CN118218745A - Alloy steel, small-diameter high-oil-intake steel piston and preparation method of friction welding small-diameter high-oil-intake steel piston - Google Patents
Alloy steel, small-diameter high-oil-intake steel piston and preparation method of friction welding small-diameter high-oil-intake steel piston Download PDFInfo
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- Pistons, Piston Rings, And Cylinders (AREA)
Abstract
The invention aims to provide a small-diameter high-oil-inlet steel piston and a preparation method thereof, wherein a section of gap is processed in advance at the position where the oil holes on the welding surface of the piston head and the skirt are aligned, the size of the gap just can accommodate extruded flash, and the height and the width of the extruded flash can be reduced after the gap is processed, so that the friction welding strength is basically not influenced, and then the head and the skirt are connected in a welding mode to form a sealed cooling oil duct without flash blocking; the bainite steel piston formed by controlling cooling through component and process improvement has the advantages of high strength, low cost, good processing performance and the like, and is particularly suitable for the production of high-performance small-cylinder-diameter steel pistons.
Description
Technical Field
The invention relates to the field of steel piston processing, in particular to a high-performance directional friction welding steel piston and a preparation method thereof.
Background
The piston is used as a key core part of the engine, and has the functions of bearing the pressure of fuel gas, driving the crankshaft to rotate through the piston connecting rod mechanism to provide power, and bearing alternating mechanical load and thermal load when in operation, and being in the conditions of high temperature, high pressure, high speed and poor lubrication for a long time, and has bad working conditions.
According to the classification of main materials, the market is mainly divided into three types of aluminum pistons, steel pistons and cast iron pistons at present. With the updating of the engine, the explosion pressure and the power of the engine are continuously improved, for example, the explosion pressure of the engine is more than 200bar, and after the power of the engine reaches 32-40 kW/L, the aluminum piston can not meet the technical requirements due to the limitation of the material strength; therefore, steel pistons are increasingly favored by the host factories.
The piston head and the piston skirt of the steel piston are usually manufactured separately and then manufactured in a friction welding mode. Currently, in order to ensure welding strength and quality, the reduction of friction welding of a steel piston is generally 2.5-5 mm, and the height of flash extruded in the welding process is generally 2.5-4 mm. As shown in fig. 1, the end face of the head of the piston is provided with an oil inlet and outlet hole of a cooling oil channel, which is limited by the structural requirement of the end part of the piston head of the diesel engine, and the oil inlet and outlet hole is often arranged at the position of a combustion chamber, so that for a large piston with the cylinder diameter of more than 110mm, the position of the oil inlet and outlet hole is optimized, and the blocking of flash extruded by friction welding to the oil inlet and outlet hole is avoided; however, for steel pistons with diameters less than 110mm, and in particular smaller diameters, the flash of the friction welding extrusion can severely clog the oil inlet and outlet holes, causing the cooling oil passages to deform and become smaller in volume, and these abnormal pistons, once they are piled, can severely impact the service performance of the engine with even more serious consequences.
Taking a small cylinder diameter piston of a certain model as an example, the diameter of an oil inlet and outlet hole is 7mm, the height of friction welding flash between the head part of the piston and the skirt part of the piston is 2.792mm, and the cross section area of the oil inlet hole is blocked by the welding flash by 39.9%. Some steel pistons with smaller diameters can even reach about 60% of oil inlet and outlet hole blockage. To avoid the above problems, piston designers consider small bore steel pistons unsuitable for friction welding, but should be welded with laser welding having a small weld flash. However, laser welding has disadvantages such as high cost, low welding strength, and easiness in generation of inclusions such as pinholes.
Therefore, how to improve the blocking of friction welding flash to the oil inlet and outlet holes, improve the oil inlet efficiency and improve the engine performance is a technical problem in the design and manufacture of small-bore friction welding pistons from the aspect of the piston structure design and manufacturing process.
Disclosure of Invention
Aiming at the problems, the invention aims to provide alloy steel suitable for being processed into small-diameter high-oil-inlet steel pistons, and solves the problems that the material processing difficulty is high and the welding strength is easily influenced by a notch in the manufacturing process of the small-diameter high-oil-inlet steel pistons.
