CN112264626A

CN112264626A - Hard alloy bar with double spiral holes and preparation method thereof

Info

Publication number: CN112264626A
Application number: CN202010929562.XA
Authority: CN
Inventors: 张福琪; 郭广杰; 刘海艳
Original assignee: Hubei Jingu Technology Materials Co ltd
Current assignee: Hubei Jingu Technology Materials Co ltd
Priority date: 2020-09-07
Filing date: 2020-09-07
Publication date: 2021-01-26

Abstract

The application relates to the technical field of hard alloy, and discloses a preparation method of a double-spiral-hole hard alloy bar, which comprises the following steps of mixing, extrusion forming, dewaxing and sintering, wherein the preparation method further comprises the following steps: and carrying out subzero treatment on the hard alloy bar obtained by sintering to obtain a finished product of the hard alloy bar with double spiral holes. The surface residual stress of a finished product of the double-spiral-hole hard alloy bar obtained by the preparation method disclosed by the embodiment of the disclosure is obviously improved, the Vickers hardness and the bending strength are increased, the magnetic performance is basically kept unchanged, and the coercive force is increased while the magnetic saturation strength of cobalt is reduced. The drill produced by the hard alloy bar material prepared by the embodiment of the disclosure can improve the deep hole processing efficiency by 50%, and can prolong the service life of the drill by one time. The application also discloses a hard alloy material.

Description

Hard alloy bar with double spiral holes and preparation method thereof

Technical Field

The application relates to the technical field of hard alloy, for example to a double-spiral-hole hard alloy bar and a preparation method thereof.

Background

Drilling is the most common modern automatic production line or machining center machining process, and in recent years, the double-spiral-hole hard alloy drill bit can improve deep hole machining efficiency, drill and cut difficult-to-machine materials and meet the requirements of automatic production lines and machining centers. The workpiece can bear large force during use, so that the workpiece is easy to generate heat and wear, especially the top of the workpiece.

The hard alloy drill bit with the inner cooling liquid hole has the advantages of better cooling effect, high chip removal efficiency, good surface finish, long service life and the like compared with the conventional hard alloy drill bit. It is popular with customers at home and abroad, and is a product with high technology and high added value. And the hard alloy drill bit with the inner cooling liquid hole is prepared by double spiral hole hard alloy bars.

In the process of implementing the embodiments of the present disclosure, it is found that at least the following problems exist in the related art: the performance of the existing double-spiral-hole hard alloy bar needs to be further improved.

Disclosure of Invention

The following presents a simplified summary in order to provide a basic understanding of some aspects of the disclosed embodiments. This summary is not an extensive overview nor is intended to identify key/critical elements or to delineate the scope of such embodiments but rather as a prelude to the more detailed description that is presented later.

The embodiment of the disclosure provides a double-spiral-hole hard alloy bar and a preparation method thereof, so as to further improve the performance of the double-spiral-hole hard alloy bar.

In some embodiments, the method for preparing the double-spiral-hole cemented carbide rod comprises mixing, extrusion forming, dewaxing and sintering, wherein the method further comprises:

and carrying out subzero treatment on the hard alloy bar obtained by sintering to obtain a finished product of the hard alloy bar with double spiral holes.

In some embodiments, the double-spiral-hole cemented carbide bar is prepared by the preparation method of the double-spiral-hole cemented carbide bar.

The double-spiral-hole hard alloy bar and the preparation method thereof provided by the embodiment of the disclosure can realize the following technical effects:

according to the preparation method of the double-spiral-hole hard alloy bar, the hard alloy bar obtained through the processes of mixing, extrusion forming, dewaxing and sintering is subjected to cryogenic treatment, so that a finished product of the double-spiral-hole hard alloy bar with better performance is obtained. The surface residual stress of a finished product of the double-spiral-hole hard alloy bar obtained by the preparation method disclosed by the embodiment of the disclosure is obviously improved, the Vickers hardness and the bending strength are increased, the magnetic performance is basically kept unchanged, and the coercive force is increased while the magnetic saturation strength of cobalt is reduced.

The foregoing general description and the following description are exemplary and explanatory only and are not restrictive of the application.

