Preparation method and application of hard alloy thin-wall eccentric hole rod

Abstract

The invention discloses a preparation method and application of a hard alloy thin-wall eccentric hole rod, and belongs to the technical field of hard alloys, and the preparation method comprises the following preparation steps: mixing 85-94% by weight of WC, 6-14% by weight of cobalt and 0-1% by weight of other carbide inhibitors, carrying out ball milling, and carrying out vacuum drying to form a powdery mixture; 3-20% by weight of a composite forming agent is added into the mixture, heating and stirring are conducted for 50-90 minutes, cooling and stirring are conducted for 40-70 minutes, a stepped mold core rod is selected, vacuum drying is conducted after forming is conducted at the proper extrusion speed, a dry blank of the eccentric hole rod with the cross section is formed, the dry blank of the eccentric hole rod is attached to the groove wall of a boat, and sintering is conducted to form the hard alloy eccentric hole rod. The thin-wall eccentric hole rod prepared through the method is not prone to perforation and high in size precision, and the problem that a hard alloy eccentric hole rod is distorted and deformed in the extrusion forming, drying and sintering processes can be solved.

Description

Technical Field

[0001] The invention relates to the technical field of cemented carbide preparation, and in particular to a preparation method and application of a cemented carbide thin-wall eccentric hole rod. Background Art

[0002] The carbide eccentric hole rod is a special-shaped hole processing tool. In the processing process with strict tolerance requirements, it can ensure the accuracy and straightness of the workpiece being processed.

[0003] Since cemented carbide eccentric hole drills have an asymmetric structure, especially thin-walled eccentric hole products are prone to perforation during the extrusion process. Uneven shrinkage during the drying and sintering process will lead to twisting and bending deformation, so the qualified rate is low, and the processing accuracy after being processed into a tool cannot be guaranteed.

[0004] Previously, eccentric hole rods were formed using straight hole matching dies. This method resulted in a large density difference in the pressed billet during the extrusion process, which was prone to distortion and deformation, and had poor straightness.

[0005] Thin-walled eccentric hole rods are more sensitive to the on-site environment and the atmosphere in the furnace. They shrink inconsistently in all directions during drying and sintering, resulting in poor straightness.

[0006] Ensuring the straightness of the finished product after the thin-walled eccentric hole rod is formed, dried, and sintered can effectively improve the processing accuracy of the tool, but there is currently no effective method to solve the distortion and bending deformation generated during the forming, drying, and sintering process. Patent No. CN116000285A discloses a hole rod with a V-groove and a preparation method thereof, providing technical inspiration for preparing cemented carbide using WC and Co through ball milling, spray drying, extrusion molding drying, and sintering, but the spherical mixture formed by spray drying involved in this method is dried by hot air circulation drying at 100-150°C, which is not suitable for the forming and drying of thin-walled eccentric hole rods. Summary of the invention

[0007] The technical problem to be solved by the present invention is the perforation, twisting and bending deformation produced during the raw material preparation, molding and drying process of thin-walled eccentric hole rods, overcoming the deficiencies and defects mentioned in the above background technology, and providing a preparation method and application of thin-walled eccentric hole rods.

[0008] To achieve the above object, the present invention provides the following technical solutions: A method for preparing a thin-walled eccentric hole rod comprises the following preparation steps: (1) 85-94% WC, 6-14% cobalt, and 0-1% other carbide inhibitors are mixed and ball-milled, vacuum-stirred, and dried to form a powdery mixture; (2) Add 3 to 20% by weight of a composite molding agent to the mixture, heat and stir for 60 to 90 minutes, cool and stir for 40 to 70 minutes, use a stepped mold core rod, and perform vacuum drying after molding at an appropriate extrusion speed to form a dry blank with an eccentric hole in the cross section.

[0009] (3) Place the eccentric hole rod dry blank in a 90-degree groove boat groove wall, with the thin wall facing downward and the thick wall facing upward, and sinter to form a cemented carbide thin-walled eccentric hole rod.

[0010] Preferably, the raw materials are mixed and ball-milled without adding a molding agent.

[0011] Preferably, the ball-milled mixture is subjected to vacuum stirring and drying to prepare a powdery mixed material.

[0012] Preferably, the extrusion molding adopts a stepped die core rod, and a suitable extrusion speed reduces the density difference of the green body during molding.

[0013] Preferably, the extruded green sheet is dried by heating with hot water under vacuum conditions, which reduces the influence of the traditional drying environment on the green sheet and is beneficial to the volatilization of the solvent and the consistency of shrinkage.

