CN114769598B - Copper-infiltration sintering method for valve guide pipe - Google Patents
Copper-infiltration sintering method for valve guide pipe Download PDFInfo
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- CN114769598B CN114769598B CN202210483180.8A CN202210483180A CN114769598B CN 114769598 B CN114769598 B CN 114769598B CN 202210483180 A CN202210483180 A CN 202210483180A CN 114769598 B CN114769598 B CN 114769598B
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- 238000005245 sintering Methods 0.000 title claims abstract description 75
- 238000001764 infiltration Methods 0.000 title claims abstract description 55
- 238000000034 method Methods 0.000 title claims abstract description 41
- 239000010949 copper Substances 0.000 claims abstract description 154
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 claims abstract description 148
- 229910052802 copper Inorganic materials 0.000 claims abstract description 148
- 230000008595 infiltration Effects 0.000 claims abstract description 53
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 17
- 239000000203 mixture Substances 0.000 claims abstract description 9
- 230000001681 protective effect Effects 0.000 claims abstract description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 4
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 4
- 239000001257 hydrogen Substances 0.000 claims abstract description 4
- 238000002386 leaching Methods 0.000 claims abstract description 4
- 229910052799 carbon Inorganic materials 0.000 claims description 45
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 44
- 239000000463 material Substances 0.000 claims description 17
- 230000002093 peripheral effect Effects 0.000 claims description 9
- 238000003825 pressing Methods 0.000 claims description 7
- 238000005496 tempering Methods 0.000 claims description 7
- 238000002844 melting Methods 0.000 claims description 4
- 230000008018 melting Effects 0.000 claims description 4
- 239000000843 powder Substances 0.000 claims description 4
- 238000010438 heat treatment Methods 0.000 claims description 3
- 230000008569 process Effects 0.000 description 20
- 239000007788 liquid Substances 0.000 description 16
- 238000004519 manufacturing process Methods 0.000 description 13
- 230000000670 limiting effect Effects 0.000 description 12
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 238000004080 punching Methods 0.000 description 7
- 230000009471 action Effects 0.000 description 6
- 239000010410 layer Substances 0.000 description 6
- 230000035515 penetration Effects 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 229910052742 iron Inorganic materials 0.000 description 4
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 239000000047 product Substances 0.000 description 4
- 238000005096 rolling process Methods 0.000 description 4
- 239000000446 fuel Substances 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 238000001816 cooling Methods 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- 239000011261 inert gas Substances 0.000 description 2
- 229910000734 martensite Inorganic materials 0.000 description 2
- 239000003345 natural gas Substances 0.000 description 2
- 229910001080 W alloy Inorganic materials 0.000 description 1
- 229910045601 alloy Inorganic materials 0.000 description 1
- 239000000956 alloy Substances 0.000 description 1
- 229910001566 austenite Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 229910052804 chromium Inorganic materials 0.000 description 1
- 230000009194 climbing Effects 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 238000005238 degreasing Methods 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 230000005484 gravity Effects 0.000 description 1
- 238000007654 immersion Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000002347 injection Methods 0.000 description 1
- 239000007924 injection Substances 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- 239000003915 liquefied petroleum gas Substances 0.000 description 1
- 238000005461 lubrication Methods 0.000 description 1
- 238000003754 machining Methods 0.000 description 1
- 239000011159 matrix material Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 239000000155 melt Substances 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229910052759 nickel Inorganic materials 0.000 description 1
- 239000012466 permeate Substances 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 238000004663 powder metallurgy Methods 0.000 description 1
- 238000002360 preparation method Methods 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000003908 quality control method Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 230000001502 supplementing effect Effects 0.000 description 1
- 230000009466 transformation Effects 0.000 description 1
- 229910052721 tungsten Inorganic materials 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
Classifications
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F5/00—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product
- B22F5/10—Manufacture of workpieces or articles from metallic powder characterised by the special shape of the product of articles with cavities or holes, not otherwise provided for in the preceding subgroups
- B22F5/106—Tube or ring forms
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/02—Compacting only
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/10—Sintering only
- B22F3/1003—Use of special medium during sintering, e.g. sintering aid
- B22F3/1007—Atmosphere
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B22—CASTING; POWDER METALLURGY
- B22F—WORKING METALLIC POWDER; MANUFACTURE OF ARTICLES FROM METALLIC POWDER; MAKING METALLIC POWDER; APPARATUS OR DEVICES SPECIALLY ADAPTED FOR METALLIC POWDER