The alloy steel comprises the following chemical components in percentage by weight, wherein the chemical components comprise ： C0.6-0.8%、Si0.5-1.5%、P0-0.025%、S0.02-0.05%、Mn1.5-2.0%、Cr0.5-1.5%、Cu0.5-1.0%、V0.05-0.2%、Mo0.1-0.3%、Ni0.5-1.5%、Nb0.03-0.06%, parts of Fe in balance; the metallographic structure of the alloy consists of bainite, a small amount of sorbite and austenite, wherein the sorbite and the residual austenite are not more than 10%; the hardness of the material is 250-310HBW, the tensile strength of the material is more than or equal to 1000Mpa, and the elongation of the material is more than 10%.
The invention further provides a small-diameter high-oil-inlet steel piston, and the technical problem that friction welding flash easily shields the oil inlet and outlet hole 202 in the manufacturing process of the small-diameter high-oil-inlet steel piston is solved.
In the embodiment or embodiments, the small-diameter high-oil-intake steel piston comprises ： C0.6-0.8%、Si0.5-1.5%、P0-0.025%、S0.02-0.05%、Mn1.5-2.0%、Cr0.5-1.5%、Cu0.5-1.0%、V0.05-0.2%、Mo0.1-0.3%、Ni0.5-1.5%、Nb0.03-0.06%, balance Fe by chemical composition; the metallographic structure of the alloy consists of bainite, a small amount of sorbite and austenite, wherein the sorbite and the residual austenite are not more than 10%; the piston comprises a piston head and a piston skirt, wherein the end faces of the piston head and the piston skirt are provided with welding faces for friction welding with the piston skirt, the piston head and the piston skirt are fixedly connected through friction welding, the welding faces of the piston head and the piston skirt are provided with concave openings, the inner sides of the openings penetrate through the inner side faces of a cooling oil channel, and the upper sides of the openings are communicated with the contact faces of the welding faces.
In the above or some embodiments, the axial depth Hx, the radial depth Lx, the gap length Dx, and the arc radius Rx of the arc transition parts at two ends of the gap; the axial depth Hx of the opening is adapted to the height of the welding flash, a structure is formed, wherein the radial direction of the structure can reduce or prevent the welding flash from shielding the oil inlet and outlet holes, and the axial depth Hx of the opening is smaller than or equal to half of the width of the welding face; the gap length Dx is matched with the diameter of the oil inlet and outlet, so that a structure that welding flash shields the oil inlet and outlet in the axial direction can be reduced or avoided.
In the above or some embodiments, the welding surfaces where the piston head and/or the piston skirt are joined are provided with the slits, respectively.
In the above or some embodiments, the welding surface portion includes a first welding portion located at the outer ring and a second welding portion located at the inner ring, the second welding portion extends obliquely upward from the edge of the combustion chamber and forms a lower space of the cooling oil channel around the first welding portion, a friction welding surface for friction welding is disposed at an end portion of the second welding portion, and an oblique included angle is formed between the friction welding surface and a horizontal plane.
The invention discloses a preparation method of a small-diameter high-oil-inlet steel piston, which solves the technical problems that the manufacturing of the small-diameter high-oil-inlet steel piston is not suitable for a friction welding process, and friction welding burrs are easy to shield an oil inlet and outlet hole 202.
Raw materials are taken for heating forging to form blanks of the piston head 100 and the piston skirt 200, the heating temperature is 1200-1240 ℃, and the forging ratio is 1:10-1:6;
Rough machining is carried out on the piston head and the skirt forging, the welding face is formed, the opening is formed on the welding face, the axial depth Hx of the opening, the radial depth Lx of the opening, the opening length Dx of the opening and the arc radius Rx of the arc transition parts at the two ends of the opening are formed; the axial depth Hx of the opening is adapted to the height of the welding flash, a structure is formed, wherein the radial direction of the structure can reduce or prevent the welding flash from shielding the oil inlet and outlet holes, and the axial depth Hx of the opening is smaller than or equal to half of the width of the welding face; the gap length Dx is matched with the diameter of the oil inlet and outlet, so that a structure that welding flash shields the oil inlet and outlet in the axial direction can be reduced or avoided;
the piston head is in friction welding with the piston skirt to form a fixedly connected integral structure;
carrying out heat treatment, carrying out integral isothermal quenching and low-temperature tempering after friction welding, wherein the hardness is 250-300HBW, the tensile strength is more than or equal to 1000Mpa, and the yield strength is more than or equal to 600Mpa;
Finish machining, namely finishing the heat-treated workpiece according to the requirements of structure, size and precision;
The oil inlet and outlet holes are formed in the position, corresponding to the opening, of the oil inlet and outlet holes, and the oil inlet and outlet holes are communicated with the cooling oil channel;
And (3) phosphating and nano-coating treatment, wherein the workpiece is subjected to phosphating and nano-coating treatment according to technical requirements after the processing is finished, so that the small-diameter high-oil-inlet steel piston is manufactured.
