CN116174515A

CN116174515A - Manufacturing process of combined steel pipe cold-drawing outer die with external die core being subjected to composite treatment of carbonitriding boron vanadium

Info

Publication number: CN116174515A
Application number: CN202310062020.0A
Authority: CN
Inventors: 苗昕旺; 谷志刚; 刘希德; 李金红; 陈志明; 成宇宁; 范旭; 臧玉郡
Original assignee: Jinzhou Jietong Railway Machinery Co ltd
Current assignee: Jinzhou Jietong Railway Machinery Co ltd
Priority date: 2023-01-19
Filing date: 2023-01-19
Publication date: 2023-05-30

Abstract

A manufacturing process of a combined steel pipe cold-drawing outer die subjected to external die core composite carbonitriding boron vanadium treatment comprises the steps of forming an outer die core and an outer die sleeve arranged on the periphery of the outer die core; the outer die core is characterized in that firstly, an outer die core matrix of 42CrMo steel or 40Cr steel which is forged and turned is subjected to carbonitriding in a cementation tank by using a solid carbonitriding agent, then, the outer die core is subjected to borovanadium cementation in the cementation tank by using a solid borovanadium cementation agent, and finally, the outer die core subjected to carbonitriding and borovanadium cementation composite cementation is required to be combined and inlaid with a 45# steel outer die sleeve, so that a combined steel pipe cold-drawing outer die is obtained. The advantages are that: the process is simple and convenient, the production efficiency is high, the wear resistance of the surface of the die hole is improved, the toughness of the core part of the die core is improved, the cold-drawing radial pressure and friction force can be better born, and the service life of the cold-drawing external die is prolonged.

Description

Manufacturing process of combined steel pipe cold-drawing outer die with external die core being subjected to composite treatment of carbonitriding boron vanadium

Technical Field

The invention belongs to the field of die manufacturing, and particularly relates to a manufacturing process of a combined steel pipe cold-drawing outer die for external die core composite carbonitriding boron vanadium treatment.

Technical Field

Seamless steel pipes are important basic materials in national economic construction, and are indispensable substances in both daily life and various production fields. In the cold drawing production process of seamless steel pipes with various specifications, the quality and the service life of a drawing die are important factors directly influencing the quality and the production efficiency of steel pipe products. For an outer die in a steel tube cold drawing die, under the cold drawing production working condition, the inner wall metal layer of a die hole of the outer die bears huge surface friction force, radial tension force and axial impact force. In particular to a large-caliber seamless steel pipe outer die, besides the huge external stress, two different wear mechanisms of adhesive wear and abrasive wear and cold-hot fatigue phenomena exist between the drawn pipe blank and the inner hole surface of the outer die, so that failure modes generated in the process of drawing the outer die in service are mainly wear of the die hole surface, contact fatigue and impact fracture of a matrix. Based on the above situation, the working part of the seamless steel tube cold-drawing outer die must have enough tensile strength and core toughness, and also has excellent inner hole surface wear resistance.

The material and the process method for manufacturing the cold-drawing outer die of the steel pipe at home and abroad are more, and the steel pipe has two types of integral and combined outer die in structural form, and for manufacturing the outer die with larger volume, the integral die is unsuitable in material cost and heat treatment processing, so that the combined outer die is more applied. For the combined outer die, the die sleeve material is mainly made of low-cost carbon structural steel in terms of material use at present, and the die core material is mainly made of hard alloy or high-carbon alloy die steel such as GCr15, cr12MoV and the like subjected to certain special heat treatment. However, whether the hard alloy or the high-carbon alloy die steel is used as the die core, the die core made of the material is extremely easy to generate integral fracture and partial stripping when being subjected to larger impact load in the service process, and therefore, for the large-caliber cold-drawing external die, the hardness and the wear resistance of the die hole surface are improved, the substrate toughness of the die core is considered, and the manufacturing cost of the integral die is also considered.

At present, in the outer mold manufacturing production of a seamless steel pipe cold drawing mold, in order to reduce the production cost and improve the performance, a combined outer mold is mostly adopted, namely, the outer mold is divided into a mold core and a mold sleeve, and the mold core is manufactured by adopting a special material and a special process and then is combined with the mold sleeve. The high-performance mold core adopted at present in China is mainly manufactured by adopting hard alloy processing or high-carbon high-alloy steel through heat treatment. Although the hard alloy die core has high hardness and excellent wear resistance, the hard alloy die core has the problems of insufficient toughness of a matrix and easy fracture when being subjected to impact vibration, and the hard alloy die core has higher price, and the high-carbon high-alloy steel die core has the problems of insufficient toughness of the core and easy fracture after being quenched.

CN 112090973A discloses a process for manufacturing a high-performance seamless steel tube cold drawing die from low-carbon low-alloy steel, which comprises the steps of placing a stainless steel infiltration tank filled with a solid carbonitriding agent and the cold drawing die into a hearth of a heat treatment furnace, electrifying and heating to 880-900 ℃ and performing carbonitriding for 1.75-2 hours at constant temperature, taking out an air-cooled normalizing device to room temperature, polishing, adding a vanadium infiltration agent (80 wt% of water borax powder, 10wt% of potassium chloride, 6wt% of vanadium pentoxide and 4wt% of aluminum powder) into a stainless steel crucible of an external heating salt bath furnace, forming a vanadium infiltration salt bath at 900 ℃, hanging the cold drawing die into the vanadium infiltration salt bath, performing vanadium infiltration at the constant temperature of 900 ℃ for 4 hours, performing water cooling quenching, and tempering in an electric furnace; and cleaning and polishing to obtain the product. The advantages are that: the toughness and the surface wear resistance of the matrix can be obviously improved, the surface cracking and the brittle failure of the matrix of the cold drawing die in service are reduced, and the service life of the seamless steel tube cold drawing die is prolonged. The defects are: (1) The thickness of the high-hardness vanadium carbide film layer obtained on the surface of the die can only be 10-15 mu m, and the thickness of the vanadium carbide film layer is too thin and is not enough to bear the damage of cold drawing radial pressure and friction force; (2) When the vanadium is permeated, the vanadium permeation agent is melted into liquid salt in a crucible for salt bath, and the capacity of the crucible is too small to be suitable for diffusion of the outer mold core with larger volume. (3) After diffusion in the salt bath, the sticking salt on the surface of the workpiece is not easy to clean.

