CN111607688B - Method for laser phase transformation hardening of shot blasting machine blade surface - Google Patents

Abstract

The invention relates to a method for laser phase transformation hardening on the surface of a shot blasting machine blade. The raw material components of the shot blasting machine blade are put into an intermediate frequency induction resistance furnace for smelting, and the temperature is raised to 1535-1555 DEG C. Casting is carried out in the shot blasting machine blade mold made of sand; after the molten iron is cooled and formed, the shot blasting machine blade is obtained, and the shot blasting machine blade is taken out from the sand mold, the residual sand and pouring riser on the surface are removed, and the shot blasting machine blade is cleaned. Select the laser processing parameters according to the performance requirements of different areas of the shot blasting machine blade and control the cooling conditions; after preheating the shot blasting machine blade to 120 °C on the laser phase transformation hardening device, the shot blasting machine blade according to Scan path for phase transformation strengthening. Laser phase transformation hardening has the characteristics of "extremely fast and extremely cold", which changes the structure of the quenched layer of the shot blasting machine blade from the original columnar martensite to acicular martensite in a very short time, avoiding long-term transition and other brittle tissue.

Description

Method for laser phase transformation hardening of shot blasting machine blade surface

technical field

The invention relates to a method for hardening the surface of a shot blasting machine blade by laser phase transformation.

Background technique

At present, with the rapid development of my country's industry, wear and tear is one of the important factors causing failure of mechanical parts and energy loss. According to data, about 30% of the world's primary energy is lost due to wear and tear, and about 70% of electromechanical energy is lost due to wear and tear. Equipment is damaged by various forms of wear and tear.

The shot blasting machine is widely used. By relying on the blades to perform work on the projectile, the parts can meet certain performance requirements such as wear resistance and high strength. For the entire shot blasting machine, the blade on the shot blasting machine is the most critical component. Due to the continuous high-speed impact of the projectile and the influence of cyclic stress, the loss of the blade is aggravated, so the blade is the most easily ground part in the shot blasting machine. Moreover, the cost of materials consumed by the wear of blades in our country is increasing every year, reaching tens of millions, which brings huge economic losses to the country and corresponding enterprises.

The purpose of quenching is to transform the supercooled austenite into martensite or bainite to obtain martensite or bainite structure. The main means of quenching the blade of the machine, thereby prolonging its wear resistance, but most companies even in developed countries have heavy heating and light cooling, the investment in research and development of the quenching and cooling process is not large, and the technology in the complex quenching and cooling process is Therefore, the standard quenching and cooling process has not been formed, so the quality of the shot blasting machine blades after quenching is unstable, and even brittle cracks may occur, delaying production efficiency.

In summary, to ensure that the blade has high impact toughness and hardness, it is not only necessary to control the chemical composition and content of the blade material, to ensure the balance of matrix and carbide in the microstructure of the blade, but also to ensure the stability of the quenching process. Avoid surface cracking.

SUMMARY OF THE INVENTION

The purpose of the present invention is to overcome the deficiencies in the prior art and provide a method for laser phase transformation hardening of the surface of a shot blasting machine blade.

The object of the present invention is achieved through the following technical solutions:

The method for laser phase transformation hardening on the surface of a shot blasting machine blade is characterized by including the following steps:

1) put the raw material composition of the shot blasting machine blade in proportion into the intermediate frequency induction resistance furnace for smelting, heat up to 1535～1555 ℃, pour the smelted molten iron into the shot blasting machine blade mold made in advance with sand for casting;

2) After the molten iron is cooled and formed, the shot blasting machine blade is obtained, the shot blasting machine blade is taken out from the sand mold, the residual sand and pouring riser on the surface are removed, and the flash and burr on the shot blasting machine blade are cleaned;

3) According to the performance requirements of different areas of the shot blasting machine blade and the control cooling conditions, select the laser processing parameters;

4) After preheating the shot blasting machine blade to 120°C on the laser phase transformation hardening device, phase transformation strengthening is performed on the shot blasting machine blade according to the scanning path.

Further, in the above-mentioned method for laser phase transformation hardening of the surface of a shot blasting machine blade, the composition and mass percentage of the shot blasting machine blade are: C: 2.8-3.2%, Cr: 4-5%, Si: 0.4-0.8 %, Mn: 0.5～1.2%, P≤0.035%, S≤0.035%, Re≤0.05%, the balance is Fe and chemical elements usually present in steelmaking.

