CN102492918B - Piston rod and production method thereof as well as carbonitriding agent for piston rod surface treatment - Google Patents
Piston rod and production method thereof as well as carbonitriding agent for piston rod surface treatment Download PDFInfo
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Abstract
The invention relates to a piston rod and a production method thereof as well as a carbonitriding agent for piston rod surface treatment. The carbonitriding agent comprises the following components by weight percent: 20-24% of urea, 13-15% of thiourea, 10-14% of barium acetate, 24-27% of calcium carbonate, 22-26% of barium carbonate and 4-10% of lithium carbonate. The carbonitriding layer tissue comprises an oxide layer, a tectorium, a compound layer, an Austria layer and a diffusion layer. The carbonitriding agent has the beneficial effects of simple formula and low cost; the piston rod produced by using the carbonitriding agent is smooth in surface, low in roughness and is airproof, the piston rod compound carbonitriding layer is more than 32mu m in thickness and has the characteristics of high corrosion resistance and abrasion resistance, low rejection ratio and long service life; in the piston rod production process, thermal treatment and anti-corrosion treatment are completed once, treatment temperature is between 600 DEG C-700 DEG C, the piston rod production process has the advantage of optimizing the machining process; and nitriding time is shortened to 30-50 minutes, production period is shortened, and production cost is reduced.
Description
Technical field
The present invention relates to carbonitriding medium and the production method thereof of piston rod, piston rod surface processing.
Background technology
Existing piston rod surface heat treatment nitrogen metallization processes mainly adopts the method for nitrogenize, can be divided into gas soft nitriding, liquid tufftriding and solid tufftride and ion nitriding, production efficiency is low, power consumption is large because the solid nitrogenize exists, environmental pollution is large, the nitriding quality is unstable, be difficult to form batch production etc., eliminated by people gradually.
Gas nitriding is used also more extensive, the major advantage surface quality is controlled easily, simple to operate, be widely used, but the production cycle is long, production efficiency is low, corrosion resisting property poor (neutral salt spray test reaches 96 hours), the deadly defect of the method for present domestic gas nitrocarburizing is exactly that gaseous constituent can not strictly be controlled, therefore quality layer is stable not, and high for common salt bath nitrocarburizing solidity to corrosion, neutral salt spray test reached more than 144 hours, and deep layer salt bath nitrocarburizing neutral salt spray test reached more than 200 hours, and this is that other thermal treatment institutes are inaccessiable.
The liquid salt bath tufftride becomes the maximum processing mode of present use, the nitriding temperature that the salt bath liquid tufftriding uses is below 580 ℃, the compound layer degree of depth is 12-22 μ m, want to make the compound layer degree of depth of piston rod to reach more than the 32 μ m, only with regard to the compound layer degree of depth of deepening the nitrogenize operation, the most direct way is exactly to improve the temperature of nitridation salt, because in the temperature nitriding below 600 ℃, the compound layer degree of depth is difficult to reach more than the 32 μ m, adopt 570-580 ℃ nitriding method, prolongation nitridation time that can only be long, but will increase the degree of depth of tectorium, and can not effectively increase the compound layer degree of depth, prolong the surface hardness that nitridation time simultaneously also can the decrease piston rod.For example: nitriding temperature is 580 ℃, and nitridation time 90 minutes, infiltration layer are 14 μ m, and tectorium is 4 μ m, surface hardness 478kg/mm
2For this reason, deepen the compound layer degree of depth and just must change salt bath formula, improve infiltration rate, improve nitriding temperature, shorten nitridation time, improve nitrogen-atoms and the velocity of diffusion of carbon atom in steel, just can accelerate the formation of compound layer, thereby form darker compound layer, and tectorium is remained in the specialized range.
The method that nitriding temperature is brought up to more than 600 ℃ also is a newer problem in metal field, the carbonitriding regional temperature of common iron and steel is at 500-600 ℃, and the temperature in carbonitriding zone is the technique clear area that steel material surface is processed in 600-700 ℃ of interval.
