Composite microparticle shot materials for high-speed shot peening on the surface of high-speed steel complex tools, preparation methods and their applications

Abstract

The present invention relates to the technical field of high-speed steel tool processing, and particularly relates to a composite microparticle shot material for high-speed shot peening on the surface of complex high-speed steel tools, a preparation method and an application thereof, including: composition design, preparation, structure design, shape design, and performance design of the composite microparticle shot material; using the designed composite microparticle shot material for high-speed microparticle shot peening treatment of the high-speed steel tools; the present invention can obtain relatively high surface residual compressive stress and surface hardness, improves the cutting performance of high-speed steel tools, specifically including hobbing tools, broaching tools, and gear shaving tools, and has great application prospects in the fields of tools and surface protection.

Description

Technical Field

[0001] The present invention relates to the technical field of high-speed steel tool processing, and particularly to a composite microparticle shot material for high-speed shot peening on the surface of a complex high-speed steel tool, a preparation method thereof, and an application thereof. Background Art

[0002] In the machinery manufacturing industry, although there are many different process forming methods, more than 90% of mechanical parts are still manufactured by cutting processes. High-speed tool steel is widely used in manufacturing various machining cutting tools with large sizes, high cutting speeds, heavy loads, and high working temperatures, and can also be used to manufacture cold and hot dies requiring wear resistance. Its characteristics include high hardness, high wear resistance; high red hardness, good hardenability; excellent strength and toughness matching. High-speed tool steel has very high hardness, compressive strength, and wear resistance, and is mainly used to manufacture medium- and high-speed cutting tools, such as complex forming tools like broaches, hobbing cutters, slotting cutters, and reamers. The rapid development of the current manufacturing industry has put forward higher and higher requirements for the cutting performance and machining performance of high-speed tool steel. The main development trend of high-speed tool steel is towards larger, more precise, more complex, and more economical and rapid development. The requirements for its comprehensive mechanical properties, high performance, and long life are getting higher and higher.

[0003] Shot peening is one of the effective methods to improve the surface hardness of materials, reduce part fatigue, and increase service life. Shot peening treatment is to spray a high-speed shot flow onto the surface of a part, causing plastic deformation on the surface layer of the part to form a strengthening layer with a certain thickness. A relatively high residual stress is formed in the strengthening layer. Due to the existence of compressive stress on the part surface, when the part bears a load, a part of the stress can be offset, thereby improving the fatigue strength of the part.

[0004] Due to the low surface hardness and poor anti-fatigue performance of complex high-speed steel tools, their performance deteriorates and they fail prematurely during cutting, especially interrupted cutting. Shot peening treatment can significantly improve the surface hardness and residual stress of high-speed steel tools. However, the existing metal shot materials have low hardness and the strengthening effect is not obvious. The ceramic shot materials are brittle and easy to break, resulting in part of the shot materials being embedded on the matrix surface. Moreover, the shot material diameter is large, which easily causes the surface roughness of the tool to be too large, and further leads to a reduction in the cutting life of the tool.

[0005] In view of the above defects, the creator of the present invention finally obtained the present invention through long-term research and practice. Summary of the Invention

[0006] The object of the present invention is to solve the problems that when shot peening is used to improve the surface hardness and residual stress of high-speed steel tools, the existing metal shot has low hardness and the strengthening effect is not obvious, the ceramic shot is brittle and easy to break, resulting in some shot peening materials being embedded on the surface of the substrate, and the shot diameter is large, which is likely to cause the surface roughness of the tool to be too large, and further lead to the reduction of the tool cutting life. The present invention provides a composite microparticle shot for high-speed shot peening on the surface of complex high-speed steel tools, a preparation method and its application.

[0007] To achieve the above object, the present invention discloses a composite microparticle shot for high-speed shot peening on the surface of complex high-speed steel tools. The composite microparticle shot includes a first shot and a second shot. The second shot is uniformly coated on the surface of the first shot. The first shot includes 88% - 92% of WC and 8% - 12% of Co. The second shot includes 8% - 0.88% of C, 0.4% - 0.45% of Si, 0.4% of Mn, 3.8% - 4.5% of Cr, 4.5% - 5.5% of Mo, 1.6% - 2.2% of V, 5.5% - 6.7% of W, and the rest is Fe.

