer in FIG. 3 is a continuous and uniform vanadium carbide hardened layer; the right side is a sheet martensite structure after the surface high carbon area is quenched; the results were: the surface is a white and compact vanadium carbide compound layer, and the thickness is about 10-17 μm; the secondary surface is an eutectoid carbonitriding layer with a certain width, the organization of the eutectoid carbonitriding layer is dark black high-carbon fine needle-shaped tempered martensite, carbonitrides and residual austenite, and the depth of the penetrating layer is 1.2 mm; the matrix structure under the inner mold seeping layer is fine low-carbon lath-shaped tempered martensite.
3) And (3) hardness testing: and (4) adopting a Rockwell hardness tester and a microhardness tester to test the hardness of the surface and the core of the inner mold and the hardness of the surface seeping layer. The gradient curve of the hardness of the surface layer after solid-liquid carbonitriding quenching (C-N + V) of the 20CrMnTi steel is shown in FIG. 6.
The detection result is as follows: the hardness of the vanadinizing layer on the surface of the die is 2800 HV; the hardness of the carbonitriding quenching area is 62 HRC; the hardness of the core of the die is 44 HRC.
4) FIG. 4 is a scanning electron microscope image of a vanadium-doped surface layer of 20CrMnTi steel after carbon-vanadium composite doping; the right broadband is a surface vanadium carbide hardened layer, and black spots on the surface of the surface are vanadium carbide particles in different directions; the right side is quenched troostite and flaky martensite after the high-carbon zone is quenched. FIG. 5 is the EDX energy spectrum of 20CrMnTi steel after C-V complex cementation. The vanadium-doped layer on the surface is a compact vanadium carbide layer through energy spectrum analysis (EDX) and X-ray diffraction analysis (XRD), and the main structures of the vanadium-doped layer are VC type and V type8C7A type carbide.
The use effect is as follows: the internal mold (phi 76mm drawing internal mold) is delivered to a seamless steel tube production line of a certain factory for drawing production trial of steel tubes with corresponding specifications, and compared with internal molds made of other materials, the internal mold has obvious excellent effect and is approved by manufacturers.
Example 2 phi 49mm swimming internal mold
(1) Phi 49mm moving inner die and test piece material preparation
The phi 49mm moving inner die is formed by turning according to the drawing requirements (the allowance is left on the outer circle), the diameter size of the outer circle is reserved with 0.2mm grinding amount on the basis of the standard size, and the requirements of the chemical components of steel materials meet the requirements of GB3077-2015 (Table 1); the test piece is made of the same material as the swimming inner mold with the diameter of 49mm, and the size of the test piece is 25 mm multiplied by 6 mm;
(2) solid carbonitriding agent ingredient
Solid carbonitriding agent ingredient
Preparing a solid carbonitriding agent: 350kg of '603' liquid carburizing agent powder and 150kg of agricultural urea particles are uniformly mixed;
(3) mould packing
Firstly paving a solid carbonitriding agent with the thickness of 2cm at the bottom of a infiltration box, then placing a layer of workpiece (phi 49mm moving inner die or test piece) on the surface of the solid carbonitriding agent, wherein the distance between the workpiece and the box wall is more than or equal to 1cm, and the sum distance between two adjacent workpieces is more than or equal to 1cm, then filling and tamping the solid carbonitriding agent, then placing a second layer of workpiece and the solid carbonitriding agent, wherein the distance between two adjacent layers of workpieces is more than or equal to 1cm, filling and tamping the solid carbonitriding agent with the thickness of more than or equal to 4cm above the last layer of workpiece, then adding a box cover, and sealing the gap between the box cover and the box wall by using refractory sealing mud;
(4) carbonitriding
Firstly, heating a heat treatment furnace to 800 ℃, then placing a stainless steel infiltration box filled with a solid carbonitriding agent and a workpiece into a hearth of the heat treatment furnace, electrifying and heating to 900 ℃, carrying out constant-temperature diffusion for 1.75 hours, then taking out the infiltration box, opening a box cover, taking out a phi 49mm moving inner die and a test piece in the solid carbonitriding agent, placing the test piece on the air, and carrying out air cooling and normalizing to room temperature;
(5) cylindrical grinding
Grinding the carbonitriding normalized moving inner die with the diameter of 49mm according to the standard size and the roughness requirement of the moving inner die with the diameter of 49mm to obtain the carbonitriding moving inner die with the diameter of 49 mm; the treatment mode of the test piece is the same as that of the phi 49mm moving internal mold;
(6) preparation of vanadinizing salt bath