Further, the above-mentioned method for laser phase transformation hardening of the surface of a shot blasting machine blade, wherein, when the temperature of the molten iron is lowered to 100-1420 ° C, it is poured into a shot blasting machine blade mold made of sand in advance for casting.

Further, the above-mentioned method for laser phase transformation hardening of the surface of a shot blasting machine blade, wherein, the performance requirements of different regions of the shot blasting machine blade, during the working process of the shot blasting machine blade, the continuous impact of the projectile generates cyclic stress, and the projectile is in the process. Rolling friction and sliding friction occur on the blade of the shot blasting machine. According to the performance requirements of the blade of the shot blasting machine, the surface of the blade is divided into an impact area and a sliding and wear area. The projectile incident angle in the impact area is 20°, and the projectile incident angle in the wear area is 0. °, the wear in the sliding and wear area is higher than that in the impact area, resulting in the deformation of the matrix material and the failure of the carbide expansion and fracture. The projectile and the shot blasting machine blade impact abrasive wear in the impact area. In the sliding and wear area, due to the large radius of centrifugal force, When large sliding friction occurs, the sliding and wear areas need to have high impact toughness and wear resistance, and the impact area needs to have smaller impact toughness and wear resistance than the sliding and wear areas.

Further, in the above-mentioned method for laser phase transformation hardening of the surface of a shot blasting machine blade, wherein the cooling conditions are controlled in different areas of the shot blasting machine blade, according to the isothermal cooling transformation curve of the supercooled austenite of the material, that is, the TTT curve, or the supercooled austenite. The continuous cooling transformation curve of cold austenite is the CCT curve, and the longest cooling time or the minimum cooling rate for the obtained structure to reach a temperature is obtained. According to the position of one end of the shot blasting machine blade ejecting the projectile as the starting point, the expected structure within a distance range is set. ; The cooling speed of the surface and the core of the shot blasting machine blade is different. The shot blasting machine blade is divided into surface area, subsurface area and core part from the surface to the center along the cross section. The surface area area can obtain the expected structure by controlling the cooling rate to meet the mechanical requirements Performance requirements, the subsurface area and the core are cooled slowly to avoid the over-tempering of the martensite or bainite structure that has been transformed in the cooling rate area due to the high temperature recovery, which affects the performance of the shot blasting machine blade.

Further, the above-mentioned method for laser phase transformation hardening of the surface of a shot blasting machine blade, wherein the laser phase transformation hardening device includes a worktable for carrying the shot blasting machine blade and a heater for preheating it, and the fiber laser output The broadband scanning rotating mirror and the laser head are arranged in sequence on the optical path. The broadband scanning rotating mirror converts the laser into a broadband laser, that is, a linear light spot, which is focused on the surface of the shot blasting machine blade on the worktable through the laser head.

Further, the above-mentioned method for laser phase transformation hardening of the surface of a shot blasting machine blade, wherein the phase transformation strengthening of the shot blasting machine blade is performed on a laser phase transformation hardening device, and the steps are as follows:

41) Blackening treatment of shot blasting machine blades;

42) Use a heater to preheat the blades of the shot blasting machine to 120°C;

43) Start the fiber laser, the light beam output by the fiber laser enters the broadband scanning rotating mirror, and the broadband scanning rotating mirror converts the laser into a broadband laser, that is, a linear spot, which is focused on the workpiece surface on the workbench through the laser head;

44) Set the laser processing power, scanning speed, spot size and scanning path according to the calculation results of the cooling speed requirements for different areas of the shot blasting machine blade.

Further, in the above-mentioned method for laser phase transformation hardening of the surface of a shot blasting machine blade, the laser processing power is 2.5KW, the scanning speed is 5mm/s, the spot size is 10mm×4mm, and the scanning path without overlap is selected.