The fusing point of present existing surface treatment carbonitriding medium is low, and use temperature is usually below 580 ℃, when use temperature surpasses 600 ℃, will very fast volatilization, and be difficult to keep the stability of cyanate radical, therefore must the new carbonitriding agent prescription of exploitation.
General surface is processed carbonitriding at present, nitriding temperature is controlled at 560-580 ℃, nitridation time was at 60-120 minute, infiltration layer is 12-22 μ m, the surface Vickers' hardness is 430-500, owing to be subjected to middle thermohaline to bathe the restriction of composition, if improve nitriding temperature, infiltration layer is difficult to reach more than the 30 μ m, salt temperature is too high, and nitrogen-atoms and carbon atom motion are accelerated, and the formation speed of infiltration layer is too fast, the salt bath volatilization is too fast, accelerate the aging of salt bath, activated nitrogen atom and carbon atom can not in time be absorbed by piece surface, and then unabsorbed activated nitrogen atom and carbon atom may be converted into inactive substance and be deposited in piece surface, form carbon black, hinder the absorption process of other activated nitrogen atom and carbon atom, piston rod produces surface imperfection easily like this, causes the thickening of piston rod tectorium, surface hardness is low, and wear resistance and erosion resistance are poor.
Summary of the invention
The object of the present invention is to provide and a kind ofly can under 600-700 ℃ of temperature, carry out the novel carbonitriding medium of piston rod deep layer salt bath nitrocarburizing, and provide and use this carbonitriding medium to carry out surface-treated piston rod and production method thereof.
Technical scheme of the present invention is:
The carbonitriding medium that a kind of piston rod surface is processed is characterized in that carbonitriding medium component and content (weight percentage) are as follows:
Urea CO (NH
2)
2: 20～24%
Thiocarbamide: 13～15%
Barium acetate Ba (CH
3COO)
2: 10～14%
Calcium carbonate CaCO
3: 24～27%
Barium carbonate BaCO
3: 22～26%
Quilonum Retard Li
2CO
3: 4～10%.
The Main Function of barium carbonate, calcium carbonate, barium acetate Quilonum Retard provides salt bath nitrogen, carbon and oozes altogether needed carbon atom, and urea, thiocarbamide provide salt bath nitrogen, carbon to ooze altogether needed nitrogen carbon atom, can accelerate the salt bath speed of response simultaneously, and reaction principle is as follows:
Chemical reaction at high temperature occurs: CO (NH
2)
2+ Ba
2CO
3→ Ba (CNO)
2+ CO
2+ H
2O, generation contains the material of cyanate radical (CNO-), CNO-at high temperature decomposes, reaction produces nitrogen-atoms and the carbon atom that activity is high, infiltration capacity is strong, activated nitrogen atom, carbon atom are absorbed at workpiece surface, form sosoloid or compound, after nitrogen, the carbon concentration of workpiece surface reach certain value, the low concentration region diffusion from the high concentration region on surface to nexine of nitrogen, carbon atom.After piston rod immerses in the nitrogenize salt bath, N, C atom that the decomposition of CNO-produces form high N gesture and C gesture at workpiece surface, because the N atomic radius only is half of iron atom, and the C atomic radius is less, so N, C atom can spread in the dot matrix gap of iron.
Concrete decomposed form:
4CNO-→CO
3 -2+2CN-+CO+2[N]
3Fe+[N]→Fe
3N
4Fe+[N]→Fe
4N
The CN-that generates simultaneously generates again CNO-after oxygen is combined, CNO-decomposes the CO that produces, and then decomposites C atom infiltration workpiece, forms carbide or sosoloid.
2CO→CO
2+C
3Fe+C→Fe
3C
Piston rod in salt bath combined heat treatment process, along with the continuous infiltration of N, C element, reach finite concentration after, formed tight zone---the compound layer (Fe of high rigidity
2-3CN).
