Deep cold treatment of high-speed steel cutting tool

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Heat up the issue of deep cold treatment of high-speed steel cutting tool that discuss domestic and internationally at present, the author passes investigation and study, think this craft is not quite mature still, raise fact of cutting tool life to belong to accidental, do not have catholicity, want to move toward industrialized production, difficult and heavy. Whether It Is In China Or Abroad, the Sub-zero Treatment Of High Speed Steel Cutting Tools Is A Hot Issue In The Industry At The Moment.

After Research, the Writer Finds That This Process Remains Immature And The Prolonged Tool Life Is Only A Result Of Chance And Cannot Be Generalized.

There Is Still A Long Way To Go For The Commercial Production Of Sub-zero Treated Cutting Tools.

High-speed steel quenchs the metallographic of temper after organizes a scheme 1 it is 20 centuries the person such as 40 time MCohen is right W18Cr4V (abbreviation W18) steel is in 1, the isothermal change curve that 290 ℃ austenite changes, will discuss W18 steel to be in according to this graph quench the change of austenite of the super-cooling in the process. Steel plants other high-speed steel to also have same transition process, the curvilinear figure of isothermal change is similar also, the temperature of only change and limits differ somewhat. Curve of change of isotherm of steel of graph 1 W18Cr4V (austenite changes temperature 1, 290 ℃ ) from the graph 1 can see, change after via normal austenite, ms nods about 210 ℃ , mf dot is made an appointment with - 100 ℃ , change quantity is made an appointment with 92% , the rudimental austenite that still has 8% (RR) . If austenite changes after rapid cold to room temperature, criterion RR quantity is in 20%25% . W6Mo5Cr4V2 (abbreviation M2) carbolic degree of saturation slightly tall at W18 steel, ms dot is inferior, make an appointment with 130 ℃ , mf also low Wu Qian person, quench after is cold measure 25%35% to the RR of room temperature, the RR quantity that HSS-E and HSS steel isotherm quench may amount to 40%50% . Usually, pass temper 34 times, every time temper eventually cold reach the temperature under 0 ℃ impossibly, reason can withhold a certain quantity of RR more or less in the organization. From measure so that the result looks, for 5% or lesser. Of all kinds high-speed steel quenchs the metallographic organization of after is: Quench martensite + RR+ not dissolve carbide. Temper process is easy the deviation that happen, if heat,temperature and heat preservation time are not worth, cool especially did not amount to room temperature to undertake again the next time temper, will increase RR amount, cent of temper eligibility level is 3 class, degree of M2 steel temper is shown 2 times like the graph. 1 class is temper sufficient, whole visual field is black temper martensite, distributinging move is even the carbide of dispersion; 2 class are temper general, specific area or part of carbide caboodle part have white area to exist, although belong to eligible organization, but RR wants than 1 class much; Temper 3 class belong to unqualified organization for temper inadequacy, relatively for the most part white area exists, loom quenchs grain. The organization of normal temper should be temper martensite + the RR+ carbide of minim. Steel of graph 2 M2 quenchs temper degree level pursues (1 -- sufficient; 2 -- general; 3 -- insufficient) Guliyayefu is in the purpose of deep cold treatment of high-speed steel cutting tool to reported 1937, use cold treatment to improve steel function example, its purpose is to make the rudimental austenite change in steel becomes martensite. Temper organizes stability to change. Arrived 50 time, have use - 78 ℃ (male ice) or the story that 0 a bit higher temperature have cold treatment improves cutting tool performance, 70 time after, by drop at fluid N2 cost, make of industrial cold treatment eventually cold temperature is reduced greatly. Now, use fluid N2 to be refrigeration agent but will eventually cold speed control is in - each temperature areas of 196 ℃ above, and controallable drop in temperature speed, from quite cold or Wu Lu is empty till cold speed throws workpiece fluid N2 directly " temper by dipping in water is cold " . General will - the processing of 0 ℃ of 100 ℃ calls " cold treatment " , will - 100 ℃ - the processing of 196 ℃ is called " deep cold treatment " . On industry commonly used - 120 ℃ - 140 ℃ , no matter be cold treatment or deep cold treatment, it is to reduce a bit RR, raise hardness, stabilize an organization, achieve the goal that improves cutting tool life finally. Steel quenchs cold the austenite in protecting existence to organize to room temperature calls rudimental austenite (RR) , RR existence quenchs at everything in steel (mild steel heats to be in to constant temperature the intense RR that quenchs cooling Yi Youwei is measured in medium) . Before already remark, high-speed steel quenchs the metallographic organization of after is quench martensite + alloy carbide + RR, pass × of 1h of 550570 ℃ × 3 times temper after, major RR change causes sclerosis 2 times into temper martensite and separate out carbide, still have make an appointment with 5%rR to be withheld to come down, necessary destroy the RR part of remnant or eliminate entirely? The fact makes clear, contain the temper under 5%rR to organize temper already very sufficient, heat treatment already amounted to acme, be necessary to have cold treatment? Austenite is C the clearance solid solution in R-Fe, it is the extremely soft photograph in steel organization, its hardness has 200HBW left and right sides only, use