Compared with the prior art, the present invention has significant advantages and beneficial effects, which are embodied in the following aspects:

For the laser phase transformation hardening process of the shot blasting machine blade surface of the present invention, because the laser phase transformation hardening has the characteristics of "extremely fast and extremely cold", that is, fast heating and fast cooling, the quenching layer of the shot blasting machine blade can be quenched in a very short time. The structure changes from the original columnar martensite to acicular martensite, avoiding the long-term transition and producing other brittle structures, thus greatly improving the performance of the shot blasting machine blade;

The shot blasting machine blade obtains the required performance or structure on the premise of avoiding cracking, and is suitable for the laser phase transformation hardening treatment of the surface of the shot blasting machine blade with different compositions, and the columnar martensite on the surface becomes acicular martensite, thereby The hardness, wear resistance and quenching layer depth of the shot blasting machine blade are greatly improved, avoiding the defects caused by the traditional quenching-tempering treatment technology, resulting in residual compressive stress on the surface of the material or part, thereby improving the mechanical properties of the surface layer. ; Not only improves the efficiency of the shot blasting machine, but also greatly improves the service performance of the shot blasting machine blade, thereby reducing the production cost.

Other features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or learned by practice of the detailed description of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims.

Description of drawings

Figure 1: Schematic diagram of the laser phase transformation hardening device on the blade surface of the shot blasting machine;

Figure 2: Schematic diagram of the laser phase transformation hardening scanning path on the surface of the shot blasting machine blade;

Figure 3: Schematic diagram of the laser phase transformation hardening process flow of the blade surface of the shot blasting machine.

Detailed ways

In order to have a clearer understanding of the technical features, objects and effects of the present invention, specific embodiments will now be described in detail.

As shown in Figure 1, the laser phase change hardening device includes a table 5 for carrying the shot blasting machine blade 4 and a heater 6 for preheating it. The broadband scanning mirror 2 and the laser head are sequentially arranged on the output optical path of the fiber laser 1 3. The broadband scanning mirror 3 converts the laser light into a broadband laser, that is, a linear light spot, which is focused on the surface of the shot blasting machine blade on the worktable through the laser head 3 .

The method of laser phase transformation hardening on the surface of the shot blasting machine blade, as shown in Figure 3, includes the following steps:

1) Put the raw material components of the shot blasting machine blades into the intermediate frequency induction resistance furnace for smelting, heat up to 1535-1555 ℃, and when the molten iron temperature is lowered to 100-1420 ℃, pour it to the cast iron made of sand in advance. Casting in a pellet mill blade mold;

2) After the molten iron is cooled and formed, the shot blasting machine blade is obtained, the shot blasting machine blade is taken out from the sand mold, the residual sand and pouring riser on the surface are removed, and the flash and burr on the shot blasting machine blade are cleaned;

3) According to the performance requirements of different areas of the shot blasting machine blade and the control cooling conditions, select the laser processing parameters;

The performance requirements of different areas of the shot blasting machine blade. During the working process of the shot blasting machine blade, the continuous impact of the projectile produces cyclic stress, and the projectile produces rolling friction and sliding friction on the shot blasting machine blade. According to the performance requirements of the shot blasting machine blade, The blade surface is divided into impact area and sliding and wear area. The projectile incident angle in the impact area is 20°, and the projectile incident angle in the sliding and wear area is 0°. The wear of the sliding and wear area is higher than that of the impact area, resulting in deformation of the matrix material and carbides The extended fracture fails. The projectile has impact and abrasive wear on the impact zone and the blade of the shot blasting machine. In the sliding and wear zone, due to the large radius of action of centrifugal force, large sliding friction also occurs. The sliding and wear zone needs to have high impact toughness and Wear resistance, the impact area needs to have less impact toughness and wear resistance than the sliding and wear areas;

The cooling conditions are controlled in different areas of the shot blasting machine blade. According to the isothermal cooling transformation curve of the supercooled austenite of the material, namely the TTT curve, or the continuous cooling transformation curve of the supercooled austenite, the CCT curve, the longest cooling time to obtain the microstructure to a temperature is obtained. Time or minimum cooling rate, according to the position of one end of the shot blasting machine blade ejecting the projectile as the starting point, the expected structure within a distance range is set; To the center, it is divided into surface area, subsurface area and core. The surface area can obtain the expected structure by controlling the cooling rate to meet the requirements of mechanical properties. The subsurface area and the core are cooled slowly to avoid the change of the cooling rate area. The intenite or bainite structure is over-tempered due to the high temperature rise, which affects the service performance of the shot blasting machine blade;

4) After preheating the shot blasting machine blade to 120°C on the laser phase transformation hardening device, phase transformation strengthening is performed on the shot blasting machine blade according to the scanning path; the specific process steps are as follows:

41) Blackening treatment of shot blasting machine blades;

42) Use the heater 6 to preheat the workpiece (blade of the shot blasting machine) 4 to 120°C;

43) Start the fiber laser 1, the beam output from the fiber laser 1 enters the broadband scanning mirror 2, and the broadband scanning mirror 2 converts the laser into a broadband laser, that is, a linear spot, and is focused on the workpiece (polishing) on the table 5 through the laser head 3. The surface of the pill machine blade) 4;

44) According to the calculation results of the cooling speed requirements for different areas of the shot blasting machine blade, set the laser processing power to 2.5KW, the scanning speed of 5mm/s, the spot size of 10mm × 4mm, and the scanning path without overlap, as shown in Figure 2.

Example:

When carrying out phase transformation strengthening of shot blasting machine blades, through the sample, understand the isothermal cooling transformation curve of supercooled austenite (TTT curve) or the continuous cooling transformation curve of supercooled austenite (CCT curve) of the material of the shot blasting machine blade, Finally, the laser quenching process parameters can be determined through the calculation of the cooling temperature field.

S1. According to the chemical composition and content contained in the blade of the shot blasting machine, its chemical composition and mass percentage are: C: 2.8-3.2%, Cr: 4-5%, Si: 0.4-0.8%, Mn: 0.5-1.2 %, P≤0.035%, S≤0.035%, Re≤0.05%, the balance is Fe and chemical elements usually present in steelmaking, when smelted in an intermediate frequency induction resistance furnace and heated to 1535 ~ 1555 ℃, the resulting When the molten iron is cooled to 1400 °C, it is poured into the shot blasting machine blade mold made of sand in advance for casting;

S2. After the molten iron is cooled and formed, the shot blasting machine blade is obtained, and the shot blasting machine blade is taken out from the inside of the sand mold, the residual sand and pouring riser on the surface are removed, and the flash and burr generated on the shot blasting machine blade are cleaned;

S3. According to the performance requirements of different areas of the shot blasting machine blade and the control cooling conditions, select the appropriate laser processing parameters, the laser power is 2.5Kw, the scanning speed is 5mm/s, and the spot size is 10mm×4mm;

According to the force and performance requirements of the blade, the blade surface is divided into impact zone (projectile incident angle is 20°) and sliding and wear zone (projectile incident angle is 0°), and the wear of sliding and wear zone is more serious than that of wear zone , causing the deformation of the matrix material and the failure of carbide expansion fracture;

The projectile has impact abrasive wear on the blade of the shot blasting machine in the impact area, and in the sliding and wear area, due to the large radius of action of centrifugal force, large sliding friction also occurs. Therefore, the sliding and wear area of the blade surface must have high impact. Toughness and wear resistance, while the impact zone has smaller impact toughness and wear resistance than the sliding and wear zone. Therefore, the blade surface of the sliding and wear zone is predicted to contain acicular martensite structure than the impact zone. The acicular martensitic structure is more;

Combined with the isothermal cooling transformation curve (TTT curve) of the supercooled austenite of the material, the appropriate one can be selected according to the relationship between the transformation amount and the transformation time during the heat preservation process at different temperatures when the austenite is cooled to below the critical point A1. transition temperature and corresponding transition time;

Combined with the supercooled austenite continuous cooling transformation curve (CCT curve) of the material, the laser heating is completed in a very short time interval and will not affect the subsequent laser quenching structure, so the heating temperature range that can be selected is wide, so in CCT The appropriate critical quenching speed Vc (upper critical speed) can be selected in the curve, because when the cooling rate is greater than the critical quenching speed Vc, the supercooled austenite only undergoes martensitic transformation;