Use carbonitriding medium of the present invention to carry out the surface-treated piston rod, the diffusion layer organization of its carbonitriding comprises oxide skin, tectorium, compound layer, austenite case and diffusion layer from outside to inside; Described oxide skin is the oxide compound of iron, and thickness is 2-5 μ m; Described tectorium and compound layer comprise Fe
2-3CN and Fe
4N, thickness are respectively 2-5 μ m and 32-50 μ m; Described austenite case is the carbonitriding thing Fe of iron
2-3CN, thickness are 8-15 μ m; Described diffusion layer is the sosoloid Fe of nitrogen in iron
4N has very large effect to the fatigue strength that improves piston rod, and thickness is 200-300 μ m.
The oxide compound of described iron is Fe
2O
3, Fe
3O
4At least a.
Oxide skin is the oxide compound of iron at the outermost layer of piston rod, and it has very high erosion resistance, matches with compound layer to form high solidity to corrosion, and it also has certain effect to wear resistance and the reduction frictional coefficient that improves piston rod surface simultaneously.
Compound layer is the most important diffusion layer organization of deep layer heat treatment technics, is that the deep layer heat treatment technics improves piston rod surface wear resistance and corrosion proof key point, and therefore forming dark densification compound layer is the purpose that the deep layer heat treatment technics is asked most.Compound layer is mainly by Fe
2-3CN wherein contains the Fe of some amount
4N.
Austenite case is the exclusive a kind of diffusion layer organization of deep layer thermal treatment carbonitriding, austenite case is a kind of tissue in the middle of compound layer and the diffusion layer, the sosoloid of nitrogen in iron, because the content of nitrogen is not enough to form compound layer, only can form nitrogenous sosoloid, austenite case only can exist in tissue more than 590 ℃.
Diffusion layer is with interior this zone to piston rod matrix core structure at austenite case, it is the sosoloid of nitrogen in iron, but its content is low, be not enough to form austenite structure, by austenite case edge to piston rod matrix heart section zone, because nitrogen content reduces gradually, its hardness also reduces gradually, consistent in heart section matrix at last, diffusion layer helps not quite wear resistance and the solidity to corrosion that improves piston rod, but the fatigue strength that improves piston rod is had very large effect.
The present invention also provides and has used carbonitriding medium of the present invention to carry out the production method of surface-treated piston rod, its algorithm comprises cleaning, pre-heating drying, nitrogenize, oxidation, cooling immersion, oven dry and polishing, described nitriding step is: nitrogenize is carried out at twice, the temperature of for the first time nitrogenize is 670-685 ℃, nitridation time is 10-20 minute, the temperature of for the second time nitrogenize is 665-675 ℃, and nitridation time is 20-30 minute.
Adopt deep layer surface treatment prescription, what at first will control is that the fusing point of salt bath composition can not be too low, and the cyanate radical in the salt bath (CNO) is controlled at 24-30%, for the degree of depth that guarantees infiltration layer and the quality of infiltration layer, from following two aspects:
1) improves the thermal treatment salt temperature
The spread coefficient of material and temperature are exponential relationship and increase, and namely improve temperature and can effectively improve the velocity of diffusion of Process of Chemical Thermal Treatment Atom in solid.Yet the raising of temperature is limited; because the selection of technological temperature at first will be satisfied the ability to bear of specification of quality and the equipment of product; for example; during the piston rod carbonitriding, temperature is high, and carburizing time is long in addition; the crystal grain of piston rod metal can be thick; make fragility or the carburizing postheat treatment complex process of piston rod, and in too high oozing altogether under the temperature, also can reduce the work-ing life of carburizing equipment.
2) adopt new technology
Adopt new technology, adopt activity and the technological temperature of segmentation control penetration enhancer, namely in the fs of thermo-chemical treatment, adopt highly active salt bath and higher technological temperature, improve concentration and the concentration gradient of infiltrating element and infiltration layer; Thereafter subordinate phase, stable salt bath process temperature, and salt bath active (CNO concentration) is reduced to the concentration of piston rod infiltration layer requirement, realize oozing by force high density gradient and the high velocity of diffusion that the stage infiltration layer has, to realize accelerating Process of Chemical Thermal Treatment, can guarantee again simultaneously that infiltration layer infiltrates concentration of element and meets the requirements, so both shorten nitridation time, guarantee again the quality of infiltration layer.
