CN104862569B - Molybdenum-based material used for hot extrusion die and surface carburizing treatment technology - Google Patents

Abstract

The molybdenum-based material of the present invention uses molybdenum powder as the base material of a high-temperature extrusion die, uses Co as a binder, and adds carbides. The mass percentages of each component are: molybdenum 60-80%, carbides 15-32%, cobalt 2-12%, adding carbon accounts for 0.01-0.1% of the total mass of molybdenum, carbide, and cobalt; the surface carburizing treatment process of molybdenum-based materials adopts charcoal powder with mass percentages of 65-80% and 10-20% Anhydrous sodium carbonate, 5-15% sodium acetate as carburizing agent, charcoal powder particle size below 100 mesh, carburizing temperature at 900-1100°C, holding time 8-10h, forming a layer of dense carbonization on the surface of the material Molybdenum thus protects the material. After carburizing the material of the present invention, the surface hardness HV can reach up to 900, while the core hardness HV is only about 530, which greatly improves the service life of the mold, and can realize rapid extrusion, thereby reducing costs and improving production efficiency.

Description

A molybdenum-based material and surface carburizing treatment process for hot extrusion die

technical field

The invention relates to the formulation of molybdenum-based materials and the technology of surface carburizing treatment of molybdenum-based materials, and belongs to the fields of powder metallurgy, hot extrusion and surface treatment.

Background technique

At present, hot work die steel is usually used as die material in the hot extrusion industry at home and abroad. my country mainly uses 3Cr2W8V steel, while Britain, the United States, the Soviet Union, and Sweden use H13\4Cr5MoVSi steel or other basic steel to make dies. Hot extrusion dies are used under severe conditions such as high temperature, high pressure, wear and thermal fatigue, and the service conditions are very harsh. For example: 20Cr and other materials, the heating temperature is 1150 ~ 1200 ℃, forming on the hydraulic press, the temperature of the mold can reach 900 ~ 950 ℃, due to high pressure forming, the larger the extruded part, the deeper the processing depth (especially reverse Extruded large workpieces), the harsher the conditions, the higher the high temperature strength requirements. Therefore, the hot work mold material should have good comprehensive properties, mainly: it should have high plastic deformation resistance; it should have high thermal stability and wear resistance at service temperature (800-950 °C); it should have high thermal stability and wear resistance under dynamic load. It should have sufficiently high toughness; in addition, low service life of hot extrusion dies and poor economic benefits are common problems.

Hot work die steel, due to its low strength at high temperature, needs to be cooled externally after each hot extrusion to reduce the temperature of the die. The strong friction between workpieces produces chemical action, which causes thermal corrosion on the surface of the mold. This causes the hot extrusion die made of hot work die steel to collapse, deform, pull grooves, burst, surface corrosion and other phenomena, resulting in die failure. Cemented carbide and ceramic materials have a hardness of about HV1000, but due to their high hardness and poor toughness, they are prone to cracks and are scrapped under the action of high temperature and high pressure.

Contents of the invention

The purpose of the invention is to provide a molybdenum-based material and a surface carburizing treatment process for a hot extrusion die.

The present invention uses molybdenum powder as the base material of the high temperature extrusion die, Co as the binder, adding carbide (tungsten carbide or titanium carbide), and the mass percentage of each component depends on the required hardness, strength, toughness and wear resistance The performance indicators such as molybdenum are determined, including 60-80% of molybdenum, 15-32% of carbide, and 2-12% of cobalt; in addition, in order to degas and purify the grain boundary, it is necessary to add 0.01-0.01% of the total mass of molybdenum, carbide and cobalt. 0.1% carbon.

The working temperature of hot extrusion die steel operating under high temperature and high pressure often exceeds the tempering temperature when it is in service. Although multiple means are used for strengthening and toughening treatment (toughening treatment + surface strengthening treatment), in order to improve service conditions and maximize the potential of the material, it is still far from meeting the requirements of performance. The present invention uses surface Carburizing technology solves such problems very well.