The shot blasting machine blade is divided into surface area, sub-surface area and core part from the surface to the center along the cross section. According to the position of one end of the shot blasting machine blade ejecting the projectile as the starting point, the expected structure is set within a suitable distance. The cooling speed of the surface and the core of the blade is different. The surface area is controlled by the cooling speed to obtain the expected structure to meet the mechanical performance requirements. The sub-surface area and the core are cooled slowly, so as to avoid the transformation of the cooling speed area. The body or bainite structure is over-tempered due to the high temperature rise, thereby reducing the performance of the shot blasting machine blade;

According to the surface heat transfer coefficient, the temperature field of the shot blasting machine blade during the cooling process is numerically simulated, and the appropriate distance of the divided area and the parameters of laser quenching processing are further determined to ensure that the surface area avoids brittle cracking, and the core position avoids quenching. occurrence of hard phenomena;

S4. After preheating treatment on the laser phase transformation hardening device, phase transformation strengthening is performed on the blades of the shot blasting machine according to the predetermined scanning path. The laser phase transformation hardening device is shown in Figure 1, and the scanning path is shown in Figure 2;

The shot blasting machine blade is sampled by a wire cutting machine, and the surface impurities are removed by acetone, and graphite and carbon ink are used for blackening treatment and air drying;

The blackened shot blasting machine blade is heated by a heater, and the temperature of the shot blasting machine blade is heated to 120 °C;

Start the laser, use the scanning mirror to convert the laser into a broadband laser, focus on the surface of the workpiece, and verify the selected result calculated according to the requirements of the cooling rate of the shot blasting machine blade to divide the different areas according to the relationship between the quenching depth and the laser specific energy density , Set the laser power required for laser phase change strengthening processing to 2.5KW, the scanning speed of 5mm/s, the spot size of 10mm × 4mm, and the use of non-lap joints to reduce the softening of the overlapped joints due to repeated heating and avoid uneven hardness on the surface.

The shot blasting machine blade prepared in the embodiment is compared with the traditional resistance furnace quenched shot blasting machine blade and the unquenched shot blasting machine blade, and the microhardness is tested by a Vickers hardness tester. The test results are shown in the following table:

It can be seen from the above table that the present invention adopts the laser phase transformation hardening process to strengthen the surface of the shot blasting machine blade, and its hardness value is significantly improved, thereby ensuring the service performance of the shot blasting machine blade.

To sum up, the process of the present invention for the laser phase transformation hardening of the surface of the shot blasting machine blade, because the laser phase transformation hardening has the characteristics of "extremely fast and extremely cold", that is, fast heating and fast cooling, and can be shot blasting in a very short time. The structure of the quenched layer of the shot blasting machine blade changes from the original columnar martensite to acicular martensite, avoiding the long-term transition and other brittle structures, thus greatly improving the performance of the shot blasting machine blade;

The shot blasting machine blade obtains the required performance or structure on the premise of avoiding cracking, and is suitable for the laser phase transformation hardening treatment of the surface of the shot blasting machine blade with different compositions, and the columnar martensite on the surface becomes acicular martensite, thereby The hardness, wear resistance and quenching layer depth of the shot blasting machine blade are greatly improved, avoiding the defects caused by the traditional quenching-tempering treatment technology, resulting in residual compressive stress on the surface of the material or part, thereby improving the mechanical properties of the surface layer. . It not only improves the efficiency of the shot blasting machine, but also greatly improves the service performance of the shot blasting machine blade, thereby reducing the production cost.

It should be noted that: the above description is only the preferred embodiment of the present invention, and is not intended to limit the scope of the right of the present invention; at the same time, the above description should be understood and implemented by professionals in the relevant technical field, so others do not deviate from the present invention. Equivalent changes or modifications accomplished under the spirit of the disclosed invention shall be included in the scope of the patent application.

Claims (5)

1. The laser phase change hardening method for the surface of the shot blasting machine blade is characterized by comprising the following steps: the method comprises the following steps:

1) putting the raw material components of the shot blasting machine blade into a medium-frequency induction resistance furnace for smelting, heating to 1535-1555 ℃, pouring the smelted molten iron into a shot blasting machine blade mould made of sand in advance for casting;

2) cooling and molding the molten iron to obtain a shot blasting machine blade, taking the shot blasting machine blade out of the sand mold, removing sand and a casting head remained on the surface, and cleaning burrs and fins on the shot blasting machine blade;

3) selecting laser processing parameters according to performance requirements and cooling control conditions of different areas of the shot blasting machine blade;

