Piston-top surface hard anodizing method
Technical field
Piston-top surface hard anodizing method of the present invention relates to engine piston end face hard anodizing technology and device, also relates to the place of the local hard anodizing of other aluminum alloy spare part requirement.
Background technology
During engine operation, piston is subjected to thermal load effect consumingly, and situations such as cracking often appear in piston-top surface, cause premature failure.The alumite for preparing one deck densification at piston-top surface can improve piston life effectively, and increases the efficiency of combustion of combustion gas, compares with differential arc oxidation method, adopts hard anodizing Processing of Preparation alumite, and energy consumption is low, technology is simple, and cost is low.But the alumite of present hard anodizing treatment process preparation is more loose, and hardness and thickness can't meet the demands better.Total institute is known, anode oxide film is made of blocking layer and porous layer, but there is not unified explanation for the Changing Pattern that forms barrier type and multi-hole type two class anode oxide film forms, the process that forms porous anodic alumina films is a complex process that relates to all many-sides such as physics, chemistry and electrochemistry, also is subjected to influences such as electrolytic solution type, anodic oxidation voltage, temperature of reaction simultaneously.At present, dissolving model under critical current density model, volumetric expansion stress model and the electric field support etc. is explained the formation mechanism of porous layer.But no matter the sort of explanation, after all, anodizing of aluminium is thermopositive reaction always, and in film process, when the speed of growth of oxide film oxide growth during greater than its dissolution rate, the oxide film dissolution rate is more little, and then the speed of growth is fast more.This shows, is that chemical dissolution or electric field hydrotropy are all relevant with oxide film heat content or temperature, and heat content is many, and the temperature height will make the meltage of oxide film big, be difficult to obtain thick film, and micropore therebetween becomes big, arranges unordered, the density reduction.Because the capacity of heat transmission of oxide film is much smaller than aluminum substrate, existing aluminium piston hardening oxidation method all can not go out the anodic oxidation reactions thermal conductance effectively, realizes thicker and and the fine and close oxide film of preparation.
Summary of the invention
Piston-top surface hard anodizing method purpose of the present invention provides and a kind ofly prepares high rigidity, thickness and the processing method of fine and close aluminum oxide rete at piston-top surface.The characteristics of piston-top surface hard anodizing method of the present invention are, utilize hard anodizing surface treatment pulse power equipment and compound cooling oxidation unit that piston-top surface is carried out surface treatment, form bigger thermograde at oxide film and aluminium piston interface place along aluminium piston matrix direction, oxidation reaction heat is derived along the aluminium piston direction perpendicular to interface, take out of by circulating cooling liquid again, obtain densification and the aluminum oxide thick film of high rigidity at piston-top surface, compound cooling oxidation unit is made up of oxidation work nest 1 and cooling tank 7, in the bottom of its oxidation work nest 1 rubber seal 4 is housed, rubber seal end cap 5, negative plate 2 and cathode cable 6 are housed in the groove, piston 3 is packed in the rubber seal, the top of piston upwards, oxidized part contacts with circular electrolyte in the oxidation work nest, rubber seal plays sealing and clamping action, with isolation piston oxidized portion and non-oxidized portion, the temperature of circular electrolyte is controlled at 2~4 ℃, piston resiliency supported anode conducting device is housed in the cooling tank 7, by conduction top board 8, spring 9, cable 10, conduction seat 11 and external cable 12 are formed, reliably conduct electricity in hard anode oxidation process with sealing function and the assurance piston of strengthening rubber seal, be connected with non-corrosive circulating cooling liquid in the groove, its temperature is controlled at-3-0 ℃, the heat that makes the generation of top land oxidizing reaction is to the not aluminium piston matrix transmission of aerobicization, with the circulating cooling liquid heat exchange, oxidation reaction heat is taken out of again.
The advantage that adopts above-mentioned piston-top surface hard anodizing method to carry out the processing of piston-top surface hardening oxidation is:
(1) can satisfy the radiating condition of oxide growth, make hot-fluid that oxide film produces to the transmission of piston matrix, and the liquid that is cooled takes away, the dissolving of oxide film reduces in a large number, and the film forming efficiency height is thick and fine and close, can reach 120~150 μ m, and hardness can reach 450~560HV.
(2) bubble that produces in the hardening oxidation process is in time taken out of by mobile electrolytic solution, and undesirable gas stirs or other stirring system, conducting electricity very well of electrolytic solution, oxidation voltage is lower, the current efficiency height has reduced bubble effectively to the film formed disadvantageous effect of oxidation, and oxide film is difficult for ablating, reliable and stable, almost there is not waste product.