- B22F3/00—Manufacture of workpieces or articles from metallic powder characterised by the manner of compacting or sintering; Apparatus specially adapted therefor ; Presses and furnaces
- B22F3/24—After-treatment of workpieces or articles
- B22F3/26—Impregnating
-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22C—ALLOYS
- C22C9/00—Alloys based on copper
Abstract
The application provides a valve guide copper infiltration sintering method, which comprises a green compact step (s 1), an assembling step (s 2) and a sintering step (s 3). In the compacting step (s 1), the iron powder mixture is compacted to a density of 6.4 to 7.0g/cm 3 Is provided with a blank of the valve guide (1); in the assembly step (s 2), a copper pillar (2) is placed in a through hole (11) of the blank to form an assembly, the diameter D of the copper pillar (2) satisfying D 2 D.ltoreq.0.1 mm, where D 2 Is the inner diameter of the through hole (11). The mass of the copper column (2) is determined according to the leaching rate of 10% -16%; and (3) in the sintering step (s 3), placing the assembly in a sintering furnace for copper infiltration sintering to obtain a sintered piece, wherein the inside of the sintering furnace is in a hydrogen protective atmosphere. The application can reduce the use of frock, reduce cost, raise the efficiency to better assurance valve guide is led the copper infiltration homogeneity of the fence, guarantees the wear-resisting heat resistance of valve guide even unanimity.
Description
Technical Field
The utility model relates to the technical field of valve guide pipe powder metallurgy sintering, in particular to a valve guide pipe copper infiltration sintering method.
Background
The valve guide pipe is one of key parts of valve actuating mechanism of automobile engine, and it can guide the up-and-down movement of valve and transfer the heat from valve stem to engine cylinder cover. The traditional fuel engine is developing towards the trend of 'low energy consumption, low emission and light weight', and with the popularization of novel engine technologies such as direct injection in a cylinder, lean fuel, turbocharging and the like and the application of clean fuels such as natural gas, LPG, ethanol and the like, the environment temperature in the engine cylinder is higher and higher, the lubrication condition is worse and worse, and great challenges are brought to the thermal conductivity and the wear resistance of a valve guide pipe.
The common iron-based guide pipe mainly uses Fe and C elements, and is added with a small amount of Ni, mo, S and other elements, so that the heat conduction performance is poor, and the density and hardness after sintering are low due to loose and porous matrix materials, so that the heat conduction and wear resistance can not meet the working condition requirements of high temperature, high pressure and Gao Cexiang force of a natural gas engine, a heavy diesel engine and a new technology engine.
If the catheter is subjected to integral copper infiltration, and meanwhile, alloy elements such as Cr, W and the like are added into a catheter base material in a certain proportion, most of pores in the catheter base material are filled with Cu, so that the hardness, density and crushing strength of the catheter can be greatly improved; secondly, the Cu element has excellent heat conductivity, so that the heat conductivity of the catheter can be greatly improved after the whole catheter is infiltrated with copper; thirdly, elements such as Cr W in the catheter base material form Fe-C-Cr-W alloy wear-resistant phase, and the side force applied by the valve stem part can be resisted, so that the physical property, the thermal conductivity and the wear resistance of the catheter are greatly improved, and the catheter becomes a novel valve catheter material with excellent performance.
The patent of publication No. CN212223081U, entitled "device for copper infiltration of valve guide", issued in the year 2020, 12 and 25, discloses a device for copper infiltration treatment using a perforated carbon plate, which comprises a lower carbon plate and an upper carbon plate suspended above the lower carbon plate, wherein the upper surface of the lower carbon plate is provided with lower mounting holes, and the lower surface of the upper carbon plate is provided with upper mounting holes corresponding to the lower mounting holes one by one in the vertical direction. The lower copper sheet is arranged in the lower mounting hole, the upper copper sheet is arranged in the upper mounting hole, and the valve guide pipe is fixed in a mode of mounting the valve guide pipe between the lower mounting hole and the corresponding upper mounting hole, so that the valve guide pipe is prevented from toppling over, and the heat transfer is uniform. Compared with single-end copper infiltration, the device improves the uniformity of copper infiltration, but the climbing distance of copper solution at two ends in a catheter blank is large, the problem of uneven copper infiltration still exists, and particularly the copper infiltration is more serious in the middle section far from the two ends of the valve catheter; according to the device, different punching carbon plates are required to be processed according to the diameter of the valve guide pipe, and the cost of approximately 2000 yuan of a single punching carbon plate is required to be increased; when the device is installed, the valve guide pipes on the same device are required to be aligned with the corresponding installation holes one by one, and under the condition that one valve guide pipe is aligned, other valve guide pipes are ejected out again, so that the operation efficiency is low.
