阅读说明：本技术 一种钨钴硬质合金烧结工艺 (Tungsten-cobalt hard alloy sintering process ) 是由 朱剑军 殷友桢 吴其广 赵俊彩 于 2020-05-27 设计创作，主要内容包括：本发明涉及一种钨钴硬质合金烧结工艺,所述工艺包括：烧结保温结束后,依次进行第一随炉冷却、气冷及第二随炉冷却；所述烧结至少包括一段烧结。本发明中,通过对钨钴合金烧结结束后冷却工艺的合理配置,实现了硬质合金中α-Co有效的保留,同时也提高了硬质合金的抗弯强度和冲击韧性。(The invention relates to a tungsten-cobalt hard alloy sintering process, which comprises the following steps: after the sintering heat preservation is finished, sequentially carrying out first furnace cooling, air cooling and second furnace cooling; the sintering at least comprises one section of sintering. According to the invention, through reasonable configuration of the cooling process after the sintering of the tungsten-cobalt alloy is finished, the effective retention of alpha-Co in the hard alloy is realized, and simultaneously, the bending strength and the impact toughness of the hard alloy are also improved.)

1. A tungsten-cobalt hard alloy sintering process is characterized by comprising the following steps: after the sintering heat preservation is finished, sequentially carrying out first furnace cooling, air cooling and second furnace cooling; the sintering at least comprises one section of sintering.

2. The process of claim 1, wherein the sintering comprises a first sintering, a second sintering, a third sintering, a fourth sintering, a fifth sintering, a sixth sintering, and a seventh sintering, which are performed sequentially.

3. The process as claimed in claim 2, wherein the end temperature of the first sintering temperature rise is 190-210 ℃;

preferably, the temperature rise time of the first sintering is 50-70 min;

preferably, the heat preservation time of the first sintering is 50-70 min;

preferably, the end temperature of the second sintering temperature rise is 310-330 ℃;

preferably, the temperature rise time of the second sintering is 75-90 min;

preferably, the holding time of the second sintering is 85-95 min.

4. The process as claimed in claim 2 or 3, wherein the end temperature of the third sintering temperature rise is 390-410 ℃;

preferably, the temperature rise time of the third sintering is 85-95 min;

preferably, the heat preservation time of the third sintering is 85-95 min;

preferably, the end temperature of the fourth sintering temperature rise is 580-620 ℃;

preferably, the temperature rise time of the fourth sintering is 95-105 min;

preferably, the heat preservation time of the fourth sintering is 55-65 min.

5. The process according to any of claims 2-4, wherein the end temperature of the fifth sintering temperature rise is 780-820 ℃;

preferably, the temperature rise time of the fifth sintering is 55-65 min;

preferably, the heat preservation time of the fifth sintering is 25-35 min.

6. The process as claimed in any one of claims 2 to 5, wherein the end point temperature of the sixth sintering temperature rise is 1230-;

preferably, the temperature rise time of the sixth sintering is 110-130 min;

preferably, the holding time of the sixth sintering is 55-65 min.

7. The process according to any one of claims 2-6, wherein the end point temperature of the seventh sintering ramp is 1420-;

preferably, the temperature rise time of the seventh sintering is 85-95 min;

preferably, the heat preservation time of the seventh sintering is 70-80 min.

8. The process as claimed in any one of claims 1 to 7, wherein the end temperature of the first furnace cooling is 730- > 770 ℃;

preferably, the time for the first furnace cooling is 380-420 min.

9. The process according to any one of claims 1-8, wherein the air cooling end point temperature is 380-420 ℃;

preferably, the air cooling time is 25-35 min;

preferably, the air cooling is performed under a protective atmosphere;

preferably, the protective atmosphere comprises nitrogen and/or an inert gas;

preferably, the purity of the gas in the protective atmosphere is more than or equal to 99.99 percent;

preferably, the end temperature of the second furnace cooling is 80-100 ℃.