Disclosure of Invention

The invention aims to solve the technical problem of providing the manufacturing process of the combined steel pipe cold-drawing outer die which has low cost, simple process and high production efficiency, can greatly improve the wear resistance of the surface of the die hole, can improve the toughness of the core part of the die core, and can prolong the service life of the cold-drawing outer die.

The surface of the outer die core of the seamless steel tube cold drawing die is subjected to carbonitriding and borovanadium co-cementation composite cementation (hereinafter referred to as C-N+B-V composite cementation) treatment to obtain a carbonitriding and borovanadium co-cementation hardening layer with the depth of more than 1mm, wherein the depth of the carbonitriding layer on the secondary surface is between 1.0mm and 1.2mm, and the quenching hardness is between 60 and 65 HRC; forming a continuous saw-tooth boron-vanadium compound hardening layer on the outer surface of the mold core hole, wherein the thickness of the boron-vanadium compound hardening layer is 90-120 mu m, and the hardness of the boron-vanadium compound hardening layer is 1300-1900 HV; and the matrix hardness of the mold core is about 45 HRC-55 HRC.

The technical scheme of the invention is as follows:

a manufacturing process of a combined steel pipe cold-drawing external mold treated by die core composite carbonitriding boron vanadium is characterized by comprising the following steps: the combined steel pipe cold-drawing outer die comprises an outer die core and an outer die sleeve arranged at the periphery of the outer die core; the specific manufacturing process is as follows: (1) Forging 42CrMo steel or 40Cr steel into an outer die core blank, forging 45# steel into an outer die sleeve blank, and performing turning processing after performing conventional annealing to obtain an outer die core matrix and an outer die sleeve; wherein the outer diameter of the outer die core matrix is 0.3-0.5 mm larger than the inner diameter of the outer die sleeve, namely, the embedding interference of 0.3-0.5 mm is ensured;

(2) The external mold core is prepared by adopting an external mold core matrix, and the specific process is as follows:

1) Preparing the penetrating agent

(1) Preparing solid carbonitriding agent

Uniformly mixing charcoal powder and agricultural urea according to a mass ratio of 6:4 to obtain a solid carbonitriding agent;

(2) preparing solid boron-vanadium co-permeation agent

Mixing boron carbide, ferrovanadium, potassium fluoborate, ammonium chloride, silicon carbide and alumina powder according to the mass ratio of 3:10:3:4:40:40 to obtain a solid boron-vanadium co-permeation agent;

2) Carbonitriding

Placing the outer mold core and the solid carbonitriding agent into a stainless steel infiltration tank together, and then covering the tank cover and sealing; putting the infiltration tank with the outer die core into a well-type electric furnace which is heated to 750 ℃, continuously heating to 850+/-10 ℃ and carrying out constant-temperature carbonitriding for 4 hours, carrying out air cooling and polishing to obtain a carbonitriding outer die core;

3) Boron-vanadium co-permeation

(1) Filling the carbonitriding outer mold core and the borovanadium carbonitriding agent into a stainless steel infiltration tank together, and then covering and sealing a tank cover;

(2) putting the infiltration tank with the carbonitriding outer die core into a well-type electric furnace which is heated to 800 ℃, and continuously heating to 900+/-10 ℃ to perform constant-temperature borovanadium co-infiltration for 4-6 hours;

(3) taking out the outer die core, putting the outer die core into quenching oil for quenching, and cooling to room temperature;

(4) performing surface cleaning on the outer die core cooled to room temperature after quenching, then placing the outer die core into a resistance furnace at 200 ℃ for tempering for 2 hours, discharging the outer die core, performing air cooling to room temperature, and performing surface cleaning by using sand paper to obtain the outer die core with high core strength and toughness, high surface hardness and high wear resistance;

(3) And combining and inlaying the outer die core subjected to carbonitriding and borovanadium carbonitriding composite cementation treatment with an outer die sleeve to obtain the combined steel pipe cold-drawing outer die.

Further, when the outer mold core is subjected to carbonitriding canning, a layer of solid carbonitriding agent with the thickness of 20mm is uniformly paved at the bottom of the canning pot, then the outer mold core is stacked on the surface of the carbonitriding agent, the distance between the outer mold core and the inner wall of the canning pot is more than or equal to 20mm, the inner hole of the mold core is tamped after being filled with the solid carbonitriding agent, and the thickness of the solid carbonitriding agent on the upper mold core is more than or equal to 50mm; and finally, covering the tank cover, and sealing the gap between the tank cover and the tank wall by using water glass clay mud.

Further, when the outer mold core carries out the boron-vanadium co-permeation canning, a layer of solid boron-vanadium co-permeation agent with the thickness of 20mm is uniformly paved at the bottom of the permeation canning, then the outer mold core is stacked on the surface of the permeation agent, the distance between the outer mold core and the inner wall of the permeation canning is more than or equal to 20mm, the inner hole of the mold core is tamped after the solid boron-vanadium co-permeation agent is filled, and the thickness of the solid boron-vanadium co-permeation agent on the upper mold core is more than or equal to 20mm; and finally, covering the tank cover, and sealing the gap between the tank cover and the tank wall by using water glass clay mud.

