CN104862569A

CN104862569A - Molybdenum-based material used for hot extrusion die and surface carburizing treatment technology

Info

Publication number: CN104862569A
Application number: CN201510250191.1A
Authority: CN
Inventors: 张聚国; 钟建华; 钟奇; 余向阳
Original assignee: Jiangxi University of Science and Technology
Current assignee: Jiangxi University of Science and Technology
Priority date: 2015-05-17
Filing date: 2015-05-17
Publication date: 2015-08-26
Anticipated expiration: 2035-05-17
Also published as: CN104862569B

Abstract

The invention relates to a formula of a molybdenum-based material and a molybdenum-based material surface carburizing treatment technology. The molybdenum-based material comprises, by weight, 60-80% of molybdenum, 15-32% of carbide and 2-12% of cobalt, and carbon accounts for 0.01-0.1% of total mass of the molybdenum, the carbide and the cobalt. According to the molybdenum-based material surface carburizing treatment technology, charcoal dust, anhydrous sodium carbonate and sodium acetate with the mass percents being 65-80%, 10-20% and 5-15% respectively serve as carburizing agents, the granularity of the charcoal dust is smaller than 100 meshes, the carburizing temperature ranges from 900 DEG C to 1100 DEG C, heat-preserving time ranges from 8 hours to 10 hours, and a layer of compact molybdenum carbide is formed on the surface of the material to protect the material. After carburizing of the material, the surface hardness HV of the material can be as high as 900, the core hardness HV of the material is only about 530, the service life of a die is greatly prolonged, quick extrusion can be achieved, cost is reduced, and production efficiency is improved.

Description

A kind of molybdenum base material for hot-extrusion mold and surface cementation treatment process

Technical field

The present invention relates to the formula of molybdenum base material and the technology of molybdenum base material surface cementation process, belong to powder metallurgy, hot extrusion and field of surface treatment.

Background technology

Usually adopt hot-work die steel to do moulding stock at present in domestic and international hot extrusion industry, China mainly uses 3Cr2W8V steel, and English the U.S. and Russia, Sweden then adopt H13 4Cr5MoVSi steel or other basic steel mfg. moulding dies.Hot-extrusion mold is on active service under the mal-conditions such as high temperature, high pressure, wearing and tearing and thermal fatigue, and service condition is very harsh.Such as: the materials such as 20Cr, Heating temperature is 1150 ~ 1200 DEG C, shaping on water pressure engine, the temperature of mould can reach 900 ~ 950 DEG C, because of high-pressure molding, the part be extruded is larger, and the degree of depth of processing is darker (particularly the large workpiece of anti-extrusion), then condition is harsher, and hot strength requires also higher.So hot forming dies materials should have good over-all properties, mainly: high plasticity_resistant deformation ability should be had; High thermostability and wear resistance is had at temperature (800 ~ 950 DEG C) under arms; Sufficiently high toughness should be had under dynamic load; In addition, hot-extrusion mold life-span low, deficiency in economic performance is a common problem.

Hot-work die steel, because hot strength is low, outside water-cooled all will be carried out to reduce die temperature after each hot extrusion, mould will stand serious cool-hot fatigue test, when extrusion molding and red-hot absorption surface, cause the strong friction between mould and workpiece, produce chemical action, make die surface produce thermal etching.This just makes the hot-extrusion mold of hot-work die steel making produce to subside, deformation, La Gou, burst, the phenomenon such as surface corrosion, cause mould invalidation.Wimet and stupalith, hardness can reach about HV1000, but because of hardness large, poor toughness, under the effect of high temperature, high pressure, easily cracks and scraps.

Summary of the invention

The object of the invention is to provide a kind of molybdenum base material for hot-extrusion mold and surface cementation treatment process.

The present invention adopts molybdenum powder as the base material of high-temperature extrusion die, Co makes binding agent, add carbide (wolfram varbide or titanium carbide) element, the mass percent of its each component is determined according to performance index such as required hardness, intensity, toughness and wear resistancies, wherein molybdenum 60 ~ 80%, carbide 15 ~ 32%, cobalt 2 ~ 12%; In addition, in order to degasification and purification crystal boundary, the carbon adding molybdenum, carbide, cobalt three total mass 0.01 ~ 0.1% is needed.

The Extrusion Die Steel of operation under High Temperature High Pressure, working temperature when it is on active service is often beyond tempering temperature.Although adopt multiple means to do highly malleablized process (highly malleablized process+surface Hardening Treatment), to scheme to improve service condition, play the potentiality of material to greatest extent, but still can not meet the requirement of use properties far away, the present invention adopts surface cementation technology well to solve problems.