The purpose Main Function of piston rod twice of nitrogenize in the deep layer salt bath: piston rod enters first first nitriding furnace, salt temperature descends, when piston rod temperature and salt temperature balance, enter again second nitriding furnace, first nitriding furnace mainly works to improve the piston rod temperature, and second nitriding furnace mainly works to infiltrate the nitrogen carbon atom.
Preferably, described cleaning step is: the piston rod that preliminary working is finished is put into Ultrasonic Cleaners and was cleaned 10-50 minute under 40-50 ℃ condition, then uses flushing with clean water, to remove the cutting impurity of piston rod surface;
Preferably, described preliminary working step is:
A, cut-out: piston rod is cut off by fixed length;
B, annealing: eliminate piston rod stress;
C, alignment: satisfy the requirement of piston rod linearity;
D, corase grind: remove the impurity such as piston rod surface iron rust;
E, high-frequency quenching: increase piston rod surface hardness;
F, tempering alignment: satisfy the requirement of piston rod linearity;
G, grinding: so that the external diameter of piston rod reaches fixed size.
Preferably, described pre-heating drying step is: will clean complete piston rod and place dryer under 350-400 ℃ condition, to heat 10-50 minute, and with the moisture of removal piston rod surface, and the temperature of increase piston rod.
Preferably, described oxidation step is: the piston rod that nitrogenize is finished places oxidation pond to carry out oxidation 20-60 minute, and the temperature of oxidation pond remains on 375-385 ℃.
Preferably, described cooling soaking step is: the piston rod stomach that oxidation is complete cools off in clear water and soaked 30-120 minute, in order to the temperature of cooling piston bar, and the salinity of decomposition piston rod surface.
Beneficial effect of the present invention is:
1) the carbonitriding agent prescription is simple, with low cost, and the CNO concentration stabilize in the salt bath is at 30-34%, and the cyanate radical in the salt bath (CNO) per hour consumes and is 0.05-0.1%.
2) piston rod surface that uses this carbonitriding medium to produce is level and smooth, roughness is low, air tight, piston rod compound infiltration layer reaches more than the 32 μ m, erosion resistance, corrosion resistance nature reached more than 280 hours, wear resistance is high, low, the long service life of scrap rate is on tensile testing machine continuously elongated 6 * 10
6Inferior, the piston rod surface oxide film does not come off.
3) in the piston rod production process thermal treatment and anti-corrosive treatment are once finished, treatment temp is at 600-700 ℃, along with being multiplied of nitrogenize layer depth, wear resistance also is multiplied, compound layer hardness through overaging is increased to 700HV by 500HV, therefore wear resistance also can be multiplied, can improve simultaneously piece surface hardness, wear resistance, corrosion stability and fatigue strength, reduce frictional coefficient, be out of shape little, nuisanceless, and reduced the fragility of piston rod, obviously enlarged the material ranges that adapts to carbonitriding, i.e. the processing of various materials all has good effect, has the advantage of optimizing machining technology operation.
4) nitridation time foreshortens to 30-50 minute, shortens the production cycle, reduces production costs.
Description of drawings
Fig. 1 is the synoptic diagram of the diffusion layer organization of piston rod carbonitriding.
Fig. 2 is the metallograph of embodiment 1.
Fig. 3 is the metallograph of embodiment 2.
Fig. 4 is the metallograph of embodiment 3.