When the outer die core and the outer die sleeve are combined and inlaid, the outer die sleeve is put into a well-type resistance furnace which is heated to 600-650 ℃ for 1-2 hours, taken out, put on a workbench, put the outer die core subjected to C-N+B-V composite infiltration treatment into an inner hole of the outer die sleeve, and then the outer die sleeve is tapped and vibrated by a hand hammer, so that the outer die core is combined and inlaid into a whole in the outer die sleeve, and then the whole outer die after inlaid and combined is immersed in water and cooled to room temperature.

And further, placing the water-cooled mosaic composite outer die into a resistance furnace with the temperature of 200 ℃ for constant temperature for 1-2 hours, and performing stress relief treatment to complete mosaic composite.

Further, the granularity of the ferrovanadium is 80 meshes, the granularity of the silicon carbide is 80-120 meshes, and the granularity of the aluminum oxide is 80-120 meshes.

Further, during carbonitriding, the constant temperature is 850 ℃; the borovanadium co-permeation temperature is 900 ℃ and the time is 4 hours.

As a further preferable mode, the depth of the carbonitriding layer of the combined steel pipe cold-drawing external mold is 1 mm-1.2 mm, and the structure is fine needle-shaped tempered martensite+granular carbon nitrogen compound; the thickness of the boron-vanadium co-permeation layer is 90-120 mu m, and the structure is serrated FeB+Fe ₂ B+vc+boron-containing cementite; the hardness of the carbonitriding layer of the mold core is 800 HV-600 HV, the hardness of the boron-vanadium co-carburized layer is 1300 HV-1900 HV, and the hardness of the core is 45 HRC-55 HRC.

As a further preference, when the steel is forged into an outer die core blank material of 42CrMo steel, the depth of a carbonitriding layer of the cold-drawn outer die of the combined steel pipe is 1 mm-1.2 mm, and the structure is fine needle-shaped tempered martensite plus granular carbon nitrogen compound; the thickness of the boron-vanadium co-permeation layer is 100-120 mu m, and the structure is serrated FeB+Fe ₂ B+vc+boron-containing cementite; the hardness of the carbonitriding layer of the mold core is 800-700 HV, the hardness of the boron-vanadium co-coating layer is 1900-1500 HV, and the hardness of the core is 50-55 HRC.

As a further preference, when the steel is forged into an outer die core blank material of 40Cr, the depth of a carbonitriding layer of the combined steel pipe cold-drawing outer die is 1 mm-1.2 mm, and the structure is fine needle-shaped tempered martensite plus granular carbon nitride; the thickness of the boron-vanadium co-permeation layer is 90-120 mu m, and the structure is serrated FeB+Fe ₂ B+vc+boron-containing cementite; the hardness of the carbonitriding layer of the mold core is 800 HV-600 HV, the hardness of the boron-vanadium co-carburized layer is 1700 HV-1300 HV, and the hardness of the core is 45 HRC-50 HRC.

The basic principle and the performance of the invention are as follows:

the cold-drawing outer die is an important component part in a seamless steel tube drawing die, and forms a complete die set in drawing production together with the inner die, and in the whole drawing production process, the inner hole surface of the outer die is tightly contacted with the outer wall of a tube blank and bears huge static tensile stress, surface friction force and impact force, so that the surface of the outer die hole is extremely easy to be worn, fatigued, local fracture and other failure damages, thereby influencing the product quality and the production efficiency.

The invention adopts a combined cold-drawing external mold, mainly from the viewpoints of reducing material cost and facilitating heat treatment operation, the whole external mold is divided into a mold core and a mold sleeve, wherein the mold core is made of materials far less than the mold sleeve, the mold core is made of materials which are mainly subjected to load and damage in the pipe drawing process, the mold core is made of 42CrMo or 40Cr alloy structural steel, the mold sleeve is made of 45 high-quality carbon structural steel, and the mold core is subjected to C-N+B-V composite infiltration hardening treatment, so that the mold core obtains a reasonable hardening gradient infiltration layer from the surface to the inside, the surface of the mold core obtains a carbon-nitrogen-boron-vanadium superhard composite infiltration layer so as to improve the hardness and the wear resistance of the surface of the external mold, and the core is made of materials far higher than the strength and toughness of hard alloy and high-carbon high alloy steel, and the mold sleeve is thermally inlaid to form the combined external mold. The method has the advantages that the cost of the die material can be reduced by adopting a combined structure, the wear resistance of the surface of the inner hole of the die can be effectively improved, and meanwhile, the method has good core toughness, so that the service life of the cold-drawn outer die of the steel tube is prolonged.

The invention is based on the problem of prolonging the service life of the seamless steel tube cold-drawing outer die. The research method starts from three aspects, and effectively solves the problems of abrasion resistance of the cold-drawn outer die surface of the seamless steel tube, toughness of the matrix and cost of die materials. Firstly, completely adopting a combined outer die to reduce the material and production and processing cost, namely dividing the whole outer die into a die sleeve and a die core, carrying out chemical heat treatment and strengthening on the die core, and then embedding the die core and the die sleeve into a whole to form the whole outer die; secondly, a certain common low-medium carbon structural steel material is used for replacing hard alloy or high-carbon high-chromium die steel to manufacture the die core so as to improve the toughness of the die core and solve the problem of brittle failure easily occurring when the die core is subjected to a larger impact load; the high-carbon high-chromium die steel has higher carbon content (1.4-2.3%), the surface is wear-resistant after heat treatment, but the core is fragile, the carbon content of the common structural steel is less than or equal to 0.5%, the core toughness is good, and the surface wear resistance can reach the strengthening purpose through carbonitriding; thirdly, the carbon nitrogen and boron vanadium composite infiltration layer with high hardness is obtained on the surface layer of the die hole of the outer die core by the surface chemical heat treatment strengthening method of carbon nitrogen and boron vanadium composite infiltration of the structural steel die core, and the wear resistance, seizure resistance and thermal fatigue resistance of the surface of the die hole of the outer die of the tube drawing can be effectively improved.

