Milling method cooperatively assisted by heat source and cold source

Abstract

The invention provides a heat-cold source cooperative auxiliary milling method, and relates to the technical field of steel milling, and the method specifically comprises the following steps: preheating a to-be-processed surface of a to-be-processed workpiece through an induction heat source; the temperature of a cutting area is controlled through the low-temperature-minimum quantity lubrication equipment when the tool is in contact with the workpiece to be machined; and the workpiece to be machined is further milled according to the preset feeding speed, the preset cutter spindle rotating speed, the preset milling width and the preset milling depth. According to the scheme, the induction heat source and the low-temperature-minimum quantity lubrication equipment have a synergistic effect on the milling machining process of the steel workpiece at the same time, so that the milling machining efficiency and machining quality of the steel workpiece are improved.

Description

Technical Field

[0001] The invention relates to the technical field of steel milling processing, in particular to a milling method assisted by a heat-cold source collaboration. Background Art

[0002] H13 hardened cast steel is widely used in the manufacturing of molds. Its high hardness (approximately 60HRC) and high thermal strength lead to high cutting forces, severe tool wear, and difficulty maintaining workpiece surface quality during conventional cutting. Research has shown that the mechanical stress of high-strength steel during shear deformation can be reduced through heat-assisted processing. However, this also concentrates more heat in the tool-chip (workpiece) contact area and in areas of plastic deformation of the workpiece, causing localized overheating in the processing area, which can lead to workpiece damage or premature tool wear, making it impossible to guarantee workpiece processing efficiency and quality. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a milling method with heat-cold source synergistic assistance, which improves the efficiency and quality of steel workpiece milling through the synergistic effect of an induction heat source and a low-temperature-minimum lubrication device.

[0004] To solve the above technical problems, an embodiment of the present invention provides a milling method with heat-cold source collaborative assistance, comprising:

[0005] Preheating the surface of the workpiece to be machined by an induction heat source;

[0006] Control the temperature of the cutting area where the tool contacts the workpiece through low-temperature-minimum-quantity lubrication equipment;

[0007] The workpiece to be machined is milled according to a preset feed speed, a preset tool spindle speed, a preset milling width, and a preset milling depth.

[0008] In one embodiment, the induction heat source is an induction heating device, which generates a gradient temperature field. The heat generated by the gradient temperature field is used to soften the surface to be processed of the workpiece to be processed, so as to reduce the yield strength and tensile strength of the surface to be processed.

[0009] In one embodiment, the heating power of the induction heating device is 20 kW to 80 kW.

[0010] In one embodiment, the low temperature-minimum quantity lubrication device reduces the temperature of the cutting area through a cooling medium and reduces the friction coefficient of the contact interface between the tool and the workpiece through a lubricating medium, thereby indirectly reducing the temperature of the cutting area.

[0011] In one embodiment, the cooling medium is a high-pressure fluid and / or a high-pressure gas, and the lubricating medium is a cutting lubricant.

[0012] In one embodiment, the oil amount of the cutting lubricating liquid is 50ml / h.

[0013] In one embodiment, the temperature of the high-pressure fluid and / or the high-pressure gas is -10℃, and the pressure is 0.6Mpa.

[0014] In one embodiment, the preset feed speed is 200mm / min~400mm / min, the preset tool spindle speed is 500r / min~1500r / min, the preset milling width is 4mm~12mm, and the preset milling depth is 0.2mm~0.8mm.

[0015] In one embodiment, the preset feed speed is 300mm / min, the preset tool spindle speed is 1000r / min, the preset milling width is 8mm, and the preset milling depth is 0.5mm.

[0016] In one embodiment, the hot-cold source synergistic assisted milling method further comprises evaluating the cutting quality of the hot-cold source synergistic assistance according to at least one of the following evaluation indexes:

[0017] Cutting force;

[0018] Cutting temperature;

[0019] Chip morphology;

[0020] Tool wear morphology;

[0021] Workpiece surface roughness;

[0022] Workpiece surface morphology integrity;

[0023] Workpiece subsurface microstructure;

[0024] Workpiece subsurface microstructure hardness.