hardness 6566HRC photograph to be able to see than after with this numerical value and high-speed steel cutting tool, overmuch RR won't make cutting tool tall apparently hardness. Japanese scholar the person such as Fandaoyizhao thinks through experiment after: 15% the following RR won't make cutting tool hardness drops, but the plasticity that can raise steel and tenacity. Accordingly, using deep cold treatment to reduce RR content to affirm to the tenacity of steel further is adverse. Classics of Guiyang tool works experiments for many times too, prove deep cold treatment and can not improve the life of cutting tool. Harbin has some of tool works to put lathe tool - 30 ℃ - cold treatment of the nature in the cold weather of 40 ℃ , also do not see lathe tool hardness and life rise, at it is people feels, would rather adopt groovy temper, withhold 5% right-and-left RR, integrated to raising cutting tool mechanical function has profit, also do not advocate use deep cold treatment. High-speed steel cutting tool and exceed photograph of hard data cutting tool to compare, the largest dominant position is tenacity a bit taller, if eliminate RR really, originally not tall tenacity is simply go up to cut spill salt. To Wu Gao classics of fast steel cutting tool quenchs normally temper after, withhold 5% right-and-left RR, I think to be used to what Wu Dao provides without harm. Close to have different view to the influence of wearability at RR. HSS steel cutting tool normally use hardness is in 6566HRC, HSS-E steel cutting tool is in 6667HRC. Carry out a proof, in other factor same situation falls, hardness is tall person wear away little, the durability of cutting tool is tall, with this judgement, although the RR that can make hardness is reduced is undesirable, but the life all through the ages of cutting tool does not talk a hero with hardness discretion, exorbitant hardness is brought about fragile soar, not only won't improve life, can change life instead. The life factor that affects high-speed steel cutting tool is many sided, cannot go after tall hardness one-sidedly, our principle is in what assure tenacity premise issues tall hardness of do one's best, but not only tall hardness, the experiment proves, the deep cold treatment of cutting tool inflict with sufficient temper, basically won't increase hardness, won't raise red rigid more, can make tenacity drops instead. If domestic some tools are shave tine knife, small the applied deep cold treatment such as modulus hob, the purpose is to remove stress, stable measure, because both be to want centering of less than diameter, in hoping cutting tool is using a process, aperture does not produce the change of dimension inside. Nextpage is analysed from above knowable, classics of high-speed steel cutting tool quenchs normally temper after, still remain in the organization a few austenite, do not have to the use of cutting tool and integral performance hinder greatly, is deep cold treatment applicable? This open to question problem, remain to carry out data and practice application in great quantities to go test and verify, but the author is held reject an attitude, enterprise of above of dimensions of domestic number a hunderd schools unmanned make inquires is a powerful argument. What what see newspapers basically is the scientific research achievement of university, institute or the child that are a lab, but to the face promotion is no good the specification has a problem. For instance craft of temper of high-speed steel cutting tool is a very deep example, know exactly about sth of new technology of so called temper, but the 1h of primitive still 550570 ℃ × that applies in big production × 3 mature craft. Technique of deep cold treatment of high-speed steel cutting tool although from change before mechanism tells deep cold treatment to should be put in quenched after temper, undertake, but from prevent to organize stress too big, prevent workpiece to consider in the angle of the craze in difficult cold process, do not advocate such doing commonly. Be aimed at the cutting tool with complex degree and different measurement, have the following kinds of technique: (1) quenchs after first at temper of low temperature of 1h of 350 ℃ × , like that after has deep cold treatment, here is close to a kind of method that quenchs after undertakes deep cold treatment is versed in most. (Juniors of temper of 2) first time goes, this is from safety and effect two respects consider a kind of relatively satisfactory method, namely air of temper of 1h of 550 ℃ × is cold to room temperature, like that after is again deep cold treatment. (Temper of 3) first time is cold arrive - 80 ℃ left and right sides, after of the 2nd temper is cold arrive - 135 ℃ - 196 ℃ . Although technology is quite sophisticated, but the effect and safety performance are belonged to excellent. (4) machines semi-manufactured goods or finished product after goes again deep cold treatment, this law effect is very small, but the safest the most convenient. Deep cold treatment of fast steel cutting tool returns the Wu Gao of discussion ancient bronze mirror of deep to high-speed steel cutting tool cold treatment is an immature heat treatment art, deny with respect to this work skill now raise a few problems such as cutting tool life to talk about bit of opinion, misgivings asks make corrections. The mechanism deep cold treatment of deep cold treatment is the continuance that heat treatment quenchs. High-speed steel quenchs the organization has 25% right-and-left RR, major in the deep cold treatment that follows after change is martensite, change of this one organization basically occurs in 0-80 ℃ , - after still has 196 ℃ deep cold treatment about 1.

