CN100341647C

CN100341647C - Production process of wire drawing hard alloy die with gradient varying performance

Info

Publication number: CN100341647C
Application number: CNB03135890XA
Authority: CN
Inventors: 刘咏; 张林秋; 羊建高; 李芳�
Original assignee: Zigong Cemented Carbide Co Ltd
Current assignee: ZIGONG CEMENTED CARBIDE CORP Ltd; Central South University
Priority date: 2003-09-24
Filing date: 2003-09-24
Publication date: 2007-10-10
Anticipated expiration: 2023-09-24
Also published as: CN1526488A

Abstract

The present invention belongs to a production method for a rigid alloy wire drawing mould, which comprises material mixing, mould pressing forming, presintering and dewaxing, sintering and carburization processing. Due to the fact that a mixed material which is compounded from Al2O3, graphite particles, carbonate or/and hydrocarbonate according to a certain proportion is adopted by the present invention as a carburizer in the process of the carburization processing, the carbonate and the hydrocarbonate in the mixed material are decomposed under the high temperature condition of the carburization processing to generate CO2, and the CO2 and the graphite particles react to generate CO gas with strong activity. The CO can rapidly enter a liquid phase to react with an eta phase to generate WC in the process of the carburization processing, the Co is prompted to inward migrate, and thereby, the forming of a gradient structure in an alloy body is accelerated. Thus, the present invention has the characteristics that the temperature of the carburization processing is low; compared with the background art, processing time can be shortened by 55% more or less; the thickness of a non-eta phase layer at the surface is enhanced more than 40%; the alloy body has an obvious binding phase gradient structure; the comprehensive mechanical properties of a rigid alloy wire drawing mould are strong; the average bending intensity of the rigid alloy wire drawing mould is 3130N; the average hardness (HRA) of the rigid alloy wire drawing mould is 91.96, etc.

Description

The production method of the sintered carbide wire drawing die tool that a kind of performance changes in gradient

Technical field

The mechanical performance that the invention belongs to the production method of the sintered carbide wire drawing die in the wire-drawing die production field, particularly a kind of mold is the production method of the sintered carbide wire drawing die tool of distribution gradient from outside to inside.

Background technology

The inside and outside mechanical performance and the metallographic structure of traditional sintered-carbide die (being the standard sintered-carbide die) are consistent, this class mould often exist be difficult to be in harmonious proportion between high rigidity, wearability and the obdurability contradiction, promptly in reducing alloy the content of cobalt (Co) when improving its hardness and wearability, the toughness of alloy body promptly descends thereupon, otherwise then influences its hardness and wearability.In addition, the sintered carbide wire drawing die of metallographic and mechanical performance unanimity, when die surface cracked, its crackle was with very fast expansion and cause entire die to be broken scrapping in drawing process.In order to overcome this disadvantage, be in the patent documentation " being suitable for the cemented carbide body of rock-boring and ore cutting most " of CN1016711B at notification number, a kind of alloy body mechanical performance carbide alloy of structure is in gradient disclosed.The production method of this cemented carbide body is that to adopt low-carbon (LC) WC and an amount of cobalt (Co) powder be raw material, after mixing and being pressed into blank, at 900 ℃ of left and right sides temperature and N ₂Pre-burning 1 hour in the atmosphere, become the alloy body of metallographic and mechanical performance uniformity at 1450 ℃ sintering temperature again; Be placed in the graphite boat then and adopt Al ₂O ₃With the graphite mixed powder as carburizer, heat treatment is more than 2 hours and to make the alloy surface layer be to contain the WC+ γ phase region that Co amount is lower than alloy mean value in 1450 ℃ carburizing atmosphere, the intermediate layer is higher than alloy mean value WC+ γ phase region for containing the Co amount, and core is then for containing the cemented carbide body of η phase.Though this invention has case hardness and wearability height, the formation of the alloy rich cobalt in middle part (Co) layer has toughness again can absorb the impact that bear on the alloy body surface by force, effectively stops characteristics such as the inside diffusion of face crack.But because carburizer is only by Al ₂O ₃Add that the granular graphite about 1.0% mixes, its prescription is simple, and the carburization reaction activity is low, therefore exists carburization processing time long, and temperature requirement is higher relatively and structure gradient formation speed is slow, and productivity ratio is low; The high-temperature carburizing processing that surpasses 2 hours will cause the grain growth of alloy, the disadvantages such as serviceability of reduction alloy again; In addition, also there is the high defective of energy consumption and production cost in the carbide alloy that employing said method manufacturing machine performance etc. changes in gradient.