[0025] The above scheme of the present application at least includes the following beneficial effects:

[0026] The hot-cold source synergistic assisted milling method provided by the above scheme of the present application, by means of an induction heat source, preheats the surface to be machined of the workpiece to be machined; and by means of a low-temperature-micro-lubrication device, controls the cutting area temperature when the tool and the workpiece to be machined are in contact; further, according to the preset feed speed, the preset tool spindle speed, the preset milling width and the preset milling depth, the workpiece to be machined is subjected to milling processing; during the workpiece milling processing, the induction heat source and the low-temperature-micro-lubrication device are synergistically used to improve the efficiency of the workpiece milling processing and the quality after the milling processing. BRIEF DESCRIPTION OF DRAWINGS

[0027] Figure 1 is a bar chart of the effect of cutting environment on the cutting force in each direction provided by an optional embodiment of the present application;

[0028] Figure 2 is a temperature distribution in the process of heat-source assisted milling provided by an optional embodiment of the present application;

[0029] Figure 3 is a bar chart of the effect of cutting environment on the cutting temperature provided by an optional embodiment of the present application;

[0030] Figure 4 is a schematic diagram of the cooling heat transfer under the condition of heat-source assisted provided by an optional embodiment of the present application;

[0031] Figure 5 is a microstructure morphology of the chip under different conditions provided by an optional embodiment of the present application;

[0032] Figure 6 is an SEM micrograph of the tool wear under dry condition provided by an optional embodiment of the present application;

[0033] Figure 7 is an SEM micrograph of the tool wear under heat-source assisted condition provided by an optional embodiment of the present application;

[0034] Figure 8 is a bar chart of the effect of cutting environment on the surface roughness of the workpiece provided by an optional embodiment of the present application;

[0035] Figure 9 is an SEM image of the milling surface under different conditions provided by an optional embodiment of the present application;

[0036] Figure 10 is a microhardness distribution diagram of the dry condition and the combined action of heat and cold sources under different heating powers provided by an optional embodiment of the present application;

[0037] Figure 11 is a microstructure diagram of the workpiece material under different conditions provided by an optional embodiment of the present application;

[0038] Figure 12 is a milling principle diagram of the heat and cold source assisted provided by an optional embodiment of the present application;

[0039] Figure 13 is a connection diagram of the low-temperature and trace lubrication equipment provided by an optional embodiment of the present application. DETAILED DESCRIPTION

[0040] Exemplary embodiments of the present disclosure will be described herein below with reference to the accompanying drawings. While exemplary embodiments of the present disclosure are shown in the drawings, it is understood that the present disclosure can be embodied in various forms and should not be limited by the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0041] In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of various disclosed embodiments. It will be apparent, however, to one skilled in the art that embodiments can be practiced without one or more of these specific details. In other instances, well-known structures and devices are not shown or described in order to avoid unnecessarily obscuring the description of embodiments.

[0042] Reference throughout this specification to "an embodiment" or "the embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase "in one embodiment" or "in an embodiment" in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, the particular features, structures, or characteristics can be combined in any suitable manner in one or more embodiments.

[0043] Referring to Figure 12 Embodiments of the present disclosure provide a hot-cold source assisted milling method, comprising:

[0044] Step 11, preheating the surface to be machined of the workpiece to be machined by an induction heat source;

[0045] Step 12, controlling the temperature of the cutting area when the tool and the workpiece to be machined are in contact by a low-temperature-micro-lubrication device;

[0046] Step 13, milling the workpiece to be machined according to the preset feed speed, the preset tool spindle speed, the preset milling width, and the preset milling depth.

