Increase the research of heat treatment technology of life of mould of 3Cr2W8V steel Die Casting

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3Cr2W8V steel is the steel of Die Casting mould that uses extensively at present, the mould of aluminous Die Casting of electric machinery rotor of factory of Inner Mongolia some electric machinery uses this kind of steeliness to build namely. Mould appearance is shown like graph L place, die Casting is undertake on machine of 130 tons of Die Casting. Mould antrum face and high temperature aluminous fluid are contacted often, because heat to be handed in with what cool and arise repeatedly,bear change stress action. In the meantime, model antrum bears very big extruding, concussion and attrition, mould work requirement is very slashing. In this kind working requirement falls, the invalidation means of the mould to stick aluminous, chap is mixed inchoate take crack, cause mould life not tall. Of the mould inchoate fragile crack the main contradiction that is invalidation, the hardness of the mould and intensity index are exorbitant and tenacity inadequacy is to bring about inchoate fragile cracked reason. To improve the life of the mould, must improve the integral performance of 3Cr2W8V steel, to this, we undertook study. Data of test of 1 experiment means is 3Cr2W8V steel, its composition is: 0.

376 ％ C, 2.

40 ％ Cr, 8.

10 ％ W, 0.

4 ％ V, ≤ 0.

4 ％ Si, ≤ 0.

4 ％ Mn. This experiment uses 10 × family name of plum of standard of 10 × 55(mm) pounds sample. Fight if the graph is shown 2 times,stick aluminium and hot fatigue sample size. Pound experiment machine, HR with JB30, 150 Rockwell hardness plan, HB, sclerometer of 3000 cloth family name, Instron, 1251 model electro-hydraulic servo is all-purpose material experiment machine determines the index such as concussion tenacity, hardness, fracture toughness. With resistor heating furnace (inside the crucible that put aluminium) heat 700 ℃ , subsequently the means of water-cooling undertakes heating up fatigue experiment. Neophot metallographic microscope observes the ball changes anneal organization, with DS, appearance of form of fracture surface of sample of fracture toughness of observation of lens of III scanning report. 2 tests result and analysis 2.

Carbon of 1 gas nitrogen in all it is normal that the influence that ooze antagonism sticks aluminium and hot fatigue property will heat up fatigue sample school after craft moves qualitative processing, undertake one part sample aeriform nitrogen carbon in 3h of 570 ℃ × again in all ooze, another part sample does not undertake azotic carbon in all ooze, undertake contrasting experimenting next. Experiment process is: The aluminium that puts sample 700 ℃ heats 5 seconds in fluid, in putting water instantly next urgent cold, repeat afore-mentioned process every time. Test result makes clear, without azotic carbon in all the sample of ooze, 3, stick aluminium 5 times circularly, and course nitrogen carbon in all the sample of ooze, hundreds of later still end appears phenomenon sticking aluminium, and drawing of patterns is light. Return discovery, without azotic carbon in all the sample of ooze, circulate via 60, sample surface appears micro-crack, and course nitrogen carbon in all the sample of ooze, the experiment begins occurrence micro-crack 160 times after the loop, proved to pass azotic carbon in all the sample of ooze is heatproof and fatigue performance is good, than without azotic carbon in all the heatproof and fatigue sex of the sample of ooze rises 1.

6 times. Azotic carbon in all the sample after ooze, its most the surface is Bai Liang layer, by more compact ε , Fe2, 3(N, c) compound is comprised [1] , this and aluminous crystal structure are different, and wellability is bad, this may be the reason that sample does not stick aluminium. The hot fatigue property of material is one of main index that decide hot mould life. Outside heating up exhaustion to wait for physical property to concern besides the coefficient of thermal conductivity with material and hot coefficient of expansion, still concern with the high temperature intensity of material and plasticity. Hot fatigue crackle often is in the area with exterior the largest thermal stress is formed, mould surface is injured a process quickly by the meeting when acuteness oxidation, it is good to be like material to fight oxidation function, can reduce loss. Carbon of sample classics nitrogen in all after ooze, high temperature succumbs intensity rises, model changes fight force to rise, deferred crackle to produce, in the meantime, azotic carbon in all the surface layer of ooze sample is had fight oxidisability, can ease the scathing process when oxidation is eroded, this may be the matter that raises heatproof and fatigue sex. 2.

2 balls change anneal craft to actor or actress the Wen Jia in choosing hot mould steel to be used commonly heats up anneal and isothermal ball to change anneal to regard pretreatment as craft, with processing of this kind of craft, 3Cr2W8V steel ball changes an organization inhomogenous, the form appearance of carbide and distributing bad, the obdurability of the mould is insufficient, service life is consequently low, 3 although improve carbide to slant,forging to the loop analyse [2] , but degrees of whole to carbide circle improvement is finite, and technology is sophisticated. To obtain petty, divide evenly, round carbide, changed anneal craft to have a large number of tests to all sorts of balls, actor singles out the pretreatment of dissolve of high temperature solid with two kinds of distinct effects the ball changes anneal technology, its see watch L, picture as a result 3, graph 4. Nextpage sees from inside the graph, the organization after actorring or actress ball of chosen two kinds of craft changes anneal is better, petty, even, circle rectifies carbide had spent. Will pursue 3 with the graph 4 photographs are compared, graph the carbide of 3 compares a figure the carbide of 4 is petty, but degrees the uniformity of carbide, circle is full are inferior to a graph 4, its hardness is taller. So, reach an operation from degrees the circle of the function of machining and carbide is full convenient consideration, choose a watch 1 medium craft 2 it is reasonable, the following experiment all uses this technology. 2.