(3) can be according to piston different size design oxidation work nest clamping piston, quantity is the amount doesn't matter, is easy to realize the production of mass high-level efficiency hard anodizing.
Description of drawings:
Fig. 1 is that the master of compound cooling oxidation unit looks synoptic diagram.
Fig. 2 is the schematic top plan view of compound cooling oxidation unit.
Fig. 3 is the scanning electronic microscope microscopic appearance (2000 *) of piston-top surface oxide film, and the aluminum oxide unit cell becomes columnar growth, the rete densification perpendicular to piston-top surface.
Embodiment
The present invention further specifies as follows in conjunction with specific embodiments:
Embodiment 1: Ф 105mmZL109 engine piston end face hard anodizing method:
(1) adopt hard anodizing surface treatment power unit, piston 3 is packed into piston-top surface is carried out the hard anodizing surface treatment in the compound cooling oxidation unit, compound cooling oxidation unit is made up of oxidation work nest 1 and cooling tank 7.
(2) negative plate 2 and the cable 6 that connects hard anodizing surface treatment power unit are housed in the oxidation work nest groove in the compound cooling oxidation unit, rubber seal 4 is housed in the hole of bottom land, arrange with matrix-style, sealing-ring 4 clamp piston 1 are made sealing function, isolation piston oxidized portion and non-oxidized portion with rising; Piston resiliency supported anode conducting device is housed in the cooling tank 7, comprises conduction top board 8, spring 9, cable 10 feeds non-corrosive circulating cooling liquid in conduction seat 11 and the external cable 12, groove.
(3) pack into after piston 3 degreasing decontaminations are cleaned in the rubber seal 4 of bottom of oxidation work nest 1, piston-top surface upwards, 40 of the quantity of packing into, the width between centers 150mm of piston space, arranged.The oxidation work nest 1 that piston will be housed according to accompanying drawing 1 places on the cooling tank 7, piston base closely contacts with conduction top board 8 in the piston resiliency supported anode conducting device, feed the sulfuric acid electrolyte of 18wt.% respectively and do not have corrosion neutral circulating cooling liquid in oxidation work nest 1 and cooling tank 7, the temperature of electrolytic solution and circulating cooling liquid is controlled at 1~2 ℃ and-3 ℃ respectively.Connect the hardening oxidation pulse power, oxidation 40~50 minutes at the oxide film of piston-top surface formation one deck densification, is tested respectively with eddy current thickness meter and microhardness tester, and thickness is 126 μ m, and hardness is 498HV.
Embodiment 2: Ф 90mmZL 108 engine piston end face hard anodizing methods:
(1) adopt hard anodizing surface treatment power unit, piston 3 is packed into piston-top surface is carried out the hard anodizing surface treatment in the compound cooling oxidation unit, compound cooling oxidation unit is made up of oxidation work nest 1 and cooling tank 7.
(2) negative plate 2 and the cable 6 that connects hard anodizing surface treatment power unit are housed in the oxidation work nest groove in the compound cooling oxidation unit, rubber seal 4 is housed in the hole of bottom land, arrange with matrix-style, sealing-ring 4 clamp piston 1 are made sealing function, isolation piston oxidized portion and non-oxidized portion with rising; Piston resiliency supported anode conducting device is housed in the cooling tank 7, comprises conduction top board 8, spring 9, cable 10 feeds non-corrosive circulating cooling liquid in conduction seat 11 and the external cable 12, groove.
(3) pack into after piston 3 degreasing decontaminations are cleaned in the rubber seal 4 of bottom of oxidation work nest 1, piston-top surface upwards, 60 of the quantity of packing into, the width between centers 150mm of piston space, arranged.The oxidation work nest that piston will be housed according to accompanying drawing 1 puts 1 on cooling tank 7, piston base closely contacts with conduction top board 8 in the piston resiliency supported anode conducting device, feed the sulfuric acid electrolyte of 18wt.% respectively and do not have corrosion neutral circulating cooling liquid in oxidation work nest 1 and cooling tank 7, the temperature of electrolytic solution and circulating cooling liquid is controlled at 1~2 ℃ and-3 ℃ respectively.Connect the hardening oxidation pulse power, oxidation 40~50 minutes at the oxide film of piston-top surface formation one deck densification, is tested respectively with eddy current thickness meter and microhardness tester, and thickness is 145 μ m, and hardness is 482HV.