A method for improving the straightness of cemented carbide sintered bars

Abstract

The present invention discloses a method for improving the straightness of cemented carbide sintered bars, belonging to the technical field of powder metallurgy, and comprising the following steps: (1) preparing surface coating materials with different component ratios according to the different diameters and lengths of bar blanks; (2) brushing the surface coating materials on the surface of the bar blanks to be sintered; (3) performing surface drying treatment on the brushed bar blanks; (4) cleaning the attachments on the surface of the bar blanks with a brush and a vacuum cleaner; (5) sintering the brushed bar blanks by a sintering process; (6) performing sandblasting treatment on the sintered bars. The present invention is designed specifically for the straightness of cemented carbide sintered bars. This solution improves the first-pass rate of the straightness of the bars after sintering by treating the bar blanks to be sintered of cemented carbide bars before sintering.

Description

Technical Field

[0001] The present invention relates to the technical field of powder metallurgy, and particularly relates to a method for improving the straightness of cemented carbide sintered bars. Background Art

[0002] Powder metallurgy is a process technology for producing metal powders or using metal powders (or mixtures of metal powders and non-metal powders) as raw materials, and manufacturing metal materials, composite materials, and various types of products through forming and sintering.

[0003] Cemented carbide is a superhard material produced by powder metallurgy process, with a series of excellent properties such as high hardness, wear resistance, good strength and toughness, heat resistance, corrosion resistance, etc. Especially its high hardness and wear resistance basically remain unchanged even at a temperature of 500°C, and still have a very high hardness at 1000°C. It is known as the "industrial teeth" and is used to manufacture cutting tools, drills, cobalt tools, and wear-resistant components, and is widely used in the fields of military, aerospace, machining, metallurgy, oil drilling, mining tools, electronic communication, construction, etc.

[0004] Cemented carbide bars are an important application field in cemented carbide cutting tools. Cemented carbide bars are the main precursor materials for solid cemented carbide tools, mainly used for making drills, milling cutters, reamers, boring cutters, etc., for cutting cast iron, non-ferrous metals, plastics, chemical fibers, graphite, glass, stone, and ordinary steel, and can also be used for cutting difficult-to-machine materials such as superalloys, heat-resistant steels, stainless steels, high-manganese steels, and tool steels. The quality of cemented carbide bars directly affects the use of tools. In the production process of cemented carbide round bars, as the length of the round bars increases, the influence of the straightness of the bars on the quality of the round bar products becomes greater.

[0005] Generally, for cemented carbide bars with a diameter less than 6 mm and a length greater than 100 mm, the number of bars with a straightness less than 0.1 - 0.2 mm after one sintering only accounts for 20 - 30%, and 70 - 80% of the products need to be straightened before further subsequent production and processing. This will not only increase the production cycle and production cost, but also cause a certain degree of cobalt layer gradient difference on the surface and core of the bars, affecting the use performance of the tools; for cemented carbide bars with a diameter greater than 6 mm, as the diameter increases and the length decreases, the number of bars with a straightness less than 0.1 - 0.2 mm after one sintering is continuously increasing, the bending deformation of the bar products decreases, and the qualified rate has a certain increase, but usually still about 50% of the products need to be straightened. Summary of the Invention

[0006] In view of the above deficiencies of the prior art, the present invention provides a method for improving the straightness of cemented carbide sintered bars; this method for improving the straightness of cemented carbide sintered bars is specifically designed to improve the straightness of cemented carbide sintered bars. This solution improves the first-pass qualification rate of the straightness of the bars after sintering by treating the green blanks of the cemented carbide bars before sintering.

[0007] To solve the above technical problems, a method for improving the straightness of cemented carbide sintered bars provided by the present invention includes the following steps:

[0008] (1) Prepare surface coating materials with different component ratios according to the different diameters and lengths of the bar blanks;

[0009] (2) Brush the surface coating material on the surface of the green bar blanks to be sintered;

[0010] (3) Perform surface drying treatment on the coated bar blanks;

[0011] (4) Clean the attachments on the surface of the bar blanks with a brush and a vacuum cleaner;

[0012] (5) Sinter the cleaned bar blanks using a sintering process;

[0013] (6) Perform sandblasting treatment on the sintered bars.

