A method for in-situ preparation of woodworking tools based on laser alloying technology

Abstract

The present invention belongs to the technical field of material surface modification, and provides a method for in-situ preparing woodworking tools based on laser alloying technology. Through the optimized design of alloying components and the effective control of the technological process, an alloying modified layer with excellent mechanical and cutting properties is in-situ formed on the edge of a cheap tool body to meet the comprehensive performance requirements of high hardness, high wear resistance, high thermal stability, good strength and toughness, etc. under the cutting conditions of high speed and impact load for woodworking tools. At the same time, the present invention has many advantages such as simple technological process, high preparation efficiency, wide adaptability and high economy.

Description

Technical Field

[0001] The present invention belongs to the technical field of material surface modification, and provides a method for in-situ preparing a woodworking tool based on laser alloying technology. Background Art

[0002] In recent years, with the rapid development of the wood-based panel industry and the wood processing industry, higher requirements have been put forward for the advancement, practicality, and manufacturing precision of woodworking tools. The materials for making tools are gradually developing from tool steel and high-speed steel to hard materials. However, due to the intrinsic brittleness and high price of hard materials, common problems such as poor processability and economy generally exist in hard woodworking tools. Based on this, currently, the following two methods are mainly used to manufacture hard woodworking tools: One is the split welding method, that is, welding a hard material blade to a steel tool body. While ensuring good impact resistance of the tool, the wear resistance of the cutting edge is improved by using hard materials. However, due to the limitations of the powder metallurgy process itself, there are great limitations in the manufacture of blades with complex geometric shapes. In addition, due to the low strength and toughness of cemented carbide, the sharpness of the cutting edge is relatively low, making it difficult to meet the requirements of fine wood processing. Moreover, the weldability of hard materials is relatively poor, and metallurgical defects such as pores and cracks are easily generated during the welding process, directly affecting the cutting performance and durability of woodworking tools. Therefore, strict requirements are imposed on the welding process and procedure, and the manufacturing process is very complex. The other is the coating method, which uses surface modification technologies such as physical and chemical vapor deposition to deposit a hard film on the surface of a tough steel tool body. By using the high wear resistance and heat resistance of the hard film, the cutting performance of the tool is improved. However, due to the weak physical interface bonding between the film and the substrate, the hard film is extremely easy to peel off during the cutting process at high speed and under alternating impact loads. Therefore, the improvement of the tool durability is very limited, and the problem of poor toughness and impact resistance of hard materials has not been fundamentally solved. In view of the bottleneck problem that it is difficult to reconcile the hardness, wear resistance, strength, and toughness of single hard materials, as well as the limitations of existing manufacturing processes, it is of great practical significance to develop new composite tool materials and explore new tool manufacturing methods by taking a different approach.

[0003] Laser alloying technology is to use a high-energy laser beam to heat and melt the surface layer of the substrate and the added elements, and make them mix and then solidify rapidly, thereby forming a new surface alloy layer based on the original substrate. This technology has many unique advantages: the microstructure is uniform and fine, and the performance is excellent; it has high flexibility and is easy to realize local treatment of complex-structured parts, and the depth of the alloyed layer is precisely controllable; the alloy system range is wide; the thermal effect of the substrate is low, and the workpiece deformation is small; the production efficiency is high, and the process cost is low. Based on this, the present invention develops a method for in-situ preparing a woodworking tool on a cheap substrate based on laser alloying technology through the optimized design of alloying components and the effective control of the process. Summary of the Invention

[0004] The object of the present invention is to overcome the bottleneck limitations of the existing woodworking tool manufacturing technology, and provide a method for in-situ preparation of woodworking tools based on laser alloying technology. Through high-throughput structure simulation analysis and a large number of experimental studies, the optimal composition ratio range of the alloying components is determined, and through the effective regulation of the alloying process parameters and process, an alloying layer with excellent mechanical and cutting properties is formed in-situ on the edge of the cheap tool body to meet the comprehensive performance requirements of woodworking tools such as high hardness, high wear resistance, high thermal stability, and good strength and toughness under high-speed and impact load-bearing cutting conditions, and significantly reduce the manufacturing cost.

[0005] To achieve the above object, the technical solution of the present invention is as follows:

[0006] A method for in-situ preparation of woodworking tools based on laser alloying technology, including rough machining of the tool body material, alloying powder composition design, preparation and pre-placement of the alloying powder, laser alloying, and subsequent machining;

[0007] The method includes the following steps:

[0008] (1) Rough machining of the tool body material: Select quenched and tempered steel or tool steel with good strength and toughness and low price as the tool body material. After blanking and straightening processes, use grinding to machine it into a tool body blank with the required shape and size;