Drawings

One or more embodiments are illustrated by the accompanying drawings, which correspond to and do not constitute a limitation on the embodiments, and wherein:

fig. 1 is a metallographic structure morphology of a cemented carbide bar provided by an embodiment of the disclosure;

FIG. 2 is a metallographic morphology of a comparative cemented carbide bar without cryogenic treatment;

FIG. 3 is a metallographic structure morphology of another cemented carbide rod provided by an embodiment of the disclosure;

FIG. 4 is a metallographic structure morphology of another cemented carbide rod provided by an embodiment of the disclosure;

FIG. 5 is a metallographic structure morphology of another cemented carbide rod provided by an embodiment of the disclosure;

FIG. 6 is a metallographic structure morphology of another cemented carbide rod provided by an embodiment of the disclosure;

FIG. 7 is a metallographic structure morphology of another cemented carbide rod provided by an embodiment of the disclosure;

FIG. 8 is a graph of ball milling time versus bending strength for cemented carbide rods provided in embodiments of the disclosure;

fig. 9 is a graph of ball milling time versus vickers hardness for cemented carbide rods provided in accordance with an embodiment of the present disclosure.

Detailed Description

So that the manner in which the features and technical contents of the embodiments of the present disclosure can be understood in detail, the embodiments of the present disclosure are described in detail below for illustrative purposes only and are not intended to limit the embodiments of the present disclosure. In the following description of the technology, for purposes of explanation, numerous details are set forth in order to provide a thorough understanding of the disclosed embodiments. However, one or more embodiments may be practiced without these details.

It should be noted that, in the case of no conflict, the embodiments and features in the embodiments of the present disclosure may be combined with each other.

The embodiment of the disclosure provides a preparation method of a double-spiral-hole hard alloy bar, which comprises the steps of mixing, extrusion forming, dewaxing and sintering, wherein the hard alloy bar obtained by sintering is subjected to cryogenic treatment to obtain a finished product of the double-spiral-hole hard alloy bar.

According to the preparation method of the double-spiral-hole hard alloy bar, the hard alloy bar obtained through the processes of mixing, extrusion forming, dewaxing and sintering is subjected to cryogenic treatment, so that a finished product of the double-spiral-hole hard alloy bar with better performance is obtained. The surface residual stress of a finished product of the double-spiral-hole hard alloy bar obtained by the preparation method disclosed by the embodiment of the disclosure is obviously improved, the Vickers hardness and the bending strength are increased, the magnetic performance is basically kept unchanged, and the coercive force is increased while the magnetic saturation strength of cobalt is reduced. The drill produced by the hard alloy bar material prepared by the embodiment of the disclosure can improve the deep hole processing efficiency by 50%, and can prolong the service life of the drill by one time.

In some embodiments, the cryogenic treatment specifically comprises: and (3) cooling the sintered hard alloy bar to a set lower limit temperature at the speed of 1-5 ℃/min, then preserving heat for 2-24 hours at the set lower limit temperature, and raising and recovering the temperature.

Optionally, the lower limit temperature is set to-190 ℃ to-180 ℃.

Optionally, cooling the sintered hard alloy bar to a set lower limit temperature at a rate of 1-3 ℃/min. Optionally, the cemented carbide bar obtained by sintering is cooled to a set lower limit temperature at a rate of 2 ℃/min.

Optionally, the temperature is kept for 2-8 h at the set lower limit temperature. Optionally, the temperature is maintained for 2 hours, 4 hours, 8 hours or any other time within the range of 2-8 hours at the set lower limit temperature.

In the embodiment of the disclosure, after the heat preservation and deep cooling treatment of the hard alloy bar at the set lower limit temperature, the temperature needs to be raised and recovered. The rising rate is consistent with the cooling rate. Namely, the temperature rise recovery rate is 1-5 ℃/min. Optionally, the rate of temperature ramp-up recovery is 1 deg.C/min, 2 deg.C/min, 3 deg.C/min, 4 deg.C/min, 5 deg.C/min, and the like.

In some embodiments, a method of making a double-spiral-hole cemented carbide rod of embodiments of the present disclosure includes the steps of:

stirring and ball-milling the raw materials of the hard alloy bar to obtain a mixture;

stirring and mixing the mixture and the forming agent, and then drying to obtain mixed feed;

putting the mixed feed into an extruder, and extruding and forming to obtain a blank;

dewaxing the blank, and sintering to obtain a hard alloy bar;

and carrying out cryogenic treatment on the sintered hard alloy bar to obtain a finished product of the double-spiral-hole hard alloy bar.