5%rR. The martensite that difficult cold process produces high-speed steel is decomposed, it is by the lattice at Fe constant is narrowed cloy and carbon cause latticedot matrix distortion to increase, bring about carbide separate out thereby thermodynamic driving force increases. But by Wu Di lukewarm atomic issueing carbon diffuses difficulty is greater, reason is in - 196 ℃ ultralow temperature falls to produce martensite not easily to decompose. By - when 196 ℃ pick up to room temperature, carbolic atomic diffuses ability increases relatively, slant around room temperature get together to be in at twin crystal boundary or blemish of other crystal structure, form the diameter is 26 μ M only and with martensite in all of case exceed carbide of class of small accept rice, decide via the analysis this carbide is M6C model. The constituent construction that RR produced to to martensite change and martensite are decomposed and exceed imperceptible carbide separate out in process of deep cold treatment transforms, make the mechanical function such as the intensity of high-speed steel, hardness rises somewhat. The hardness that deep cold treatment raised cutting tool and wearability are made by Wu Shen cold treatment a few RR change becomes temper martensite, add the carbide with dispersive class of rice of separate out accept, these two kinds of elements make hardness rise somewhat (<0.

5HRC) , is not a lot of data tell can rise 12.

5HRC. M2 steel quenchs after hardness is 63HRC, via deep cold treatment after hardness rises to 65.

5HRC, cannot saying is deep cold treatment raised hardness, however 2 sclerosis with inherent high-speed steel are characteristic, do not manage in classics, and via × of 1h of 550 ℃ × 3 groovy temper, hardness is achieved all the same 65.

5HRC. Rise somewhat as hardness, wearability raises be nature. The red rigid red rigid that deep cold treatment won't raise steel is the ability of bate of high temperature of resistance pointing to steel, it should return above all result at M2C and MC carbide very strong fight collect ability. Quench in high-carbon steel and low-alloy steel to room temperature, get many RR possibly also, the temperature RR that controls in 550 ℃ decomposes the hardness that won't add steel commonly. The RR in these steel is decomposed below inferior temperature normally, and the Fe3C of separate out carbide gathers quickly below a few more tallish temperature is the immediate cause that produces bate. In high-speed steel, the separate out of carbide becomes very petty particle and RR decomposed both to cause sclerosis 2 times jointly, and carbide retains its imperceptible measure all the time, brought up red rigid necessarily. To specific steel character, it follows only quench heat temperature and heat time is concerned, specifically, the alloy that follows austenite is spent, the deliquescent degree of carbide is concerned, follow the deep cold treatment of after did not concern almost. The carbide when if quench,heating is deliquescent and bad, again good deep cold treatment won't make red rigid rises. In high-speed steel, the largest to red rigid influence element may be W and Mo, the atomic dimension of W and Mo is compared other any elements should be gotten greatly much, can anticipate they will have diffuse inferiorly speed, and must admit to undertake going down to make gather, not only need Cr and V diffuse, also need W at the same time (or Mo) with C diffuse. Wait for the cutting tool with need red particularly tall rigid like lathe tool, hob, tool works is used rise quench the practice of temperature, never hear of deep cold treatment lift. Deep cold treatment mounds to the influence of tenacity result of test of institute of new mining industry: Quench with convention, temper condition photograph is compared, high-speed steel classics is different methodological deep cold treatment, concussion tenacity (α K) the value increases 8.

