The place before be like is narrated, naCN can let melt time and deterioration, cementite can be reduced, period analysis CN wants in working so, when CN is insufficient, add designation supply agent, the steel foil that before maintaining cementite to be able to be in, face place narrates experiments but simple and easy try a cementite can, have because of NaCN hygroscopic, in if will contain the supply agent of moisture to throw,adding stew, meet spray, the adiabatic wall that must use heat is dry. Can quench directly after cementite cease, when cementite temperature is high nevertheless, but first immerge maintains quench in the neuter salt bath of temperature, quench next. Next watches are all sorts of quenching methodological comparison. Temper fastens the rudimental stress that when purify quenchs, happens. And will partial remain Wo Sitian iron turns into Ma Tian comes loose iron. Temperature is exorbitant criterion hardness can be reduced, general with 150 ～ 200 ℃ are optimum. 4, aeriform cementite law: Aeriform cementite, because suit mass-produced change, exercise can simplify, quality control calculates a characteristic easily, be used the most generally at present. This law has become gas (or say to produce gas) reach drop note pattern kind. The means that turns gas into means is carbonization gas (C4H10, c3H8, CH4) with air look mixture evacuation is entered become furnace (Gas Generator) , in the 1000 ～ inside furnace the high temperature of 1100 ℃ falls, make hydrocarbon is generated with air reaction alleged become gas (Converted Gas) , have all sorts of name by the gas that becomes furnace place to generate, the article is convenient on be called become gas. Become gas with CO, H2, N2, give priority to component, embedded minim CO2, H2O, CH4, cementite applies inside the heating furnace that sends this gas into leak of the gas outside notting have to enter next. When cementite, the cementite concentration that requires because of place is different, in become the C4H10 that proper capacity adds inside gas, C3H8, CH4 to so that move cementite chroma,wait. The reaction that aeriform cementite concerns is shown as follows: 〕 of C of 2CO = 〔 + CO2... (1) 〕 of C of 〔 of CO + H2 = + H2O... (2) 〕 of C of CH4 = 〔 + 2 H2... (3) 〕 of C of C2H6 = 〔 + CH4 + H2... (4) 〕 of C of C3H8 = 〔 + C2H6 + H2... (5) here separate out, diffuse in steel of this carbon infiltration and cementite. Advanced hydrocarbon with type (4) , (5) reaction is decomposed according to foreword, become elementary hydrocarbon, become CH4 finally, have type (3) decompose, type (4) , (5) decompose speed to compare style (3) fast. The deputy reaction H2 + CO2 = CO + H2O that these reaction still can cause next showing... (6) CH4 + CO2 = 2CO + 2 H2... (7) CH4 + H2O = CO + 3 H2... (8) the basic response that above is aeriform cementite. When undertaking aeriform cementite, need aforementioned gas turns furnace, processing furnace and other into accessory equipment, belong to air hermetic body of heater, there is fan to make cementite and temperature are changed equably inside furnace. In the cementite sex gas that becomes furnace, with correspondence the gas at handling an end is comprised or the gas of dew point guides processing furnace. This gas participates in the cementite of steel, can deputy unripe CO2, sex of bring down cementite, for from CO2 of eliminate of rolled steel surface, be necessary to make with some speed above cementite sex gas flows, move discharge of solar term body, make the gas inside furnace every 1 hour of displacement 5 ～ 10, to prevent the oxidisability gas interfuse outside furnace, force of furnace internal pressure should keep tallish at 1 gas. Take out, during loading substandard goods, want to carry out igneous defect shade, prevent air interfuse, lest explodes. Undertake quenching after cementite cease, nevertheless cementite temperature regards as quench the too tall word when temperature, can reduce aeriform carbon potential, drop furnace temperature, become quench comfortable lukewarm hind temper by dipping in water is cold. Quench be like impropriety with oil, although be inside furnace,be brilliant condition, temper by dipping in water is entered also can oxidize when oil is medium chromatic, the end that short of brightness handles; The character that the factor of sex of brightness of quenching oil encumber has the oil such as carbon of oily oxidation, remain, sulfur content or the person that concern with composition directly, or the work of the