In some embodiments, compounding comprises: stirring and ball-milling the raw materials of the hard alloy bar to obtain a mixture; wherein the ball milling time is 4-10 h. In this embodiment, a vertical agitator ball mill is used for the agitation ball milling. The mixing mode of stirring and ball milling shortens the ball milling time, improves the mixing efficiency and the fluidity of the mixture, reduces the oxygen content of the mixture, improves the bending strength and the Vickers hardness after sintering, and has even metallographic structure, thereby ensuring that the quality of the produced product is more stable.

Optionally, the ball milling time is 5-8 h. Optionally, the ball milling time is 7-8 h. Alternatively, the ball milling time was 7 h.

In some embodiments, the amount of the forming agent used in the mixing is 5% to 7% of the total mass of the raw material (i.e., the mixture) of the cemented carbide rod. Alternatively, the amount of forming agent is 6% of the total mass of the raw material (i.e. the mix) of the cemented carbide rod.

Optionally, the forming agent comprises paraffin. Paraffin is used as a forming agent, so that the total carbon content of the prepared mixed feed reaches an ideal degree, and the stability of the carbon content in the hard alloy bar is ensured.

In some embodiments, the extrusion speed is 2 to 15mm/min in the extrusion molding. By adopting the extrusion speed within the range, the inner hole of the obtained double-spiral-hole hard alloy bar finished product is not eccentric, the hole pitch and the screw pitch are stable, the straightness accuracy qualified rate after sintering is high, and the size can meet the tolerance requirement.

Optionally, the extrusion speed is 2-10 mm/min. Optionally, the extrusion speed is 4-8 mm/min. Alternatively, the extrusion speed is 6 mm/min.

Optionally, the extrusion molding adopts vacuum extrusion molding, and after the extrusion molding is finished, the blank obtained by extrusion molding is stored for a set time under vacuum. The vacuum preservation time is not limited, and optionally, the vacuum preservation time is 20-60 h. Optionally, the vacuum preservation time is 30-50 h. Optionally, the vacuum holding time is 40 h.

Alternatively, extrusion may be carried out using an extruder, such as LOOMIS (45t-75t-120t) manufactured by LOOMIS equipment manufacturing company.

In some embodiments, the dewaxing includes vacuum dewaxing at 580-620 ℃ for 10-30 min.

Alternatively, the dewaxing temperature is 600 ℃.

Optionally, the dewaxing time is 20-30 min.

Alternatively, the dewaxing time is 30 min.

In some embodiments, the sintering temperature is 1320-1400 ℃ and the sintering pressure is 8-9 MPa.

Alternatively, in the sintering, the sintering temperature is 1390 ℃ and the sintering pressure is 9 MPa.

In some embodiments, dewaxing and sintering are performed using a dewaxing pressure sintering integrated furnace. The compactness of the hard alloy bar can reach 99.99 percent, and the abnormal growth of WC grains (tungsten carbide grains) can be inhibited.

Alternatively, a pressure sintering furnace manufactured by PVA corporation of germany is used as the dewaxing pressure sintering integrated furnace.

In the method for preparing a double-spiral-hole hard alloy bar according to the embodiment of the present disclosure, the raw material of the hard alloy bar is not limited.

In some embodiments, the raw material of the cemented carbide bar comprises ultrafine tungsten carbide powder (WC powder) and cobalt powder (Co powder), wherein the content of the Co powder is 8-12% of the total weight of the raw material. Wherein the grain diameter of the superfine WC powder is 0.6-0.8 μm.

Optionally, the content of the Co powder is 10% of the total weight of the raw materials.

The embodiment of the disclosure provides a double-spiral-hole hard alloy bar which is prepared by the preparation method of the double-spiral-hole hard alloy bar.

The surface residual stress of the finished product of the double-spiral-hole hard alloy bar is obviously improved, the Vickers hardness and the bending strength are increased, the magnetic performance is basically kept unchanged, and the coercive force is increased while the magnetic saturation strength of cobalt is reduced.

Specific examples of the embodiments of the present disclosure are given below.

Example 1

A preparation method of a double-spiral-hole hard alloy bar comprises the following steps:

s11, stirring and ball-milling the raw materials of the hard alloy bar for 7 hours to obtain a mixture; the hard alloy bar comprises a raw material and a hard alloy bar body, wherein the raw material comprises superfine WC and Co, and the content of Co is 10% of the total weight of the raw material.

S12, mixing the mixture with paraffin to obtain a mixed feed; the amount of paraffin wax was 6% by weight of the mix.

S13, putting the mixed feed into an extruder, and performing vacuum extrusion molding at the extrusion speed of 6mm/min to obtain a blank; and the blank obtained by extrusion molding is stored for 40 hours under vacuum.