Surface carburizing of the present invention adopts 65～80% charcoal powder (particle size is below 100 orders), 10～20% anhydrous sodium carbonate, 5～15% sodium acetate as carburizing agent, and its each component is quality Percentage, the carburizing temperature is between 900°C and 1100°C, and the holding time is 8h to 10h, forming a dense layer of molybdenum carbide on the surface of the material to protect the material.

After the material of the present invention is carburized, the surface hardness HV can reach up to 900, while the core hardness HV is only about 530. The surface not only has the hardness of cemented carbide, but also has the toughness of steel material. And it has good creep resistance at high temperature, low linear expansion coefficient and extremely low vapor pressure, high elastic modulus, less affected by temperature, excellent electrical conductivity, thermal conductivity, high temperature strength and low friction Coefficient, excellent lubricating performance and so on. The service life of the mold is greatly improved, and rapid extrusion can be realized, thereby reducing costs and improving production efficiency.

detailed description

The invention utilizes the molybdenum-based material to directly shape the hot extrusion die through the powder metallurgy method, which satisfies the service performance under high temperature and high pressure conditions, so as to improve the service life of the die, save raw materials, save energy, reduce costs and improve production efficiency. The following percentages are all percentages by mass.

Embodiment one:

Get molybdenum powder 60%, tungsten carbide powder 32%, cobalt powder 8%, carbon powder accounts for 0.1% of the total mass of molybdenum powder, tungsten carbide powder, cobalt powder, ball mills 20 hours with the speed of 300 rev/min in ball mill to make powder Mix evenly, and then use the pre-made mold to cold press on a 200MP isostatic press, put it into a vacuum sintering furnace for pressure sintering (sintering temperature 1400°C-1500°C, pressure 10MPa), after polishing the surface and working belt, Then carry out surface carburizing treatment, the carburizing thickness is 10μm, and then carry out mold assembly, and test the mold on the extruder, repair the mold appropriately according to the situation of the mold test, and finally put it into production and application.

Embodiment two:

Get molybdenum powder 80%, titanium carbide powder 15%, cobalt powder 5%, carbon powder accounts for 0.05% of the total mass of molybdenum powder, titanium carbide powder, cobalt powder, ball mills 24 hours with the speed ball mill of 350 rpm in ball mill to make powder Mix evenly, and then use the pre-made mold to cold press on a 200MP isostatic press, put it into a vacuum sintering furnace for pressure sintering (sintering temperature 1400°C-1500°C, pressure 10MPa), after polishing the surface and working belt, Then carry out surface carburizing treatment, the carburizing thickness is 8μm, then carry out mold assembly, and test the mold on the extruder, repair the mold appropriately according to the situation of the mold test, and finally put it into production and application.

Embodiment three:

Get 75% charcoal powder (particle size is below 100 orders), 13% anhydrous sodium carbonate, 12% sodium acetate, carry out mixing with 60 rev/min rotating speed ball mills two hours on ball mill, carburizing agent and carburizing agent After the carbon parts are placed in the sealed box, the temperature is raised to 1000 °C at a heating rate of 6 °C/min and then kept for 10 hours. After carburizing, the carburized parts are taken out and heated to 1000°C for 2 hours for water quenching, and then the surface of the working part of the carburized parts is polished, and then the mold assembly test is carried out, and finally put into actual production.

Claims (2)

1. a kind of molybdenum base material for hot-extrusion mold, is characterized in that: using molybdenum powder as high-temperature extrusion die base material, with Co makees binding agent, adds carbide, the mass percent of its each component is: molybdenum 60～80%, carbide 15～32%, and cobalt 2～ 12%；In addition, for degasification and purifying crystal boundary, need to add molybdenum, carbide, the carbon of cobalt three's gross mass 0.01～0.1%；

Described carbide is tungsten carbide or titanium carbide.

2. the molybdenum base material case-carbonizing handling process for hot-extrusion mold described in pair claim 1, is characterized in that: adopts Mass percent is respectively 65～80% charcoal powder, 10～20% natrium carbonicum calcinatum, and 5～15% sodium acetate is as carburizing Agent, below 100 mesh, between 900 DEG C～1100 DEG C, temperature retention time 8h～10h, in material for carburizing temperature for the granularity of charcoal powder Surface forms one layer of fine and close molybdenum carbide thus protection materials.