moisture of minim and air interfuse, also can reduce brightness to spend. Temperature is reduced to quench directly later to 800 ℃ after aeriform cementite in water or oil, if use the processing that hemp quenchs to be able to decrease,quench right now be out of shape, the organization after aeriform cementite, its skin contains carbolic concentration and core ministry to contain carbon there is notable difference between the quantity, so inflict of the beard after cementite diffuses anneal (950 ℃ of 900 ～ ) , after this quenchs in 800 ℃ , after quenching, must be in 180 ℃ of 150 ～ temper of inflict low temperature. The heat treatment after cementite depends on cementite temperature commonly and cent is 2 kinds: (1) cementite temperature is in steel when the Ac3 upper part of the primary capacity that contain carbon, the organization of part of the center after cementite becomes imperceptible, skin is bulky, right now heat treatment simply handles cuticular bulky grain imperceptible grain can, the steel after reason general cementite, heat to A1 a bit upper part (near 780 ℃ ) quench can. (2) if cementite temperature is in,very high temperature manages Ac3 upper part, medium core grain also is become bulky, need right now via 2 heat treatment. The purpose that quenchs the 1st times depends on making not by cementite core organization is changed imperceptibly, heat to go up to Ac3 namely a Wo Sitian iron is abnormal, and when crystallization bead just was changed imperceptibly, quench, reason temperature is higher. Here at the same time temperature falls, the iron of carbon of meshy Xue Ming of the tall carbon part of cementite layer can originally iron of Si Tian of frit Yu Wo, there is iron of carbon of meshy Xue Ming to exist no longer after quenching so. But this quenchs temperature, regard cementite as the layer quench temperature is exorbitant rather, must make the 2nd times in inferior temperature again quench. This temperature to cementite layer character, be equivalent to 760 ℃ are made an appointment with between A1 and Acm around, the shovel that reason classics quenchs the 2nd times, cementite surface layer is iron of hemp Tian San, there are a lot of bulbiform carbides to exist in base, reason wearability is tall. Temper fastens the rudimental stress that when purify quenchs, happens, and will partially remain Wo Sitian iron turns into Ma Tian comes loose iron. Temperature is exorbitant criterion hardness can be reduced, common with 150 ～ 200 ℃ are optimum. When be like the hardness with taller beard, criterion appropriate is in 170 ℃ of 100 ～ temper, when be like the sex that need pliable but strong, criterion appropriate is in 400 ℃ above, of Ac1 the following temper, get organization of iron of temper coarse spot. 5, aeriform cementite nitrogen changes a way: When aeriform cementite nitrogen is changed, cementite and nitriding action go at the same time. The gas that the aeriform cementite that aeriform cementite uses uses uses generation cementite function, and N H3 gas uses generation nitriding function. Aeriform cementite nitrogen changes temperature to be 704 ～ 900 ℃ , its processing time is shorter than aeriform cementite law, get thinner sclerotic layer, earning cementite nitrogen changes a result to be similar to the person that liquid cementite nitrogen turns gain. The sclerosis that handles a layer can, it is good by the cementite layer of cementite earning to compare, change cementite nitrogen so and quench when cooperating appropriately, carbolic steel or low-alloy steel also can get layer of very stable tall hardness sclerosis. From this the sclerotic layer deepness of law earning is 0. 07 ～ 0.
75 ㎜. Oil hardening can be used when quenching, can carry out gas to quench sometimes will prevent to quench be out of shape and still can get tall exterior hardness. The steel that cementite nitrogen converts place to use by with low carbon construction uses steel and low alloy construction to be given priority to with steel, its are main the purpose is to improve wearability. If want to satisfy at the same time,be able to bear or endure loading sex and wearability, above all cementite 1.
5 ～ 1.
8 ㎜, carry out cementite nitrogen to change next, try next oil hardening. Because contain N,aeriform cementite nitrogen changes a layer, repellency of its temper bate is big, the person that so temper temperature should quench than aeriform cementite is tall. Normally temper at 190 ～ when 210 ℃ , exterior hardness is HRC58 above CNC Milling
CNC Machining