Disclosure of Invention
Because the copper infiltration device using the punching carbon plate to infiltrate copper has the problems of to-be-lifted copper infiltration uniformity, high cost and low efficiency, the technical scheme of the application provides a copper infiltration sintering method of the valve guide pipe.
The copper-infiltrated sintering method of the valve guide pipe comprises a compacting step, an assembling step and a sintering step;
in the compacting step, the iron powder mixture is compacted to a density of 6.4-7.0 g/cm 3 Is provided with a blank of a valve guide;
placing a copper column in the through hole of the blank in the assembling step to form an assembly, wherein the diameter D of the copper column meets D 2 D.ltoreq.0.1 mm, where D 2 Is the inner diameter of the through hole. The mass of the copper column is determined according to the leaching rate of 10% -16%;
and in the sintering step, the assembly is placed in a sintering furnace for copper infiltration sintering to obtain a sintered piece, and the inside of the sintering furnace is in a nitrogen or inert gas protective atmosphere.
Specifically, the copper column comprises the following material components in percentage by weight: 90-97.6% of Cu; 1-3% of Fe; mn 1.2-2.5%; si 0.2-0.9%.
Specifically, the valve guide copper infiltration sintering method further comprises a copper column pressing step, wherein the copper column pressing step comprises the following steps of: 90-97.6% of Cu; 1-3% of Fe; mn 1.2-2.5%; the copper pillars are pressed from a powder mixture of 0.2-0.9% Si.
Specifically, the copper pillars are placed at the midpoint of the through holes in the blank during the step of placing the copper pillars in the through holes to form an assembly.
Specifically, the step of placing the assembly in a sintering furnace for copper infiltration sintering in the sintering step comprises the following steps:
a presintering step of raising the temperature of the sintering furnace to 500-700 ℃ and keeping for 2-3 hours;
and the sintering step is to heat the temperature of the sintering furnace to 1080-1180 ℃ and keep the temperature for 1.5-3 hours.
Specifically, in the sintering step, the assembly is placed on a carbon plate at intervals, and the carbon plate with the assembly placed is placed in the sintering furnace.
Specifically, the valve guide copper infiltration sintering method further comprises a tempering treatment step, wherein the tempering treatment step comprises the following steps:
a cold treatment step of keeping the temperature of the sintered part at-180 to-150 ℃ for 1-1.5 hours;
and (3) placing the sintered part into a heat treatment step of preserving heat for 2-3 hours at the temperature of 600-700 ℃.
According to the copper infiltration sintering method for the valve guide pipe, the copper infiltration agent is manufactured into the copper column which can be plugged into the inner hole of the valve guide pipe, so that copper infiltration of copper infiltration sheets at two ends of the valve guide pipe is avoided, the use of a punching carbon plate is avoided, and the production cost is saved; after the operation mode of plugging the copper column is changed, the assembly can be horizontally placed on the complete carbon plate, the operation of aligning the positioning holes in sequence is not needed, and the production efficiency is improved; after the copper column is plugged, under the proper diameter of the copper column, the molten copper of the copper column is adsorbed on the inner wall of the valve guide pipe along the circumferential direction under the action of surface tension, only the wall thickness distance of the front valve guide pipe is required in the radial direction, only the distance from one end of the copper column to one end of the valve guide pipe which is close to the end is required to advance in the axial direction, compared with the copper-penetrating sheet at two ends, the copper-penetrating sheet is adopted, the flow distance is short, and the copper-penetrating sheet can be horizontally placed, the gravity can not produce an obstructing effect on the copper-penetrating process, is easier to penetrate uniformly, and also because the copper column is placed in the inner hole of the guide pipe to penetrate copper, the leveling process of the copper liquid along the surface of the inner hole firstly occurs, the copper-penetrating effect is generated again, the leveling process can ensure quite good uniformity due to the existence of the surface tension of the copper liquid, and the copper-penetrating distance of the copper-penetrating process is only the wall thickness of the guide pipe, so that the copper-penetrating uniformity can be ensured; and as the starting point of copper infiltration is positioned on the inner wall of the valve guide pipe, the wear resistance and heat transfer performance of the inner wall serving as a working surface can be better ensured.