10. The process according to any one of claims 1 to 9, wherein the process comprises: after the sintering heat preservation is finished, sequentially carrying out first furnace cooling, air cooling and second furnace cooling; the sintering at least comprises a section of sintering;

the sintering comprises a first sintering, a second sintering, a third sintering, a fourth sintering, a fifth sintering, a sixth sintering and a seventh sintering which are sequentially carried out; the end temperature of the first sintering temperature rise is 190-210 ℃; the temperature rise time of the first sintering is 50-70 min; the heat preservation time of the first sintering is 50-70 min; the end temperature of the second sintering temperature rise is 310-330 ℃; the temperature rise time of the second sintering is 75-90 min; the heat preservation time of the second sintering is 85-95 min; the end temperature of the third sintering temperature rise is 390-410 ℃; the temperature rise time of the third sintering is 85-95 min; the heat preservation time of the third sintering is 85-95 min; the end temperature of the fourth sintering temperature rise is 580-620 ℃; the temperature rise time of the fourth sintering is 95-105 min; the heat preservation time of the fourth sintering is 55-65 min; the terminal temperature of the fifth sintering temperature rise is 780-820 ℃; the temperature rise time of the fifth sintering is 55-65 min; the heat preservation time of the fifth sintering is 25-35 min; the end temperature of the sixth sintering temperature rise is 1230-; the temperature rise time of the sixth sintering is 110-130 min; the heat preservation time of the sixth sintering is 55-65 min; the terminal temperature of the seventh sintering temperature rise is 1420-1450 ℃; the temperature rise time of the seventh sintering is 85-95 ℃; the heat preservation time of the seventh sintering is 70-80 min; the end temperature of the first furnace cooling is 730-770 ℃; the time for cooling the first furnace is 380-420 min; the air cooling end temperature is 380-420 ℃; the air cooling time is 25-35 min; and the end temperature of the second furnace cooling is 80-100 ℃.

Technical Field

The invention relates to the field of hard alloy sintering, in particular to a tungsten-cobalt hard alloy sintering process.

Background

The tungsten-cobalt hard alloy is hard alloy consisting of tungsten carbide and metal cobalt. As the cobalt content and WC grain size increase, the hardness of the alloy decreases and the bending strength and impact resistance increase. The W-Co hard alloy may be used in cutting cast iron, non-ferrous metal and non-metal material, and may be also used as antiwear tool for drawing die, cold punching die, nozzle, roller, anvil, measuring tool, cutting tool, etc. and mine tool.

In the production of cemented carbide, the key factor determining the quality of the product is the molecular structure of the alloy. In the high-temperature sintering stage, alpha-Co is taken as the main component in the gamma phase of the solid solution phase, and the crystal lattice of the gamma phase is an fcc face-centered cubic structure which has good toughness and can absorb more strain energy and relaxation stress under the action of external force. When the material is slowly cooled after sintering is finished, the alpha-Co is converted to the-Co, the-Co is in a stable state at normal temperature, the crystal lattice of the material is an hcp close-packed hexagonal structure, and the structure has poor capability of absorbing strain energy and relaxing stress and poor toughness. CN110578067A discloses a sintering method of ultra-fine cemented carbide, comprising the following steps: mixing WC powder, Co powder, an inhibitor and a forming agent, wet-grinding, drying after wet grinding, and pressing into a pressed blank; heating the pressed compact to a sintering temperature under the atmosphere of H2, and then carrying out heat preservation sintering under the atmosphere of argon; after sintering, cooling to a first-stage temperature at a first-stage cooling rate under the conditions of electrification and pressure maintaining, and preserving heat; then, cooling to a second-stage temperature at a second-stage cooling speed, and preserving heat; then, cooling to a third-stage temperature at a third-stage cooling rate; then cutting off the power and quickly cooling to below 50 ℃ to obtain the hard alloy. The method of the invention properly reduces the sintering temperature, adopts the step-by-step slow cooling process under electrification and pressure after heat preservation and pressure maintaining, can reduce the abnormal growth probability of the ultrafine hard alloy crystal grains, improves the uniformity of the microstructure, and improves the fracture toughness and the use stability of the alloy. CN109957671A discloses a hard alloy sintering process, which comprises the following sintering processes at high temperature stage: step 1, sintering at 1340-1500 ℃, pressurizing at 1-10 MPa for 5-15 minutes, and then releasing the pressure to less than or equal to 1 MPa; and 2, repeating the operations of pressurizing, pressure maintaining and pressure relief in the step 1 for 1-3 times, and finally cooling and relieving the pressure to normal temperature and normal pressure to obtain the hard alloy. The hard alloy sintering process provided by the invention can be used for selecting, grinding and pressing raw materials according to the requirement by adopting the prior art, and in the high-temperature and high-pressure sintering process, the density of the prepared hard alloy is improved by repeated pressurization, pressure maintaining and pressure relief operations under the heat preservation condition, so that a hard alloy product with excellent hardness, fracture toughness, bending strength and other properties, compact tissue, uniform grain size and complete grain development is obtained.