[0008] The diameter of the composite microparticle shot is 50 - 150 μm. The shape of the composite microparticle shot is spherical, and the surface is covered with small particles.

[0009] The present invention also discloses a preparation method of the composite microparticle shot for high-speed shot peening on the surface of the above complex high-speed steel tools. The specific process is as follows: Weigh the component raw materials of the first shot and the second shot according to the ratio. Add polyethylene glycol binder and polyacrylamide dispersant to the weighed first shot and second shot for mixing to obtain a slurry. Use a spray dryer for granulation. After the spray drying process is completed, screen the collected composite shot to obtain a composite microparticle shot with the second shot uniformly coated on the surface of the first shot.

[0010] The mass ratio of the polyethylene glycol binder to the polyacrylamide dispersant is 2:1. The inlet temperature of the spray dryer is 240 °C, the outlet temperature is 120 °C, and the rotation speed of the atomizer is 45000 r / min.

[0011] The present invention also discloses the application of the composite microparticle shot for high-speed shot peening on the surface of the above complex high-speed steel tools in improving the surface performance of complex high-speed steel tools. The complex high-speed steel tools include broaches, hobbing cutters, gear shapers and other complex forming tools. The material of the complex high-speed steel tools is M42 high-speed steel or powder metallurgy high-speed steel.

[0012] The shot peening pressure of the microparticle shot peening is 0.65 MPa

[0013] The speed of the microparticle shot peening is 200 m / s - 250 m / s.

[0014] The shot peening time of the microparticle shot peening is 30 s to 90 s.

[0015] The nozzle of the microparticle shot peening is silicon nitride, with a diameter of 3 mm to 4 mm. The distance between the nozzle and the high-speed steel complex tool is 4 cm to 6 cm, and the coverage rate is 220%.

[0016] The beneficial effects of the present invention compared with the prior art are as follows:

[0017] 1. Compared with the existing shot peening materials, the composite microparticles of the present invention have the advantages of high hardness, small particle size, good toughness, etc.

[0018] 2. Compared with the conventional shot peening treatment, the surface roughness of the high-speed steel tool treated with the composite microparticles of the present invention is lower, the residual stress is higher, the surface integrity is higher, and at the same time, a refined grain layer (i.e., the white bright layer) can be formed on the surface layer, which can improve the cutting performance of the coated tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 is the surface morphology of the prepared composite microparticles;

[0020] Figure 2 is the three-dimensional surface morphology of the shot peening layer after different treatment times with microparticles of 80 μm size (a) 30 s, (b) 60 s, and (c) 90 s;

[0021] Figure 3 is the three-dimensional surface morphology of the shot peening layer after different treatment times with microparticles of 80 - 150 μm size (a) 30 s, (b) 60 s, and (c) 90 s;

[0022] Figure 4 (a) is the cross-sectional morphology of the high-speed steel shot peened with common steel shot material in Example 2, and 4(b) is the grain refinement layer formed on the surface layer of the high-speed steel after shot peening with composite microparticles of 80 - 150 μm size and a treatment time of 60 s;

[0023] Figure 5 (a) is the wear morphology diagram of the high-speed steel shot peened with common steel shot material in Example 2, Figure 5 (b) is the wear morphology diagram of the hob after failure after shot peening with composite microparticles of 80 - 150 μm size and a treatment time of 60 s. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0024] The above and other technical features and advantages of the present invention will be described in more detail below with reference to the accompanying drawings.

[0025] Example 1

[0026] The test selected M42 high-speed steel specimen pieces, hobs, broaches, and gear shapers made of the same material, and their surfaces were cleaned. They were then inspected.

[0027] Example 2

[0028] The preparation of the high-speed steel specimens and tools was the same as in Example 1.