[0047] In this embodiment, the induction heat source is located in front of the milling cutter. By applying the external induction heat source to the surface of the workpiece to be machined, the preheating temperature increases the dislocation activity of the material of the workpiece to be machined, increases the grain size, and reduces the total number of grain boundaries, thereby reducing the yield strength and microhardness of the material, making the material more likely to deform plastically rather than brittlely when subjected to force, thereby reducing the difficulty of milling processing;

[0048] The low-temperature-micro-lubrication device is located at the inclined side of the milling cutter, and in an optional embodiment of the application, the low-temperature-micro-lubrication device reduces the temperature of the cutting area by the cooling medium and reduces the friction coefficient of the contact interface between the cutter and the workpiece by the lubricating medium, so as to indirectly reduce the temperature of the cutting area; here, the cooling medium can reduce the temperature of the cutting area; at the same time, the cooling medium can also effectively remove the chips in the cutting area, reducing the influence of the chips on the surface quality of the workpiece; the lubricating medium can effectively reduce the friction coefficient between the cutter and the chip, thereby indirectly reducing the temperature of the cutting area; at the same time, the lubricating film formed by the lubricating medium can establish an isolation layer between the cutter and the chip, which helps to reduce the wear caused by friction and the damage caused by high temperature.

[0049] Here, the low-temperature-micro-lubrication device refers to a low-temperature cold air-minimal quantity lubrication (CMQL) system that combines cooling technology and minimal quantity lubrication technology. As shown in Figure 13 The low-temperature cold air-minimal quantity lubrication system can mainly include a cold air compressor, a storage tank for storing lubricating medium, a mixing chamber, a nozzle, a plurality of connecting pipelines, a plurality of valves, and a plurality of pressure gauges. The cold air compressor provides low-temperature compressed gas to the mixing chamber, and the lubricating medium in the storage tank is pumped into the mixing chamber. After mixing in the mixing chamber, the valve is opened, and the mixture is sprayed out through the nozzle.

[0050] By using the non-contact enhanced induction heat source heating technology, the temperature of the surface layer of the workpiece to be machined can be efficiently and controllably controlled, thereby reducing the deformation resistance of the material removal layer. At the same time, the forced cooling and lubrication environment formed by the low-temperature micro-lubrication act on the cutting area to improve the friction and heat transfer in the cutter-chip (workpiece) contact area and the plastic deformation area of the workpiece, thereby effectively improving the cutting processing efficiency and quality.

[0051] In an optional embodiment of the application, the induction heat source is an induction heating device, and the induction heating device generates a gradient temperature field. The heat generated by the gradient temperature field is used to soften the surface to be machined of the workpiece to be machined, so as to reduce the yield strength and tensile strength of the surface to be machined.

[0052] In this embodiment, compared with the uneven temperature field of traditional gas flame assisted machining, the high equipment cost of laser assisted machining and the high energy consumption problem of thermal plasma assisted machining, the workpiece is heated by the induction heating equipment, which is uniform, low in energy consumption, green and clean, and the price of the induction heating equipment is affordable. Here, the preheating temperature of the induction heating equipment can be precisely controlled by heating power, coil turns, diameter, current frequency, straight-line distance from the coil to the workpiece surface, and coil residence time, etc. Preferably, the heating power of the induction heating equipment can be 20kw~80kw; wherein the horizontal distance between the induction coil and the milling cutter can be 5mm~10mm.

[0053] In the preheating process of the material on the surface of the workpiece to be machined, when the alternating current passes through the induction coil in the induction heating equipment, a high-frequency alternating magnetic field is generated. The high-frequency alternating magnetic field will induce an induced current in the workpiece and form a closed current loop, thereby causing the generation of eddy current, and similar to direct current, the eddy current will also generate heat and follow Joule's law, thereby heating the workpiece material. And when the workpiece is in the alternating magnetic field changing with time, the eddy current formed will also produce eddy current loss and hysteresis loss on the surface of the workpiece, and the loss generated will also be converted into heat energy, so that the local surface temperature of the workpiece rises, realizing the preheating and softening process of the material. The induction coil with high-frequency alternating current is placed in front of the milling cutter to preheat the surface to be machined, and then the softened surface material of the workpiece is removed by a precision milling cutter, thereby completing the whole process of induction assisted milling.