Drawings
FIG. 1 is a schematic diagram illustrating the operation of a prior art copper infiltration apparatus;
fig. 2 is a schematic view of the valve guide 1 of the present application;
fig. 3 is a schematic view of the copper pillar 2 in section in the through hole 11 of the valve guide 1;
fig. 4 is a schematic illustration of the placement of the valve guide 1 of the present application in the limiting carbon plate 3;
fig. 5 is a flow chart of a valve guide copper infiltration sintering method of the present application.
s1, a green compact step s2, an assembling step s3, a sintering step s4, a copper column pressing step s5, a tempering treatment step 1, a valve guide 2, a copper column 3, a limit carbon plate 11, a through hole, a limit groove 91, an upper carbon plate 92, a lower carbon plate 93, a bottom carbon plate 111, an inner peripheral surface 112 and an outer peripheral surface
Detailed Description
The present utility model will be described in detail below with reference to the drawings and the specific embodiments, and in the present specification, the dimensional proportion of the drawings does not represent the actual dimensional proportion, but only represents the relative positional relationship and connection relationship between the components, and the components with the same names or the same reference numerals represent similar or identical structures, and are limited to the schematic purposes.
In the prior art, as shown in fig. 1, the technical equipment for copper infiltration treatment of the valve guide tube is required to be provided with an upper carbon plate 91 and a lower carbon plate 92, and the upper carbon plate 91 and the lower carbon plate 92 are provided with mounting holes. During copper infiltration treatment, the two ends of the valve guide 1 are placed in the corresponding mounting holes of the upper carbon plate 91 and the lower carbon plate 92, so that on one hand, the position of the valve guide 1 is fixed, the movement and the collision of the valve guide 1 are avoided, and on the other hand, the mounting holes are also used for placing copper infiltration sheets, so that the copper infiltration sheets are in contact with the two end surfaces of the valve guide 1. The copper infiltration method needs at least two punching carbon plates, a bottom plate is additionally arranged in a separate scheme, the material cost of the Shan Zhangtan plate is close to 2000 yuan, the production cost is high, and a large number of valve guide pipes 1 are required to be placed in batches between the same upper carbon plate 91 and the same lower carbon plate 92 in the process device, so that the upper end part of the valve guide pipe 1 is always interfered with the upper carbon plate 91 during placement, and the fact that after the upper end part of one part of the valve guide pipe 1 enters the mounting hole of the upper carbon plate 91, the upper end part of the other part of the valve guide pipe 1 is ejected out of the mounting hole is ensured, so that the assembly process is time-consuming and labor-consuming, and the production efficiency is seriously reduced.
More importantly, because the length-diameter ratio of the valve guide pipe is high, for example, for a valve guide pipe with a certain specification, the outer diameter is 13mm, but the length is 50mm, so that under the condition that copper is permeated from two ends of the valve guide pipe, the permeation distance of copper liquid reaches twice the length of the valve guide pipe, namely about 25mm, and by capillary action under the copper permeation effect, the copper liquid is difficult to drive to flow for a certain distance, and meanwhile, the copper liquid is distributed uniformly, so that the condition of low copper content in the middle of the valve guide pipe can occur, uneven copper permeation is caused, and the middle performance of the valve guide pipe is insufficient.
Therefore, the technical scheme of the application provides a novel valve guide copper infiltration sintering method. The valve guide copper infiltration sintering method comprises a compacting step s1, an assembling step s2 and a sintering step s3. In the compacting step s1, the iron powder mixture is compacted to a density of 6.4 to 7.0g/cm 3 Is provided with a blank of the valve guide 1; in the assembling step s2, the copper pillar 2 is placed in the through hole 11 of the blank to form an assembly; and in the sintering step s3, the assembly is placed in a sintering furnace for copper infiltration and sintering to obtain a sintered piece, and the inside of the sintering furnace is in a hydrogen protective atmosphere.