S14, putting the blank into a dewaxing and pressure sintering integrated furnace, dewaxing in vacuum, and then sintering in pressure to obtain a hard alloy bar; wherein the dewaxing temperature is 600 ℃, and the dewaxing time is 30 min; the sintering temperature is 1390 ℃, and the sintering pressure is 9 MPa.

And S15, carrying out cryogenic treatment on the hard alloy bar obtained by pressure sintering to obtain a finished product of the hard alloy bar with the double spiral holes. Wherein, cryogenic treatment specifically comprises: cooling to the set lower limit temperature (-190 ℃) at the speed of 2 ℃/min, then preserving the heat for 2 hours at the set lower limit temperature, and then raising the temperature to the room temperature at the speed of 2 ℃/min.

The finished product of the double-spiral-hole hard alloy bar prepared in the embodiment 1 is marked as bar I (subjected to cryogenic treatment), and the performance parameters of the bar I are shown in Table 1.

In example 1, the cemented carbide bar prepared in steps S11 to S14 (i.e., the comparative bar i, which is not subjected to the cryogenic treatment) was subjected to corresponding performance tests, and the test structure is shown in table 1.

TABLE 1

As can be seen from Table 1, the surface residual stress of the finished product of the double-spiral-hole hard alloy bar obtained by the cryogenic treatment is remarkably improved, the Vickers hardness and the bending strength are increased, the magnetic performance is basically kept unchanged, and the coercive force is increased while the magnetic saturation strength of cobalt is reduced. All the performances are superior to the prior level.

The 1500-fold-enlarged metallographic structure morphology of the bar i of this example 1 is shown in fig. 1, and the 1500-fold-enlarged metallographic structure morphology of the comparative bar i is shown in fig. 2, although the phases of the comparative bar i are uniformly distributed, the compactness is good, and the WC particle size is uniform and the distribution is uniform. However, comparing fig. 1 and fig. 2, it can be seen that, after the deep cooling treatment, the phases of the bar material I are distributed more uniformly, and the compactness of the hard alloy is obviously improved.

Example 2

In the present embodiment 2, the heat retention time for heat retention at the set lower limit temperature in step S15 is changed based on the embodiment 1; the remaining steps and parameters were the same.

And when the heat preservation time is 4 hours, the obtained finished product of the double-spiral-hole hard alloy bar is marked as a bar II-1 (heat preservation time is 4 hours), and the performance parameters of the bar II-1 are shown in Table 2. When the heat preservation time is 8 hours, the obtained finished product of the double-spiral-hole hard alloy bar is marked as a bar II-2 (heat preservation time is 8 hours), and the performance parameters of the bar II-2 are shown in Table 2.

TABLE 2

As can be seen from Table 2, in the deep cooling treatment, the holding time of holding at the set lower limit temperature is not as long as possible, and the comprehensive performance of the double-spiral-hole hard alloy bar finished product obtained at 2h is better.

Example 3

In this example 3, the sintering temperature in step S14 was changed based on example 1, and the rest of the steps and parameters were the same.

Wherein, when the sintering temperature is 1320 ℃, the obtained double-spiral-hole hard alloy bar finished product is marked as bar III-1 (1320 ℃). When the sintering temperature is 1360 ℃, the obtained finished product of the double-spiral-hole hard alloy bar is marked as bar III-2 (1360 ℃). When the sintering temperature is 1400 ℃, the obtained finished product of the double-spiral-hole hard alloy bar is marked as bar III-3 (1400 ℃). The performance parameters of bar III-1, bar III-2 and bar III-3 are shown in Table 3.

TABLE 3

As can be seen from Table 3, the compressive sintering temperature is 1390-1400 ℃ during the compressive sintering, and the obtained double-spiral-hole hard alloy bar finished product has better comprehensive performance.

The metallographic structure morphology of the bar iii-1, the bar iii-2, and the bar iii-3 in this example 3 is shown in fig. 3, 4, and 5, respectively. The metallographic structure of the bar III-1 shown in FIG. 3 at 200 times showed a morphology pattern with marked sand holes. As shown in the metallographic structure morphology diagram of the bar III-2 shown in the figure 4 under 1500 times, a cobalt pool phenomenon appears. As shown in the metallographic structure morphology chart of 1500 times of the bar III-3 shown in the figure 5, all phases are uniformly distributed and have good compactness.

Example 4

In this example 4, the dewaxing time in step S14 was changed based on example 1, and the rest of the steps and parameters were the same.