[0054] Preferably, when using the induction heating equipment to heat the surface of the workpiece to be machined, a high-frequency (30 kHz~80kHz) or ultrahigh-frequency (200kHz~1.1MHz) induction heating equipment is usually used to heat the surface of the workpiece to ensure that the heat affected zone is mainly concentrated on the surface of the workpiece, thereby reducing the yield strength and surface hardness of the surface material of the workpiece, thereby reducing the cutting force to improve the service life and machining efficiency of the tool.

[0055] In an optional embodiment of the present application, the cooling medium is a high-pressure fluid and / or a high-pressure gas, and the lubricating medium is a cutting lubricating liquid. In the low-temperature-micro-lubrication equipment assisted milling process, the cutting lubricating liquid can enter the grinding area (strong penetration and low-temperature lubricating oil is not easy to volatilize) under the pushing action of the high-pressure fluid and / or high-pressure gas, thereby significantly reducing the friction effect. At the same time, the cutting lubricating liquid and the high-pressure fluid and / or high-pressure gas can timely remove the grinding debris generated in the grinding process to reduce the additional problems caused by the coating effect, thereby improving the cutting machining performance.

[0056] Preferably, the oil amount of the cutting lubricating liquid is 50ml / h, and more preferably, the temperature of the cutting lubricating liquid is -45℃~0℃; preferably, the temperature of the high-pressure fluid and / or the high-pressure gas can be -10℃, and the pressure can be 0.6Mpa; the cutting lubricating liquid and the high-pressure fluid and / or the high-pressure gas acting on the surface of the workpiece can accelerate the transfer and dissipation of heat, thereby inhibiting the temperature rise of the cutting area.

[0057] In an optional embodiment of the present application, the preset feed speed is 200mm / min~400mm / min, the preset tool spindle speed is 500r / min~1500r / min, the preset milling width is 4mm~12mm, and the preset milling depth is 0.2mm~0.8mm.

[0058] Further, the preset feed speed can be 300mm / min, the preset tool spindle speed can be 1000r / min, the preset milling width can be 8mm, and the preset milling depth can be 0.5mm.

[0059] In an optional embodiment of the present application, the above-mentioned milling method assisted by the heat-cold source in cooperation further comprises: step 14, evaluating the cutting quality assisted by the heat-cold source in cooperation according to at least one evaluation index; the at least one evaluation index can include: cutting force, cutting temperature, chip morphology, tool wear morphology, workpiece surface roughness, workpiece surface morphology integrity, workpiece subsurface microstructure, and workpiece subsurface microhardness.

[0060] In this embodiment, the key process performance parameter evaluation indexes such as cutting force, cutting temperature, chip morphology, tool wear morphology, workpiece surface roughness and surface morphology integrity, and workpiece subsurface microstructure and microhardness are used to illustrate the synergistic mechanism of the heat-softening effect of induction heating and the low-temperature micro-lubrication cooling lubrication mechanism.

[0061] In the following, the method described in the above embodiment will be illustrated by comparing the milling performance differences in dry cutting, single low-temperature micro-lubrication (CMQL), single induction heating (IAM), and heat-cold source cooperative assistance (HCHAM) environments with the parameters set in Table 1, specifically:

[0062] The oil quantity under the low-temperature micro-lubrication environment is 50 ml / h, the high-pressure gas temperature and pressure are -10°C and 0.6 Mpa respectively; the workpiece material is quenched die steel (H13 steel) after stress relief annealing treatment, the specific structure is three-dimensional convex, the Rockwell hardness is 45HRC, and the size is 120 mm (length) x 40 mm (width) x 120 mm (height). The tool uses a rhombus 80° blade, the size is 11.30 x 6.25 mm, the APMT1135PDER-FM slot type indexable numerical control vertical milling cutter with a tool tip circular arc radius of 0.8 mm. The inductive coil material in the induction heating equipment is pure copper; the specific contrast parameter design is shown in Table 1.