[0014] Preferably, the eccentric hole rod dry blank is placed in contact with the groove wall of the 90-degree groove boat dish, with the thin wall facing downward and the thick wall facing upward, and the highest point of the circular hole of the eccentric hole rod cannot exceed the top of the groove.

[0015] During extrusion molding, a straight-through mold core rod is conventionally used. This thin-walled asymmetric structure will lead to distortion, perforation and bending deformation during molding. The wet billet is dried using traditional hot air circulation drying, which is prone to shrinkage inconsistency and causes deformation of the dry billet.

[0016] The present invention changes the design of the die core rod, controls the extrusion speed, heats and dries the wet blank under vacuum conditions, and during sintering, the thin wall of the dry blank faces downward and the thick wall faces upward, and the highest point of the circular hole of the eccentric hole rod cannot exceed the top of the groove. The method ensures the stability and consistency of product quality.

[0017] Preferably, during the ball milling process in step (1), the carbide inhibitor is pre-milled for 2 hours, and then other raw materials are added, with a ball-to-material ratio of 4:1, anhydrous alcohol as the ball milling medium is added in an amount of 250 ml to 400 ml / kg, and the ball milling time is 24 to 75 hours.

[0018] Preferably, in step (2), the heating and stirring temperature is 55-85° C., the heating time is 60-90 minutes, the cooling and stirring temperature is 20-35° C., and the cooling and stirring time is 40-70 minutes.

[0019]

[0023] Preferably, the extrusion molding in step (3) is specifically as follows: when the mold is assembled, the thin wall line faces downward, and the extruded wet billet is dried at a temperature of 90 to 100°C for a holding time of 72 to 200 hours to form a thin-walled eccentric hole rod dry billet.

[0020] Preferably, the sintering in step (4) is performed by heating the temperature in a sintering furnace to 1380-1430° C. and performing high-temperature pressure sintering at an air pressure of 50-90 bar.

[0021] Under the same technical concept, the present invention also provides a method for preparing a thin-walled eccentric hole rod.

[0022] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing a thin-walled eccentric hole rod. This product has an asymmetric structure and is prone to distortion and perforation during extrusion. The free shrinkage of the wet blank during drying will cause uneven force on the thin-walled eccentric hole rod, and bending deformation and large and small heads will appear after sintering. The present invention improves the density distribution of the pressed green sheet by changing the structure of the die core rod, reasonably controlling the extrusion speed and heating and drying under vacuum conditions, and reasonably placing the pressed green sheet in a 90-degree groove boat dish wall, thereby ensuring the consistency of shrinkage during drying and sintering, and greatly reducing the bending deformation of the product. The thin-walled eccentric hole rod prepared by the method of the present invention has high strength and hardness, and can solve the perforation bending deformation in the production process. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0024] Figure 1 This is the mold core rod structure of the thin-walled eccentric hole rod in Example 1.

[0025] Figure 2 This is the mold core rod structure of the thin-walled eccentric hole rod in comparative example 1. DETAILED DESCRIPTION

[0026] The present invention is described in detail below with reference to the embodiments Example

[0027] 86.0% WC by weight, 13% cobalt by weight, 1.0% Cr3C2 by weight Grinding rods were added at a ball-to-material ratio of 5:1, and alcohol was added at 380ml / kg for ball milling for 42 hours. After vacuum stirring and drying for 5 hours, the mixture was sieved into a powdery mixture. 10% of plasticizer was added to the mixture, heated and stirred at 85 degrees for 90 minutes, and then cooled at 20 degrees for 60 minutes. A stepped mold core rod was selected and extruded at a speed of 3-4mm / s. The formed wet blank was loaded into a vacuum drying furnace, heated to 99 degrees under vacuum conditions and kept warm for 120 hours. After drying, the internal solvent can be removed to obtain a thin-walled eccentric hole rod dry blank. The dry blank was placed in a 90-degree groove boat dish groove wall, with the thin wall facing down and the thick wall facing up. The highest point of the circular hole of the eccentric hole rod could not exceed the top of the groove. After sintering at 1390℃, the thin-walled eccentric hole rod was checked for a straightness of <0.2mm and a qualified rate of 98%, a Vickers hardness of 1560, and a strength of 3000Mpa. Example