Wherein the diameter D of the copper pillar 2 in the assembling step s2 satisfies D 2 -d≤0.1mm，D 2 Is the inner diameter of the through hole 11. And the mass of the copper pillar 2 is determined according to the infiltration rate of 10% -16%, wherein the infiltration rate refers to the mass percentage of infiltrated copper in the blank, for example, if 20g of copper is infiltrated in 100g of blank, the infiltration rate is 20%.
Specifically, the present application provides example 1 corresponding to the above-described valve guide copper infiltration sintering method, in which example 1, as shown in fig. 2, the valve guide 1 to be manufactured is required to have dimensions of outer diameter d=13 mm, inner diameter d=6.5 mm, length l=80 mm, and pressed blank density ρ=6.7 g/cm 3 Pressing the blank, wherein the mass M of the blank is as follows:
accordingly, the mass m of the copper pillar 2 calculated as the leaching ratio μ=15% is:
m＝M·μ
＝8g
if the density ρ of the copper pillars 2 is used 2 7.0g/cm 3 (for pressed copper pillars, the press performance is restricted, the density is generally not more than 7.0g/cm 3 ) The diameter d of the copper pillar 2 is 6.4mm, and the required length L of the copper pillar 2 can be obtained 2 The method comprises the following steps:
namely, a copper column 2 with the length of 35mm and the diameter of 6.4mm can be used as copper-infiltrated material to be placed in the inner hole of the valve guide 1. Fig. 3 is a schematic view of the copper pillar 2 in section in the through hole 11 of the valve guide 1. When the assembly shown in fig. 3 is sintered in a sintering furnace with a nitrogen or inert gas blanket, copper is first converted to a liquid state during the temperature increase process, since the melting point of copper is about 1080 c and the melting point of iron is about 1530 c. When copper melts to a liquid state, the blank is still solid, and the melted copper is uniformly adsorbed on the whole circumference of the inner peripheral surface 111 due to the fact that the diameter of the copper column is very close to the diameter of the inner hole of the blank, and extends to two end surfaces of the valve guide 1 along the inner peripheral surface due to the action of surface tension, so that a uniform liquid copper coating layer is finally formed on the inner peripheral surface 111. The liquid copper coating layer diffuses and permeates along the micropores of the blank into the radial direction of the valve guide 1 under the action of the capillary force of the blank of the valve guide 1 until reaching the outer peripheral surface 112. In the whole process, the liquid copper layer can form quite uniform distribution on the inner peripheral surface 111 due to the action of the surface tension of the liquid copper layer, on the basis, the penetration distance of the liquid copper layer is 1/8-1/25 of the length of the valve guide pipe 1, and the wall thickness is generally only 1/8-1/25 of the length of the valve guide pipe 1, and capillary action almost can be considered to be unchanged along the radial direction in the blank of the valve guide pipe 1, so that the penetration process can also ensure uniform penetration very well, and finally, the valve guide pipe finished product with uniform copper element distribution and uniform wear resistance and heat resistance is obtained.
On the basis of this, it is further clear that the copper pillar 2 should be placed at the midpoint of the through hole (11), which is the middle position of the through hole 11, so that the distances between the two end surfaces of the copper pillar 2 and the corresponding end surfaces of the valve guide 1 are equal. Therefore, the distance and time from the melted liquid copper layer to the two end surfaces of the valve guide 1 are basically consistent, and the uniformity of the copper layer is improved, so that the final performance of the finished product is improved.
For the material of the copper pillar 2 for copper infiltration in the above method, cu element should be included first, and furthermore, since iron in the ingot is eroded to some extent during copper infiltration sintering, 1 to 3% of Fe element should be added to the material composition of the copper pillar 2 for supplementing the eroded Fe element in the ingot. The preparation method of the copper column has no special requirement, however, the copper column is generally prone to being pressed by powder mixture as the blank in control of the production process, so that the production condition of a factory can be well utilized, and the production process of the copper column is placed in the control of the factory, thereby being beneficial to quality control and process improvement.