The invention has the beneficial effects that:

(1) The combined steel pipe cold-drawing outer die comprises an outer die core and an outer die sleeve, wherein the outer die core and the outer die sleeve are combined in a thermal mosaic mode, the outer die core is made of 42CrMo or 40Cr alloy structural steel, the outer die sleeve is made of 45# high-quality carbon structural steel, the material cost is reduced, and the outer die core is convenient to carry out composite infiltration hardening treatment on the outer die core C-N+B-V.

(2) The outer mold core adopts C-N+B-V composite infiltration, so that the mold core obtains a reasonable hardening gradient infiltration layer from the outside to the inside; the surface of the mold core is provided with a carbonitriding vanadium superhard composite carburized layer to improve the hardness and wear resistance of the surface of the outer mold, and the core part of the mold core is provided with the toughness far higher than that of hard alloy and high-carbon high-alloy steel, so that the service life of the steel pipe cold drawing outer mold is prolonged (3) after carbonitriding, solid cementation is carried out by using a solid boron vanadium cementation agent, the mold is suitable for carrying out diffusion of a larger outer mold, and the surface of a workpiece is easy to clean after the diffusion; and a plurality of workpieces can be added into the infiltration barrel at one time to carry out the boron-vanadium co-infiltration agent, so that the production efficiency is high. When the boron-vanadium co-permeation layer is serrated FeB+Fe ₂ The thickness of the B+VC+boron-containing cementite can reach 80-120 mu m, and the cold-drawing radial pressure and friction force can be better borne.

(4) The external mold manufactured by combining the external mold cores subjected to the C-N+B-V composite infiltration hardening treatment has the advantages of simple method and low production cost, and the research result is applied to the tube drawing production of a certain domestic steel tube factory in batches, so that good benefits are obtained, and the method is suitable for application requirements of steel tube production enterprises.

Drawings

FIG. 1 is a schematic diagram of a C-N+B-V composite cementation treatment process according to the present invention;

FIG. 2 is a schematic diagram of a cold-drawing outer die of a combined steel pipe in the invention;

FIG. 3 is a schematic illustration of a solid process carbonitriding and solid borovanadium co-cementation canning for use in the present invention;

FIG. 4 is a cross-sectional micro Vickers hardness gradient profile of a 42CrMo steel and a 40Cr steel sample according to the present invention after being subjected to a C-N+B-V composite infiltration hardening treatment by a solid method;

FIG. 5 is a photograph of a metallographic structure of a cementation layer 100 times lower after a composite cementation hardening treatment of a 42CrMo steel sample according to the present invention;

FIG. 6 is a photograph showing a metallographic structure of a surface cementation layer 500X times higher after a C-N+B-V composite cementation hardening treatment by a 42CrMo steel sample according to the present invention.

Detailed Description

Inventive examples 1 to 4 were prepared using an outer mold material: the round steel 42CrMo or 40Cr is selected as the die core material of the outer die, and the steel 45 is selected as the die sleeve material of the outer die, and the chemical composition requirements are as follows:

table 1 chemical composition (wt%) of test steel (GB/T3077-2015, GB/T699-1999)

Steel grade

C

Si

Mn

S

P

Cr

Mo

Ni

Cu

42CrMo

0.38-0.45

0.17-0.37

0.50-0.80

≤0.030

0.90-1.20

0.15-0.25

≤0.3

≤0.03

40Cr

0.37-0.44

0.17-0.37

0.50-0.80

≤0.030

0.80-1.10

——

≤0.3

≤0.03

45# steel

0.42-0.50

0.17-0.37

0.50-0.80

≤0.030

≤0.25

——

≤0.3

≤0.25

Examples

The invention relates to a manufacturing process of a combined steel pipe cold-drawing outer die treated by die core composite carbonitriding boron vanadium, wherein the combined steel pipe cold-drawing outer die comprises an outer die core and an outer die sleeve arranged on the periphery of the outer die core; as shown in fig. 1, the specific manufacturing process is as follows:

(1) Manufacturing of 42CrMo steel phi 102mm combined cold-drawing external die and sample

Upsetting 42CrMo/40Cr round steel to prepare an outer die core blank, annealing, turning and forming, wherein the chemical components meet the requirements of GB3077-2015 (Table 1), and obtaining an outer die core matrix; the size of the sample is phi 25 multiplied by 6mm, and the sample is made of the same material as the outer die core; upsetting 45# round steel to prepare an outer die sleeve blank, annealing and turning to obtain an outer die sleeve, wherein the chemical components meet the requirements of GB/T699-1999 (Table 1);

wherein the outer diameter of the outer die core matrix is 0.3-0.5 mm larger than the inner diameter of the outer die sleeve, namely, the embedding interference of 0.3-0.5 mm is ensured;

(2) Tank permeation preparation

Welding a cylindrical infiltration tank with the inner diameter dimension larger than the outer diameter of the mold core by using a stainless steel plate with the thickness of 6 mm;

(3) Preparation of C-N+B-V composite infiltration equipment

A well-type resistance furnace that can be heated to 950 ℃;

(4) The external mold core is prepared by adopting an external mold core matrix solid method C-N+B-V composite infiltration hardening treatment, and the specific process is as follows: 1) Preparing solid carbonitriding agent and solid borovanadium co-curing agent according to a certain proportion