Aqueous borax powder (Na)2B4O7·10H280kg of O), 10kg of potassium chloride (KCl) and vanadium pentoxide (V)2O5)6kg of aluminum powder and 4kg of aluminum powder;
(7) vanadinizing quenching
Putting the water-containing borax powder into a stainless steel crucible of a salt bath furnace, then setting the temperature, electrifying and heating to 800 ℃, adding vanadium pentoxide after the water-containing borax powder is completely melted, then adding aluminum powder and continuously stirring uniformly, finally heating to the vanadizing process temperature of 900 ℃, adding potassium chloride, stirring salt bath melt uniformly after the water-containing borax powder is completely melted to form a vanadizing salt bath, hanging an inner phi 49mm swimming inner die and a test piece into the vanadizing salt bath, keeping the temperature of 900 ℃ for 4 hours, then taking out the phi 49mm swimming inner die and the test piece from the vanadizing salt bath, removing the phi 49mm swimming inner die and the salt adhered to the test piece, then cooling and quenching the phi 49mm swimming inner die and the test piece in water, immediately putting into an electric furnace at 200 ℃ after quenching, and tempering for 1.5 hours;
(8) and (3) carrying out infiltration post-treatment:
placing the tempered moving internal mold with the diameter of 49mm and the test piece into a sodium hydroxide solution with the mass content of 10%, boiling, and keeping the temperature for 1 hour to remove the residual vanadizing agent on the surfaces of the moving internal mold with the diameter of 49mm and the test piece; and then polishing the phi 49mm moving internal mold and the surface of the test piece, and coating oil on the phi 49mm moving internal mold after polishing to obtain the phi 49mm moving internal mold with high toughness and high wear resistance, wherein the test piece is used for performance inspection.
The invention embodiment 2 is used for checking the structure and the performance of the processed workpiece
1) Preparing a metallographic test piece by simultaneously processing the test piece and the phi 49mm moving inner die;
2) and (3) metallographic examination: adopting a metallographic microscope to carry out metallographic examination on the edge and the center of the test piece, and obtaining the following results: the surface is a white and compact vanadium carbide compound layer, and the thickness is about 10-15 μm; the secondary surface is an eutectoid carbonitriding layer with a certain width, the organization of the eutectoid carbonitriding layer is dark black high-carbon fine needle-shaped tempered martensite, carbonitrides and residual austenite, and the depth of the penetrating layer is 0.8 mm; the matrix structure under the inner mold seeping layer is fine low-carbon lath-shaped tempered martensite.
3) And (3) hardness testing: and performing hardness gradient test on the surface and core hardness and the surface infiltration layer of the inner mold by adopting a Rockwell hardness tester and a microhardness tester.
The detection result is as follows: the hardness of the vanadinizing layer on the surface of the die is 2500 HV; the hardness of the carbonitriding quenching area is 60 HRC; the hardness of the core of the die is 40 HRC.
The above is merely a comparison between the specific implementation example of the present invention and the actual field application, and is not intended to limit the extension and the range of the present invention. For the technical personnel in the production field, the invention can be changed according to the objective actual conditions of the personnel, which is more beneficial to the production of the personnel. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (4)
1. A process for manufacturing a high-performance seamless steel pipe cold-drawing die by using low-carbon low-alloy steel is characterized by comprising the following steps of:
the method comprises the following specific steps:
(1) material selection for cold-drawing dies
The method is characterized in that 20CrMnTi round steel is selected as a material for manufacturing a cold-drawing die, and the chemical composition requirements are as follows: 0.17 to 0.23 percent of C, 0.17 to 0.37 percent of Si, 0.80 to 1.10 percent of Mn, less than or equal to 0.035 percent of S, less than or equal to 0.035 percent of P, 1.00 to 1.30 percent of Cr, 0.04 to 0.10 percent of Ti, less than or equal to 0.030 percent of Ni and less than or equal to 0.030 percent of Cu;
the microstructure requirement is as follows: pearlite and ferrite structures having a banded structure grade of not more than 3;
(2) machining
When the cold-drawing die is an inner die, turning the inner die, and reserving the grinding amount of 0.2mm on the basis of the standard size of the diameter size of the outer circle of the inner die; when the cold-drawing die is an external die, turning the external die, and reserving 0.2mm grinding amount on the basis of the standard size of the inner diameter of the external die;
(3) solid carbonitriding agent ingredient
Preparing a solid carbonitriding agent, wherein the solid carbonitriding agent consists of 603 liquid carburizing agent powder and carbon nitride powder in a mass ratio of 7: 3;