Embodiment
The following describes specific embodiments of the invention:
Specific embodiment 1:
The carbonitriding medium that a kind of piston rod surface is processed, composition is as follows:
Urea: 20%, thiocarbamide: 13%, barium acetate: 12%, calcium carbonate: 24%, barium carbonate: 22%, Quilonum Retard: 9%;
A kind of production method of using this carbonitriding medium to carry out the surface-treated piston rod comprises the steps:
(1) piston rod preliminary working
A, cut-out: piston rod is cut off by fixed length;
B, annealing: eliminate piston rod stress;
C, alignment: satisfy the requirement of piston rod linearity;
D, corase grind: remove the impurity such as piston rod surface iron rust;
E, high-frequency quenching: increase piston rod surface hardness;
F, tempering alignment: satisfy the requirement of piston rod linearity;
G, grinding: so that the external diameter of piston rod reaches fixed size;
(2) piston rod surface thermal treatment
A, cleaning: the piston rod that preliminary working is finished is put into Ultrasonic Cleaners and was cleaned 10 minutes under 40-50 ℃ condition, then uses flushing with clean water, to remove the cutting impurity of piston rod surface;
B, pre-heating drying: will clean complete piston rod and place dryer under 350-400 ℃ condition, to heat 10 minutes, with the moisture of removal piston rod surface, and the temperature of increase piston rod;
C, nitrogenize: nitrogenize is carried out at twice, the piston rod of oven dry is placed first nitriding furnace that fills carbonitriding medium, the temperature in nitrogenize pond is 670-685 ℃, nitrogenize 20 minutes, then piston rod enters second nitriding furnace again, the temperature in nitrogenize pond remains on 665-675 ℃, and nitridation time is 25 minutes;
D, oxidation: the piston rod that nitrogenize is finished places oxidation pond to carry out oxidation 20 minutes, and the temperature of oxidation pond remains on 375-385 ℃; Wherein, the composition of oxygenant is as follows: sodium hydroxide: 25%, and potassium hydroxide: 12%, SODIUMNITRATE: 63%;
E, cooling are soaked: the piston rod stomach that oxidation is complete cools off in clear water and soaked 80 minutes, in order to the temperature of cooling piston bar, and the salinity of decomposition piston rod surface;
F, cleaning, oven dry, polishing.
Embodiment 1 metallograph is seen Fig. 2, magnification 200 (doubly), and product performance index is:
1) piston rod diffusion layer organization thickness: oxide skin thickness: 4 μ m, tectorium thickness 3 μ m, compound layer thickness: 32 μ m, austenite case thickness: 9 μ m, thickness of diffusion layer: 260 μ m;
2) solidity to corrosion of piston rod: carry out neutral salt spray test at 285 hours non-corrosives according to the GB/T10125-1997 standard;
3) surfaceness of piston rod: 0.06 μ m, 0.07 μ m, 0.08 μ m, 0.07 μ m, 0.06 μ m;
4) the surperficial Vickers' hardness of piston rod: 654,635,643,642,650, unit is kg/mm
2
Specific embodiment 2:
The carbonitriding medium that a kind of piston rod surface is processed, composition is as follows:
Urea: 22%, thiocarbamide: 14%, barium acetate: 12%, calcium carbonate: 25%, barium carbonate: 23%, Quilonum Retard: 4%;
A kind of production method of using this carbonitriding medium to carry out the surface-treated piston rod comprises the steps:
(1) piston rod preliminary working
A, cut-out: piston rod is cut off by fixed length;
B, annealing: eliminate piston rod stress;
C, alignment: satisfy the requirement of piston rod linearity;
D, corase grind: remove the impurity such as piston rod surface iron rust;
E, high-frequency quenching: increase piston rod surface hardness;
F, tempering alignment: satisfy the requirement of piston rod linearity;
G, grinding: so that the external diameter of piston rod reaches fixed size;
(2) piston rod surface thermal treatment
A, cleaning: the piston rod that preliminary working is finished is put into Ultrasonic Cleaners and was cleaned 10 minutes under 50 ℃ condition, then uses flushing with clean water, to remove the cutting impurity of piston rod surface;
B, pre-heating drying: will clean complete piston rod and place dryer under 350-400 ℃ condition, to heat 10 minutes, with the moisture of removal piston rod surface, and the temperature of increase piston rod;
C, nitrogenize: nitrogenize is carried out at twice, the piston rod of oven dry is placed first nitriding furnace that fills carbonitriding medium, the temperature in nitrogenize pond is 670-685 ℃, nitrogenize 10 minutes, then piston rod enters second nitriding furnace again, the temperature in nitrogenize pond remains on 665-675 ℃, and nitridation time is 20 minutes;
D, oxidation: the piston rod that nitrogenize is finished places oxidation pond to carry out oxidation 20 minutes, and the temperature of oxidation pond remains on 375-385 ℃; Wherein, the composition of oxygenant is as follows: sodium hydroxide; 30%, potassium hydroxide: 18%, SODIUMNITRATE: 52%;
E, cooling are soaked: the piston rod that oxidation is complete places the clear water cooling to soak 80 minutes, in order to the temperature of cooling piston bar, and the salinity of decomposition piston rod surface;
F, cleaning, oven dry, polishing.