[0028] 91.2% by weight WC, 8% by weight Co, 0.8% by weight Cr3C2 Grinding rods were added at a ball-to-material ratio of 5:1, and alcohol was added at 350ml / kg for ball milling for 48 hours. After vacuum stirring and drying for 5 hours, the mixture was sieved into a powdery mixture. 8% of plasticizer was added to the mixture, heated and stirred at 80 degrees for 100 minutes, and then cooled at 20 degrees for 50 minutes. A stepped mold core rod was selected and extruded at a speed of 5-4mm / s. The formed wet blank was loaded into a vacuum drying furnace, heated to 90 degrees under vacuum conditions and kept warm for 180 hours. After drying, the internal solvent can be removed to obtain a thin-walled eccentric hole rod dry blank. The dry blank was placed in a 90-degree groove boat dish groove wall with the thin wall facing down and the thick wall facing up. The highest point of the circular hole of the eccentric hole rod could not exceed the top of the groove. After sintering at 1410℃, the thin-walled eccentric hole rod was checked for straightness <0.2mm and the qualified rate was 98%, the Vickers hardness was 1600, and the strength was 2800Mpa. Example

[0029] 93.1% by weight WC, 6% by weight Co, 0.9% by weight Cr3C2 Grinding rods were added at a ball-to-material ratio of 5:1, and alcohol was added at 320 ml / kg for ball milling for 60 hours. After vacuum stirring and drying for 5 hours, the mixture was sieved into a powdery mixture. 6% of plasticizer was added to the mixture, heated and stirred at 75 degrees for 120 minutes, and then cooled at 20 degrees for 45 minutes. A stepped mold core rod was selected and extruded at a speed of 3-4 mm / s. The formed wet blank was loaded into a vacuum drying furnace, heated to 95 degrees under vacuum conditions and kept warm for 150 hours. After drying, the internal solvent can be removed to obtain a thin-walled eccentric hole rod dry blank. The dry blank was placed in a 90-degree groove boat dish groove wall, with the thin wall facing down and the thick wall facing up. The highest point of the circular hole of the eccentric hole rod could not exceed the top of the groove. After sintering at 1430°C, the thin-walled eccentric hole rod was checked for a straightness of <0.2mm and a qualified rate of 97%, a Vickers hardness of 1650, and a strength of 2200Mpa.

[0030] Comparative Example 1: The remaining steps are the same as those in Example 1, using a straight-through mold structure, extrusion molding at a speed of 8 to 10 mm / s, and the wet blanks after molding are loaded into a common drying box. The straightness of the thin-walled eccentric hole rods is checked to be less than 0.2 mm, and the qualified rate is 58%.

[0031] Comparative Example 2: The remaining steps are the same as those in Example 2, using a straight-through die structure, extrusion molding at a speed of 8 to 10 mm / s, and the wet blanks after molding are loaded into a common drying box. The straightness of the thin-walled eccentric hole rods is checked to be less than 0.2 mm, and the qualified rate is 53%.

[0032] Comparative Example 3: The remaining steps are the same as those in Example 3, using a straight-through die structure, extruding at a speed of 8-10 mm / s, and placing the wet blanks into a common drying box. The straightness of the thin-walled eccentric hole rods is checked to be less than 0.2 mm, and the qualified rate is 63%. The following is a table comparing the information of the example and the comparative example: From the above table, we can analyze in detail the advantages of Examples 1 to 3 over Comparative Examples 1 to 3. The following is a specific analysis: Advantages of Example 1: The qualified rate of the thin-walled eccentric hole rod with a straightness of less than 0.2 mm in Example 1 is 98%, which is significantly higher than 58% in Comparative Example 1, 53% in Comparative Example 2, and 63% in Comparative Example 3. This shows that the process parameters and the stepped mold core rod adopted in Example 1 more effectively control the straightness of the product and improve the product quality.

[0033] The Vickers hardness of Example 1 is 1560 and the strength is 3000 MPa, while the comparative example does not provide these two data. However, considering the specific process conditions and component ratios in Example 1, it can be reasonably inferred that its hardness and strength performance are better than those of the comparative example, because these properties are usually closely related to the composition and processing of the material.

[0034] Example 1 uses vacuum stirring drying and vacuum drying oven for drying. These advanced processes help to better control the internal structure of the material and the removal of solvents, thereby possibly improving the overall performance of the product. In contrast, the comparative example only uses a common drying oven, which may not be as good as Example 1 in terms of solvent removal and internal structure control.