In the above or some embodiments, the friction welding adopts a second-order friction welding process, a piston head and a skirt are assembled in a tool and clamped, the piston head is not moved, and the piston skirt and a sliding table are separated by about 3mm after being close to the head at a certain speed; the head of the piston and the flywheel are accelerated to a set rotating speed, and then the driving source is disconnected; the piston skirt is contacted with the head under the preset first-order pressure and rubs to generate heat, so that the temperature of the welding surface of the head and the skirt of the piston reaches about 1200 ℃; the rotating speed of the flywheel is reduced to 0, and the height of the piston is reduced to 3.5+/-0.4 mm; then applying the preset pressure in the second stage to perform upsetting, maintaining the pressure for 3-8 seconds, then reducing the pressure to 0, loosening the clamp, taking down the piston to finish welding,
In the above or some embodiments, the piston head and the piston skirt blank formed by forging are cooled, shot blasting is performed for three times, flaw detection is performed, and the unqualified blank is removed.
Therefore, the method has the advantages that a gap is formed in the position where the oil holes of the welding surface of the piston head and the skirt are aligned in advance, the extruded flash can be just contained in the gap, the height and the width of the extruded flash can be reduced after the gap is formed, the friction welding strength is basically not affected, then the head and the skirt are connected in a welding mode to form a sealed cooling oil duct without flash blocking, the application of friction welding in the field of small-cylinder-diameter pistons can be greatly improved by implementing the novel technology, the cooling performance of the friction welding small-cylinder-diameter pistons is improved, the engine performance is further improved, and the method has good market prospect; the bainite steel piston formed by controlling cooling through component and process improvement has the advantages of high strength, low cost, good processing performance and the like, and is particularly suitable for the production of high-performance small-cylinder-diameter steel pistons.
Drawings
FIG. 1 is a schematic diagram of the distribution structure of the piston head, the piston skirt, the oil inlet and outlet holes and the cooling oil channels of the present invention.
FIG. 2 is a schematic illustration of a piston skirt structure in accordance with an embodiment of the present invention.
FIG. 3 is a schematic diagram of a piston head in accordance with one embodiment of the present invention.
Fig. 4 is a schematic diagram of a notch structure according to the present invention.
FIG. 5 is a flow chart of a method for manufacturing a friction welded small diameter high oil intake steel piston according to the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
In the description of the present invention, the meaning of "a plurality" is two or more, unless explicitly defined otherwise.
The alloy steel comprises the following chemical components in percentage by weight: 0.78% of C, 1.49% of Si, 0.15% of P, 0.023% of S, 1.9% of Mn, 0.5% of Cr, 1.0% of Cu, 0.1% of V, 0.15% of Mo, 0.55% of Ni, 0.032% of Nb and the balance of Fe; the metallographic structure of the alloy consists of bainite, a small amount of sorbite and austenite, wherein the sorbite and the residual austenite are 5%; the hardness of the material is 270HBW, the tensile strength of the material is 1050Mpa, and the elongation of the material is 12%.
The alloy steel comprises the following chemical components in percentage by weight: 0.8% of C, 0.51% of Si, 0.019% of P, 0.023% of S, 2.0% of Mn, 0.95% of Cr, 0.95% of Cu, 0.15% of V, 0.12% of Mo, 1.5% of Ni, 0.031% of Nb and the balance of Fe; the metallographic structure of the alloy consists of bainite, a small amount of sorbite and austenite, wherein the sorbite and the residual austenite are 2%; the hardness of the material is 290HBW, the tensile strength of the material is 1250Mpa, and the elongation of the material is 10%.