However, at present, in order to keep more α -Co to the normal temperature state, a water rapid cooling system is basically adopted, but the effect is not particularly good, and the cooling speed is faster than the furnace cooling, but is unstable.

Disclosure of Invention

In view of the problems in the prior art, the invention aims to provide a sintering process for a tungsten-cobalt hard alloy, which can effectively retain alpha-Co in the hard alloy and improve the bending strength and impact toughness of the hard alloy.

In order to achieve the purpose, the invention adopts the following technical scheme:

the invention provides a tungsten-cobalt hard alloy sintering process, which comprises the following steps: after the sintering heat preservation is finished, sequentially carrying out first furnace cooling, air cooling and second furnace cooling; the sintering at least comprises one section of sintering.

According to the invention, through reasonable configuration of the cooling process after the sintering of the tungsten-cobalt alloy is finished, the effective retention of alpha-Co in the hard alloy is realized, and simultaneously, the bending strength and the impact toughness of the hard alloy are also improved.

In the present invention, the tungsten-cobalt cemented carbide may be YG8, YG13, YG11, YG18c, or the like.

As a preferable embodiment of the present invention, the sintering includes a first sintering, a second sintering, a third sintering, a fourth sintering, a fifth sintering, a sixth sintering, and a seventh sintering, which are performed in this order.

In the invention, through multi-stage sintering, the performance of the product is improved by reasonably utilizing the action of each temperature and the synergistic effect among the multi-stage sintering.

In a preferred embodiment of the present invention, the end point temperature of the first sintering temperature rise is 190-210 ℃, and may be, for example, 190 ℃, 195 ℃, 200 ℃, 205 ℃, or 210 ℃, but is not limited to the above-mentioned values, and other values not shown in the above range are also applicable.

Preferably, the temperature rise time of the first sintering is 50 to 70min, for example, 50min, 52min, 54min, 56min, 58min, 60min, 62min, 64min, 66min, 68min or 70min, etc., but not limited to the recited values, and other values not recited in the range are also applicable.

Preferably, the first sintering is performed for 50-70min, such as 50min, 52min, 54min, 56min, 58min, 60min, 62min, 64min, 66min, 68min or 70min, but not limited to the values listed, and other values not listed in the range are also applicable.

Preferably, the end point temperature of the second sintering temperature rise is 310-330 ℃, such as 310 ℃, 315 ℃, 320 ℃, 325 ℃, or 330 ℃, but not limited to the recited values, and other values not recited in the range are also applicable.

Preferably, the temperature rise time of the second sintering is 75 to 90min, for example, 75min, 80min, 85min or 90min, but not limited to the values listed, and other values not listed in the range are also applicable.

Preferably, the holding time for the second sintering is 85-95min, such as 85min, 86min, 87min, 88min, 89min, 90min, 91min, 92min, 93min, 94min or 95min, but not limited to the values listed, and other values not listed in this range are also applicable.

In a preferred embodiment of the present invention, the temperature at the end point of the third sintering temperature rise is 390-410 ℃, and may be, for example, 390 ℃, 392 ℃, 394 ℃, 396 ℃, 398 ℃, 400 ℃, 402 ℃, 404 ℃, 406 ℃, 408 ℃ or 410 ℃, but is not limited to the above-mentioned values, and other values not listed in this range are also applicable.

Preferably, the temperature rise time of the third sintering is 85 to 95min, for example, 85min, 86min, 87min, 88min, 89min, 90min, 91min, 92min, 93min, 94min or 95min, etc., but not limited to the values listed, and other values not listed in the range are also applicable.