[0063] Table 1, contrast parameter design table

[0064]

[0065] As shown in Figure 1 , it can be seen that, compared with dry and low-temperature micro-lubrication auxiliary machining, the cutting forces F x and F z under the induction heating (P = 80 kw) and hot-cold source composite cutting environment (P = 80 kw) are significantly reduced; compared with dry machining, the cutting forces F x are reduced by 31.5% and 22.3% respectively; compared with CMQL, the cutting forces F x are reduced by 32.5% and 24.2% respectively, which shows that the thermal softening effect plays a key role in reducing the cutting forces F x , can significantly reduce the deformation resistance in the material removal process, and thus optimize the cutting performance. Secondly, compared with hot-cold source cooperative auxiliary machining, the thermal softening effect under IAM is stronger, which leads to further reduction of the cutting forces F x and F z . At the same time, by comparing dry and CMQL machining conditions, it can be seen that the cutting force F y under the CMQL environment is actually increased, which is because the high-temperature and high-pressure machining environment causes the micro-lubrication liquid to be unable to effectively penetrate to the tool-work (chip) contact surface, and cannot form an effective lubricating film.

[0066] Under the condition of heat- cold source synergistic auxiliary milling machining with heating power P = 20kw and 50kw, compared with dry machining, the milling force in each direction is improved, which is not consistent with the expected result of thermal softening effect. The main reason is that during the induction heating process, the H13 steel material is quenched, and its hardness increases first and then decreases in a certain range. Therefore, compared with dry cutting, the cutting under the condition of heat- cold source composite is higher when the preheating temperature is lower (~ 300℃). When P = 80kw, the cutting force in each direction decreases significantly, because the preheating temperature at this time reaches the critical transition temperature of H13 steel material, which leads to the coarsening and uniform distribution of the material internal grains, thereby sharply reducing the hardness and strength of the material, and significantly reducing the deformation resistance of the material in the cutting process.

[0067] Figure 2 The influence of three different heating powers (P = 20kw, P = 50kw, P = 80kw) on the cutting temperature distribution under the condition of setting the milling process parameters (feed speed 200mm / min, spindle speed 500r / min, milling width 8mm, milling depth 0.5mm) is shown. As can be seen from the figure, the induction coil in front of the milling cutter preheats the workpiece material to be machined, and then the softened layer is cut by the indexable vertical carbide milling cutter, and obvious spark chips are generated in the process. At the same time, through the CMQL nozzle, low-temperature and trace lubricating liquid is sprayed to the tool- work (chip) contact area, and the flowing cutting fluid effectively takes away the heat of the tool and the workpiece surface.

[0068] As Figure 3 shown, compared with dry machining, the cutting temperature under the action of CMQL is reduced by about 16.2%, the main reason is that the low-temperature cooling liquid (-10℃) sprayed on the tool- work (chip) contact interface accelerates the heat dissipation of the cutting area through forced convection heat exchange. In the process of induction auxiliary milling machining, compared with dry machining, the cutting temperature increases significantly, because the superposition effect of induction heat source and cutting heat leads to the fact that the heat in the machining area cannot be dissipated in time and effectively. Under the combined action of heat- cold source, the low-temperature and trace lubricating liquid introduced can effectively inhibit the cutting temperature rise, and compared with single induction heating auxiliary machining, the cutting temperature under the condition of heat- cold source synergistic auxiliary machining is reduced by about 13.4%.

[0069] Figure 4The heat transfer mechanism diagram under the hot-cold source composite environment is shown. From the figure, it can be clearly observed that the heat in the cutting area mainly comes from the induction heat source, the cutting heat in the cutting process and the friction heat of the tool-workpiece (chip) contact interface. The accumulation of these heat can easily lead to the increase of cutting temperature, and then affect the machined surface quality and tool life. Therefore, by introducing low-temperature micro-lubrication medium to actively regulate the cutting area temperature, the tool wear and workpiece surface deformation or burn caused by high temperature are avoided.