Summary of the invention

The objective of the invention is disadvantage at the background technology existence, the production method of the sintered carbide wire drawing die tool that a kind of performance of research and design changes in gradient, the sintered carbide wire drawing die tool carried out in the Carburization Treatment process accelerating speed that the mold gradient-structure forms, shortening carburization processing time, the comprehensive mechanical performance, serviceability and the productivity ratio that improve wire drawing die, the service life of prolongation mould to reach, purpose such as reduce energy consumption and production costs.

Defectives such as solution of the present invention is long at the background technology carburization processing time, and the carburizer composition is simple, reactivity is low, Carburization Treatment efficient is low adopt to contain Al when Carburization Treatment ₂O ₃, granular graphite and carbonate or/and the mixed powder of bicarbonate as carburizer.Promptly utilize carbonate or bicarbonate under carburizing temperature, to decompose and obtain CO ₂, CO ₂Generate CO gas with granular graphite reaction, the CO gas of this moment has stronger activity, can enter rapidly liquid phase and with alloy body in η (W mutually ₃CO ₃C, W ₂CO ₄C etc.) react generation WC, thereby achieve the goal.Its chemical principle is as follows:

R _XCO ₃＝R _XO+CO ₂ (1)

2R(HCO ₃) _X＝2RO _X/2+2XCO ₂+XH ₂O (2)

CO ₂+C＝2CO (3)

W ₃CO ₃C+4CO＝3WC+3CO+2CO ₂ (4)

W ₂CO ₄C+2CO＝2WC+4CO+CO ₂ (5)

Above-mentioned reaction is all carried out under 1380～1500 ℃ of temperature, and R wherein can be elements such as Na or Ca, Ba, K, Mg, Al.

Therefore, the inventive method comprises:

A, batching: by weight percentage, the cobalt powder of low-carbon (LC) WC powder 92～95wt% and 5～8wt% is placed in the ball mill, mixed 24～48 hours, make WC-5～8wt%Co mixed powder, add then after mixed powder weighs the paraffin of 2.0～2.5wt% and mix, stand-by;

B, compression molding: above-mentioned stand-by powder is placed the wire drawing die die cavity, be pressed into the wire drawing die biscuit, blank strength is 25～40% of a mould final strength;

C, pre-burning, dewaxing: the base substrate of compression moulding is sent in the stove, at vacuum condition or under hydrogen and nitrogen, the inert gas shielding of argon gas class, pre-burning under 800～1000 ℃ of temperature, dewaxing 40～80min;

D, sintering: through the blank of dewaxing treatment, send into again in the low pressure sintering stove, under 3.5～6.0Mpa pressure and 1380～1450 ℃, carry out sintering processes, sintering time 30～150min, blank cooling back is stand-by;

E, Carburization Treatment: will cool off stand-by blank and contain Al through sintering ₂O ₃: 30～50wt%, granular graphite 10～30wt%, carbonate are imbedded in the carburizer in the graphite boat and with each blank or/and the carburizer of bicarbonate 30～50wt% is packed into, send in the heat-treatment furnace then in 1390～1450 ℃ temperature range, Carburization Treatment 50～120min, the cooling back.

Above-mentioned carbonate and bicarbonate are carbonate or the bicarbonate of Na or Ca, Ba, K, Mg, Al.And the particle diameter of described granular graphite is 0.3～2.0mm.And low-carbon (LC) WC powder is lower than the WC powder of stoichiometry 0.1～0.7wt% for C content.

The present invention is owing to the carbonate in the carburizer in the Carburization Treatment process obtains CO or/and bicarbonate decomposes under carburizing temperature ₂Then generate active stronger CO gas again with the granular graphite reaction, this gas enters liquid phase rapidly and generates WC with η phase reaction in the alloy body, Co and impel its inside migration dissociates, make the mould top layer become W+ γ mutually and Co content be lower than the phase region of mold mean value, and have high hardness and wearability; The intermediate layer is that W+ γ phase and Co content are higher than the phase region of mould mean value, and has high toughness; The core of mold still contains the η phase constitution because chemical reaction does not almost take place in carburizing process, its rigidity is strong.Therefore, the product structure gradient that the present invention produces is obvious, carburization processing time short, surface no η phase layer thickness value height, formation speed are fast, compare with background technology and can shorten carburizing time about 55%, the no η phase thickness raising in surface more than 40%, mean intensity raising 20～25% under the gradient of condition of equivalent thickness; Compare with the standard sintered carbide wire drawing die, improve about 65% its service life; And have characteristics such as productivity ratio height, production cost and energy consumption are low.

Description of drawings

Fig. 1 is an embodiment wire-drawing die structural representation.

Among the figure: 1, die ontology, 2, calibrating strap, 3, the outlet of silk material, 4, pre-drawstring, 5, pre-drawstring collar extension (anchor ring).

The specific embodiment

Present embodiment is an example to produce S13～17 type bar wire drawing dies:

A, batching: be that the WC powder 93kg of 5.25wt% mixed 36 hours with ball milling in 7kg Co powder drops into ball mill with total phosphorus content, the WC-7wt%Co compound that makes is sent in the mechanical agitation blender, under stirring condition, spray into 2.2kg paraffin, after mixing, stand-by;

B, compacting wire drawing die biscuit: above-mentioned compound is sent in S13～17 pattern chambeies in batches, under the pressure of 200KN, be pressed into the biscuit that intensity is final strength 30%;

C, pre-burning, dewaxing: the biscuit of compression moulding is sent in the hydrogen sintering furnace, and pre-burning 60min removes the paraffin in the base substrate under 900 ℃ of temperature;

D, sintering: send in the low pressure sintering stove through the blank of dewaxing treatment, at 5.0Mpa pressure and 1400 ℃ of temperature sintering time 100min, blank cooling back is stand-by; The sintered body of gained, its microstructure is even, and the mutually tiny and even dispersion of η is distributed in the whole wire drawing die base substrate.

E, Carburization Treatment: will contain Al ₂O ₃40wt%, granularity are that the granular graphite 20wt% of 1.2mm, the carburizer 2.0kg of technical pure sodium carbonate 40wt% place graphite boat, and after being embedded in the wire drawing die base substrate after the sintering processes in the carburizer, sending into and in 1400～1410 ℃ carburizing atmosphere, promptly get final products S13～17 type bar wire drawing dies in the Muffle furnace behind the Carburization Treatment 100min.

This wire-drawing die body 1, diameter phi 50.0mm, 16 ° of the angles of pre-drawstring 4, the anchor ring radian of its collar extension 5 are R5mm, calibrating strap 2 diameter phi 17.50mm, high 5.5mm, and the silk material exports 60 ° of 3 chamferings (conical ring face), axial high 4.5mm.Present embodiment detects through metallographic, the low cobalt layer in surface (no η is layer mutually) the average thick 2.8mm of 1-1, the about 2.5mm of rich cobalt layer 1-2 average thickness; The core microstructure still with Carburization Treatment before identical, chemical reaction does not promptly almost take place in carburizing process.Sample mean bending strength 3130N/mm ², average hardness (HRA) 91.96.

Embodiment 2

It is the calcium bicarbonate 45wt% of technical grade that present embodiment adopts purity, and purity is 99.5% Al ₂O ₃40wt% and C content are 99.9%, the mixed powder of the granular graphite 15wt% of particle mean size 1.0mm is as carburizer; All the other technological parameters are all same with embodiment 1.

Claims

1, the production method of the sintered carbide wire drawing die tool that changes in gradient of a kind of performance; It is characterized in that this method comprises:

C, pre-burning, dewaxing: the base substrate of compression moulding is sent in the stove, at vacuum condition or under hydrogen and nitrogen, the inert gas shielding of argon gas class, pre-burning under 800～1000 ℃ of temperature, dewaxing treatment 40～80min;

2,, it is characterized in that described carbonate and bicarbonate are carbonate or the bicarbonate of Na or Ca, Ba, K, Mg, Al by the production method of the described sintered carbide wire drawing die tool of claim 1.

3, by the production method of the described sintered carbide wire drawing die tool of claim 1, the particle diameter that it is characterized in that described granular graphite is 0.3～2.0mm.

4, by the production method of the described sintered carbide wire drawing die of claim 1, it is characterized in that described low-carbon (LC) WC powder is lower than the WC powder of stoichiometry 0.1～0.7wt% for C content.