Preferably, the heat preservation time of the third sintering is 85-95min, such as 85min, 86min, 87min, 88min, 89min, 90min, 91min, 92min, 93min, 94min or 95min, but not limited to the enumerated values, and other unrecited values in the range are also applicable.

Preferably, the end point temperature of the fourth sintering temperature rise is 580-620 ℃, for example 580 ℃, 585 ℃, 590 ℃, 595 ℃, 600 ℃, 605 ℃, 610 ℃, 615 ℃ or 620 ℃, but not limited to the recited values, and other values not recited in the range are also applicable.

Preferably, the temperature rise time of the fourth sintering is 95 to 105min, for example, 95min, 96min, 97min, 98min, 99min, 100min, 101min, 102min, 103min, 104min or 105min, etc., but not limited to the recited values, and other values not recited in the range are also applicable.

Preferably, the heat preservation time of the fourth sintering is 55-65min, such as 55min, 56min, 57min, 58min, 59min, 60min, 61min, 62min, 63min, 64min or 65min, but not limited to the values listed, and other values not listed in the range are also applicable.

In a preferred embodiment of the present invention, the end point temperature of the fifth sintering temperature rise is 780-820 ℃, for example 780 ℃, 785 ℃, 790 ℃, 795 ℃, 800 ℃, 805 ℃, 810 ℃, 815 ℃ or 820 ℃, but is not limited to the above-mentioned values, and other values not shown in the above range are also applicable.

Preferably, the temperature rise time of the fifth sintering is 55-65min, for example, 55min, 56min, 57min, 58min, 59min, 60min, 61min, 62min, 63min, 64min or 65min, but not limited to the values listed, and other values not listed in the range are also applicable.

Preferably, the heat preservation time of the fifth sintering is 25-35min, such as 25min, 26min, 27min, 28min, 29min, 30min, 31min, 32min, 33min, 34min or 35min, but not limited to the enumerated values, and other unrecited values in the range are also applicable.

In a preferred embodiment of the present invention, the temperature at the end of the sixth sintering temperature rise is 1230-.

Preferably, the temperature rise time of the sixth sintering is 110-130min, such as 110min, 112min, 114min, 116min, 118min, 120min, 122min, 124min, 126min, 128min or 130min, but not limited to the values listed, and other values not listed in the range are also applicable.

Preferably, the holding time for the sixth sintering is 55-65min, such as 55min, 56min, 57min, 58min, 59min, 60min, 61min, 62min, 63min, 64min or 65min, but not limited to the values listed, and other values not listed in the range are also applicable.

In a preferred embodiment of the present invention, the terminal temperature of the seventh sintering temperature rise is 1420-.

Preferably, the temperature rise time of the seventh sintering is 85 to 95min, for example, 85min, 86min, 87min, 88min, 89min, 90min, 91min, 92min, 93min, 94min or 95min, etc., but not limited to the values listed, and other values not listed in the range are also applicable.

Preferably, the heat preservation time of the seventh sintering is 70 to 80min, for example, 70min, 71min, 72min, 73min, 74min, 75min, 76min, 77min, 78min, 79min or 80min, etc., but not limited to the recited values, and other values not recited in the range are also applicable.

As a preferred embodiment of the present invention, the end point temperature of the first furnace cooling is 730-770 deg.C, such as 730 deg.C, 735 deg.C, 740 deg.C, 745 deg.C, 750 deg.C, 755 deg.C, 760 deg.C, 765 deg.C or 770 deg.C, but not limited to the values listed, and other values not listed in this range are also applicable.

Preferably, the first furnace cooling time is 380-420min, such as 380min, 385min, 390min, 395min, 400min, 405min, 410min, 415min, or 420min, but not limited to the values listed, and other values not listed in the range are also applicable.

In a preferred embodiment of the present invention, the end point temperature of the air cooling is 380-420 ℃, and may be 380 ℃, 385 ℃, 390 ℃, 395 ℃, 400 ℃, 405 ℃, 410 ℃, 415 ℃ or 420 ℃, for example, but not limited to the values listed, and other values not listed in the range are also applicable.