[0014] In a further improvement of the present invention, the surface coating material in step (1) includes a glue solution and solids. The glue solution includes hydroxymethyl cellulose and pure water, and the ratio of hydroxymethyl cellulose to pure water is 1:10; the solids are selected from Al2O3, ZrC, Y2O3, TiO2, and carbon black according to the diameter and length of the bars, as well as the sectional magnetic saturation value of the bars after direct sintering, to form component compositions and component mass ratios.

[0015] In a further improvement of the present invention, in step (2), according to the magnetic saturation level of the bars, apply multiple coats to the parts with low magnetic saturation and one coat to the parts with normal magnetic saturation.

[0016] In a further improvement of the present invention, in step (3), use a hot air circulation oven to perform surface drying treatment on the coated bars at 40°C for 60 - 120 minutes, and introduce Ar inert gas or N2 inert gas throughout the drying process for protection.

[0017] In a further improvement of the present invention, in step (4), first use a soft brush to sweep across the surface of the bars, and then use a handheld vacuum cleaner to clean up the floating objects swept down by the soft brush.

[0018] In a further improvement of the present invention, in step (5), the temperature range of the sintering process is 1400°C - 1600°C, and the holding time is 40 - 80 minutes.

[0019] Compared with the prior art, the present invention has the following beneficial effects:

[0020] The present invention is designed specifically for the straightness of cemented carbide sintered bars. By treating the to-be-sintered blanks of cemented carbide bars before sintering, the first-pass qualification rate of the straightness of the bars after sintering is improved. Specific Embodiments

[0021] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative efforts shall fall within the protection scope of the present invention.

[0022] Currently, for cemented carbide bars with a diameter less than 6 mm and a length greater than 100 mm, the number of bars with a straightness less than 0.1 - 0.2 mm after one-time sintering only accounts for 20 - 30%. 70 - 80% of the products need to be straightened before further subsequent production and processing. This will not only increase the production cycle and production cost, but also cause a cobalt layer gradient difference on the surface and core of the bars to a certain extent, affecting the use performance of the cutting tools. For cemented carbide bars with a diameter greater than 6 mm, as the diameter increases and the length decreases, the number of bars with a straightness less than 0.1 - 0.2 mm after one-time sintering is increasing continuously. The bending deformation of the bar products decreases, and the qualification rate has a certain improvement, but usually about 50% of the products still need to be straightened.

[0023] Therefore, the present application proposes the following technical solutions to improve the first-pass qualification rate of the straightness of the bars after sintering by treating the to-be-sintered blanks of cemented carbide bars before sintering.

[0024] A method for improving the straightness of cemented carbide sintered bars includes the following steps:

[0025] (1) Prepare surface coating materials with different component ratios according to the different diameters and lengths of the bar blanks; (wherein, the composition ratio of the coating material is selected based on the magnetic saturation detection results of the directly sintered samples of the to-be-sintered bars)

[0026] (2) Brush the surface coating materials on the surface of the to-be-sintered bar blanks; (wherein, the coating is applied to the to-be-sintered bars according to the magnetic saturation detection situation)

[0027] (3) Perform surface drying treatment on the coated bar blanks.

[0028] (4) Clean the surface attachments with a brush and a vacuum cleaner;

[0029] (5) Sinter the cleaned bar blanks using a sintering process;

[0030] (6) Perform sandblasting on the sintered bars;

[0031] (7) Check the straightness of the bars after sandblasting.

[0032] Among them, the components of the surface coating material are selected according to the different diameters and lengths of the bar blanks, and the selection basis is shown in the following table.

[0033]

[0034] The surface coating material in step (1) includes a glue solution and solids. The glue solution includes hydroxymethyl cellulose and pure water, and the ratio of hydroxymethyl cellulose to pure water is 1:10. The solids are selected from Al2O3, ZrC, Y2O3, TiO2, and carbon black according to the diameter and length of the bar, as well as the sectional magnetic saturation value of the bar after direct sintering, and the component mass ratios are as shown in the following table.

[0035]

[0036] In step (2), after uniformly mixing the surface coating material, gently brush the surface coating material on the surface of the bar blank before sintering. According to the magnetic saturation level of the bar, apply multiple coats to the parts with low magnetic saturation and one coat to the parts with normal magnetic saturation.

[0037] In step (3), use a hot air circulation oven to perform a surface drying treatment on the coated bars at 40°C for 60 - 120 minutes, and introduce Ar inert gas or N2 inert gas throughout the drying process for protection.

[0038] In step (4), first sweep the surface of the bar with a soft brush, and then use a handheld vacuum cleaner to clean up the floating objects swept by the soft brush.

[0039] In step (5), the temperature range of the sintering process is 1400°C - 1600°C, and the holding time is 40 - 80 minutes.

[0040] Set a control experiment for the present invention (sintering after coating), that is, sinter bars of the same specification using direct sintering, and use the same detection method (platform plus feeler gauge) to detect the bars after sintering. The detection results are shown in the following table.

[0041]

[0042] As can be seen from the above comparison, in the present invention, a special coating material is applied to the surfaces of blanks with different diameters and lengths, dried and cleaned, and then sintered, which can effectively improve the straightness of bar products, reduce the straightening and re-sintering caused by poor straightness, improve the first-pass rate in the production process, reduce the energy consumption caused by multiple sinterings, and reduce the degradation of the properties of bar products.

[0043] Example 1

[0044] Select 100 cemented carbide bars with the grade of YG10X and the model of Bφ6×330. The Com test firing results before batch sintering are shown in the following table.

[0045]

[0046] According to the results in the table, configure 150 g of carbon black containing 60%, 50 g each of alumina and yttrium oxide each containing 20%, and then add 50% of the total weight of the coating of pure water. After stirring evenly, obtain 375 g of carbon black-alumina-yttrium oxide mixture. Then add 190 g of glue solution dissolved in a ratio of 1:10, and stir evenly to obtain the final surface coating.

[0047] Apply the prepared coating evenly on the surface of the bars to be sintered, and apply it twice on about 1 / 6 of the length at both ends of the bars. After the coating is completed, place the bars in a graphite trough boat.

[0048] Place the trough boat containing the cemented carbide bars coated with the coating in a hot air circulation oven at 40°C and bake for 60 minutes.

[0049] Take out the trough boat, gently brush the surface of the bars with a soft brush, and then use a vacuum cleaner to clean the excess coating on the surfaces of the bars and the boat.

[0050] Place the sorted trough boat containing the coated bars in a pressure sintering furnace for normal sintering. The sintering temperature is 1410°C and the holding time is 60 minutes.

[0051] Then cool it to room temperature with the furnace. After sintering is completed, perform sandblasting on the bars.

[0052] Perform straightness detection on the sandblasted bar products. The detection results show that the straightness of 80 bars is 0.1 - 0.15 mm, and the straightness of 20 bars is 0.15 - 0.2 mm.

[0053] Example 2

[0054] Select 100 cemented carbide bars with the grade of YG10X and the model of Bφ6×330. The Com test firing results before batch sintering are shown in the following table.

[0055]

[0056] According to the results in the table, prepare 10g of 4% carbon black, 48% of aluminum oxide and 48% of yttrium oxide, 120g each, and then add 50% of the total weight of pure water to the coating. After stirring evenly, 250g of carbon black-aluminum oxide-yttrium oxide mixture is obtained. Then, 125g of glue dissolved in a ratio of 1:10 is added and stirred evenly to obtain the final surface coating.

[0057] Apply the prepared coating evenly on the surface of the rod to be sintered, and apply it twice on about 1 / 4 of the length at both ends of the rod.

[0058] After painting, place the rods in a graphite boat, and then place the boat containing the coated carbide rods in a hot air circulation oven at 40°C for 60 minutes.

[0059] Take out the slot boat, use a soft brush to gently brush the surface of the rod, and then use a vacuum cleaner to clean the excess paint on the surface of the rod and the boat.

[0060] The arranged slot boat containing the painted rods is placed into the pressure sintering furnace for normal sintering, and the slot boat containing the coated carbide rods is placed into the pressure sintering furnace for normal sintering. The sintering temperature is 1410℃ and the holding time is 60 minutes.

[0061] Then the furnace is cooled to room temperature. After sintering, the rod is sandblasted.

[0062] The straightness of the rod products after sandblasting was tested, and the test results showed that the straightness of 85 rods was 0.1~0.15mm, and the straightness of 15 rods was 0.15~0.2mm.