8%52% ; Heibei industry university thinks: Condition of deep cold treatment of appearance of big Wu Tong plays the scope that deep cold treatment increases high-speed steel toughness, of intensity increase scope, toughness of concussion of W18 steel, M2 steel maximizes extent is amounted to 57.

7% with 43% ; Shanghai hands in steel of pairs of big M2 to make deep cold treatment after points out: The concussion tenacity of sample of deep cold treatment rises somewhat, not deep cold treatment person for 23J/cm2, deep cold treatment person for 23.

5J Cm2; Result of test of institute of Shanghai mechanical workmanship thinks deep cold treatment is right tenacity of M2 steel concussion does not have an influence, do not rise not to fall. Still a lot of concern the report that deep cold treatment affects to high-speed steel tenacity, without opposite opinion, it is to tell completely rise. The author thinks, deep cold treatment raises the evidential inadequacy of tenacity, reason is inadequate, tell normally, RR decreased, hardness rose, tenacity should drop, how is Mo elevatory? The comrade that makes high-speed steel cutting tool has such experience: It is easy to should achieve tall hardness, the tenacity that is about to make cutting tool keeps tall below tall hardness is very difficult. So, our view is in ensure the premise of tenacity issues tall hardness of do one's best. We are pressing hope visibility raises hardness not to die to report ceaselessly again to cutting tool deep cold treatment. Actual condition is, no matter be HSS or HSS-E steel cutting tool, saline bath quenchs temper after, highest hardness often exceeds craft level, must raise temper temperature to fall hardness, ensure tenacity, sacrificial hardness. Can deep cold treatment improve cutting tool life? EbNH of N Б Л points out, be in directly quench after or undertake in fluid N2 again through temper deep cold high-speed steel milling cutter, its service life raises 44%150% . Twist drill of straight power of 7mm of M2 steeliness φ raises 1 times via life of deep cold treatment, thick milling cutter of gear of 28mm of φ 120mm × , machine raises 50% above with reamer service life, high-speed steel machine also achieves the favorable result that improves life via deep cold treatment with saw blade. Still a lot of deep cold treatment raise the example of cutting tool life, it is odd mostly or sample data, without conviction. XeB of Л of Y of A П Γ point out through experiment after, high-speed steel cold treatment won't make steel gets particularly high cutting performance, but, cold treatment is the RR in eliminating steel method, the effect that it has also is mixed for many times temper is same, nevertheless, they point out again, cold treatment is in the following below two kinds of circumstances, can make cutting function rises: Replace temper for many times with temper, or quench with inferior temperature. The person such as GARoberts also thinks cold treatment can not improve cutting performance certainly, but for correctional quench overheat organization and stable dimension, use cold treatment is appropriate. Works of our home some tools reachs opposite conclusion, they think deep cold treatment not only the life that cannot improve cutting tool, make brittleness increases instead. Visible, so far, conclusion of deep cold treatment of high-speed steel cutting tool is abhorrent still, this basically is by become random still at the martensite photograph that produces below in 0 ℃ law but abide, additional, the method of the experiment is skimble-scamble, studies steel is planted unpopular, deep cold the variable of parameter of heat treatment craft before is big, the conditional otherness that undertakes cutting experiments is big, together with is factitious influencing factor is much, also be the reason that must not give same conclusion. Accordingly, pardonable someone says " deep cold treatment or a kind of heat treatment method that had not have studied adequately " . Conclusion 1, high-speed steel cutting tool quenchs after of classics convention temper, RR does not exceed 5% , temper is very sufficient already, not was necessary to have deep cold treatment. Temper is bad classics deep cold treatment, cutting tool life raises the error that is heat treatment, is not the contribution of deep cold treatment. 2, deep cold treatment is good to raising wearability, but adverse to tenacity, won't raise red rigid more, raise X of cutting tool life times suspect. 3, outside dividing finished product deep cold treatment, other method deep cold treatment is carried out very hard, and may appear the malady such as craze. 4, particularly tall to dimension precision requirement accurate cutting tool, finished product cutting tool can have deep cold treatment. In process of existing writings writing, get Zhang Hongkang of Shanghai tool works teachs the guidance of class senior engineer, get a surname of institute of technology of golden China profession jumps over teacher and Anhui the help of limited company of cutting tool of fine dragon high speed steel and support, in this acknowledgment! CNC Milling CNC Machining