Preferably, the air cooling time is 25-35min, such as 25min, 26min, 27min, 28min, 29min, 30min, 31min, 32min, 33min, 34min or 35min, but not limited to the recited values, and other values not recited in the range are also applicable.

Preferably, the air cooling is performed under a protective atmosphere.

Preferably, the protective atmosphere comprises nitrogen and/or an inert gas.

In the present invention, the inert gas may be 1 or a combination of at least 2 of helium, neon, argon, or the like.

Preferably, the purity of the gas in the protective atmosphere is 99.99% or more, and may be, for example, 99.99%, 99.991%, 99.992%, 99.993%, 99.994%, 99.995%, 99.996%, 99.997%, 99.998%, or 99.999%, etc., but is not limited to the recited values, and other values not recited in this range are also applicable.

Preferably, the end point temperature of the second furnace cooling is 80-100 ℃, for example 80 ℃, 82 ℃, 84 ℃, 86 ℃, 88 ℃, 90 ℃, 92 ℃, 94 ℃, 96 ℃, 98 ℃ or 100 ℃, but not limited to the recited values, and other values not recited in this range are also applicable.

The gas cooling process in the process adopts a mode of adding protective gas between 730-770 ℃, so that the alloy product can be reduced to about 400 ℃ within half an hour, and then is cooled along with the furnace, and the conversion temperature can be basically avoided.

As a preferable technical scheme of the invention, the process comprises the following steps: after the sintering heat preservation is finished, sequentially carrying out first furnace cooling, air cooling and second furnace cooling; the sintering at least comprises a section of sintering;

the sintering comprises a first sintering, a second sintering, a third sintering, a fourth sintering, a fifth sintering, a sixth sintering and a seventh sintering which are sequentially carried out; the end temperature of the first sintering temperature rise is 190-210 ℃; the temperature rise time of the first sintering is 50-70 min; the heat preservation time of the first sintering is 50-70 min; the end temperature of the second sintering temperature rise is 310-330 ℃; the temperature rise time of the second sintering is 75-90 min; the heat preservation time of the second sintering is 85-95 min; the end temperature of the third sintering temperature rise is 390-410 ℃; the temperature rise time of the third sintering is 85-95 min; the heat preservation time of the third sintering is 85-95 min; the end temperature of the fourth sintering temperature rise is 580-620 ℃; the temperature rise time of the fourth sintering is 95-105 min; the heat preservation time of the fourth sintering is 55-65 min; the terminal temperature of the fifth sintering temperature rise is 780-820 ℃; the temperature rise time of the fifth sintering is 55-65 min; the heat preservation time of the fifth sintering is 25-35 min; the end temperature of the sixth sintering temperature rise is 1230-; the temperature rise time of the sixth sintering is 110-130 min; the heat preservation time of the sixth sintering is 55-65 min; the terminal temperature of the seventh sintering temperature rise is 1420-1450 ℃; the temperature rise time of the seventh sintering is 85-95 ℃; the heat preservation time of the seventh sintering is 70-80 min; the end temperature of the first furnace cooling is 730-770 ℃; the time for cooling the first furnace is 380-420 min; the air cooling end temperature is 380-420 ℃; the air cooling time is 25-35 min; and the end temperature of the second furnace cooling is 80-100 ℃.

Compared with the prior art, the invention has the following beneficial effects:

(1) according to the invention, through reasonable configuration of sectional sintering and sectional cooling of the tungsten-cobalt alloy, effective retention of alpha-Co in the hard alloy is realized, and simultaneously, the bending strength and the impact toughness of the hard alloy are also improved. The bending strength of the obtained hard alloy can reach more than 2150MPa, the volume ratio of alpha-Co at normal temperature reaches more than 65%, and the effective service time of the alloy product sintered by the process is prolonged by 20-40% through destructive tests.

(2) The sintering process not only improves the use efficiency of equipment, but also saves the equipment cost. Meanwhile, the service performance of the hard alloy is greatly improved.

The present invention is described in further detail below. The following examples are merely illustrative of the present invention and do not represent or limit the scope of the claims, which are defined by the claims.

Detailed Description

To better illustrate the invention and to facilitate the understanding of the technical solutions thereof, typical but non-limiting examples of the invention are as follows: