CN1526488A

CN1526488A - Production process of wire drawing hard alloy die with gradient varying performance

Info

Publication number: CN1526488A
Application number: CNA03135890XA
Authority: CN
Inventors: 咏刘; 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: 2004-09-08
Anticipated expiration: 2023-09-24
Also published as: CN100341647C

Abstract

The production process of wire drawing hard alloy die includes compounding material, molding to form, pre-sintering and dewaxing, sintering and carbonization. During the carbonization, the mixture of Al2O3, graphite grain and carbonate and/or bicarbonate in certain proportion is used as carbonizing agent, the carbonate and/or bicarbonate is high temperature decomposed into CO2, CO2 is further reacted with graphite grain into active CO gas capable of entering into liquid phase and reacting to produce WC, and the inward immigration of CO speeds the formation of the gradient structure inside the alloy. The said carbonization procedure has relatively low temperature, short period and relatively thick surface layer without eta phase, and the alloy has obvious gradient adhering phase structure, high comprehensive mechanical performance, high average bending strength and high average hardness.

Description

Production method of hard alloy wire drawing die with gradient change of performance

Technical Field

The invention belongs to a production method of a hard alloy wire drawing die in the production field of wire drawing dies, and particularly relates to a production method of a hard alloy wire drawing die with the mechanical properties of the die body being in gradient distribution from outside to inside.

Background

The internal and external mechanical properties and metallographic structure of the traditional hard alloy die (i.e. standard hard alloy die) are consistent, and the die often has the contradiction that the high hardness, the wear resistance and the toughness are difficult to be reconciled, namely when the content of cobalt (Co) in the alloy is reduced to improve the hardness and the wear resistance, the toughness of an alloy body is reduced, otherwise, the hardness and the wear resistance are influenced. In addition, when cracks are generated on the surface of the die in the wire drawing process, the cracks can quickly expand to cause the whole die to break and be discarded. In order to overcome this disadvantage, in "cemented carbide body most suitable for rock drilling and ore cutting" in patent document No. CN1016711B, a cemented carbide having a structure in which the mechanical properties of the alloy body are graded is disclosed. The production method of the hard alloy body adopts low-carbon WC and proper amount of cobalt (Co) powder as raw materials, the raw materials are uniformly mixed and pressed into a blank, and the blank is heated to about 900 ℃ and N₂Presintering for 1 hour in the atmosphere, and sintering at 1450 ℃ to obtain an alloy body with uniform metallographic and mechanical properties; it was then placed in a graphite boat and Al was used₂O₃The mixed powder of graphite and graphite is used as carburizing agent, and is heat-treated in carburizing atmosphere at 1450 deg.C for more than 2 hr to obtain alloy with WC + gamma phase region with Co content lower than the average alloy value, middle WC + gamma phase region with Co content higher than the average alloy value and hard alloy body with η phase in the core₂O₃The graphite grain is mixed with about 1.0 percent of graphite grains, the formula is simple, the carburizing reaction activity is low, so the carburizing treatment time is long, the temperature requirement is relatively high, the structure gradient forming speed is slow, and the productivity is low; the high-temperature carburization treatment for more than 2 hours can cause the defects of growth of alloy grains, reduction of the service performance of the alloy and the like; in addition, adopt above-mentioned method to produce the machineCemented carbide with graded mechanical properties, etc., andhas the defects of high energy consumption and production cost.

Disclosure of Invention

The invention aims to research and design a production method of a hard alloy wire-drawing die with gradient change of performance aiming at the defects in the background technology, so as to achieve the purposes of accelerating the forming speed of the gradient structure of the die body, shortening the carburizing treatment time, improving the comprehensive mechanical performance, the service performance and the production rate of the wire-drawing die, prolonging the service life of the die, reducing the energy consumption and the production cost and the like in the carburizing treatment process of the hard alloy wire-drawing die.

The solution of the invention is to adopt Al-containing in the carburization treatment aiming at the defects of long carburization treatment time, simple components of the carburizing agent, low reactivity, low carburization treatment efficiency and the like in the background technology₂O₃Graphite particles and mixed powder of carbonate or/and bicarbonate are used as a carburizing agent. I.e. CO is obtained by decomposition of carbonates or bicarbonates at the carburizing temperature₂，CO₂The CO gas is reacted with the graphite particles to generate CO gas, and the CO gas has stronger activity and can rapidly enter a liquid phase and be in phase η (W) in the alloy body₃CO₃C、W₂CO₄C, etc.) to generate WC, thereby achieving the aim. The chemical reaction principle is as follows:

(1)

(2)

(3)

(4)

(5)

the above reactions are all carried out at 1380-1500 ℃, wherein R can be Na or Ca, Ba, K, Mg, Al and other elements.

Thus, the method of the invention comprises:

A. preparing materials: putting 92-95 wt% of low-carbon WC powder and 5-8 wt% of cobalt powder into a ball mill, mixing for 24-48 hours to prepare WC-5-8 wt% of Co mixed powder, adding paraffin wax accounting for2.0-2.5 wt% of the mixed powder, and uniformly mixing for later use;

B. compression molding: placing the powder to be used in a die cavity of a wire-drawing die, and pressing the powder into a wire-drawing die biscuit, wherein the strength of a blank body is 25-40% of the final strength of the die;

C. pre-burning and dewaxing: feeding the pressed and formed blank into a furnace, presintering at 800-1000 ℃ under vacuum condition or under the protection of hydrogen, nitrogen and argon inert gases, and dewaxing for 40-80 min;

D. and (3) sintering: the blank subjected to dewaxing treatment is sent into a low-pressure sintering furnace, sintering treatment is carried out under the pressure of 3.5-6.0 Mpa and the temperature of 1380-1450 ℃, the sintering time is 30-150 min, and the blank is cooled for later use;

E. carburizing: the blank which is sintered and cooled for standby use and the Al-containing blank₂O₃: and (2) filling 30-50 wt% of carburizing agent, 10-30 wt% of graphite particles and 30-50 wt% of carbonate or/and bicarbonate into the graphite boat, embedding each blank into the carburizing agent, then feeding the blank into a heat treatment furnace, carburizing for 50-120 min at the temperature of 1390-1450 ℃, and cooling to obtain the product.

The carbonate and bicarbonate are Na or Ca, Ba, K, Mg, Al carbonate or bicarbonate. The particle size of the graphite particles is 0.3-2.0 mm. The low-carbon WC powder is WC powder with the C content lower than 0.1-0.7 wt% of the stoichiometric amount.

In the invention, the carbonate or/and bicarbonate in the carburizing agent are decomposed at the carburizing temperature to obtain CO in the carburizing treatment process₂Then reacts with graphite grains to generate CO gas with strong activity, the gas quickly enters into liquid phase and reacts with η in the alloy body to generate WC, Co is liberated and promoted to migrate inwards, the surface layer of the die becomes W + gamma phaseThe high-toughness hard alloy wire drawing die has the advantages that the Co content is lower than that of a phase region of an average value of the die body, the high-toughness hard alloy wire drawing die has high hardness and wear resistance, the middle layer is a W + gamma phase region, the Co content is higher than that of the phase region of the average value of the die body, the middle layer has high toughness, and a core part of the die body still contains η phase structures due to almost no chemical reaction in the carburizing process, so that the rigidity of the core part is high.

Drawings and description of the drawings

FIG. 1 is a schematic structural view of a wire drawing die according to an embodiment.

In the figure: 1. the die comprises a die body, 2, a sizing belt, 3, a wire outlet, 4, a pre-stretching belt, 5 and an outer opening (ring surface) of the pre-stretching belt.

Example 1

In the present embodiment, the production of the S13-17 type rod drawing die is taken as an example:

A. preparing materials: putting 93kg of WC powder with the total carbon content of 5.25 wt% and 7kg of Co powder into a ball mill, ball-milling and mixing for 36 hours, feeding the prepared WC-7 wt% Co mixture into a mechanical stirring mixer, spraying 2.2kg of paraffin under the stirring condition, stirring and mixing uniformly for later use;

B. pressing a drawing die biscuit: feeding the mixture into anS13-17 type die cavity in batches, and pressing under the pressure of 200KN to prepare a biscuit with the strength of 30% of the final strength;

C. pre-burning and dewaxing: sending the biscuit into a hydrogen sintering furnace, presintering at 900 ℃ for 60min to remove paraffin in the biscuit;

D. and (3) sintering, namely, feeding the dewaxed blank into a low-pressure sintering furnace, sintering for 100min under the pressure of 5.0MPa and the temperature of 1400 ℃, cooling the blank for later use, wherein the obtained sintered body has a uniform microstructure, and η phases are fine and are uniformly dispersed in the whole wire-drawing die blank.

E. Carburizing: will contain Al₂O₃40 wt% of graphite particles with the granularity of 1.2mm and 20 wt% of industrial pure sodium carbonate, and 2.0kg of carburizing agent with the granularity of 40 wt% are placed in a graphite boat, the sintered wire-drawing die blank is embedded in the carburizing agent, and then the wire-drawing die blank is sent into a muffle furnace to be carburized for 100min in a carburizing atmosphere at 1400-1410 ℃ to obtain the final product S13-17 type rod wire-drawing die.

The wire drawing die body 1 has a diameter phi of 50.0mm, the angle of the pre-stretching belt 4 is 16 degrees, the radian of the ring surface of the outer opening 5 is R5mm, the diameter phi of the sizing belt 2 is 17.50mm, the height of the sizing belt is 5.5mm, the outlet 3 of a wire is chamfered (conical ring surface) by 60 degrees and the axial height of the wire is 4.5mm, through metallographic detection, the average thickness of a surface low cobalt layer (without η phase layer) 1-1 is 2.8mm, the average thickness of a cobalt-rich layer 1-2 is about 2.5mm, the microstructure structure of a core part is still the same as that before carburization, namely, almost no chemical reaction occurs in the carburization process, and the average bending strength of a sample is 313²Average Hardness (HRA) 91.96.

Example 2

In this example, an Al compound having a purity of 45 wt% and a purity of 99.5% was used in combination with calcium bicarbonate of technical grade₂O₃40 wt% and mixed powder containing 99.9% of C and 15 wt% of graphite particles with average grain size of 1.0mm are used as carburizing agents; the rest of the process parameters were the same as in example 1.

Claims

1. A method for producing a hard alloy wire drawing die with gradient change of performance; the method is characterized by comprising the following steps:

A. preparing materials: putting 92-95 wt% of low-carbon WC powder and 5-8 wt% of cobalt powder into a ball mill, mixing for 24-48 hours to prepare WC-5-8 wt% of Co mixed powder, adding paraffin wax accounting for 2.0-2.5 wt% of the mixed powder, and uniformly mixing for later use;

2. A method of producing a drawing die for cemented carbide according to claim 1, characterized in that the carbonates and bicarbonates are carbonates or bicarbonates of Na or Ca, Ba, K, Mg, Al.

3. The method for producing a hard alloy wire drawing die according to claim 1, wherein the graphite particles have a particle size of 0.3 to 2.0 mm.

4. The method for producing a cemented carbide wire-drawing die according to claim 1, wherein the low carbon WC powder is WC powder having a C content of less than 0.1 to 0.7 wt% of the stoichiometric amount.