The sintering step in the above sintering step s3 also affects the performance of the valve guide 1 after copper infiltration sintering. The preferred sintering steps in the technical scheme of the application are as follows:
firstly, the sintering furnace temperature is raised to 500-700 ℃ through a presintering step, and is kept for 2-3 hours, and the blank of the valve guide 1 and the copper column 2 are subjected to high-temperature degreasing treatment at the temperature. At this temperature, the fat components entering the billets and copper pillars 2 during powder compaction or during handling are pyrolytically converted into gas and escape along the pores of the compacted material into the shielding gas of the sintering furnace. The influence of residual impurities in the blank and the copper column 2 on the subsequent sintering process is avoided.
And then the sintering temperature is raised to 1080-1180 ℃ through the sintering step, the temperature is kept for 1.5-3 hours, the melting point of pure copper is about 1080 ℃, after the temperature is raised to more than 1080 ℃, the copper column 2 is gradually dissolved into a liquid copper layer in the sintering process, the copper column 2 is uniformly diffused on the inner peripheral surface of the blank of the copper column 2, and then the copper element is uniformly distributed in the inner pores of the blank of the valve guide 1 along the radial direction of the blank of the valve guide 1, so that the performance consistency of the valve guide 1 is improved.
In the sintering process, the assembly needs to be placed in a sintering furnace set to be in a hydrogen protective atmosphere, and in order to avoid the new problems of disordered placement, mutual collision of the assembly and the like, the assembly can be generally and neatly placed on a carbon plate. Preferably, in order to avoid rolling collisions of the assembly on the carbon plate, parallel grooves may also be provided on the carbon plate to limit rolling of the blank of the valve guide 1. The parallel grooves are arranged, namely the material which is supposed to be in the grooves can be removed on the carbon plate, and the parallel stop blocks can be added between the parts which are supposed to be the grooves. Fig. 4 shows a schematic view of the placement of the valve guide 1 in the limiting carbon plate 3 in the above technical solution of the present application, because the existence of the limiting groove 31 on the limiting carbon plate 3 limits the rolling of the valve guide 1 in the direction perpendicular to the limiting groove 31 on the surface of the limiting carbon plate 3, the valve guide 1 is well positioned in the sintering process. It should be noted that, in the drawings, only the solution in which the limiting groove 31 has a rectangular cross section is shown, and in fact, for the limiting effect, it is critical to provide a block for each of two sides of the valve guide 1 in the extending direction perpendicular to the limiting groove 31, so that the valve guide 1 is limited in the limiting groove 31, so it should be understood that the limiting groove 31 only needs to have a ridge line for limiting the rolling of the valve guide 1 on each of two sides thereof, and the specific shape requirement should not be set for the cross section thereof.
In order to improve the performance of the copper-infiltrated sintered product, a tempering treatment step s5 can be further arranged after the sintering step s3. The grains of the sintered part are correspondingly changed through heat treatment of the sintered part, so that the performance of the sintered part is correspondingly improved. Specifically, the tempering step s5 includes:
and (3) a cooling step: after the sintering process is finished, the mixture is rapidly cooled to-180 to-150 ℃ and then kept for 1 to 1.5 hours. The valve guide tube is generally soaked in liquid nitrogen or gasified by low-temperature nitrogen to absorb heat, so that the valve guide tube can complete the transformation from austenite to martensite in the material in the low-temperature environment, and the mechanical properties of the valve guide tube, such as wear resistance, hardness and impact toughness, are improved.
And (3) heat preservation: after the cooling step, the temperature is raised to 600-700 ℃ and kept for 2-3 hours. On one hand, the internal stress of the material in the cryogenic process is eliminated, and on the other hand, the arrangement of carbon atoms in a martensitic array is adjusted, so that the mechanical property of the material is optimized.
In summary, the valve guide 1 sintered by copper infiltration is finally obtained after the production flow in fig. 5, and the sintered part for subsequent oil immersion and machining is obtained. Since the operation of placing the copper pillar 2 in the through hole of the blank of the valve guide 1 is used when combining the blank of the copper pillar 2 with the copper-infiltrated material, the following effects are produced:
firstly, copper infiltration is not needed, so that copper infiltration is not needed to be prepared by pressing, even if the copper pillars still need to be pressed, the number of the copper pillars needed to be used is reduced by half compared with the mode of placing copper infiltration at two ends of a blank, and the production time and the production number are both reduced, so that the production cost is reduced.