[0063] Although the present invention has been described in detail by way of preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, ordinary technicians in this field can make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions should all be within the scope of the present invention. Any technician familiar with this technical field can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should all be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A method for improving the straightness of cemented carbide sintered rods, characterized in that: The following steps are included: (1) According to the different diameters D and lengths L of the bar blanks, the surface coating materials with different composition ratios are prepared as follows: For rods with a diameter of D ≤ 6 mm, when the length L ≤ 100 mm, the surface coating material formula is Al2O3, Y2O3, carbon black, hydroxymethyl cellulose, and pure water; when the length is 100 mm < L, the surface coating material formula is Al2O3, Y2O3, carbon black, hydroxymethyl cellulose, and pure water; For rods with a diameter of 6 mm or less and a diameter of D less than or equal to 16 mm, when the length L is less than or equal to 100 mm, the surface coating material formula is ZrC, Y2O3, carbon black, hydroxymethyl cellulose, and pure water; when the length L is less than or equal to 100 mm, the surface coating material formula is ZrC, Y2O3, carbon black, hydroxymethyl cellulose, and pure water. For rods with a diameter of 16 mm or less and a diameter of D less than or equal to 32 mm, when the length L is less than or equal to 100 mm, the surface coating material formula is Al2O3, ZrC, TiO2, carbon black, hydroxymethyl cellulose, and pure water; when the length L is less than or equal to 100 mm, the surface coating material formula is Al2O3, ZrC, TiO2, carbon black, hydroxymethyl cellulose, and pure water. For rods with a diameter of 32 mm and a diameter of D less than or equal to 50 mm, when the length L is less than or equal to 100 mm, the surface coating material formula is ZrC, Y2O3, TiO2, carbon black, hydroxymethyl cellulose, and pure water; when the length L is less than or equal to 100 mm, the surface coating material formula is ZrC, Y2O3, TiO2, carbon black, hydroxymethyl cellulose, and pure water. The surface coating material includes a glue and a solid, wherein the glue includes hydroxymethyl cellulose and pure water; the solid is composed of Al2O3, ZrC, Y2O3, TiO2 and carbon black according to the diameter and length of the rod and the segmented magnetic saturation value of the rod after direct sintering. The specific mass ratio of the selected components is as follows: For rods with a diameter of D≤6mm, when the magnetic saturation of the rod is less than 75%, Al2O3:Y2O3:carbon black=1:1:3; when the magnetic saturation of the rod is greater than 75%, Al2O3:Y2O3:carbon black=1:1:0.5; For rods with a diameter of 6 mm or less and a diameter of D less than or equal to 16 mm, when the magnetic saturation of the rod is less than 75%, the ratio of ZrC:Y2O3:carbon black is 1:1:3; when the magnetic saturation of the rod is greater than 75%, the ratio of ZrC:Y2O3:carbon black is 1:2:

2. For rods with a diameter of 16 mm or less and a diameter of D less than or equal to 32 mm, when the magnetic saturation of the rod is less than 75%, the ratio of Al2O3: ZrC: TiO2: carbon black is 1:1:1:3; when the magnetic saturation of the rod is greater than 75%, the ratio of Al2O3: ZrC: TiO2: carbon black is 1:1:2:

2. For rods with a diameter of 32 mm or less and a diameter of D less than or equal to 50 mm, when the magnetic saturation of the rod is less than 75%, the ratio of ZrC:Y2O3:TiO2:carbon black is 1:1:1:3; when the magnetic saturation of the rod is greater than 75%, the ratio of ZrC:Y2O3:TiO2:carbon black is 1:1:2:

2. (2) Brushing the surface coating material on the surface of the rod blank to be sintered; (3) Drying the surface of the painted bar blank; (4) Use a brush and a vacuum cleaner to clean the attachments on the surface of the bar blank; (5) The cleaned bar blank is sintered using a sintering process; (6) Sandblasting the sintered rods.

2. The method for improving the straightness of cemented carbide sintered rod according to claim 1, characterized in that: In step (3), the surface of the coated rod is dried in a hot air circulation oven at 40°C for 60 to 120 minutes, and Ar inert gas or N2 inert gas is introduced throughout the drying process for protection.

3. The method for improving the straightness of cemented carbide sintered rod according to claim 1, characterized in that: In step (4), first use a soft brush to sweep the surface of the rod, and then use a handheld vacuum cleaner to clean up the floating objects swept by the soft brush.

4. The method for improving the straightness of cemented carbide sintered rod according to claim 1, characterized in that: In step (5), the temperature range of the sintering process is 1400°C~1600°C, and the holding time is 40~80min.

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