The alloy steel comprises the following chemical components in percentage by weight: 0.65% of C, 1.3% of Si, 0.012% of P, 0.029% of S, 1.6% of Mn, 0.59% of Cr, 0.9% of Cu, 0.2% of V, 0.3% of Mo, 0.8% of Ni, 0.06% of Nb and the balance of Fe; the metallographic structure of the alloy consists of bainite, a small amount of sorbite and austenite, wherein the sorbite and the residual austenite are 1%; the hardness of the material is 260HBW, the tensile strength of the material is 1100Mpa, and the elongation of the material is 13.1%.
Weighing each raw material accurately, weighing each component according to the proportion, and smelting by adopting an intermediate frequency induction furnace at 1550-1650 ℃; standing the melted molten iron for 15 minutes; then adopting a copper mold for water cooling, then carrying out hot rolling and air cooling, heating to 1200-1240 ℃, and carrying out forging treatment after reaching the temperature, wherein the forging ratio is 1: and 6, performing temperature control cooling after forging at the final forging temperature of 950-1050 ℃, firstly performing air blowing cooling to 500-550 ℃, and then performing heat preservation in an incubator at 450-500 ℃ for 1-3 hours to obtain a blank for manufacturing the steel piston. The metallographic structure of the alloy consists of bainite, a small amount of sorbite and austenite, wherein the sorbite and the residual austenite are not more than 10%; the hardness of the material is 250-310HBW, the tensile strength of the material is more than or equal to 1000Mpa, and the elongation of the material is more than 10%. The material forms a bainite structure by strictly requiring the limitation of sulfur and phosphorus elements and adding elements such as copper, nickel, molybdenum and the like and controlling the cooling speed after forging, so that the strength of the material is obviously improved; meanwhile, the cutting performance of the piston is further improved through the proportion of manganese and sulfur.
In the above or some embodiments, the forging ratio may be 1:10, the forging ratio change has the effect that the crystal grains are finer and the strength is higher after the forging ratio is increased.
A steel piston structurally comprises a piston head 100 and a piston skirt 200, wherein a welding face 300 for friction welding with the piston skirt 200 is arranged at the end faces of the piston head 100 and the piston skirt 200, and the piston head 100 and the piston skirt 200 are fixedly connected through friction welding.
In the above or some embodiments, when the piston is provided with the cooling oil duct, the welding surface 300 includes a first welding portion 301 located at the outer ring and a second welding portion 302 located at the inner ring, where the second welding portion 302 extends obliquely upward from the edge of the combustion chamber and forms a lower space of the cooling oil duct 201 around the first welding portion 301, and a friction welding surface for friction welding is disposed at the end of the second welding portion 302, where an oblique included angle is formed between the friction welding surface and a horizontal plane, where the included angle is determined according to the product structure, and it is required to ensure that the welding flash does not interfere with the combustion chamber of the piston, where the included angle is in a range of greater than 0 ° and less than or equal to 45 °, and where, in order to meet the requirement that the wall of the piston oil duct does not interfere with each other, an included angle of 10 ° to 30 ° is preferably selected, and a circular arc R0.5 to 0.7 of the welding surface is used to change the flow direction of metal in the welding process, and control the size and shape of the flash, that is to control the width a and the height b size of the flash, reducing the risk of interference between the welding flash and the combustion chamber or the oil duct, and the dislocation deformation caused by the welding flash. The first welding part 301 and the second welding part 302 positioned at the piston head and the piston skirt part are welded and surrounded to form a cooling oil duct when friction welding is performed. Naturally, in order to avoid the shielding and blocking of the friction welding flash on the oil inlet and outlet holes of the cooling oil duct, a concave notch 400 is provided at the welding surface of the welding surface 300, especially the joint of the second welding portion 302, the inner side of the notch 400 penetrates through the inner side surface of the cooling oil channel 201, the upper side of the notch 400 is communicated with the contact surface of the welding surface 300, the position of the notch is opposite to the oil inlet and outlet holes, a structure for giving way to the oil inlet and outlet holes is formed, and the formed welding flash is controlled to sink inwards to avoid shielding or blocking the oil inlet and outlet holes.