And when the dewaxing time is 10min, marking the obtained finished product of the double-spiral-hole hard alloy bar as a bar IV-1 (dewaxing for 10 min). And when the dewaxing time is 20min, marking the obtained finished product of the double-spiral-hole hard alloy bar as a bar IV-2 (dewaxing for 20 min). The performance parameters of the rods IV-1 and IV-2 are shown in Table 4.

TABLE 4

As can be seen from Table 4, the overall performance of the finished product of the double-spiral-hole cemented carbide bar obtained when the dewaxing time was 30min was better in the vacuum dewaxing.

The metallographic structure of the bar IV-1 and the bar IV-2 in this example 4 is shown in FIGS. 6 and 7, respectively. As shown in the metallographic structure morphology diagram of the bar IV-1 shown in the figure 6 under the condition of 200 times, obvious carburization and serious carburization occur. The metallographic structure of the bar IV-2 at 200 times showed a morphology in FIG. 7, in which carburization was significantly reduced, but carburization, slight carburization, was still observed. Compared with a metallographic structure morphology chart of the bar I shown in the figure 1, which is 1500 times lower, the carburization phenomenon does not occur, all phases are uniformly distributed, and the compactness is high.

Example 5

In this example 5, the ball milling time in step S11 was changed based on example 1, and the rest of the steps and parameters were the same. Wherein the ball milling time is 4-10 h.

In example 5, the bending strength and hardness of the double-spiral-hole cemented carbide bar finished product obtained by different ball milling times were tested, and a ball milling time-bending strength curve (as shown in fig. 8) and a ball milling time-vickers hardness curve (as shown in fig. 9) were obtained. As can be seen from fig. 8, when the ball milling time is less than 7h, the bending strength of the hard alloy bar product is not much improved, and as the ball milling time is prolonged, the bending strength is always increased, and reaches the highest peak at 7h, and when the ball milling time is greater than 7h, the bending strength is in a downward trend. As can be seen from fig. 9, the hardness of the hard alloy bar finished product increases with the increase of the ball milling time, and the ball milling time tends to be stable and reaches a peak value within 4-10 hours.

The above description sufficiently illustrates embodiments of the disclosure to enable those skilled in the art to practice them. Other embodiments may include structural and other changes. The examples merely typify possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and features of some embodiments may be included in or substituted for those of others. The embodiments of the present disclosure are not limited to the structures that have been described above, and various modifications and changes may be made without departing from the scope thereof. The scope of the present disclosure is limited only by the appended claims.

Claims

1. A preparation method of a double-spiral-hole hard alloy bar comprises the steps of mixing, extrusion forming, dewaxing and sintering, and is characterized by further comprising the following steps:

2. The production method according to claim 1, wherein the cryogenic treatment comprises: and cooling the sintered hard alloy bar to a set lower limit temperature at the speed of 1-5 ℃/min, then preserving heat for 2-24 hours at the set lower limit temperature, and raising and recovering the temperature.

3. The preparation method according to claim 2, wherein the cemented carbide bar obtained by sintering is cooled to a set lower limit temperature at a rate of 1-3 ℃/min, then is kept at the set lower limit temperature for 2-8 h, and then is raised and recovered.

4. The production method according to claim 1, 2 or 3,

the mixing comprises the following steps: stirring and ball-milling the raw materials of the hard alloy bar to obtain a mixture; wherein the ball milling time is 4-10 h.

5. The method according to claim 1, 2 or 3, wherein the extrusion speed is 2 to 15mm/min in the extrusion molding.

6. The method of claim 5, wherein the extrusion speed is 6 mm/min.

7. The method of claim 1, 2 or 3, wherein the dewaxing comprises vacuum dewaxing, the dewaxing temperature is 580-620 ℃, and the dewaxing time is 10-30 min.

8. The production method according to claim 1, 2 or 3, wherein in the sintering, the sintering temperature is 1320 to 1400 ℃ and the sintering pressure is 8 to 9 MPa.

9. The production method according to claim 8, wherein in the sintering, a sintering temperature is 1390 ℃ and a sintering pressure is 8 to 9 MPa.

10. The method for preparing the hard alloy bar according to the claim 1, 2 or 3, wherein the raw material of the hard alloy bar comprises superfine WC and Co, wherein the content of Co is 8-12% of the total weight of the raw material.

11. A double-spiral-hole cemented carbide rod produced by the method according to any one of claims 1 to 10.