Surface cementation of the present invention adopts the wood charcoal powder (granularity is below 100 orders) of 65 ~ 80%; the anhydrous sodium carbonate of 10 ~ 20%; the sodium acetate of 5 ~ 15% is as carburizing agent; its each component is mass percent; carburizing temperature is between 900 DEG C ~ 1100 DEG C; soaking time 8h ~ 10h, forms the molybdenum carbide of one deck densification thus protecting materials at material surface.

After material carburizing of the present invention, surface hardness HV reaches as high as 900, and centre hardness HV only has about 530.Surface not only has the hardness of Wimet, also has the toughness of steel.And at high temperature have good creep-resistant property, the vapour pressure that linear expansivity is low and extremely low, high Young's modulus, by the feature such as less, the excellent conduction of the impact of temperature, thermal conductivity, frictional coefficient that hot strength is high and low, lubricity be excellent.Greatly increase the mold use life-span, and can crushing failure at high speed be realized, thus reduce costs and enhance productivity.

Embodiment

The present invention utilizes molybdenum base material through powder metallurgy process direct forming hotwork extrusion mould, meets use properties under high-temperature and high-pressure conditions, to improve die life, save material, save the energy, reduce costs and enhance productivity.Following per-cent is mass percent.

Embodiment one:

Get molybdenum powder 60%, tungsten carbide powder 32%, cobalt powder 8%, carbon dust accounts for molybdenum powder, tungsten carbide powder, 0.1% of cobalt powder total mass, speed ball milling with 300 revs/min in ball mill makes powder mix in 20 hours, after on 200MP isostatic pressing machine, utilize the mold cold pressing formation made in advance, put into vacuum sintering furnace pressure sintering (sintering temperature 1400 DEG C-1500 DEG C, pressure 10MPa), through polished surface and work strip, carry out surface cementation process again, carburizing thickness 10 μm, then die assembly is carried out, and at extrusion machine upper testing mould, suitably repair a die according to die trial situation, finally put into production in the middle of applying.

Embodiment two:

Get molybdenum powder 80%, carbonized titanium powder 15%, cobalt powder 5%, carbon dust accounts for molybdenum powder, carbonized titanium powder, 0.05% of cobalt powder total mass, speed ball milling with 350 revs/min in ball mill makes powder mix in 24 hours, after on 200MP isostatic pressing machine, utilize the mold cold pressing formation made in advance, put into vacuum sintering furnace pressure sintering (sintering temperature 1400 DEG C-1500 DEG C, pressure 10MPa), through polished surface and work strip, carry out surface cementation process again, carburizing thickness 8 μm, then die assembly is carried out, and at extrusion machine upper testing mould, suitably repair a die according to die trial situation, finally put into production in the middle of applying.

Embodiment three:

Get the wood charcoal powder (granularity is below 100 orders) of 75%, the anhydrous sodium carbonate of 13%, 12% sodium acetate, rotating speed ball milling with 60 revs/min on ball mill carries out batch mixing in two hours, carburizing agent and carburizing part are put into the heat-up rate of 6 DEG C/min after watertight chest, after being warmed up to 1000 DEG C, be incubated 10 hours.Take out carburizing part after carburizing to be heated to 1000 DEG C of insulations and to carry out shrend in 2 hours, then carry out die assembly die trial after carrying out carburizing part working portion surface finish process, finally drop into actual production.

Claims

1. for a molybdenum base material for hot-extrusion mold, it is characterized in that: make binding agent with Co, add carbide formers, the mass percent of its each component is: molybdenum 60 ~ 80%, carbide 15 ~ 32%, cobalt 2 ~ 12%; In addition, in order to degasification and purification crystal boundary, the carbon adding molybdenum, carbide, cobalt three total mass 0.01 ~ 0.1% is needed;

Described carbide is wolfram varbide or titanium carbide.

2. pair molybdenum base material surface cementation treatment process for hot-extrusion mold according to claim 1; it is characterized in that: adopt mass percent to be respectively the wood charcoal powder of 65 ~ 80%; the anhydrous sodium carbonate of 10 ~ 20%; the sodium acetate of 5 ~ 15% is as carburizing agent; the granularity of wood charcoal powder is below 100 orders; carburizing temperature is between 900 DEG C ~ 1100 DEG C, and soaking time 8h ~ 10h, forms the molybdenum carbide of one deck densification thus protecting materials at material surface.