Secondly, the punching carbon plates are not needed, and meanwhile, the number of the needed carbon plates is changed from three to one, so that the comprehensive cost of the materials used for the carbon plates and punching is reduced by about 80%, and an effective cost reduction effect is brought.
And thirdly, the production process of copper infiltration operation is simplified, and the production efficiency is improved. The complex combination of a plurality of carbon plates is not needed, the operation of repeatedly placing and aligning the copper seepage sheets is omitted, and the problem that valve guide blanks interfere with the upper carbon plates when the upper perforated carbon plates are placed is not needed to be treated, so that the repeated alignment operation is not needed, and the efficiency of the ornament is improved well.
Fourth, the performance of the sintered part is improved. Since the copper pillars are provided in the through holes of the ingot, the process of uniform leveling of the inner surface and infiltration by capillary force through the micro gaps of the ingot toward the outer surface is performed as described above. The penetration distance is small in the whole process, the penetration process is easy to complete, and the problem of low local copper content caused by insufficient capillary force to overcome penetration resistance due to overlong distance is avoided. The uniformity leveling process ensures the uniformity of the copper liquid on the inner surface, and the radial thickness of the valve guide is generally only 1/8-1/25 of the length of the valve guide, so that the capillary force along the radial direction can be approximately regarded as unchanged, the uniformity of the copper content on the radial thickness can be ensured, the uniformity of the copper content of the final sintered part is very good, and the uniformity of the wear resistance and heat resistance of different areas of the same product is outstanding.
The foregoing is merely illustrative of the preferred embodiments of the present utility model and is not intended to limit the scope of the utility model, and various modifications and improvements made by those skilled in the art to which the utility model pertains will fall within the scope of the utility model as defined by the appended claims without departing from the spirit of the utility model.
Claims (4)
1. The valve guide copper infiltration sintering method comprises a compacting step (s 1), and is characterized by further comprising an assembling step (s 2) and a sintering step (s 3);
in the compacting step (s 1), the iron powder mixture is compacted into a blank of a valve guide pipe (1) with the density of 6.4-7.0 g/cm < 3 >;
placing a copper pillar (2) in a through hole (11) of the blank in the assembling step (s 2) to form an assembly;
in the sintering step (s 3), the assembly is horizontally placed in a sintering furnace for copper infiltration sintering to obtain a sintered piece, wherein the inside of the sintering furnace is in a hydrogen protective atmosphere;
the diameter D of the copper column (2) meets the requirement D 2 D.ltoreq.0.1 mm, where D 2 Is the inner diameter of the through hole (11); the mass of the copper column (2) is determined according to the leaching rate of 10% -16%; the copper column contacts the whole periphery of the inner peripheral surface of the blank after melting during sintering;
the copper column (2) comprises the following material components in percentage by weight: 90-97.6% of Cu; 1-3% of Fe; mn 1.2-2.5%; si 0.2-0.9%;
the step of placing the assembly in a sintering furnace for copper infiltration sintering in the sintering step (s 3) comprises the following steps:
a presintering step of raising the temperature of the sintering furnace to 500-700 ℃ and keeping for 2-3 hours;
the sintering step, the sintering furnace temperature is raised to 1080-1180 ℃ and kept for 1.5-3 hours;
the valve guide copper infiltration sintering method further comprises a tempering treatment step (s 5), wherein the tempering treatment step (s 5) comprises the following steps:
a cold treatment step of keeping the temperature of the sintered part at-180 to-150 ℃ for 1-1.5 hours;
and (3) placing the sintered part into a heat treatment step of preserving heat for 2-3 hours at the temperature of 600-700 ℃.
2. The valve guide copper infiltration sintering method according to claim 1, further comprising a copper pillar pressing step (s 4), wherein the copper pillar (2) pressing step comprises the following steps in percentage by weight: 90-97.6% of Cu; 1-3% of Fe; mn 1.2-2.5%; the copper pillars (2) are pressed from a powder mixture of 0.2-0.9% Si.
3. A valve guide copper infiltration sintering method according to claim 1, characterized in that the copper pillar (2) is placed in the middle point of the through hole (11) in the step of placing the copper pillar (2) in the through hole (11) of the blank to form an assembly.
4. The valve guide copper infiltration sintering method according to claim 1, wherein the assembly is placed on a carbon plate at intervals in the sintering step (s 3), and the carbon plate with the assembly placed is placed in the sintering furnace.
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