Embodiment 2 piston rod metallographs are seen Fig. 3, magnification 200 (doubly), and product performance index is:
1) piston rod diffusion layer organization thickness: oxide skin thickness: 5 μ m, tectorium thickness: 4 μ m, compound layer thickness: 33 μ m, austenite case thickness: 10 μ m, thickness of diffusion layer: 280 μ m;
2) solidity to corrosion of piston rod: carry out neutral salt spray test at 290 hours non-corrosives according to the GB/T10125-1997 standard;
3) surfaceness of piston rod: 0.08 μ m, 0.08 μ m, 0.07 μ m, 0.07 μ m, 0.07 μ m;
4) the surperficial Vickers' hardness of piston rod: 651,628,659,641,635, unit is kg/mm
2
Specific embodiment 3:
The carbonitriding medium that a kind of piston rod surface is processed, composition is as follows:
Urea: 20%, thiocarbamide: 15%, barium acetate: 12%, calcium carbonate: 25%, barium carbonate: 22%, Quilonum Retard 6%;
A kind of production method of using this carbonitriding medium to carry out the surface-treated piston rod comprises the steps:
(1) piston rod preliminary working
A, cut-out: piston rod is cut off by fixed length;
B, annealing: eliminate piston rod stress;
C, alignment: satisfy the requirement of piston rod linearity;
D, corase grind: remove the impurity such as piston rod surface iron rust;
E, high-frequency quenching: increase piston rod surface hardness;
F, tempering alignment: satisfy the requirement of piston rod linearity;
G, grinding: so that the external diameter of piston rod reaches fixed size;
(2) piston rod surface thermal treatment
A, cleaning: the piston rod that preliminary working is finished is put into Ultrasonic Cleaners and was cleaned 10 minutes under 50 ℃ condition, then uses flushing with clean water, to remove the cutting impurity of piston rod surface;
B, pre-heating drying: will clean complete piston rod and place dryer under 350-400 ℃ condition, to heat 10 minutes, with the moisture of removal piston rod surface, and the temperature of increase piston rod;
C, nitrogenize: nitrogenize is carried out at twice, the piston rod of oven dry is placed first nitriding furnace that fills carbonitriding medium, the temperature in nitrogenize pond is 670-685 ℃, nitrogenize 20 minutes, then piston rod enters second nitriding furnace again, the temperature in nitrogenize pond remains on 665-675 ℃, and nitridation time is 20 minutes;
D, oxidation: the piston rod that nitrogenize is finished places oxidation pond to carry out oxidation 20 minutes, and the temperature of oxidized still remains on 375-385 ℃; Wherein, the composition of oxygenant is as follows: sodium hydroxide: 27%; Potassium hydroxide: 15%; SODIUMNITRATE: 58%;
E, cooling are soaked: the piston rod that oxidation is complete places the clear water cooling to soak 80 minutes, in order to the temperature of cooling piston bar, and the salinity of decomposition piston rod surface;
Clean, dry, polish.
The metallographic structure picture of embodiment 3 is seen Fig. 4, magnification 200 (doubly), and product performance index is:
1) piston rod diffusion layer organization thickness: oxide skin thickness: 5 μ m, tectorium thickness 5 μ m, compound layer thickness: 33 μ m, austenite case thickness: 8 μ m, thickness of diffusion layer: 240 μ m;
2) solidity to corrosion of piston rod: carry out neutral salt spray test at 290 hours non-corrosives according to the GB/T10125-1997 standard;
3) surfaceness of piston rod: 0.07 μ m, 0.08 μ m, 0.08 μ m, 0.06 μ m, 0.08 μ m;
4) the surperficial Vickers' hardness of piston rod: 649,633,620,630,625, unit is kg/mm
2
The product performance index of three embodiment is listed as follows:
Solidity to corrosion and the common salt bath heat treated solidity to corrosion contrast of piston rod after the thermal treatment of deep layer salt bath is as follows:
Above experimental data explanation, the solidity to corrosion of the piston rod of deep level of processing is 2.26 times that common salt bath is processed piston rod.