(1) Preparing solid carbonitriding agent

The solid carbonitriding agent comprises the following materials: the crushed charcoal powder is 60wt%; the weight of the round granular agricultural urea is 40 percent;

(2) preparing solid boron-vanadium co-permeation agent

The solid borovanadium co-penetrating agent comprises the following materials: 3% by weight of boron carbide (analytically pure); 10wt% of ferrovanadium (80 meshes); 3% by weight of potassium fluoroborate (analytically pure); ammonium chloride (analytically pure) 4wt%; 40wt% of silicon carbide (80-120 meshes); 40wt% of alumina (80-120 meshes);

2) Carbonitriding

(1) Uniformly paving a layer of solid carbonitriding agent with the thickness of 20mm on the bottom surface of a stainless steel barrel-type infiltration tank, then stacking 3 mold cores and samples on the surface of the infiltration agent, wherein the distance between an outer mold core/sample and the inner wall of the infiltration tank is more than or equal to 20mm, tamping after filling the inner holes of the mold cores with the solid carbonitriding agent, and filling the solid carbonitriding agent with the thickness of 50mm above the uppermost outer mold core and tamping; then adding a tank cover, and sealing the gap between the tank cover and the tank wall with water glass clay mud;

(2) placing the stainless steel infiltration tank filled with the outer mold core and the solid carbonitriding agent into a hearth of a well-type electric furnace which is heated to 750 ℃, continuously heating to 850+/-10 ℃, performing constant-temperature infiltration for 4-6 hours at the temperature, taking out the infiltration tank from the hearth, and placing the infiltration tank on an air-ground air-cooling to room temperature;

(3) taking out the carbonitriding outer die core and the sample from the carbonitriding tank, cleaning, clamping on a lathe spindle chuck, polishing the surface of a die hole by using abrasive cloth, removing surface attachments until the bright metallic color is exposed, and then removing to obtain the carbonitriding outer die core;

3) Boron-vanadium co-permeation

(1) Uniformly paving a layer of solid boron-vanadium co-cementation agent with the thickness of 20mm on the bottom surface of a stainless steel barrel-type cementation tank, then stacking 3 carbonitriding outer die cores on the surface of the cementation agent, and performing a test, wherein the distance between each outer die core/sample and the inner wall of the cementation tank is more than or equal to 20mm, tamping after filling the inner holes of the die cores with the solid boron-vanadium co-cementation agent, and filling the solid boron-vanadium co-cementation agent with the thickness of 20mm above the uppermost outer die core; then adding a tank cover at the gap between the tank cover and the tank wall, and sealing with water glass clay mud;

(2) putting a infiltration tank filled with an external mold core and a solid boron-vanadium co-infiltration agent into a hearth of a well type electric furnace which is heated to 800 ℃, continuously heating to 900+/-10 ℃, performing constant-temperature infiltration for 4-6 hours at the temperature, taking out the infiltration tank from the hearth, pouring out the mold core, the sample and the infiltration agent after a tank cover is opened, immediately immersing the mold core and the sample into quenching oil, and cooling to the room temperature;

(3) placing the mold core and the sample subjected to the boron-vanadium co-infiltration quenching into a resistance furnace at 200 ℃ for tempering for 2 hours, taking out, air-cooling to room temperature, and then performing surface cleaning by using sand paper to obtain a C-N+B-V composite infiltration outer mold core;

(5) The outer die core and the outer die sleeve are combined and embedded, and the specific operation process is as follows:

1) Placing the outer die sleeve into a pit furnace which is heated to 600-650 ℃ for heating, and keeping the temperature for 1-2 hours after the furnace temperature is restored to 600-650 ℃;

2) Taking out the heated outer die sleeve from the furnace, horizontally placing the outer die sleeve on the plane of a workbench, slightly placing the cold state of the C-N+B-V composite infiltrated outer die core into a cavity of the hot outer die sleeve, and tapping the vibrating outer die sleeve by a hand hammer to enable the outer die core to be integrated with the hot outer die sleeve into a whole by implementation in the die sleeve;

3) Quickly immersing the whole set of outer die after the thermal mosaic combination into a water tank to cool to room temperature (the die sleeve firmly holds the die cores with interference to form a whole through thermal expansion and cold contraction);

4) Placing the combined outer die into a tempering furnace at 200 ℃ to eliminate stress and keep the temperature for 1-2 hours, and taking out the outer die to be oiled and rust-proof; and finishing the whole set of outer die.

Example 1

Upsetting 42CrMo round steel with the diameter of phi 160mm is adopted to manufacture an outer die core blank, the outer die core blank is subjected to turning forming after annealing, and chemical components meet the requirements of GB3077-2015 (table 1) to obtain an outer die core matrix; the size of the sample is phi 25 multiplied by 6mm, and the sample is made of the same material as the outer die core;

upsetting the phi 186 type 45# round steel to prepare an outer die sleeve blank, annealing and turning, wherein the chemical components meet the requirements of GB/T699-1999 (table 1) to obtain an outer die sleeve;

the outer diameter of the outer die core matrix is 0.3mm larger than the inner diameter of the outer die sleeve, namely, the embedding interference of 0.3mm is ensured;

(2) Tank permeation preparation

Welding a cylindrical infiltration tank with an inner diameter dimension larger than 40mm of the outer diameter of the mold core by using a stainless steel plate with a thickness of 6mm (as shown in figure 3);

(3) Preparation of C-N+B-V composite infiltration equipment

A well-type resistance furnace that can be heated to 950 ℃;