[0070] Specifically, the low-temperature coolant (-10℃) acting on the tool-workpiece (chip) contact area significantly enhances the heat transfer efficiency due to the large temperature difference between the coolant and the cutting area, thereby accelerating the dissipation of the induction heat and the cutting heat. At the same time, the continuous spray impacting on the tool / workpiece surface will be broken into tiny droplets under the action of pressure, and the ratio of surface area to total volume will increase, so that more droplet surfaces come into contact with the heated surface, thereby improving the heat transfer efficiency.

[0071] As shown in Figure 5 , the micro-morphology of the chip under different cutting environments (dry, low-temperature micro-lubrication, hot-cold source composite) is systematically characterized under the setting of milling process parameters (V f =200mm / min, n=500r / min, a p =0.5mm, a e =8mm). Compared with dry and low-temperature micro-lubrication environments, the high-temperature pre-treatment significantly enhances the plastic deformation ability of the material under the hot-cold source cooperative auxiliary working condition. As can be clearly observed from the figure, under the hot-cold source composite working condition, the chip fracture length is significantly reduced, the wrinkle distribution gradually tends to be uniform, and the chip morphology gradually transitions from the sawtooth type to the continuous type. At the same time, the chip segmentation frequency gradually decreases, the degree of sawtooth is gradually weakened, the tooth height and tooth width of each tooth gradually tend to be consistent, and the sawtooth of the chip edge gradually presents trapezoidal distribution. This change shows that the material exhibits better plastic flow characteristics at high temperature, thereby reducing tool chatter and improving the stability of the cutting process. In addition, during the machining of the workpiece, the dislocation torque limits the deformation of the material under low temperature (such as room temperature), resulting in a large strain on the shear surface and the formation of a fracture; while under high temperature conditions, due to the weakening of the restriction of dislocation torque, the strain hardening phenomenon of the material is alleviated, thereby reducing the formation of the fracture.

[0072] Figure 6 , Figure 7The wear morphology of the rake and flank faces of the tool under dry and hot-cold source combined conditions is compared. Compared with the dry milling condition, the chipping area under the hot-cold source combined condition is smaller, and the width of the crater wear area on the rake face is also significantly reduced. This shows that under the same milling time, the tool under the dry condition bears greater mechanical and thermal loads, resulting in higher stress concentration, thus exacerbating the severity of tool chipping. Under the hot-cold source combined condition, the thermal softening effect of the induction heat source effectively reduces the mechanical load borne by the tool, while the low-temperature cooling lubricating medium significantly improves the thermal load distribution of the tool. In addition, the scouring effect of the low-temperature cooling liquid under the hot-cold source combined condition inhibits the formation of the built-up edge, making its distribution range smaller and its thickness thinner. Compared with dry machining, the thermal softening effect of the induction heat source effectively reduces the mechanical load borne by the tool, while the low-temperature cooling lubricating medium significantly improves the thermal load distribution of the tool. At the same time, the scouring effect of the low-temperature cooling liquid can also well inhibit the formation of the built-up edge, thereby prolonging the service life of the tool.

[0073] Figure 8 The influence of cutting environment on surface roughness value under the condition of setting milling process parameters (V f = 200 mm / min, n = 500 r / min, a p = 0.5 mm, a e = 8 mm) is compared and analyzed. As can be seen from the figure, the surface roughness value under the IAM machining condition is the lowest, and the surface roughness value under the CMQL condition is higher than that under the dry machining condition, indicating that the lubricating oil film has not been fully formed, and the tool-work (chip) contact interface friction has intensified, resulting in surface damage.