[0035] Advantages of Example 2: Similar to Example 1, Example 2 also showed an extremely high straightness pass rate (98%), far exceeding Comparative Examples 1 to 3. This once again proves the importance of the stepped mold core rod and optimized process parameters in controlling product straightness.

[0036] The Vickers hardness of Example 2 is 1600 and the strength is 2800 MPa, which are also better than those of the comparative example (although the comparative example does not provide specific data). These performance improvements may be attributed to the specific component ratio and fine processing process in Example 2.

[0037] In the process of Example 2, a longer ball milling time (48 hours) and specific heating, stirring and cooling times are used. These detailed process controls may help to form a more uniform and dense material structure, thereby improving the performance of the product. In contrast, the control of the comparative example in these aspects may be relatively extensive.

[0038] In summary, the main advantages of Examples 1 to 3 over Comparative Examples 1 to 3 are higher straightness pass rate, better Vickers hardness and strength performance, and more sophisticated processing and drying process control. These advantages together contribute to the significant improvement of the overall quality and performance of the Example products.

Claims

1. A method for preparing a cemented carbide thin-walled eccentric hole rod, characterized in that: The method comprises the following preparation steps: (1) 85-94% WC, 6-14% cobalt, and 0-1% other carbide inhibitors are mixed and ball-milled, vacuum-stirred, and dried to form a raw powder mixture; (2) Add 3 to 20% by weight of a composite molding agent to the mixture, heat and stir for 50 to 90 minutes, cool and stir for 40 to 70 minutes, extrude and mold using a stepped die core rod, and then vacuum dry to form a dry blank with an eccentric hole in the cross section. (3) The eccentric hole rod dry blank is placed on the groove wall of the 90-degree groove boat dish and sintered to form a cemented carbide thin-walled eccentric hole rod.

2. The method for preparing the cemented carbide thin-walled eccentric hole rod according to claim 1, characterized in that: The ball mill does not need to add a molding agent. When the thin-walled eccentric hole rod is extruded, the side closest to the eccentric hole contacts the boat tank wall. In its asymmetric structure, the thin wall part faces upward and the thick wall part faces downward.

3. The method for preparing the cemented carbide thin-walled eccentric hole rod according to claim 2, characterized in that: The thin-walled eccentric hole rod adopts a stepped die core rod, is extruded at a high speed, and then vacuum dried to form a cross-section eccentric hole rod dry blank.

4. The method for preparing the cemented carbide thin-walled eccentric hole rod according to claim 3, characterized in that: The thin-walled eccentric hole rod adopts a 90-degree V-shaped groove to contact the material and is flanging before sintering. In its asymmetric structure, the thin wall part faces downward and the thick wall part faces upward, and the highest point of the circular hole of the eccentric hole rod is ≤ the top of the groove.

5. The method for preparing the cemented carbide thin-walled eccentric hole rod according to claim 1, characterized in that: In the ball milling process of step (1), the carbide inhibitor is pre-milled for 2 hours, and then other raw materials are added, with a ball-to-material ratio of 5:1, anhydrous alcohol as the ball milling medium is added in an amount of 250 ml to 400 ml / kg, and the ball milling time is 24 to 75 hours.

6. The method for preparing the cemented carbide thin-walled eccentric hole rod according to claim 1, characterized in that: In step (2), the heating and stirring temperature is 50-85° C., the heating time is 60-90 minutes, the cooling and stirring temperature is 20-35° C., and the cooling and stirring time is 40-70 minutes.

7. The method for preparing a cemented carbide thin-walled eccentric hole rod according to claim 1, characterized in that: The extrusion molding in step (3) is specifically as follows: using a stepped mold core rod, assembling the mold with the thin wall line facing downward, and adopting a suitable extrusion speed. The extruded wet blank is dried at a temperature of 90 to 100° C. under vacuum conditions for a holding time of 72 to 200 hours to form a thin-walled eccentric hole rod dry blank.

8. The method for preparing the cemented carbide thin-walled eccentric hole rod according to claim 1, characterized in that: The sintering in step (4) is performed by heating the temperature in a sintering furnace to 1380-1430° C. and performing high-temperature pressure sintering at an air pressure of 50-90 bar.

9. A thin-walled eccentric hole rod, characterized in that: The eccentric hole rod prepared by any preparation method as claimed in claims 1-5 has an outer circle part straightness of ≤0.2mm, a Vickers hardness of ≥1600Mpa, and a bending strength of ≥2000Mpa.

10. Application of a thin-walled eccentric hole rod, characterized in that: The eccentric hole rod is used in eccentric drilling.

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