Tension test and the tension test of the common salt bath thermal treatment piston rod contrast of piston rod after the thermal treatment of deep layer salt bath is as follows:
Above experimental data explanation, the yield strength of deep layer surface-treated piston rod, tensile strength and elongation index all are better than the index that general surface is processed piston rod.
Claims (4)
1. the carbonitriding salt medium processed of a piston rod surface is characterized in that carbonitriding salt medium component and content (weight percentage) are as follows:
Urea CO (NH
2)
2: 20～24%
Thiocarbamide: 13～15%
Barium acetate Ba (CH
3COO)
2: 10～14%
Calcium carbonate CaCO
3: 24～27%
Barium carbonate BaCO
3: 22～26%
Quilonum Retard Li
2CO
3: 4～10%.
2. one kind is used carbonitriding salt medium as claimed in claim 1 to carry out the surface-treated piston rod, it is characterized in that the diffusion layer organization of piston rod comprises oxide skin, tectorium, compound layer, austenite case and diffusion layer from outside to inside; Described oxide skin is the oxide compound of iron, and thickness is 2-5 μ m; Described tectorium and compound layer comprise Fe
2-3CN and Fe
4N, thickness are respectively 2-5 μ m and 32-50 μ m; Described austenite case is the carbonitriding thing Fe of iron
2-3CN, thickness are 8-15 μ m; Described diffusion layer is the sosoloid Fe of nitrogen in iron
4N has very large effect to the fatigue strength that improves piston rod, and thickness is 200-300 μ m.
3. piston rod as claimed in claim 2 is characterized in that, the oxide compound of described iron is Fe
2O
3, Fe
3O
4At least a.
4. production method of using carbonitriding salt medium as claimed in claim 1 to carry out the surface-treated piston rod, its algorithm comprises cleaning, pre-heating drying, nitrogenize, oxidation, cooling immersion, oven dry and polishing, described nitriding step is: nitrogenize is carried out at twice, the temperature of for the first time nitrogenize is 670-685 ℃, nitridation time is 10-20 minute, the temperature of for the second time nitrogenize is 665-675 ℃, and nitridation time is 20-30 minute;
Described cleaning step is: the piston rod that preliminary working is finished is put into Ultrasonic Cleaners and was cleaned 10-50 minute under 40-50 ℃ condition, then uses flushing with clean water, to remove the cutting impurity of piston rod surface;
The preliminary working step is:
A, cut-out: piston rod is cut off by fixed length;
B, annealing: eliminate piston rod stress;
C, alignment: satisfy the requirement of piston rod linearity;
D, corase grind: remove the impurity such as piston rod surface iron rust;
E, high-frequency quenching: increase piston rod surface hardness;
F, tempering alignment: satisfy the requirement of piston rod linearity;
G, grinding: so that the external diameter of piston rod reaches fixed size;
Described pre-heating drying step is: will clean complete piston rod and place dryer under 350-400 ℃ condition, to heat 10-50 minute, and with the moisture of removal piston rod surface, and the temperature of increase piston rod;
Described oxidation step is: the piston rod that nitrogenize is finished places oxidation pond to carry out oxidation 20-60 minute, and the temperature of oxidation pond remains on 375-385 ℃;
Described cooling soaking step is: the piston rod that oxidation is complete places the clear water cooling to soak 30-120 minute, in order to the temperature of cooling piston bar, and the salinity of decomposition piston rod surface.
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| CN103981482B (en) * | 2014-05-05 | 2016-08-24 | 福建省南平铝业股份有限公司 | A kind of the Aluminum-Extruding Die surface toughening processes technique |
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| CN101580926A (en) * | 2009-07-06 | 2009-11-18 | 青岛张氏机械有限公司 | Salt-bath heat treatment technology of piston rod |
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