Mould steel quenchs analysis of 10 kinds of crackle and measure

1, fore-and-aft crackle crackle shows axial, figure is thin and long. When complete temper by dipping in water appears the mould to quench involuntarily namely, core change is specific volume the biggest quench martensite, generation is tangential pull stress, the quantity containing carbon of mould steel heals tall, of generation tangential pull stress to heal big, bring about fore-and-aft crackle to form when pulling stress to be more than limit of this steel intensity. The following element aggravate the generation of fore-and-aft crackle: (The low melting point such as more S, P, *** , Bi, Pb, Sn, As is contained in 1) steel harmful impurity, direction of rolling of the edge when steel ingot rolling is shown fore-and-aft and serious slant analyse distributings, easy generation stress is formed centrally fore-and-aft quench crackle, or after raw material rolling fast cold formation fore-and-aft crackle is raw drop reservation to be brought about in the product quench crackle expands finally form fore-and-aft crackle; (2) mould dimension cracks sensitive measure scope in the temper by dipping in water of steel inside (temper by dipping in water of carbolic tool steel cracks dangerous dimension to be 8-15mm, measure of low-alloy steel risk is 25-40mm) in or choose those who quench cooling medium exceeds this steel greatly is critical quench when cooling rate all easy form fore-and-aft crackle. Precautionary measures: (Put in storage of 1) strict raw material is checked, exceed mark rolled steel to harmful matter content not put into production; (2) chooses vacuum smelt as far as possible, the fine outside furnace or heavy fusible pattern of electric broken bits provide rolled steel; (3) improves heat treatment technology, use vacuum to heat, protective atmosphere heats and bath furnace of salt of sufficient to oxigenate heats reach classification quench, isotherm quenchs; (4) becomes inadvertently to quench to quench purposely namely not complete temper by dipping in water is appeared, win the measure such as the organization of body of family name issueing shellfish with tall obdurability, reduce substantially pull stress, can avoid a mould effectively fore-and-aft craze and quench distortion. 2, feature of transverse crackle crackle is perpendicular at axial. Not temper by dipping in water shows a pattern, in temper by dipping in water hard area and not oil hard division transfers to exist to drag stress peak value greatly partly, when large mould cools quickly easy form drag stress peak value greatly, be more than because of formation axial stress tangential stress, bring about generation transverse crackle. Forging the S in module, P. *** , bi, pb, sn, the low melting point such as As is harmful of foreign matter transverse slant analyse or module existence are transverse and microscopical crackle, transverse crackle is formed via expanding after quenching. Precautionary measures: (1) module should reasonable forging, of raw material length and diameter be in than had better be being chosen than forginging namely 2, 3 between, forging use double crossed deformation to forging, via 5 Dui 5 unplug much fire forgings, make the carbide in steel and impurity are shown fine, small, matrix of divide evenly distributinging Yu Gang, forging fibre around model antrum is not had directional distributing, raise module substantially transverse and mechanical function, decrease and eliminate stress source; (2) chooses good cooling rate and cooling medium: The Ms dot above in steel is fast cold, be more than this steel critical quench cooling rate, the stress that austenite of the super-cooling in steel produces is thermal stress, surface layer is press stress, lining is tensile stress, mutual and quits, prevent thermal stress crackle effectively to form, the Ms in steel, delay is cold between Mf, reduce substantially form quench the constituent stress when martensite. Add up to when the thermal stress in steel and corresponding stress (tensile stress) when, easy oil is cracked, be when losing, not easy temper by dipping in water is cracked. Make full use of thermal stress, reduce change stress, control stress adds up to negative, can avoid effectively transverse quench crackle happens. CL-1 organic quench medium is idealer quenching medium, can decrease at the same time and avoid to quench mould distortion, controallable still sclerotic layer is reasonable distributing. Square CL-1 quenching medium is different chroma deserves to compare, available different cooling rate, obtain place to need sclerotic layer to distributing, satisfy demand of different pattern steel. 3, arc shape crackle often happens in the appearance such as flash of wiring of horn of mould edges and corners, breach, cavity, sunken model choppy place. Because,this is, the stress that place of the edges and corners when quenching produces is flowing surface 10 times of average stress. Additional, (Carbon is contained in 1) steel (C) quantity and alloying element content heal tall, steel Ms dot heals low, ms dot reduces 2 ℃ , criterion temper by dipping in water cracks the tendency to increase 1. 