CN104087878A

CN104087878A - Method for preparing composite material for engine cylinder piston

Info

Publication number: CN104087878A
Application number: CN201410306561.4A
Authority: CN
Inventors: 任淑彬; 许慧; 洪庆楠; 何新波; 曲选辉
Original assignee: University of Science and Technology Beijing USTB
Current assignee: University of Science and Technology Beijing USTB
Priority date: 2014-06-30
Filing date: 2014-06-30
Publication date: 2014-10-08
Anticipated expiration: 2034-06-30
Also published as: CN104087878B

Abstract

The invention discloses a method for preparing a composite material for an engine cylinder piston, and belongs to the field of metal matrix composite materials. The method comprises the following steps: firstly, evenly mixing diamond micro-powder, alumina fibers, titanium carbide fiber-reinforced body powder and a polyvinyl alcohol solution at a volume ratio of (20-25%):(5-10%):(5-10%):(55-70%), and then pressing and forming the mixture so as to obtain a reinforced green body; baking the green body in air at 50-60 DEG C for 4-5 hours, then putting the green body into a melt infiltration furnace graphite die and preheating; then pouring molten aluminum alloy of which the ingredients are 10-12% of Al to Si at the temperature of 700-750 DEG C into the graphite die and pressurizing; obtaining diamond particles, alumina fibers and aluminum matrix composite blocks which are compositely enhanced by a titanium silicon carbon fiber generated by in-situ reaction of titanium carbide and aluminum silicon alloy in the melt impregnation process after pressurizing is ended, and then processing according to the final piston size, so as to obtain the product. The piston prepared by the method is light in weight, high in dimensional stability in the use procedure, and good in thermal diffusivity and wear-resisting property, and can be used for comprehensively improving the working stability and reliability of a cylinder.

Description

The preparation method of matrix material for a kind of engine cylinder piston

Technical field

The invention belongs to metal-base composites field, relate to the preparation method of a kind of engine cylinder piston matrix material.

Background technology

Along with improving constantly of rotating speed of automobile engine, velocity of piston also improves thereupon, and piston of gasoline engine speed can reach 11-16m/s, and diesel engine piston speed can reach 6-8.5m/s, or higher.The high speed of engine, makes to act on mass force on piston also increasing, and the compression ratio of engine is corresponding raising also, combustionvelocity in combustion chamber sharply increases, in cylinder, easily form local pressure poor, make piston generation forced vibration, thereby cause cavitation pitting or engine knock phenomenon.In addition, piston crown, under the effect of alternating thermal stress, easily produces thermal distortion or decrepitation.So, except the performances such as the normal temperature strength to piston material, hardness, unit elongation, thermal expansivity have certain requirement, also to its high-temperature behavior, as high temperature tensile strength, high temperature fatigue intensity, thermal conductivity and wear resisting property have higher requirement.Aluminum alloy materials, cast iron materials and the cast steel etc. that are using are at present owing to there being separately certain performance shortcomings, although as little in aluminum alloy materials density, but the coefficient of expansion is large, high-temperature behavior is poor, cast iron and cast steel density are excessive etc., are difficult to meet the over-all properties requirement of modern high performance automobile to piston.

Summary of the invention

The present invention seeks to prepare a kind of piston material of excellent combination property, make up the performance deficiency of current material, meet the over-all properties requirement of the wear resistance of modern high performance automobile to piston, working process size temperature, thermal conductivity, mechanical behavior under high temperature etc.

The preparation method of matrix material for a kind of engine cylinder piston, on the basis of existing aluminium alloy, by adding a certain amount of diamond particles, sapphire whisker and mixing enhancing by titanium carbide and the generated in-situ titanium silicon-carbon of aluminum silicon alloy fiber, can further improve the dimensional stability of existing aluminium-alloy piston, thermal conductivity and mechanical behavior under high temperature, especially wear resistance.Concrete technology: first prepare the porous reinforcement base substrate being formed by diamond particles, sapphire whisker and titanium carbide fibre, then obtain by infiltration process the aluminum matrix composite that fine and close diamond, sapphire whisker and titanium silicon-carbon blending in of fibers strengthen, the titanium silicon-carbon fiber in wild phase generates by titanium carbide and aluminum silicon alloy reaction in－situ.The preparation of porous reinforcement is that first compound concentration is 4～5% polyvinyl alcohol solution, then polyvinyl alcohol solution and 10-20 μ m diadust, the sapphire whisker of diameter 10 μ m, the titanium carbide fibre reinforcement powder of diameter 5-10 μ m is pressed to (55～70%): (20～25%); (5～10%): the volume ratio of (5～10%) mixes and is placed in punching block and is pressed into base substrate, the size of base substrate is determined flexibly according to the size of final piston, then base substrate is placed in baking oven and after 4～5 hours, obtains porous reinforcement base substrate in 50～60 DEG C of oven dry.Infiltration process is, first porous reinforcement base substrate is placed in to infiltration stove graphite jig, and be preheated to 300～350 DEG C, then be Al～(10～12) Si% by composition, temperature is that the molten aluminium alloy of 700～750 DEG C is poured the infiltration that pressurizes in the graphite jig that base substrate is housed into, moulding pressure is 5～10MPa, pressing speed is 3～5mm/min, titanium carbide fibre in infiltration process in base substrate by with melting Al-Si alloy in Si there is reaction in－situ and generate titanium silicon-carbon fiber, after having pressurizeed like this, obtain diamond particles, sapphire whisker and reacted with aluminum silicon alloy infiltration process situ by titanium carbide generate titanium silicon-carbon fiber composite strengthen aluminum matrix composite block, then process and obtain finished product according to final piston size.