In the above or some embodiments, the axial depth Hx, the radial depth Lx, the length Dx of the opening 400, and the arc radius Rx of the arc transition parts at the two ends of the opening 400; the axial depth Hx of the notch 400 is adapted to the height of the welding flash, for example, equal to or greater than the height of the welding flash, so as to form a structure in which the welding flash can be reduced or prevented from shielding the oil inlet and outlet 202 in the radial direction, and the axial depth Hx of the notch 400 is less than or equal to half the width of the welding face 300 in order to control the welding strength; the length Dx of the notch 400 is matched with the diameter of the oil inlet and outlet, for example, the length Dx is larger than or equal to the diameter of the oil inlet and outlet, so that the welding flash can be reduced or avoided from shielding the oil inlet and outlet 202 in the axial direction.
In the above or some embodiments, in order to achieve better oil inlet and outlet effects, the welding surfaces where the piston head 100 and the piston skirt 200 are joined are provided with the slits 400, respectively.
After the piston head and the skirt are processed, adopting a nitrogen protection friction welding technology, and keeping the openings processed by the head and the skirt aligned with each other in the welding process, wherein the piston head 100 and the piston skirt 200 are in friction welding to form a fixed connection integral structure, the nitrogen flow of the protective atmosphere is 8-10 m/h, the pressure is 0.25-0.5MPa, the purity is over 99.999 percent, and the welding quantity is 2.5+/-0.3 mm;
carrying out heat treatment, carrying out integral isothermal quenching and low-temperature tempering after friction welding, wherein the hardness is 250-300HBW, the tensile strength is more than or equal to 1000Mpa, and the yield strength is more than or equal to 600Mpa;
Finish machining, namely finishing the heat-treated workpiece according to the requirements of structure, size and precision;
An oil inlet and outlet hole 202 communicated with the cooling oil channel 201 is formed at the position corresponding to the notch 400;
Phosphating and nano-coating treatment, wherein the workpiece is subjected to phosphating and nano-coating treatment according to technical requirements after the processing is finished, so that a small-diameter high-oil-inlet steel piston is manufactured; and forming the surface of the piston skirt with the roughness RZ larger than 100 by adopting a high Wen Meng phosphorus co-permeation technology, wherein the thickness of a manganese phosphorus co-permeation layer is 6+/-4 microns, and then carrying out a novel nano coating technology, wherein the thickness of the coating is 11+/-5 microns.
In the above or some embodiments, the friction welding adopts a second-order friction welding process, the piston head 100 and the skirt are assembled into the tool and clamped, the piston head 100 is not moved, and the piston skirt 200 and the sliding table are separated by about 3mm after being close to the head collision at a certain speed; the piston head 100 and flywheel accelerate to a set rotational speed, and then the drive source is disconnected; the piston skirt 200 contacts and rubs with the head under a predetermined first-order pressure to generate heat, so that the temperature of the piston head 100 and the skirt welding surface 300 reaches about 1200 ℃; the rotation speed of the flywheel is reduced to 0, and the height of the piston is reduced to 3.5 plus or minus 0.4mm; then applying a second stage of preset pressure to perform upsetting, keeping the pressure for 3-8 seconds, then reducing the pressure to 0, and loosening the clamp and taking down the piston to finish welding;
In the above or some embodiments, the blanks of the piston head 100 and the piston skirt 200 formed by forging are cooled, shot blasting is performed three times, and flaw detection is performed to remove the unqualified blanks.