2 times, ms dot reduces 8 ℃ , temper by dipping in water cracks the tendency to increase 8 times; (The sex when constituent change and same organization change are distinct differs in 2) steel, because different organization compares tolerance, cause huge organization stress, bring about constituent boundary to form arc shape crackle; (After 3) quenchs not seasonable temper, or temper is inadequate, austenite of the remains in steel transforms not adequately, reservation is in use condition, stimulative stress distributings afresh, or when the mould enlists in army, leftover austenite produces martensite photograph to change the internal stress with new generation, form arc shape crackle when integrated stress is more than limit of this steel intensity; (4) has steel of the 2nd kind of temper brittleness, delay of temper of the high temperature after quenching is cold, bring about the P in steel, the harmful impurity compound such as S separate out of edge crystal boundary, reduce crystal boundary adhesion and obdurability greatly, increase brittleness, when enlisting in army, arc shape crackle is formed below outside force action. Precautionary measures: (1) improves a design, make appearance symmetrical as far as possible, reduce appearance mutation, add craft aperture and reinforcement, or use combination to assemble; (By the side of acting right angle of 2) round horn and pointed horn acute, aperture of blind of perforative Kong Dai, improve treatment precision and surface are bright and clean degree, reduce stress to center a source, the point such as aperture of edge of acute of orthogonal to cannot avoiding, pointed horn, blind is general hardness demand is not high, can wait to be plunged into into luggage with rope of iron wire, asbestine, fireproof mud or ram, create cooling protective screen artificially, made slow refrigeration quenchs, prevent stress concentration, crackle of shape of the arc when preventing to quench is formed; (3) quenchs steel should seasonable temper, eliminate a part to quench internal stress, prevent to quench stress expands; (4) is longer temper, raise a mould to fight rupture tenacity value; (5) sufficient temper, get stabilizing constituent function; For many times temper makes leftover austenite change is mixed adequately eliminate new stress; (7) reasonable temper, raise steel exhaustion fights force and integrated and mechanical mechanical function; To having high temperature of steel of mould of the 2nd kind of temper brittleness answer after temper fast cold (cold) of water-cooling or oil, can eliminate 2 kinds of temper brittleness, crackle of shape of the arc when prevent and avoiding to quench is formed. 4, when coming off crackle mould enlists in army, fall in stress action, quench sclerotic layer together piece come off from inside steel matrix. Because organization of mould surface layer and core organize specific volume to differ, the surface layer when quenching is formed axial, tangential quench stress, radial generation pulls stress, inward ministry is choppy, in stress urgent revulsion changes range narrower place generation comes off crackle, often happen in process of refrigeration of mould of thermo-chemical treatment of classics surface layer, the sex when because express a chemical modified and steel matrix photograph to change,differring causes layer of inside and outside to quench martensite expands not to undertake at the same time, the bearing with large generation changes stress, bring about chemistry to handle ooze layer to come off from inside matrix organization. Nitrogen of hard layer of temper by dipping in water of if blaze surface temper by dipping in water is hard layer, high frequency surface, cementite layer, carbon in all boracic layer of ooze layer, nitriding layer, ooze, ooze metal layer. After chemical ooze layer quenchs, should not be fast temper, especially microtherm temper heats quickly under 300~C, can make surface layer form pull stress, and steel matrix core and transfer the layer is formed reduce stress, should pull stress to be more than when reducing stress, bring about chemical ooze layer to be come off by rip. Precautionary measures: (1) should make mould steel learns ooze layer chroma and hardness to come by the watch inside gently reduce, enhance ooze layer and matrix adhesion, undertake diffusing handling can making chemical ooze layer and matrix transfer after ooze even; (The ongoing travel that chemistry of 2) mould steel handles diffuses anneal, ball changes anneal, attune to be handled character, refine primitive organization adequately, can prevent effectively and avoid to come off crackle arises, ensure product quality. 5, meshy crackle crack depth is more shallow, make an appointment with greatly commonly 0.

01-1.

5mm, submit radiation form, alias chap. The reason basically has: (1) raw material has deeper decarburized layer, cold cutting is machined not purify, or finished product mould heats in oxidation atmosphere furnace cause oxidation decarbonization; (Organization of metal of surface layer of 2) mould decarbonization and steel matrix martensite contain carbolic quantity to differ, specific volume is different, the generation when steel decarbonization surface layer quenchs pulls stress greatly, accordingly, surface layer metal often edge crystal boundary by rip reticulate; (3) raw material is thick grain steel, primitive organization is bulky, put in chunk shape ferrite, convention quenchs cannot eliminate, reservation is in quench in the organization, or accuse lukewarm forbid, appearance is out of order, produce constituent overheat, burn too even, grain is thick change, lose crystal boundary adhesion, the mould quenchs the separate out of crystal boundary of carbide edge austenite of the steel when refrigeration, crystal boundary intensity is reduced greatly, tenacity is poor, brittleness is big, in pull crystal boundary of the edge below stress action to show meshy crack. Precautionary measures: (Composition of chemistry of 1) strict raw material. Metallographic organization and flaw detection are checked, unqualified raw material and thick grain steel should not be mould material; (2) chooses electric steel of fine grain steel, vacuum, deepness of raw material decarburized layer checks before put into production, cold cutting mental allowance must be more than decarburized layer deepness; (3) formulate is advanced and reasonable heat treatment craft, choose personal computer to charge lukewarm meter, control precision achieves ± 1.