[0009] (2) Alloying powder composition design: Select WC, TiC, NbC, Mo, Al, and La powders with a particle size of 10 - 50μm as raw materials, and the optimal composition ratio range is: (10 - 20wt.%) TiC - (0.5 - 1.0wt.%) NbC - (0.2 - 0.6wt.%) Mo - (0.4 - 0.8wt.%) Al - (0.5 - 1.0wt.%) La - WC;

[0010] (3) Preparation and pre-placement of the alloying powder: Weigh and mix the alloying powder according to the chemical composition in step (2), place it in a ball mill, mix it with absolute ethanol as the ball milling medium at a rotation speed of 100 - 150rpm for 6 - 10h, then use a suspension of absolute ethanol and shellac with a volume ratio of 99:1 to adjust the mixed alloying powder into a suspension, and spray it evenly onto the rake face of the tool body with a spray gun to form a sprayed layer with a thickness of 0.4 - 0.8mm;

[0011] (4)Laser alloying: After the sprayed coating is naturally dried, place the tool body in the fixture on the laser processing system platform, and then under the drive of the numerical control system, perform laser alloying treatment along the contour of the cutting edge of the rake face to form an alloying modification layer with high hardness, high wear resistance, high thermal stability, and good strength and toughness on the surface of the cutting edge; the optimized laser alloying parameters are: laser power is 1.5 - 2.5 KW, scanning speed is 6 - 15 mm / s, spot size is 2 - 6 mm, overlap rate is 0 - 50%, and the flow rate of the protective gas is 15 - 20 L / min;

[0012] (5)Subsequent machining: After the laser alloying treatment, precisely grind the rake face with a tool grinder, the grinding depth is less than 0.1 mm, and then use a profiling grinder to grind the flank face to machine it into the final cutting edge shape and dimensional accuracy, so as to realize the preparation of the woodworking tool.

[0013] Implementing the embodiments of the present invention will have the following beneficial effects:

[0014] (1)Excellent mechanical properties: Due to the formation of a fine composite structure reinforced by multiple hard phases, the in-situ alloyed cutting edge exhibits excellent mechanical properties. Its hardness at room temperature and 600 °C is equivalent to that of cemented carbide, reaching HRC65 - 78 and HRC58 - 72 respectively, while the flexural strength and impact toughness are increased by 17 - 28% and 20 - 35% respectively compared with the latter.

[0015] (2)Excellent cutting performance and high durability: Due to the excellent mechanical properties and high thermal stability of the alloyed cutting edge, not only can the cutting edge be ground very sharp, effectively improving the quality and accuracy of wood processing, but also the wear resistance of the tool is significantly increased, resulting in its service life being 1 - 2 times longer than that of cemented carbide tools.

[0016] (3)Strong interface bonding: Different from surface modification technologies such as physical and chemical vapor deposition, the laser alloying modification layer and the substrate have a firm metallurgical interface bonding. And due to the characteristic that the temperature field in the laser action area is radially distributed, the microstructure shows a gradual transition from the alloying layer to the substrate, which can effectively slow down the stress concentration generated during the cutting process at high speed and under impact load, thereby inhibiting the initiation and propagation of cracks and improving the service life of the tool.

[0017] (4)High applicability: The materials suitable for laser alloyed tool bodies are very wide (such as various quenched and tempered steels and tool steels, etc.), and the ratio of alloying components can be flexibly adjusted based on the properties of the base material to achieve the required target performance, and local laser alloying can be flexibly implemented on any tool body with complex geometric shapes. Therefore, it can be widely used in the manufacture of various woodworking planer knives and milling cutters.

[0018] (5) High economy: Since local alloying is carried out on the cutting edge of a relatively inexpensive tool body, the alloying powder material is used less and has a high utilization rate. Coupled with the simple laser alloying process and high efficiency, without the cumbersome powder metallurgy and subsequent welding processes, the processing cost is reduced by 50-70% compared with the integral welded cemented carbide, and the economic benefit is very objective. Specific implementation mode

[0019] The technical solution of the present invention will be further described below in conjunction with specific embodiments.

[0020] Example 1:

[0021] Select normalized 9SiCr alloy tool steel as the tool body material of the profiling tool. After blanking and straightening, use a tool grinder to grind it into a profiling tool blank with dimensions of 300mm×30mm×3mm.

[0022] Weigh and mix WC, TiC, NbC, Mo, Al and La powders with a particle size of 10μm~50μm according to the mass percentage of 83.5:14:0.5:0.5:0.5:1, and place them in a ball mill. Use anhydrous ethanol as the ball milling medium and mix at a speed of 150r / min for 8h. Then, use anhydrous ethanol and shellac with a volume ratio of 99:1 to prepare the alloying powder into a suspension, and spray it evenly on the rake face of the tool body with a spray gun (the thickness of the sprayed coating is about 0.8mm).