Compared with the traditional small-diameter friction welding steel piston process, the directional friction welding technology of the technical scheme accurately controls the flash shape near the friction welding oil inlet and outlet hole, eliminates the blocking of welding flash to the piston oil inlet and outlet hole, improves the oil inlet and outlet efficiency of a cooling oil channel, further improves the cooling process of engine oil to the piston in the running process of the engine, and effectively reduces the temperature in the working process of the piston. The specific process has the advantages and disadvantages compared as follows:
| Item times | Traditional friction welding technology | Welding process of this patent |
| Oil hole blocking condition | The blocking rate is more than or equal to 40 percent | ≤10% |
| Welding process | No requirement is required | Directional friction welding |
| Height of welding root | ≥1.0mm | ≥1.0mm |
| Microhardness of weld zone | 380-430HV1 | 380-430HV1 |
| Tensile test | ≥850Mpa | ≥850Mpa |
| Weld zone organization | Tempered sorbite | Tempered sorbite |
In addition, compared with the traditional welding surface structure, the structural design of the inclined welding surface in the technical scheme has the advantages that the structural strength is equivalent to that of the traditional welding surface structure, the control direction of the flash is obviously advantageous, the applicability is wider, and the specific contrast is as follows:
| Item times | Traditional welding technology | Welding technology of this patent | Index influence |
| Weld face design | Straight welding surface | Inclined welding surface | |
| Welding flash | Interfering with combustion chamber | No interference with combustion chamber | Weld strength performance |
| Weld hardness | <430HV | <430HV | Workability and workability of the product |
| Weld strength | ≧850Mpa | ≧850Mpa | Durability of |
| Cooling performance | Preferably, it is | In general | High temperature durability |
| Application scope | Does not meet the high design requirement of ultra-low compression (steel piston with cylinder diameter/CH more than 45 percent) | Can meet the design requirement of ultra-low compression and high design (cylinder diameter/CH < 45% steel piston) | Application range of steel piston |
Therefore, in the present patent, a section of gap 400 is machined in advance at the position where the oil holes of the welding surface of the piston head 100 and the skirt are aligned, the size of the gap 400 just can accommodate the extruded flash, and the height and width of the extruded flash can be reduced without affecting the friction welding strength basically after the gap 400 is machined, and then the head and the skirt are connected in a welding mode to form a sealed cooling oil duct without flash blocking; the bainite steel piston formed by controlling cooling through component and process improvement has the advantages of high strength, low cost, good processing performance and the like, and is particularly suitable for the production of high-performance small-cylinder-diameter steel pistons. The inner cooling oil ducts of the cast iron pistons at the present stage are all formed by lost foam casting, the surfaces of the inner cooling oil ducts are not processed any more, the residual oxide layers are more, loose oxide layers can fall off in the running process of the pistons, and serious consequences such as cylinder pulling, occlusion and the like are caused; the cooling oil duct of piston head and skirt is processed through adjusting the processing procedure in advance, do not bore into the oil outlet earlier, in this way at piston head, skirt friction welding, the interior cold oil duct of post weld heat treatment in-process is equivalent to sealing environment, interior cold oil duct surface is at welding, the post weld heat treatment in-process can not form the oxide layer, can avoid finishing process iron fillings to get into in the interior cold oil duct blind hole equally, after other sizes of piston machine finishes, adopt electrochemical corrosion to process out the piston oil inlet oil outlet again, the interior cold oil duct of piston of formation like this, surface quality is good, no oxidation, no impurity, moreover in friction welding, the post weld heat treatment in-process need not to adopt atmosphere stove or vacuum furnace to prevent the oil duct oxidation, reduce manufacturing cost by a wide margin, improve interior cold oil duct performance.
Claims (8)
1. The alloy steel comprises the following chemical components in percentage by weight, wherein the chemical components comprise ： C0.6-0.8%、Si0.5-1.5%、P0-0.025%、S0.02-0.05%、Mn1.5-2.0%、Cr0.5-1.5%、Cu0.5-1.0%、V0.05-0.2%、Mo0.1-0.3%、Ni0.5-1.5%、Nb0.03-0.06%, parts of Fe in balance; the metallographic structure of the alloy consists of bainite, a small amount of sorbite and austenite, wherein the sorbite and the residual austenite are not more than 10%; the hardness of the material is 250-310HBW, the tensile strength of the material is more than or equal to 1000Mpa, and the elongation of the material is more than 10%.
2. The small-diameter high-oil-inlet steel piston is manufactured by alloy steel according to claim 1 and comprises a piston head (100) and a piston skirt (200), a welding face (300) for friction welding with the piston skirt (200) is arranged at the end faces of the piston head (100) and the piston skirt (200), and the piston head (100) and the piston skirt (200) are fixedly connected through friction welding.
3. The small-diameter high oil feed steel piston according to claim 2, wherein the axial depth Hx and the radial depth Lx of the gap (400), the length Dx of the gap (400) and the arc radius Rx of the arc transition parts at the two ends of the gap (400); the axial depth Hx of the notch (400) is matched with the height of the welding flash, a structure is formed, wherein the radial direction can reduce or prevent the welding flash from shielding the oil inlet and outlet hole (202), and the axial depth Hx of the notch (400) is smaller than or equal to half of the width of the welding face (300); the length Dx of the notch (400) is matched with the diameter of the oil inlet and outlet, so that a structure that welding flash can be reduced or avoided from shielding the oil inlet and outlet (202) in the axial direction is formed.