(1) Preparing solid carbonitriding agent

(2) preparing solid boron-vanadium co-permeation agent

2) Carbonitriding

(1) Uniformly paving a layer of solid carbonitriding agent with the thickness of 20mm on the bottom surface of a stainless steel barrel-type infiltration tank, then stacking 3 mold cores and samples on the surface of the infiltration agent, wherein the distance between an outer mold core/sample and the inner wall of the infiltration tank is more than or equal to 20mm, tamping after filling the inner holes of the mold cores with the solid carbonitriding agent, and filling the solid carbonitriding agent with the thickness of 50mm above the uppermost outer mold core and tamping; then adding a tank cover, and sealing the gap between the tank cover and the tank wall with water glass clay mud (shown in figure 3);

(2) placing the stainless steel infiltration tank filled with the outer mold core and the solid carbonitriding agent into a hearth of a well-type electric furnace which is heated to 750 ℃, continuously heating to 850 ℃, performing constant-temperature infiltration for 4 hours at the temperature, taking out the infiltration tank from the hearth, and placing the infiltration tank on an air-ground to air-cool to room temperature;

3) Boron-vanadium co-permeation

(1) Uniformly paving a layer of solid boron-vanadium co-cementation agent with the thickness of 20mm on the bottom surface of a stainless steel barrel-type cementation tank, then stacking 3 carbonitriding outer die cores on the surface of the cementation agent, and performing a test, wherein the distance between each outer die core/sample and the inner wall of the cementation tank is more than or equal to 20mm, tamping after filling the inner holes of the die cores with the solid boron-vanadium co-cementation agent, and filling the solid boron-vanadium co-cementation agent with the thickness of 20mm above the uppermost outer die core; then a tank cover is added at the gap between the tank cover and the tank wall, and the tank cover is sealed by using water glass clay mud (shown in figure 3);

(2) putting the infiltration tank filled with the external mold core and the solid boron-vanadium co-infiltration agent into a hearth of a well-type electric furnace which is heated to 800 ℃, continuously heating to 900 ℃, performing constant-temperature infiltration for 4 hours at the temperature, taking out the infiltration tank from the hearth, pouring out the mold core, the sample and the infiltration agent after opening a tank cover, and immediately immersing the mold core and the sample into quenching oil to be cooled to room temperature; (3) placing the mold core and the sample subjected to the boron-vanadium co-infiltration quenching into a resistance furnace at 200 ℃ for tempering for 2 hours, taking out, air-cooling to room temperature, and then performing surface cleaning by using sand paper to obtain a C-N+B-V composite infiltration outer mold core;

1) Placing the outer die sleeve into a pit furnace which is heated to 650 ℃ for heating, and keeping the temperature for 1 hour after the furnace temperature is restored to 650 ℃;

2) Taking out the heated outer die sleeve from the furnace, horizontally placing the outer die sleeve on the plane of a workbench, slightly placing the cold state of the C-N+B-V composite infiltrated outer die core into a cavity of the hot outer die sleeve, and tapping the vibrating outer die sleeve by a hand hammer to enable the outer die core to be integrated with the hot outer die sleeve (as shown in figure 2);

4) Placing the combined outer die into a tempering furnace at 200 ℃ to eliminate stress and preserve heat for 2 hours, and taking out the oil coating and rust prevention; and finishing the whole set of outer die.

Organization of samples and performance test results

1) Preparing a 42CrMo steel sample subjected to C-N+B-V composite infiltration hardening treatment in the same furnace as a mold core into a metallographic phase and hardness sample;

2) And (3) metallographic examination: adopting a metallographic microscope to carry out metallographic examination on the edge and the core of the sample, and the result is that: the outer surface of the sample is a white and bright serrated boron vanadium compound layer with the average thickness of 100-120 mu m, and the groupWoven into zigzag FeB+Fe ₂ B+VC+boron-containing cementite, as shown in FIG. 6, can be seen in the form of a saw-tooth white-bright iron-boron compound (Fe ₂ B) And particulate interdental distribution of vanadium carbide; the subsurface is a uniform carbonitriding layer, the structure of the surface is dark high-carbon fine needle-shaped martensite, carbon nitrogen compound and residual austenite, and the depth of the carbonitriding layer is 1.0-1.2 mm; while the matrix structure of the co-infiltrated layer inward is lath tempered martensite (as shown in fig. 6).

3) And (3) hardness test: and (3) carrying out hardness gradient test on the C-N+B-V composite infiltration hardening treated 42CrMo steel sample from the surface to the center by adopting a micro Vickers hardness tester. The detection result is: the hardness of the boron-vanadium co-permeation compound layer on the surface of the sample is 1900-1500 HV in sequence; the hardness of the carbonitriding quenching layer on the subsurface is 800 HV-700 HV in sequence; the hardness of the die core is 50 HRC-55 HRC. The hardness distribution of the sample from the surface to the center portion was uniformly and gently decreased (as shown in FIG. 4).

Example 2

the outer diameter of the outer die core matrix is 0.4mm larger than the inner diameter of the outer die sleeve, namely, the embedding interference of 0.4mm is ensured;

(2) Tank permeation preparation

(3) Preparation of C-N+B-V composite infiltration equipment

A well-type resistance furnace that can be heated to 950 ℃;

(1) Preparing solid carbonitriding agent

(2) preparing solid boron-vanadium co-permeation agent

2) Carbonitriding

(2) placing the stainless steel infiltration tank filled with the outer mold core and the solid carbonitriding agent into a hearth of a well-type electric furnace which is heated to 750 ℃, continuously heating to 840 ℃, performing constant-temperature infiltration for 4 hours at the temperature, taking out the infiltration tank from the hearth, and placing the infiltration tank on an air-ground to air-cool to room temperature;