[0074] As shown in Figure 9 , the surface micro-morphology under dry machining and hot-cold source combined conditions with different heating powers (P = 20 kw, P = 50 kw, P = 80 kw) is shown. As can be seen from the figure, under the dry cutting condition, material adhesion, pits, cracks, and irregular tool extrusion marks / indentations, etc. surface damage are easily produced on the machined surface. The main reason for this phenomenon is that, during dry milling, the lack of effective cooling and lubricating medium leads to a significant increase in friction / extrusion between the tool-work (chip) contact interface, and the tool chatter is large, accompanied by rapid accumulation of thermal load. Under the hot-cold source combined environment, when the workpiece surface preheating temperature is high, the pits, cracks, and other obvious defects on the machined workpiece surface are reduced, indicating that the thermal softening effect of the induction heat source causes the fracture mechanism of the chip to change from brittle fracture to ductile fracture, thereby avoiding the formation of surface pits during chip fracture.

[0075] Figure 10The microhardness distribution under dry cutting and the combined action of heat and cold source under different heating power is shown. The analysis shows that under the dry cutting condition, the workpiece surface layer is obviously work-hardened, and along with the increase of the depth of the machined surface, the microhardness gradually decreases. Under the combined action of heat and cold source, due to the action of the induction heat source, the surface layer of H13 steel material is quenched, resulting in the precipitation of a large number of fine granular carbides, the refinement of part of the grains, and the increase of dislocation density, thereby increasing the cutting force in the cutting process. The change of the material organization and performance further intensifies the work-hardening effect of the workpiece surface layer, making it more significant. When the preheating temperature under the combined action of heat and cold source further rises to 550℃, the grain size increases under the action of thermal softening, the grain coarsening phenomenon is significant, the cutting force decreases significantly, the work-hardening effect is obviously weakened, the temperature rises, promoting the movement of dislocations in the crystal, and the resistance to grain deformation is weakened due to the grain coarsening, so that the work-hardening effect is weakened.

[0076] As shown in Figure 11 The microstructure of the material under different working conditions is shown in Figure 11 (a1) and (a2) respectively show the band contrast (BC) and inverse pole figure (IPF) of the workpiece surface layer under dry milling machining condition. It can be seen that in the dry milling process, the material surface layer has undergone serious plastic deformation, resulting in a dark area near the workpiece surface, and the grains in these areas are elongated to form strip-shaped structures due to the severe plastic flow. Part of the grains are even divided into smaller units under the action of mechanical force. At the same time, due to the continuous action of external force, a large number of dislocations are generated inside the grains. When the dislocation density reaches a certain level, part of the grains are refined through recrystallization, which is the main reason for the work-hardening phenomenon. Along the depth direction downward, it can be observed that part of the grains appear coarsening phenomenon, which may be because the high temperature generated at the tool-work (chip) interface during cutting is transmitted to the workpiece interior. In the high temperature environment, the grain boundary energy is reduced, and the grains gradually coarsen by absorbing surrounding small grains or merging adjacent grains, thereby forming new deformed grains.

[0077] As shown in Figure 11 (b1) and (b2) show the BC and IPF of the workpiece surface layer after cutting under the combined action of heat and cold source when the preheating temperature reaches 200℃. Figure 11 (c1) and (c2) show the BC and IPF of the workpiece surface layer after cutting under the combined action of heat and cold source when the preheating temperature reaches 300℃. Figure 11(d1), (d2) are shown as in the heat-cold source complex effect, when the preheating temperature reaches 550 DEG C, by observing the cutting processing, the workpiece surface layer BC chart and IPF chart can be found, the workpiece surface layer grain dense arrangement and size difference is smaller. At the same time, the grain has the significant recrystallization phenomenon, the grain boundary is obviously coarsened, and the boundary between the grain boundary becomes blurred. The main reason for this phenomenon is that when the workpiece material is preheated to the appropriate temperature, the activity of atoms is enhanced, the resistance of grain boundary migration is reduced, and the movement of dislocation in the crystal is promoted, and the conditions for grain growth are improved, so that the material is more prone to plastic deformation rather than brittle fracture.