[0029] The size of the steel shot commonly used in the market was 600 μm to 1400 μm, and the hardness was HRC56 to HRC60.

[0030] Micro-particle shot peening steps:

[0031] First step, select the nozzle material for steel shot peening as silicon nitride, with a diameter of 6 mm, and the distance from the nozzle to the complex high-speed steel tool is 6 cm;

[0032] Second step, select the shot peening pressure for steel shot peening as 0.65 MPa.

[0033] Third step, select the shot peening time for steel shot peening as 60 s.

[0034] Fourth step, select the coverage rate of steel shot peening as 220%.

[0035] Example 3

[0036] The preparation of the high-speed steel specimens and tools was the same as in Example 1.

[0037] Composite micro-particle preparation steps:

[0038] First step, select shot material 1 (composition: 90% WC, 10% Co) and shot material 2 (composition: 0.8% C, 0.45% Si, 0.4% Mn, 4.5% Cr, 5.5% Mo, 2.2% V, 6.7% W, and the rest is Fe);

[0039] Second step, add shot material 1 and shot material 2 to a polyethylene glycol binder (PEG) and a dispersant (polyacrylamide) with a mass ratio of 2:1 for mixing to obtain a slurry, and use a spray dryer for granulation. The specific parameters are inlet / outlet temperature 240 / 120 °C, and the atomizer speed is 45000 r / min. After the spray drying process is completed, the collected composite shot material is screened to obtain composite shot material with shot material 2 uniformly coated on the surface of shot material 1; the diameters of the prepared composite micro-particle shot materials are 80 μm and between 80 μm and 150 μm respectively; the shape of the shot material is spherical, and its surface is covered with small particles; the hardness of the prepared composite micro-particle shot material is HRC94;

[0040] Micro-particle shot peening steps:

[0041] In the first step, select the nozzle material for micro-particle shot peening as silicon nitride, with a diameter of 3 mm and a distance of 6 cm from the nozzle to the high-speed steel complex tool;

[0042] In the second step, select the shot peening pressure for composite micro-particle shot peening as 0.65 MPa.

[0043] In the third step, select the speed of composite micro-particle shot peening as 250 m / s.

[0044] In the fourth step, select the shot peening time for composite micro-particle shot peening as 30 s.

[0045] In the fifth step, select the coverage rate of composite micro-particle shot peening as 220%.

[0046] Example 4

[0047] The preparation of the high-speed steel specimen and tool is the same as that in Example 1.

[0048] Steps for preparing composite micro-particles:

[0049] In the first step, select shot material 1 (composition: 90% WC, 10% Co) and shot material 2 (composition: 0.8% C, 0.45% Si, 0.4% Mn, 4.5% Cr, 5.5% Mo, 2.2% V, 6.7% W, and the rest is Fe);

[0050] In the second step, add a polyethylene glycol binder (PEG) and a dispersant (polyacrylamide) with a mass ratio of 2:1 for mixing to obtain a slurry, and use a spray dryer for granulation. The specific parameters are inlet / outlet temperature 240 / 120 °C and atomizer rotation speed 45000 r / min. After the spray drying process, screen the collected composite shot material. The obtained composite shot material is that the second shot material uniformly coats the surface of the first shot material. The diameters of the prepared composite micro-particle shot materials are 80 μm and between 80 μm and 150 μm respectively; the shape of the shot material is spherical, and its surface is covered with small particles; the hardness of the prepared composite micro-particle shot material is HRC94;

[0051] Steps for micro-particle shot peening:

[0052] In the first step, select the nozzle material for micro-particle shot peening as silicon nitride, with a diameter of 3 mm and a distance of 6 cm from the nozzle to the high-speed steel complex tool;

[0053] In the second step, select the shot peening pressure for composite micro-particle shot peening as 0.65 MPa.

[0054] In the third step, select the speed of composite micro-particle shot peening as 250 m / s.

[0055] In the fourth step, select the shot peening time for composite micro-particle shot peening as 60 s.

[0056] The fifth step is to select the coverage of composite microparticle shot peening to be 220%.

[0057] Example 5

[0058] The high speed steel specimen and tool preparation are the same as in Example 1.

[0059] Preparation steps of composite microparticles:

[0060] In the first step, shot 1 (90% WC, 10% Co) and shot 2 (0.8% C, 0.45% Si, 0.4% Mn, 4.5% Cr, 5.5% Mo, 2.2% V, 6.7% W, and the rest Fe) are selected;

[0061] In the second step, polyethylene glycol binder (PEG) and dispersant (polyacrylamide) with a mass ratio of 2:1 are added to mix to obtain a slurry, and a spray dryer is used for granulation. The specific parameters are inlet / outlet temperature 240 / 120°C and atomizer speed 45000r / min. After the spray drying process is completed, the collected composite pellets are sieved, and the obtained composite pellets are the second pellets uniformly coated on the surface of the first pellets. The diameters of the prepared composite microparticle pellets are 80μm and between 80μm and 150μm respectively; the pellets are spherical, and their surface is covered with small particles; the hardness of the prepared composite microparticle pellets is HRC94;

[0062] Microparticle shot peening steps:

[0063] In the first step, the nozzle material of the micro-particle shot peening was selected to be silicon nitride, with a diameter of 3 mm and a distance of 6 cm from the nozzle to the high-speed steel complex tool;

[0064] In the second step, the shot peening pressure of composite microparticle shot peening is selected to be 0.65MPa.

[0065] The third step is to select the composite particle shot peening speed as 250m / s.

[0066] The fourth step is to select the shot peening time of composite microparticles as 90s.

[0067] The fifth step is to select the coverage of composite microparticle shot peening to be 220%.

[0068] Figure 1 The surface morphology of the prepared composite microparticles. At low magnification (×320), the microparticles are spherical in shape, with a size of about 50μm to 150μm, with an average size of 80μm. Figure 1 It can be found that there are a large number of irregular "tumor"-like substances on the surface of the microparticles.

[0069] The composite microparticles prepared in this patent were compared with the existing steel shot used in Example 2, and the size and hardness results are shown in Table 1.

[0070] Table 1 Size and hardness of composite microparticles and existing steel shot

[0071] Dimension Hardness Existing steel shot material 600μm to 1400μm HRC56 to HRC60 The composite microparticles of this patent 80μm to 150μm HRC92 to HRC96

[0072] The hardness of the untreated high-speed steel substrate and the high-speed steel substrate treated by microparticle shot peening was detected, and the detection results are shown in Table 2.

[0073] Table 2 Shot peening layer hardness on the surface of high-speed steel after existing steel shot, microparticles of different sizes and different shot peening times

[0074]

[0075] Table 2 shows the shot peening layer hardness on the surface of high-speed steel after microparticles of different sizes and different microparticle shot peening. It can be found that the hardness of the high-speed steel substrate is 782 Hv0.1. For the existing steel shot, when the shot peening times are 30 s, 60 s and 90 s respectively, the shot peening layer hardness values are 810.3 Hv0.1, 820.7 Hv0.1 and 815.1 Hv0.1 respectively; for the microparticles with a size of 80 μm, when the shot peening times are 30 s, 60 s and 90 s respectively, the shot peening layer hardness values are 860.7 Hv0.1, 891.6 Hv0.1 and 886.2 Hv0.1 respectively; for the microparticles with a size of 80 - 150 μm, when the shot peening times are 30 s, 60 s and 90 s respectively, the shot peening layer hardness values are 880.1 Hv0.1, 976.2 Hv0.1 and 944.5 Hv0.1 respectively. It can be found that: (1) After microparticle shot peening, the hardness of the shot peening layer on the surface of high-speed steel increases, and its hardness is higher than that treated with steel shot; (2) With the increase of the shot peening time, the hardness of the shot peening layer increases, and the hardness is the highest at 60 s. Further increasing the shot peening time, the hardness value no longer increases; (3) As the microparticle size increases, the hardness of the shot peening layer increases.