3) Boron-vanadium co-permeation

(2) putting the infiltration tank filled with the external mold core and the solid boron-vanadium co-infiltration agent into a hearth of a well-type electric furnace which is heated to 800 ℃, continuously heating to 890 ℃, performing constant-temperature infiltration for 6 hours at the temperature, taking out the infiltration tank from the hearth, pouring out the mold core, the sample and the infiltration agent after opening a tank cover, and immediately immersing the mold core and the sample into quenching oil to be cooled to room temperature; (3) placing the mold core and the sample subjected to the boron-vanadium co-infiltration quenching into a resistance furnace at 200 ℃ for tempering for 2 hours, taking out, air-cooling to room temperature, and then performing surface cleaning by using sand paper to obtain a C-N+B-V composite infiltration outer mold core;

1) Placing the outer die sleeve into a pit furnace which is heated to 600 ℃ for heating, and keeping the temperature for 2 hours after the furnace temperature is restored to 650 ℃;

4) Placing the combined outer die into a tempering furnace at 200 ℃ to eliminate stress and preserve heat for 1 hour, and taking out the oil coating and rust prevention; and finishing the whole set of outer die.

Example 3

the outer diameter of the outer die core matrix is 0.5mm larger than the inner diameter of the outer die sleeve, namely, the embedding interference of 0.5mm is ensured;

(2) Tank permeation preparation

(3) Preparation of C-N+B-V composite infiltration equipment

A well-type resistance furnace that can be heated to 950 ℃;

(1) Preparing solid carbonitriding agent

(2) preparing solid boron-vanadium co-permeation agent

2) Carbonitriding

(2) placing the stainless steel infiltration tank filled with the outer mold core and the solid carbonitriding agent into a hearth of a well-type electric furnace which is heated to 750 ℃, continuously heating to 860 ℃, performing constant-temperature infiltration for 4 hours at the temperature, taking out the infiltration tank from the hearth, and placing the infiltration tank on an air-ground to air-cool to room temperature;

3) Boron-vanadium co-permeation

(2) putting the infiltration tank filled with the external mold core and the solid boron-vanadium co-infiltration agent into a hearth of a well-type electric furnace which is heated to 800 ℃, continuously heating to 910 ℃, performing constant-temperature infiltration for 5 hours at the temperature, taking out the infiltration tank from the hearth, pouring out the mold core, the sample and the infiltration agent after opening a tank cover, and immediately immersing the mold core and the sample into quenching oil to be cooled to room temperature; (3) placing the mold core and the sample subjected to the boron-vanadium co-infiltration quenching into a resistance furnace at 200 ℃ for tempering for 2 hours, taking out, air-cooling to room temperature, and then performing surface cleaning by using sand paper to obtain a C-N+B-V composite infiltration outer mold core;

1) Placing the outer die sleeve into a pit furnace which is heated to 620 ℃ for heating, and keeping the temperature for 1.5 hours after the furnace temperature is restored to 620 ℃;

4) Placing the combined outer die into a tempering furnace at 200 ℃ to eliminate stress and preserve heat for 1.5 hours, and taking out the outer die to be oiled and rust-proof; and finishing the whole set of outer die.

Example 4

And manufacturing a combined cold-drawing outer die with the phi of 76mm made of 40Cr steel.

The forging, machining, C-N+B-V composite infiltration hardening treatment of the mold core, the integral inlay combination and the test sample inspection method are identical to those of the embodiment 1, and are not repeated here.

Structure and performance test result of 40Cr steel sample after C-N+B-V composite infiltration hardening treatment

1) And (3) metallographic examination: the metallographic examination of the edges and the core of the sample was performed with a metallographic microscope, with the result that: the outer surface of the sample is a serrated boron vanadium compound layer with the average thickness of about 90-120 mu m, and the tissue is serrated FeB+Fe ₂ B+vc+boron-containing cementite; the subsurface is a uniform black carbonitriding layer which is fine needle-shaped tempered martensite, carbon nitride and residual austenite, and the depth of the carbonitriding layer is 1.0-1.2 mm; and the matrix structure of the carbonitriding layer inward is lath tempered martensite.

2) And (3) hardness test: the hardness gradient test is carried out on the 40Cr steel sample subjected to C-N+B-V composite infiltration hardening treatment by adopting a micro Vickers hardness tester. The detection result is: the hardness of the boron-vanadium co-permeation compound layer on the surface is 1700 HV-1300 HV in sequence; the hardness of the carbonitriding quenching layer on the subsurface is 800 HV-600 HV in sequence; the hardness of the die core is 45 HRC-50 HRC. The hardness distribution of the sample from the surface to the center portion was uniformly and gently decreased (as shown in FIG. 4).

The using effect is as follows: the combined outer die (the inner hole bearing is phi 102 mm) of the embodiment 1 is entrusted to a certain steel pipe factory, and batch drawing production trial of steel pipes with corresponding specifications is carried out on a seamless steel pipe drawing machine production line, so that the combined outer die has obvious strength and toughness advantages compared with the combined outer die of the hard alloy die core, the service life of the outer die is obviously prolonged, and the problems that the hard alloy die core is easy to break and lose efficacy and the die cost is too high are solved, so that the combined outer die is accepted by the production enterprise.