[0078] The above-mentioned embodiment of the present application provides a hot-cold source assisted milling method, which can significantly reduce the deformation resistance in the cutting process. The hot softening effect of the induction heat source significantly reduces the cutting force by reducing the yield strength and tensile strength of the material. At the same time, the hot-cold source complex effect environment reduces the risk of tool rake face collapse, and effectively reduces the thickness of the accumulated layer of the tool flank face. In the cutting process, the hot softening effect of the induction heat source reduces the yield strength of the material, so that the mechanical load borne by the tool rake face is significantly reduced. At the same time, the introduction of low-temperature cooling liquid accelerates the dissipation of heat on the tool surface, and the flushing effect inhibits the formation of the accumulated layer, so that its distribution range is smaller and the thickness is thinner. The synergistic effect of the two improves the thermal-mechanical related wear failure mode of the tool.

[0079] At this point, those skilled in the art should recognize that, although the exemplary embodiments of the present application have been shown and described in detail herein, many other variations and modifications can be determined or deduced directly from the disclosure of the present application in accordance with the principles of the present application without departing from the spirit and scope of the present application. Therefore, the scope of the present application should be understood and recognized as covering all these other variations or modifications.

[0080] The foregoing description of specific exemplary embodiments of the application is intended to be illustrative only and is not intended to limit the application to the precise forms disclosed. Many modifications and variations are possible in light of the above teachings without departing from the spirit or scope of the application. It is intended to cover options and modifications that are within the scope of the application. The scope of the application is to be defined by the claims and their equivalents.

Claims

1. A milling method with heat-cold source assisted cooperation, characterized in that: include: Preheating the surface of the workpiece to be machined by an induction heat source; Control the temperature of the cutting area where the tool contacts the workpiece through low-temperature-minimum quantity lubrication equipment; The workpiece to be machined is milled according to a preset feed speed, a preset tool spindle speed, a preset milling width, and a preset milling depth.

2. The milling method with heat-cold source synergy assistance according to claim 1, characterized in that: The induction heat source is an induction heating device, which generates a gradient temperature field. The heat generated by the gradient temperature field is used to soften the surface to be processed of the workpiece to be processed, so as to reduce the yield strength and tensile strength of the surface to be processed.

3. The milling method with heat-cold source synergy assistance according to claim 2, characterized in that: The heating power of the induction heating equipment is 20kw~80kw.

4. The milling method with heat-cold source synergy assistance according to claim 1, characterized in that: The low temperature-minimum quantity lubrication device reduces the temperature of the cutting area through the cooling medium and reduces the friction coefficient of the contact interface between the tool and the workpiece through the lubricating medium, thereby indirectly reducing the temperature of the cutting area.

5. The milling method with heat-cold source synergy assistance according to claim 4, characterized in that: The cooling medium is high-pressure fluid and / or high-pressure gas, and the lubricating medium is cutting lubricant.

6. The milling method with heat-cold source synergy assistance according to claim 5, characterized in that: The oil volume of the cutting lubricant is 50 ml / h.

7. The milling method with heat-cold source synergy assistance according to claim 5, characterized in that: The temperature of the high-pressure fluid and / or the high-pressure gas is -10°C and the pressure is 0.6 MPa.

8. The milling method with heat-cold source synergy assistance according to claim 1, characterized in that: The preset feed speed is 200 mm / min to 400 mm / min, the preset tool spindle speed is 500 r / min to 1500 r / min, the preset milling width is 4 mm to 12 mm, and the preset milling depth is 0.2 mm to 0.8 mm.

9. The milling method with heat-cold source synergy assistance according to claim 8, characterized in that: The preset feed speed is 300 mm / min, the preset tool spindle speed is 1000 r / min, the preset milling width is 8 mm, and the preset milling depth is 0.5 mm.

10. The milling method with heat-cold source synergistic assistance according to claim 1, characterized in that: The method also includes evaluating the cutting quality of the heat-cold source assisted cutting according to at least one of the following evaluation indicators: Cutting force; Cutting temperature; Chip morphology; Tool wear morphology; Workpiece surface roughness; The integrity of the workpiece surface morphology; Subsurface microstructure of the workpiece; Subsurface microstructure hardness of workpiece.

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