[0076] Figure 2 and Figure 3 The three-dimensional morphologies of the shot peening layer surface after different treatment times for microparticles with sizes of 80 μm and 80 - 150 μm respectively. It can be found that with the increase of the shot peening time, the "protrusions" on the shot peening layer surface become larger and denser, that is, the roughness value increases.

[0077] Table 3 shows the roughness detection of the shot-peened layer on the surface of high-speed steel after using existing steel shot, different-sized microparticles, and different shot-peening times, and the corresponding Sa and Sq values are obtained. It can be found that: (1) The surface roughness of the substrate treated with steel shot is significantly higher than that treated with microparticle shot-peening; (2) As the shot-peening time increases, the surface roughness values Sa and Sq of the shot-peened layer both increase. When it further increases to 90 s, the roughness value slightly decreases instead; (3) As the microparticle size increases, the surface roughness of the shot-peened layer increases.

[0078] Table 3 Roughness Sa and Sq of the shot-peened layer on the surface of high-speed steel after existing steel shot, different-sized microparticles, and different shot-peening times

[0079]

[0080] Figure 4 They are the cross-sectional morphologies of high-speed steel after conventional shot-peening and shot-peening with composite microparticles with a size of -80 to 150 μm, respectively. From Figure 4 (a), it can be found that there is no obvious change in the cross-section of high-speed steel treated by conventional shot-peening, while from Figure 4 (a), it can be found that a grain refinement layer with a thickness of about 80 μm is formed on the cross-section of high-speed steel after shot-peening with composite microparticles with a size of -80 to 150 μm. This is because the hardness of the composite microparticles is high and the shot-peening speed is extremely high, reaching 250 m / s. At such a high speed, it will cause a very high temperature to be generated instantaneously on the surface of high-speed steel, resulting in rapid melting / solidification and grain refinement.

[0081] Table 4 shows the residual stresses of the shot-peened layer on the surface of high-speed steel after existing steel shot, different-sized microparticles, and different microparticle shot-peening. It can be found that the residual stress of the high-speed steel substrate is -90 MPa. For microparticles with a size of 80 to 150 μm, when the shot-peening times are 30 s, 60 s, and 90 s respectively, the residual stresses of the shot-peened layer are -1254 MPa, -1183 MPa, and -1210 MPa respectively. That is, after microparticle shot-peening, the surface residual compressive stress of the shot-peened layer increases sharply, but the shot-peening time has no significant effect on the residual stress. At the same time, the residual stress of the shot-peened layer on the surface of the specimen with a microparticle size of 80 μm and a shot-peening time of 90 s is detected, and its value is -1132 MPa, slightly lower than that of the specimen treated with microparticles with a size of 80 to 150 μm.

[0082] Table 4 Residual stresses of the shot-peened layer on the surface of high-speed steel after existing steel shot, different-sized microparticles, and different shot-peening times

[0083]

[0084] Table 5 shows the number of workpieces processed by three typical complex high-speed steel cutting tools after shot peening with steel shot and composite microparticles of different sizes when reaching the wear standard (the average wear width of the flank face is 0.2 mm). It can be found that the number of workpieces processed by the unprocessed hobbing cutter, broach and gear shaper cutter are 12, 800 and 1,100 respectively. The number of workpieces processed by the hobbing cutter, broach and gear shaper cutter after steel shot peening are 14, 1,000 and 1,200 respectively, and the service life is improved. After shot peening with composite microparticles with a size of 80 μm of the invention patent application, under the same processing conditions, the number of workpieces processed are 18, 1,260 and 1,800 respectively; after shot peening with composite microparticles with a size of 80 - 150 μm, the number of workpieces processed are 24, 1,560 and 2,300 respectively, and the service life is increased by more than 80%, and there is also a significant improvement compared with steel shot peening. After the worn flank face is re-ground for the second time, the number of workpieces processed by the unprocessed hobbing cutter, broach and gear shaper cutter are 11, 800 and 1,050 respectively. The number of workpieces processed by the hobbing cutter, broach and gear shaper cutter after steel shot peening are 12, 800 and 1,050 respectively. After shot peening with composite microparticles with a size of 80 μm of the invention patent application, under the same processing conditions, the number of workpieces processed are 16, 1,200 and 1,850 respectively; after shot peening with composite microparticles with a size of 80 - 150 μm, under the same processing conditions, it still shows high processing performance, and the number of workpieces processed are 24, 1,500 and 2,250 respectively.