4) preheating the blades of the shot blasting machine to 120 ℃ on a laser phase change hardening device, and then carrying out phase change strengthening on the blades of the shot blasting machine according to a scanning path, wherein the steps are as follows:

41) carrying out blackening treatment on the shot blasting machine blade;

42) preheating the shot blasting machine blade to 120 ℃ by using a heater;

43) starting the fiber laser, enabling a light beam output by the fiber laser to enter a broadband scanning rotating mirror, converting laser into broadband laser by the broadband scanning rotating mirror, namely linear light spots, and focusing the laser on the surface of a workpiece on a workbench through a laser head;

44) setting the processing power, scanning speed, spot size and scanning path of a laser according to the calculation result of the cooling speed requirements of different areas divided by the shot blasting machine blades;

the method comprises the steps that different areas of the blades of the shot blasting machine are required to have high performance, the blades of the shot blasting machine are continuously impacted to generate cyclic stress, the shot generates rolling friction and sliding friction on the blades of the shot blasting machine, according to the performance requirements of the blades of the shot blasting machine, the surfaces of the blades are divided into an impact area and a sliding and abrasion area, the shot incident angle of the impact area is 20 degrees, the shot incident angle of the sliding and abrasion area is 0 degree, the abrasion of the sliding and abrasion area is higher than that of the impact area, so that deformation of a base material and expansion and fracture failure of carbide are caused, the shot generates impact abrasive material abrasion with the blades of the shot blasting machine in the impact area, the sliding and abrasion area generates large sliding friction due to large acting radius of centrifugal force, the sliding and abrasion area needs to have high impact toughness and abrasion resistance, and the impact area needs to have smaller impact toughness and abrasion resistance than the sliding and abrasion area;

controlling cooling conditions in different areas of the shot blasting machine blade, obtaining the longest cooling time or the minimum cooling rate when the obtained tissue reaches a certain temperature according to a supercooled austenite isothermal cooling transformation curve (TTT curve) or supercooled austenite continuous cooling transformation curve (CCT curve) of the material, and setting an expected tissue in a distance range by taking one end position of the shot ejected by the shot blasting machine blade as a starting point; the cooling speed of the surface and the core of the shot blasting machine blade is different, the shot blasting machine blade is divided into a surface layer area, a sub-surface layer area and a core from the surface to the center along the cross section, the surface layer area obtains an expected structure by controlling the cooling speed so as to meet the requirement of mechanical property, and the sub-surface layer area and the core are cooled slowly, so that the phenomenon that the martensite or bainite structure converted in the cooling speed area is over-tempered due to the fact that the temperature rises back to be too high and the use performance of the shot blasting machine blade is influenced is avoided.

2. The method for laser phase change hardening of the surface of the shot blasting machine blade as recited in claim 1, wherein: the shot blasting machine blade comprises the following components in percentage by mass: c: 2.8-3.2%, Cr: 4-5%, Si: 0.4-0.8%, Mn: 0.5-1.2%, P is less than or equal to 0.035%, S is less than or equal to 0.035%, Re is less than or equal to 0.05%, and the balance is Fe and chemical elements existing in common steel making.

3. The method for laser phase change hardening of the surface of the shot blasting machine blade as recited in claim 1, wherein: and when the temperature of the smelted molten iron is reduced to 100-1420 ℃, pouring the molten iron into a shot blasting machine blade mould made of sand in advance for casting.

4. The method for laser phase change hardening of the surface of the shot blasting machine blade as recited in claim 1, wherein: the laser phase change hardening device comprises a workbench for carrying the shot blasting machine blades and a heater for preheating the shot blasting machine blades, a broadband scanning rotating mirror and a laser head are sequentially arranged on an output light path of the optical fiber laser, and the broadband scanning rotating mirror converts laser into broadband laser, namely linear light spots, and the broadband laser is focused on the surfaces of the shot blasting machine blades on the workbench through the laser head.

5. The method for laser phase change hardening of the surface of the shot blasting machine blade as recited in claim 1, wherein: the power of laser processing is 2.5KW, the scanning speed is 5mm/s, the spot size is 10mm multiplied by 4mm, and a non-overlapping scanning path is selected.

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