4. A small diameter high oil filled steel piston according to claim 2, wherein said slits (400) are provided at the weld face where said piston head (100) and/or piston skirt (200) are joined, respectively.
5. The small-diameter high oil feed steel piston according to claim 1, wherein the welding face portion (300) comprises a first welding portion (301) located at the outer ring and a second welding portion (302) located at the inner ring, the second welding portion (302) extends obliquely upward from the edge of the combustion chamber and forms a lower space of the cooling oil channel (201) around the first welding portion (301), a friction welding face for friction welding is provided at the end portion of the second welding portion (302), and an oblique included angle is formed between the friction welding face and a horizontal plane.
6. The method for preparing the small-diameter high-oil-intake steel piston according to any one of claims 2 to 5, which is characterized in that:
raw materials are taken for heating forging to form blanks of the piston head (100) and the piston skirt (200), the heating temperature is 1200-1240 ℃, and the forging ratio is 1:10-1:6;
Rough machining is carried out on the piston head (100) and the skirt forging, the welding face (300) is formed, the notch (400) is formed on the welding face (300), the axial depth Hx and the radial depth Lx of the notch (400), the length Dx of the notch (400) and the arc radius Rx of the arc transition parts at the two ends of the notch (400) are formed; the axial depth Hx of the notch (400) is matched with the height of the welding flash, a structure is formed, wherein the radial direction can reduce or prevent the welding flash from shielding the oil inlet and outlet hole (202), and the axial depth Hx of the notch (400) is smaller than or equal to half of the width of the welding face (300); the length Dx of the notch (400) is matched with the diameter of the oil inlet and outlet, so that a structure that welding flash can be reduced or avoided from shielding the oil inlet and outlet (202) in the axial direction is formed;
the piston head (100) and the piston skirt (200) are friction welded to form a fixedly connected integral structure;
carrying out heat treatment, carrying out integral isothermal quenching and low-temperature tempering after friction welding, wherein the hardness is 250-300HBW, the tensile strength is more than or equal to 1000Mpa, and the yield strength is more than or equal to 600Mpa;
Finish machining, namely finishing the heat-treated workpiece according to the requirements of structure, size and precision;
Machining an oil inlet and outlet hole (202), wherein the oil inlet and outlet hole (202) communicated with the cooling oil channel (201) is formed in the position, opposite to the opening (400);
And (3) phosphating and nano-coating treatment, wherein the workpiece is subjected to phosphating and nano-coating treatment according to technical requirements after the processing is finished, so that the small-diameter high-oil-inlet steel piston is manufactured.
7. The method for manufacturing the small-diameter high-oil-intake steel piston according to claim 6, wherein the friction welding adopts a second-order friction welding process, a piston head (100) and a skirt are assembled into a tool and clamped, the piston head (100) is not moved, and the piston skirt (200) and a sliding table are separated by about (3) mm after being close to the head at a certain speed and collision; the piston head (100) and the flywheel are accelerated to a set rotating speed, and then the driving source is disconnected; the piston skirt (200) is contacted with the head under the preset first-order pressure and rubs to generate heat, so that the temperature of the piston head (100) and the skirt welding surface (300) reaches about 1200 ℃; the rotating speed of the flywheel is reduced to 0, and the height of the piston is reduced to 3.5+/-0.4 mm; and then applying a second stage of preset pressure to perform upsetting, maintaining the pressure for 3-8 seconds, then reducing the pressure to 0, and loosening the clamp and removing the piston to finish welding.
8. The method for manufacturing a small-diameter high-oil-intake steel piston according to claim 6, wherein the forged blanks of the piston head (100) and the piston skirt (200) are cooled, shot-blasted three times, and subjected to flaw detection to remove unqualified blanks.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410570962.4A CN118218745A (en) | 2024-05-09 | 2024-05-09 | Alloy steel, small-diameter high-oil-intake steel piston and preparation method of friction welding small-diameter high-oil-intake steel piston |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202410570962.4A CN118218745A (en) | 2024-05-09 | 2024-05-09 | Alloy steel, small-diameter high-oil-intake steel piston and preparation method of friction welding small-diameter high-oil-intake steel piston |
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| CN118218745A true CN118218745A (en) | 2024-06-21 |
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