[0085] Table 5 Number of workpieces processed by hobbing cutters, broaches and gear shaper cutters after shot peening with existing steel shot and composite microparticles of different sizes

[0086]

[0087] Figure 5 Figure 10 shows the flank face morphology of a hobbing cutter after failure after shot peening with conventional shot material and composite microparticles with a size of 80 - 150 μm. From Figure 5 (a), it can be found that the wear width of the flank face of the hobbing cutter after shot peening with conventional shot material is relatively wide, while Figure 5 (b), it can be found that the wear width of the flank face of the hobbing cutter after shot peening with composite microparticles with a size of 80 - 150 μm is relatively small, and the cutting edge is relatively intact.

[0088] The above are only the preferred embodiments of the present invention, which are illustrative rather than restrictive to the present invention. Those skilled in the art understand that many changes, modifications and even equivalents can be made within the spirit and scope defined by the claims of the present invention, but all will fall within the protection scope of the present invention.

Claims

1. A preparation method of composite microparticle shot for high-speed shot peening on the surface of high-speed steel complex tools, characterized in that, The specific process is as follows: Weigh the component raw materials of the first pellet material and the second pellet material according to the ratio. Add polyethylene glycol binder and polyacrylamide dispersant to the weighed first pellet material and the second pellet material and mix them to obtain a slurry. Use a spray dryer for granulation. After the spray drying process ends, screen the collected composite pellet material to obtain a composite microparticle pellet material with the second pellet material evenly coated on the surface of the first pellet material. The composite microparticle pellet material includes the first pellet material and the second pellet material, and the second pellet material is evenly coated on the surface of the first pellet material. The first pellet material includes 88% - 92% WC and 8% - 12% Co. The second pellet material includes 8% - 88% C, 0.4% - 0.45% Si, 0.4% Mn, 3.8% - 4.5% Cr, 4.5% - 5.5% Mo, 1.6% - 2.2% V, 5.5% - 6.7% W, and the rest is Fe. The high-speed steel complex cutting tools include broaches, hobbing cutters, and gear shapers.

2. The preparation method of the composite microparticle shot for high-speed shot peening on the surface of a high-speed steel complex tool according to claim 1, characterized in that, The diameter of the composite microparticle pellet material is 80 - 150 μm, and the shape of the composite microparticle pellet material is spherical.

3. The preparation method of the composite microparticle shot for high-speed shot peening on the surface of a high-speed steel complex tool according to claim 1, characterized in that, The mass ratio of the polyethylene glycol binder to the polyacrylamide dispersant is 2:

1. The inlet temperature of the spray dryer is 240 °C, the outlet temperature is 120 °C, and the rotation speed of the atomizer is 45000 r / min.

4. Application of a composite microparticle pellet material for high-speed shot peening on the surface of a high-speed steel complex cutting tool prepared by the preparation method according to any one of claims 1 to 3 in improving the surface performance of the high-speed steel complex cutting tool.

5. Application of a composite microparticle shot material for high-speed shot peening on the surface of a high-speed steel complex tool as described in claim 4, characterized in that, The shot peening pressure of the composite microparticle pellet material is 0.65 MPa.

6. Application of a composite microparticle shot for high-speed shot peening on the surface of a high-speed steel complex tool according to claim 4, characterized in that, The speed of the composite microparticle pellet material is 200 m / s - 250 m / s.

7. Application of a composite microparticle shot material for high-speed shot peening on the surface of a high-speed steel complex tool according to claim 4, characterized in that, The shot peening time of the composite microparticle pellet material is 30 s - 90 s.

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