[0023] After the sprayed coating is naturally dried, place the tool body in a water-cooled copper fixture on the working platform of a 6KW fiber laser, and then perform a zigzag lap laser scan along the complex geometric contour of the cutting edge on the rake face under the drive of the numerical control system to reduce thermal stress and reduce tool body deformation. The specific process parameters are laser power 1.8kW, spot diameter 6mm, scanning speed 13mm / s, overlap amount 50%, argon gas flow rate 20L / min, and finally a laser alloying modified layer with a depth of 2.0mm and a width of 10mm is obtained on the cutting edge.

[0024] After laser alloying, use a profiling grinder to finely grind the rake and flank faces of the profiling tool to the final shape and dimensional accuracy (grinding depth is less than 0.1mm) to prepare a profiling tool with a complex geometric shape on the cutting edge.

[0025] Example 2:

[0026] Select quenched and tempered 45 steel as the tool body material of the double-sided edge planer. After blanking and straightening, use a tool grinder to grind it into a double-sided edge planer blank with dimensions of 330mm×17mm×4.5mm.

[0027] Weigh and mix WC, TiC, NbC, Mo, Al, and La powders with a particle size of 10 μm to 50 μm according to a mass percentage of 76.6:20:1:0.6:0.8:1, and place them in a ball mill. Use absolute ethanol as the ball milling medium and mix at a rotation speed of 100 r / min for 10 h. Then, use a suspension composed of absolute ethanol and shellac with a volume ratio of 99:1 to prepare the alloyed powder into a suspension, and evenly spray it onto the rake face of the tool body with a spray gun (the thickness of the spray coating is about 0.6 mm).

[0028] After the spray coating is naturally dried, place the tool body in a water-cooled copper fixture on the working platform of a 6KW fiber laser. Then, under the drive of the numerical control system, perform laser scanning along the edge contours on both sides of the rake face of the tool body in sequence. The specific process parameters are as follows: laser power 2.0 kW, spot diameter 5 mm, argon gas flow rate 20 L / min, overlap amount 50%. Alloying is carried out on both side edges successively at two different scanning speeds of 9 mm / s and 10 mm / s to solve the problem of differences in the microstructure and deformation of both side edges caused by heat accumulation. Finally, laser alloying modified layers with a depth of 1.8 mm and a width of 6 mm are obtained on both side edges of the tool respectively;

[0029] After laser alloying treatment, precisely grind the rake face with a tool grinder (grinding depth less than 0.1 mm), and then use a profiling grinder to grind both sides of the flank face in sequence to machine it into the final edge shape and dimensional accuracy, thereby preparing a double-edged planer tool.

[0030] The above embodiments only represent several implementation manners of the present invention. The description is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent application. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present invention, several deformations and improvements can still be made, and these all belong to the protection scope of the present invention. Therefore, the protection scope of this invention patent shall be subject to the appended claims.

Claims

1. A method for in-situ preparation of woodworking tools based on laser alloying technology, characterized in that: Including rough machining of tool body material, design of alloying powder composition, preparation and presetting of alloying powder, laser alloying and subsequent mechanical processing; The method comprises the following steps: (1) Rough processing of the tool body material: Select quenched and tempered steel or tool steel with good strength and toughness and low price as the tool body material. After cutting and straightening processes, use grinding to make it into a tool body blank of the required shape and size; (2) Alloying powder composition design: WC, TiC, NbC, Mo, Al and La powders with a particle size of 10-50 μm were selected as raw materials, and the optimal composition ratio range was: (10-20 wt.%) TiC-(0.5-1.0 wt.%) NbC-(0.2-0.6 wt.%) Mo-(0.4-0.8 wt.%) Al-(0.5-1.0 wt.%) La-WC; (3) Preparation and presetting of alloying powder: The alloying powder is weighed and proportioned according to the chemical composition in step (2), and placed in a ball mill. It is mixed with anhydrous ethanol as a ball milling medium at a speed of 100-150 rpm for 6-10 hours. Then, anhydrous ethanol and shellac in a volume ratio of 99:1 are used to prepare a suspension of the mixed alloying powder, and the suspension is evenly sprayed onto the front cutting edge of the blade body with a spray gun to form a spray layer with a thickness of 0.4-0.8 mm. (4) Laser alloying: After the spray layer is naturally dried, the tool body is placed in a fixture on the laser processing system platform, and then laser alloying treatment is performed along the contour of the front blade under the drive of the CNC system to form an alloyed modified layer with high hardness, high wear resistance, high thermal stability and good toughness on the blade surface; the optimized laser alloying parameters are: laser power of 1.5~2.5KW, scanning speed of 6~15mm / s, spot size of 2~6mm, overlap rate of 0~50%, and shielding gas flow rate of 15~20L / min; (5) Subsequent machining: After the laser alloying treatment, the front cutting edge is finely ground by a tool grinder with a grinding depth of less than 0.1 mm, and then the back cutting edge is sharpened by a profile grinder to achieve the final cutting edge shape and dimensional accuracy, thereby realizing the preparation of woodworking tools.