The above is only a specific embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A manufacturing process of a combined steel pipe cold-drawing external mold treated by die core composite carbonitriding boron vanadium is characterized by comprising the following steps: the combined steel pipe cold-drawing outer die comprises an outer die core and an outer die sleeve arranged at the periphery of the outer die core; the specific manufacturing process is as follows:

(1) Forging 42CrMo steel or 40Cr steel into an outer die core blank, forging 45# steel into an outer die sleeve blank, and performing turning processing after performing conventional annealing to obtain an outer die core matrix and an outer die sleeve; wherein the outer diameter of the outer die core matrix is 0.3-0.5 mm larger than the inner diameter of the outer die sleeve, namely, the embedding interference of 0.3-0.5 mm is ensured;

1) Preparing the penetrating agent

(1) Preparing solid carbonitriding agent

(2) preparing solid boron-vanadium co-permeation agent

2) Carbonitriding

3) Boron-vanadium co-permeation

2. The process for manufacturing the combined steel pipe cold-drawing external mold treated by the die core composite carbonitriding boron vanadium according to claim 1, which is characterized in that: when the outer mold core is subjected to carbonitriding and canning, a layer of solid carbonitriding agent with the thickness of 20mm is uniformly paved at the bottom of the carbonitriding tank, then the outer mold core is stacked on the surface of the carbonitriding agent, the distance between the outer mold core and the inner wall of the carbonitriding tank is more than or equal to 20mm, the inner hole of the mold core is tamped after being filled with the solid carbonitriding agent, and the thickness of the solid carbonitriding agent on the upper mold core is more than or equal to 50mm; and finally, covering the tank cover, and sealing the gap between the tank cover and the tank wall by using water glass clay mud.

3. The process for manufacturing the combined steel pipe cold-drawing external mold treated by the die core composite carbonitriding boron vanadium according to claim 1, which is characterized in that: when the outer mold core carries out boron-vanadium co-permeation canning, a layer of solid boron-vanadium co-permeation agent with the thickness of 20mm is uniformly paved at the bottom of the permeation canning, then the outer mold core is stacked on the surface of the permeation agent, the distance between the outer mold core and the inner wall of the permeation canning is more than or equal to 20mm, the inner hole of the mold core is tamped after the solid boron-vanadium co-permeation agent is filled, and the thickness of the solid boron-vanadium co-permeation agent on the upper mold core is more than or equal to 20mm; and finally, covering the tank cover, and sealing the gap between the tank cover and the tank wall by using water glass clay mud.

4. The process for manufacturing the combined steel pipe cold-drawing external mold treated by the die core composite carbonitriding boron vanadium according to claim 1, which is characterized in that: when the outer die core and the outer die sleeve are combined and inlaid, the outer die sleeve is placed in a well-type resistance furnace which is heated to 600-650 ℃ for 1-2 hours, taken out and placed on a workbench, the outer die core subjected to C-N+B-V composite infiltration treatment is placed in an inner hole of the outer die sleeve, and then the outer die core is tapped and vibrated by a hand hammer, so that the outer die core is combined and inlaid into a whole in the outer die sleeve, and then the whole outer die after inlaid and combined is immersed in water and cooled to room temperature.

5. The process for manufacturing the combined steel pipe cold-drawing external mold treated by the die core composite carbonitriding boron vanadium according to claim 1, which is characterized in that: and (3) placing the water-cooled mosaic composite outer die into a resistance furnace with the temperature of 200 ℃ for constant temperature for 1-2 hours, and performing stress relief treatment to complete mosaic composite.

6. The process for manufacturing the combined steel pipe cold-drawing external mold treated by the die core composite carbonitriding boron vanadium according to claim 1, which is characterized in that: the granularity of the ferrovanadium is 80 meshes, the granularity of the silicon carbide is 80-120 meshes, and the granularity of the aluminum oxide is 80-120 meshes.

7. The process for manufacturing the combined steel pipe cold-drawing external mold treated by the die core composite carbonitriding boron vanadium according to claim 1, which is characterized in that: when carbonitriding, the constant temperature is 850 ℃; the borovanadium co-permeation temperature is 900 ℃ and the time is 4 hours.

8. The process for manufacturing the combined steel pipe cold-drawing external mold treated by the die core composite carbonitriding boron vanadium according to claim 7, which is characterized in that: the depth of the carbonitriding layer of the combined steel pipe cold-drawing outer die is 1 mm-1.2 mm, and the structure of the combined steel pipe cold-drawing outer die is fine needle-shaped tempered martensite plus granular carbon nitrogen compound; the thickness of the boron-vanadium co-permeation layer is 90-120 mu m, and the structure is serrated FeB+Fe ₂ B+vc+boron-containing cementite; carbonitriding layer hardening of mold coreThe degree is 800 HV-600 HV, the hardness of the boron-vanadium co-permeation layer is 1300 HV-1900 HV, and the core hardness is 45 HRC-55 HRC.

9. The process for manufacturing the combined steel pipe cold-drawing external mold treated by the die core composite carbonitriding boron vanadium according to claim 7, which is characterized in that: when the steel is forged into an outer die core blank made of 42CrMo steel, the depth of a carbonitriding layer of the combined steel pipe cold-drawing outer die is 1 mm-1.2 mm, and the structure is fine needle-shaped tempered martensite plus granular carbon nitrogen compound; the thickness of the boron-vanadium co-permeation layer is 100-120 mu m, and the structure is serrated FeB+Fe ₂ B+vc+boron-containing cementite; the hardness of the carbonitriding layer of the mold core is 800-700 HV, the hardness of the boron-vanadium co-coating layer is 1900-1500 HV, and the hardness of the core is 50-55 HRC.

10. The process for manufacturing the combined steel pipe cold-drawing external mold treated by the die core composite carbonitriding boron vanadium according to claim 7, which is characterized in that: when the steel is forged into an outer die core blank material of 40Cr, the depth of a carbonitriding layer of the combined steel pipe cold-drawing outer die is 1 mm-1.2 mm, and the structure is fine needle-shaped tempered martensite plus granular carbon nitrogen compound; the thickness of the boron-vanadium co-permeation layer is 90-120 mu m, and the structure is serrated FeB+Fe ₂ B+vc+boron-containing cementite; the hardness of the carbonitriding layer of the mold core is 800 HV-600 HV, the hardness of the boron-vanadium co-carburized layer is 1700 HV-1300 HV, and the hardness of the core is 45 HRC-50 HRC.