The piston material that adopts above-mentioned technique to prepare, owing to having added diamond particles, therefore the wear resisting property of material, dimensional stability, especially thermal conductivity is greatly improved, heat-sinking capability can significantly increase pistons work time, add friction stability and the mechanical behavior under high temperature that can effectively increase material after appropriate sapphire whisker, and the titanium silicon-carbon generating by reaction in－situ has better toughness and thermal conductivity compared with aluminum oxide and titanium carbide, can further improve the heat dispersion of material, wear resisting property and high-temperature behavior, also can make up the deficiency of sapphire whisker aspect toughness.Adopt in a word infiltration process to there is excellent over-all properties by add appropriate diamond, sapphire whisker and the prepared piston of titanium silicon-carbon fiber in aluminum silicon alloy, as high thermal conductivity, wear-resistant, size temperature is high, the coefficient of expansion is little and high-temperature behavior is excellent etc., can be good at meeting the harsh performance requriements of Modern Engine cylinder to piston material.

Brief description of the drawings:

Fig. 1 is process flow sheet of the present invention:

Embodiment:

(1) preparation size is the piston blank of Φ 200mm (external diameter) × 30mm (thick)

First press diamond, sapphire whisker and titanium carbide fibre volume accounting in final matrix material is respectively 20%, 5%, 5% carries out raw material powder mixing, the diamond grit adopting is 10 μ m, sapphire whisker diameter 10 μ m, titanium carbide fibre diameter 10 μ m, according to corresponding density calculation, the quality of three kinds of raw materials is respectively 670 grams, 186 grams and 222 grams, after raw material mixes, pour in 5% polyvinyl alcohol solution that fills 565 milliliters and stir, then expect that by stirring the punching block that is placed in Φ 200mm carries out press forming, pressing pressure is 3-5MPa.Shaping base is placed in to 50 DEG C of baking ovens dries 5 hours, then base substrate is placed in to infiltration stove graphite jig and carries out preheating, graphite jig diameter is Φ 200mm, 350 DEG C of preheating temperatures, be that Al～10Si%, temperature are that 750 DEG C of quality are that the aluminium alloy of 1500 grams is poured in mould and then carried out machinery pressurization again by composition, moulding pressure is 10MPa, and pressing speed is 3mm/min, treat that aluminium alloy all infiltrates recession pressure in base substrate and obtains piston blank, then carry out precision work according to final dimension.

(2) preparation size is the piston blank of Φ 100mm (external diameter) × 20mm (thick)

First press diamond, sapphire whisker and titanium carbide fibre volume accounting in final matrix material is respectively 25%, 10%, 10% carries out raw material powder mixing, the diamond grit adopting is 20 μ m, sapphire whisker diameter 10 μ m, titanium carbide fibre diameter 5 μ m, according to corresponding density calculation, the quality of three kinds of raw materials is respectively 140 grams, 62 grams and 74 grams, after raw material mixes, pour in 5% polyvinyl alcohol solution that fills 86 milliliters and stir, then expect that by stirring the punching block that is placed in Φ 100mm carries out press forming, pressing pressure is 3-5MPa.Shaping base is placed in to 50 DEG C of baking ovens dries 4 hours, then base substrate is placed in to infiltration stove graphite jig and carries out preheating, graphite jig diameter is Φ 100mm, 300 DEG C of preheating temperatures, be that Al～12Si%, temperature are that 700 DEG C, quality are that the aluminium alloy of 230 grams is poured in mould and then carried out machinery pressurization by composition, moulding pressure is 5MPa, and pressing speed is 5mm/min, treat that aluminium alloy all infiltrates recession pressure in base substrate and obtains piston blank, then carry out precision work according to final dimension.

Claims

1. the preparation method of an engine cylinder piston use matrix material, it is characterized in that first by 10-20 μ m diadust, the sapphire whisker of diameter 10 μ m, the polyvinyl alcohol solution that the titanium carbide fibre reinforcement powder of diameter 5-10 μ m and concentration are 4～5% is 20～25% according to volume accounting, 5～10%, 5～10%, after mixing, 55～70% ratio carries out the press forming body base substrate that is enhanced, base substrate is dried within 4～5 hours, to be placed in infiltration stove graphite jig in 50～60 DEG C and is carried out preheating in air, preheating temperature is 300～350 DEG C, then be Al～(10～12) Si% by composition, temperature is that the molten aluminium alloy of 700～750 DEG C is poured in graphite jig and pressurizeed, moulding pressure is 5～10MPa, pressing speed is 3～5mm/min, after having pressurizeed, obtain diamond particles, sapphire whisker and reacted with aluminum silicon alloy infiltration process situ by titanium carbide generate titanium silicon-carbon fiber composite strengthen aluminum matrix composite block, then process and obtain finished product according to final piston size.