After 3 different temperature quench the hardness after temper and concussion tenacity use 3Cr2W8V steel new technology ball to change anneal, treatment becomes concussion sample to quench via different temperature temper hind, do concussion test, determine the Rockwell hardness of the sample that let oven, its see a picture as a result 5. From the graph 5a can see, along with quench elevatory, hardness raises temperature, same temperature temper, quench temperature is high person, hardness is tall also, demonstrative high temperature quenchs can raise red rigid. From the graph 5b can see, rise quench temperature, concussion tenacity is reduced; Quench temperature, time, lift along with temper temperature, concussion tenacity rises. Same temperature temper, quench temperature is low person, concussion tenacity is tall. From concussion tenacity considers, appropriate of Die Casting mould uses inferior temperature to quench the craft with high temperature temper. But 850 ℃ quench quench than 900 ℃ the concussion tenacity of sample is reduced somewhat, likelihood and heat temperature is too low, the alloying element that dissolve enters austenite is rare close. Because dissolve enters the alloying element of matrix to decrease, can reduce the intensity of matrix, affect those who pound tenacity to rise. 2.

Contrast of 4 concussion tenacity changes the sample of anneal to different technology ball. Quench via different temperature again temper, to the concussion of sample tenacity undertakes comparative, its see a picture as a result 6, see by the graph, in identical quench temperature falls, through tall Wen Gurong pretreatment ball changes the sample of anneal, concussion tenacity is tall. Pounding the matter that tenacity raises is [3] , after through tall Wen Gurong pretreatment ball changes anneal, make carbide petty and even. Nextpage2.

Test test uses 5 fracture toughness KIc to curved sample at 3 o'clock, sample size is 100 × 20 × L0(mm) . Have heat treatment via different technology, with φ 0.

Breach of cut of 15mm molybdenum silk, prefab on machine of experiment of Amsler high frequency exhaustion crackle, what apply bear to be the 30 ％ of sample intensity, be in next Instron, 1251 model electro-hydraulic servo determines on machine of all-purpose material experiment. Experimental method carries out GB416, 84 " method of experiment of KIc of fracture toughness of metallic stuff planar meet an emergency " , test result sees a table 2. By the watch 2 see, through tall Wen Gurong pretreatment ball changes anneal, again via quenching the sample of temper, have tall fracture toughness, its KIc is worth groovier processing to rise 1.

36 Pou. The sample that quenchs through high temperature also has taller fracture toughness, its K1c is worth groovier processing to raise 1 times. But the hardness after temper has bigger effect to KIC, be like 09 sample. Graph the appearance of 7 form of scanning report lens that are area of center of sample fracture surface. See by graph 7a, sample ruptures the feature is appearance of accurate cleavage form. Have a few small hole, because cleavage face is more, reason KIC is inferior. See by graph 7b, sample fracture surface still is appearance of accurate cleavage form, but the small hole feature that has tenacity to rupture, so, KIc remarkable heighten. Graph 7c is through tall Wen Gurong pretreatment ball changes anneal again via quenching the appearance of form of lens of report of sample fracture surface of temper, the tenacity that has a typical case ruptures appearance of form of nest of pliable but strong, so KIc is worth apparent heighten. When the amount that contain carbon is certain, the fracture toughness of steel decreases along with the average distance of carbide (refine through carbide particle) and increase [4] , accordingly, because high temperature originallies,dissolve pretreatment makes carbide is refined is the main reason that increases 3Cr2W8V steel KIc. 2.

The mould of 3Cr2W8V steel Die Casting that 6 actual application handle with groovy craft, every pairs of mould can Die Casting300, mould life is low, hind classics nitrogen carbon in all ooze processing, mould life rises. But the phenomenon of inchoate craze happens from time to tome. Should use new technology + azotic carbon in all after ooze is handled integratedly, avoided a mould inchoate rupture phenomenon, drawing of patterns is successful, mould life rises significantly. The result sees a table 3. From the watch 3 can see, use new technology + azotic carbon in all ooze (1150 ℃ oil is cold + 800 ℃ furnace is cold + 1075 ℃ oil is cold + 680 ℃ temper 2 + azotic carbon in all ooze) , obtained satisfactory result. 3 conclusion (1) 3Cr2W8V steel uses new technology of pretreatment of dissolve of high temperature solid to be able to make carbide petty, even, degrees the circle is full good, in the meantime, pound tenacity, fracture toughness KIc rises. (2) life of Die Casting mould raises the aluminium of rotor of 3Cr2W8V steel electric machinery that uses integrated craft processing significantly. CNC Milling