5 ℃ , appearance of time spot desired result; (Final processing chooses 4) mould product furnace of atmosphere of vacuum electric stove, protection and heat via bath furnace of salt of sufficient to oxigenate the measure such as mould product, prevent effectively and avoid meshy crackle to form. 6, steel of mould of cold treatment crackle is more in, tall carbon alloy steel, there still is partial super-cooling austenite to did not transform after quenching martensite, reservation becomes leftover austenite in use condition, influence performance characteristics. If continue to cool under park zero, can make leftover austenite produce martensite change, accordingly, the essence of cold treatment is to quench continue. Quench below room temperature below stress and zero stress overlay, cold treatment crackle is formed when should folding response force to exceed limit of this data strength. Precautionary measures: (Before the cold treatment after 1) quenchs will boil in mould park boiling water 30, 60min, can eliminate 15 ％ - 25 ％ quench internal stress makes leftover austenite stability is changed, reentry goes - cold treatment of 60 ℃ convention, or undertake - 120 ℃ deep cold treatment, temperature heals low, leftover austenite change heals into martensite quantity much, but cannot total change is over, the experiment makes clear, have 2 ％ about - reservation of 5 ％ leftover austenite comes down, by need reservation a few leftover austenite can slacken stress, have amortize effect, because of leftover austenite soft pliable but strong, can absorb martensite to change partly expand quickly energy, alleviation photograph changes stress; (In the mould is being taken out to throw hot water after 2) cold treatment ends, warm up, can eliminate 40 ％ - stress of 60 ％ cold treatment, warm up to answer to room temperature hind seasonable temper, cold treatment stress is eliminated further, avoid cold treatment crackle to form, acquire firm methodize property, ensure to distortion does not produce in mould product is deposited and be being used. 7, grinding crackle often happens in mould finished product to quench, in process of cold working of the grinding after temper, the tiny flaw that majority forms and grinding direction are perpendicular, make an appointment with greatly 0.

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0mm. (Pretreatment of 1) raw material is undeserved, fail to remove raw material adequately lump, meshy, banding carbide and produce serious decarbonization; (2) quenchs finally heat temperature is exorbitant, produce overheat, grain is bulky, generate more leftover austenite; (3) produces stress to cause when grinding change, make leftover austenite change is martensite, constituent stress is great, add, stay more remains pulls stress, organize stress overlay with grinding, or reach refrigeration greatly because of quantity of grinding speed, feed undeserved, bring about heat of grinding of metallic surface layer to warm up quickly to quench heat temperature, subsequently grinding fluid is cooling, cause grinding surface layer 2 times to quench, a variety of stress are integrated, exceed limit of this data strength, cause crackle of grinding of surface layer metal. Precautionary measures: (1) undertakes changing forge to raw material, for many times double crossed deformation unplugs to Dui forging, via 4 Dui 4 unplug, make forging fibre around model antrum or axes show waviness semmetry to distributing, use last fire high temperature more than heat undertakes quenching, catch high temperature temper, can eliminate adequately lump, meshy, banding with chain certificate carbide, make carbide is refined to 2-3 class; (The heat treatment technology with 2) advanced formulate, control quenchs leftover austenite content does not exceed bid finally; (After 3) quenchs have temper in time, eliminate quench stress; (4) reduces amount of grinding speed, grinding appropriately, grinding cooling rate, can prevent effectively and avoid grinding crackle to form. 8, this crackle gives line cut crackle to quench in the course now, online cut machines the module of temper in the process, this process changed metallic surface layer, intermediate layer and core stress field to distributing condition, quench overbalance of leftover internal stress is out of shape, some area appears to pull stress greatly, this pulls stress to work energetically scamper is brought about to crack when limit of strength of this mould data, crackle is crackle of layer of metamorphism of bold of arc end account. The experiment makes clear, line cut process is discharge of local high temperature and quick cooling procedure, make metallic surface layer forms dendritic casting condition to organize caky layer, generation 600-900MPa is pulled stress and thick about 0. The tall stress of 03mm quenchs 2 times white bright layer. Crackle produces an account: (The carbide with serious existence of 1) raw material slants analyse; (2) appearance is out of order, quench heat temperature is exorbitant, grain is bulky, reduce material obdurability, increase brittleness; (3) quenchs not seasonable temper mixes workpiece temper is inadequate, the leftover internal stress with too large presence and the overlay of new internal stress that the line forms in cut process bring about line cut crackle. Precautionary measures: (1) is checked before put in storage of strict raw material, ensure raw material organizes composition qualification, must undertake changing forge to unqualified raw material, attack broken carbide, make chemical composition, metallographic is organized etc obtain technical condition rear but put into production. Finished product of the treatment before module heat treatment needs to stay sufficient after grinding a quantity certainly, quench. Cut of temper, line; (2) enters appearance of the desired result before furnace, choose personal computer to accuse lukewarm, accuse lukewarm precision ± 1.