(4) mould packing
Putting the cold-drawing die and the solid carbonitriding agent into a stainless steel plate infiltration box together, and sealing the box cover;
(5) carbonitriding
Firstly, heating a heat treatment furnace to 800 ℃, then placing a stainless steel infiltration box filled with a solid carbonitriding agent and a cold drawing die into a hearth of the heat treatment furnace, electrifying and heating to 880-900 ℃, carrying out constant-temperature diffusion for 1.75-2 hours, then taking out the infiltration box, opening a box cover, taking out the cold drawing die in the solid carbonitriding agent, placing the cold drawing die on the air, and carrying out air cooling and normalizing to room temperature;
(6) cylindrical grinding
Grinding the cold-drawing die after carbonitriding normalizing according to the standard size and roughness requirement of the cold-drawing die to obtain a carbonitriding cold-drawing die;
(7) preparation of vanadinizing salt bath
The vanadinizing agent comprises the following components in percentage by weight: aqueous borax powder (Na)2B4O7·10H280% of O), 10% of potassium chloride (KCl) and vanadium pentoxide (V)2O5)6 percent of aluminum powder and 4 percent of aluminum powder;
(8) vanadinizing quenching
Adding the prepared vanadinizing agent into a stainless steel crucible of an external heating salt bath furnace, forming a vanadinizing salt bath at 900 ℃, hanging an internal cold-drawing die into the vanadinizing salt bath, keeping the temperature at 900 ℃ for 4 hours, taking out the cold-drawing die from the vanadinizing salt bath, removing salt adhered to the cold-drawing die, cooling and quenching the cold-drawing die in water, immediately putting the cold-drawing die into an electric furnace at 200 ℃ for tempering for 1.5 hours after quenching;
(9) and (3) carrying out infiltration post-treatment:
and (3) putting the tempered cold-drawing die into a sodium hydroxide solution with the mass content of 10%, boiling, preserving the temperature for 1 hour, polishing the surface of the cold-drawing die, and coating oil after polishing to obtain the cold-drawing die with high toughness and high wear resistance.
2. The process for manufacturing the cold-drawing die for the high-performance seamless steel tube from the low-carbon low-alloy steel as claimed in claim 1, wherein the cold-drawing die comprises the following steps: when the liquid vanadinizing agent is prepared, firstly, the water-containing borax powder is put into a stainless steel crucible of a salt bath furnace, then the temperature is set and the electric heating is carried out to 800 ℃, after the borax is completely melted, the vanadium pentoxide is added, then the aluminum powder is added and the mixture is continuously stirred evenly, finally, the temperature is raised to the vanadinizing process temperature of 900 ℃, the potassium chloride is added, and after the borax is completely melted, the salt bath melt is stirred evenly for standby application.
3. The process for manufacturing the cold-drawing die for the high-performance seamless steel tube from the low-carbon low-alloy steel as claimed in claim 1, wherein the cold-drawing die comprises the following steps: when the molds are boxed, a solid carbonitriding agent with the thickness of 2cm is paved at the bottom of a infiltration box, then a layer of cold-drawing mold is placed on the surface of the solid carbonitriding agent, the distance between the cold-drawing mold and the box wall is more than or equal to 1cm, the sum of the distance between two adjacent cold-drawing molds is more than or equal to 1cm, then the solid carbonitriding agent is buried and tamped, then a second layer of cold-drawing mold and the solid carbonitriding agent are placed, the distance between two adjacent cold-drawing molds is more than or equal to 1cm, the solid carbonitriding agent with the thickness of more than or equal to 4cm is buried and tamped above the last layer of cold-drawing mold, then a box cover is added, and a gap between the box.
4. The process for manufacturing the cold-drawing die for the high-performance seamless steel tube from the low-carbon low-alloy steel as claimed in claim 1, wherein the cold-drawing die comprises the following steps: the depth of the carbonitriding hardened layer of the high-toughness and high-wear-resistance cold-drawing die is 0.8 mm-1.2 mm, the structure of the high-toughness and high-wear-resistance cold-drawing die is fine needle-shaped tempered martensite and granular carbon nitrogen compounds distributed in a dispersing way, and the hardness of the high-toughness and high-wear-resistance cold-drawing die is 60 HRC-62 HRC; the outermost layer is coated with a white and bright vanadized hardened layer with a hardness of 2500HV0.1～2800HV0.1(ii) a The core structure of the die is fine lath-shaped tempered martensite, and the hardness of the die is 40 HRC-45 HRC; the vanadium-impregnated layer on the surface is a compact vanadium carbide layer, and the main structures of the vanadium-impregnated layer are VC type and V type8C7A type carbide.
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