5 ℃ , vacuum furnace, protective atmosphere furnace heats, take strict precautions against overheat and oxidation decarbonization; (3) is used classification quench, after isotherm quenchs and quenching seasonable temper, for many times temper, eliminate internal stress adequately, the cut that it is a line creates a condition; (4) formulate science is reasonable line cut craft. 9, when fatigue fracture mould enlists in army, handing in change the microscopical and fatigue crackle that stress forms below action repeatedly is slow and patulous, bring about abrupt fatigue fracture. (Grain of hair of existence of 1) raw material, slant badly from dot, hole, loose, metalloid be mingled with, carbide metallurgy of ferrite of dissociate of analyse, banded structure, lump organizes blemish, destroyed matrix the organization is successional, form inhomogenous stress concentration. In steel ingot 112 did not eliminate, white spot is formed when bringing about rolling. *** , Bi, Pb, Sn, As and S, P exists to wait for harmful impurity in steel, the P in steel is easy cause cold short, and S is easy cause heat fragile, s, p harmful impurity exceeds bid all easy form fatigue source; (Heavy panel of layer of 2) chemical ooze, chroma crosses layer of big, ooze excessive, sclerotic layer crosses hardness of shallow, intermediate zone low can bring about material exhaustion intensity is reduced quickly; (3) machines coarse, precision when modular face low, bright and clean spend difference, and Dao Wen, carve characters on a seal, nick, touch, corrode hemp face to wait to cause stress easily also to bring about fatigue fracture centrally. Precautionary measures: (1) strict select material, ensure material is qualitative, metalloid matter content of the impurity of low melting point such as control Pb, As, Sn and S, P does not exceed bid; (2) undertakes material is checked character before put into production, unqualified raw material not put into production; (3) choosing appliance has chasteness to spend tall, impurity little, chemical composition even, grain is fine. Carbide it is small, good to wait for tropism, fatigue intensity is advanced the steel-making of essence of remelting of electric broken bits of the characteristic, aggrandizement of modified of layer of chemical to aggrandizement of bolus of gush of mould face face and surface ooze is handled, make metallic surface layer is press stress beforehand, of the generation when quits mould enlists in army pull stress, increase strength of mould face exhaustion; (4) raises mould face to machine precision and bright and clean degree; (5) improves chemical ooze layer and performance of sclerotic layer organization; Use personal computer to control ply of chemical ooze layer, chroma and sclerotic layer ply. 10, stress corrodes crackle this crackle often happens in use process. Because metallic mould is chemical reaction or electrochemistry reaction process, cause come from the watch inside constituent structure attaint corrodes action and produce craze, this is stress corrodes crackle. Mould steel differs because of the organization after heat treatment, the function that fight corrode is different also. Most be able to bear or endure corrode organization is austenite (A) , corrode an organization the most easily to be troostite (T) , ordinal for ferrite (one martensite of F) (one pearlite of M) (P) alls alone family name body (S) . Accordingly, mould steel heat treatment is unfavorable get T is organized. Quench steel although classics temper, but because temper is inadequate, quench internal stress still exists more or less, when the mould enlists in army, outer strength effect falls to also can produce new stress, every has metal of stress consist in there can be stress to corrode crackle happening in the mould. Precautionary measures: (Seasonable temper answers after 1) mould steel quenchs, sufficient temper, for many times temper, quench in order to eliminate internal stress; (After 2) mould steel quenchs, should not be commonly in 350-400~C temper, because T is organized,often appear in this temperature, happen T organizes a mould to answer retexture, the mould should undertake antirust processing, improve the performance that fight corrode; (Microtherm warm-up undertakes before 3) heats up a mould to enlist in army, leng Zunmo is provided enlist in army microtherm temper makes eliminate stress after a phase, can prevent not only and avoid stress to corrode crackle happening, still can improve mould service life substantially, kill two birds with one stone, have remarkable technology economic benefits. CNC Milling