Summary: Pointed out pair of high-speed steel to use - deep cold treatment of 196 ℃ liquid nitrogen can make constituent happening changes apparently, make change of body of rudimental austenite Xiang Ma and the separate out that exceed fine carbide effectively, make the mould is obtained relatively the integrated and mechanical function of beautiful, groovier heat treatment improves the service life of mould of the high-speed steel after deep cold treatment 3 times above, have very fundamental use value. Since 1 foreword high-speed steel came out 1990 oneself, it is celebrated with making metallic cutting cutting tool all the time, develop as the leap of science and technology, the applied limits of high-speed steel expands ceaselessly. Begin from 60 time, japan is a center with industry of car, bicycle, try out high-speed steel does a mould to gain a success, the high-speed steel that produces now has 15% to be used at creating a pattern about. High-speed steel basically is to be used make cold extruding mould and cold mound tool set provide, especially Mo department high-speed steel fastens high-speed steel tenacity than W more advantageous. High-speed steel depends on the control of heat treatment technology with the main craft difficulty at the mould. At present our country uses the most extensive high-speed steel is tungsten department W18Cr4V (abbreviation 18-4-1) steel and tungsten department W6Mo5Cr4V2 (abbreviation 6-5-4-2) steel  . The tradition of these two kinds of steel quenchs temper craft characteristic is: After high temperature quenchs, need to be in inside sclerotic limits temper 3, in order to obtain tall hardness and hot rigid, if craft standard expresses 1 to show. Main drawback is in certain room hardness is not worth. To improve mould obdurability, in recent years the tradition of high-speed steel quenchs temper craft also happened to change. Express 1 high-speed steel of norms of commonly used heat treatment 2 deep cold treatment the cold treatment of law principle and process high-speed steel offers in 30 time later period, press traditional idea, the purpose of cold treatment is to will quench steel refrigeration arrives 0 times (it is commonly - 60 ℃ -- - 70 ℃ ) , make the leftover austenite change inside steel is martensite. High-speed steel cold treatment is used to basically apply at shortening on past industry heat treatment production is periodic, use namely quench + cold treatment + temper replaces a processing technique  , be in namely - 100 ℃ -- - 196 ℃ (liquid nitrogen) processing quenchs spare parts, be in ever since 400 ℃ temper, not indispensible and original 2 ― 3 repeat temper. Improve further via the hardness of the spare parts after deep cold treatment and wearability, wearability can rise 40% , shorten already temper time, saved energy, improved mould service life apparently again. 20 centuries since 70 time, work domestic and internationally to the research of deep cold treatment fruitful, before the wearability of the service life that the country such as Russia, United States, Japan all uses deep cold treatment successfully already to raise industry pattern, workpiece and dimension stability. (1) the constituent change after deep cold treatment. Via deep cold treatment quench high-speed steel not only caused austenite change, also caused martensite change at the same time. What emphasized a few years in the past is leftover austenite change, martensite decomposes this one new discovery to be able to perceive the new progress that in recent years high-speed steel deep cold treatment studies. The martensite that high-speed steel plants transforms finally bit of Mf is very low, for example the Mf dot of W18Cr4V steel is made an appointment with - 100 ℃ , because this quenchs refrigeration can remain to room temperature many austenite, the austenite that thinks the remain in steel is more commonly is harmful, the hardness that can reduce steel, wearability reachs service life, still make a lot of physics function heat up function and magnetism to drop especially. The experiment proves: Use deep cold treatment to be able to make austenite of the remain in steel falls to lowermost limit, by the watch 2 can see W18Cr4V high-speed steel classics quenchs, after temper, deep cold treatment can make the quantity reduces the rudimental austenite after temper 24% . Express technology of 2 different processing to remain to W18Cr4V steel the influence of austenite (concentration percentage by volume is counted % ) university of industry of Leningrad of the Russia before studied - the influence that the deep cold treatment of the 15min in 196 ℃ liquid nitrogen transforms to high-speed steel, test result makes clear, - 70 ℃ -- - 75 ℃ arrive - 130 ℃ -- - martensite change produces when deep cold treatment having inside 140 ℃ limits, arrive when refrigeration - backwater of the change when 196 ℃ . Be in - 90 ℃ -- - inside limits of 120 ℃ temperature, of occurrence sample cubage get effective, this proof martensite already was decomposed partly and the separate out on bad side of v/arc be on the throne carbolic atom and formed super- microscopical carbide. Visible, company cold treatment makes the grain of carbide of high-speed steel separate out apparent grow in quantity, and dispersion is even, w18Cr4V steel increases about via grain of the carbide after deep cold treatment 8% , the carbide grain of W6Mo5Cr4V2 steel separate out increases about 76% , matrix organizes Yi Mingxian to refine. (2) the influence of deep cold treatment to high-speed steel function. In process of deep cold treatment, much rudimental austenite change is martensite, especially the metastable of supersaturation decides martensite to be in from - 196 ℃ reduce supersaturation to spend to the meeting in room temperature process, separate out dispersion, dimension is 20 ― 60A only and maintain with matrix in all case concerns exceed imperceptible carbide, can make distortion of martensite crystal lattice is reduced, microcosmic stress is reduced, and the carbide of petty dispersion is OK when material plasticity is out of shape block up wrong motion, thereby aggrandizement matrix organization. At the same time because exceed imperceptible carbide separate out, distributing to go up in martensite matrix equably, abate crystal boundary catalysis, and matrix organizes refine already abate foreign matter element is in of crystal boundary slant get together degree, produced effect of crystal boundary aggrandizement again, improved the performance of high-speed steel thereby, make tenacity of hardness, concussion and wearability rise significantly  . Mould hardness is tall, its wearability is good also, rise by 60HRC like hardness to 62-63HRC, mould wearability increases 30% ― 40% . The opposite wearability that can see the pattern after deep cold treatment rises 40% , after extending time of deep cold treatment, below the circumstance that does not have too big change in hardness, increase somewhat relative to wearability ξ  . (3) process of deep cold treatment of high-speed steel mould is prevent high-speed steel mould (especially the pattern with mixed appearance) happen to rupture and become fragile in deep cold treatment, the high-speed steel mould after the proposal quenchs is in deep cold treatment of liquid nitrogen of travel of reentry of 1h of 560 ℃ temper, undertake final temper 30-60min in 400 ℃ next, craft of this kind of heat treatment not only can rupture in order to prevent a mould and fragile change, and can improve mould life 1.
5 ― 2 times. Process of deep cold treatment of high-speed steel mould is " , the mould puts the → in heat preservation canister except oily dirty → a few for many times → of 4h of heat preservation of → of infuse liquid nitrogen takes out mould → 45min of 400 ℃ temper. Deep cold treatment of mould of 3 high-speed steel applies example (1) punch: The high-speed steel punch of car plant, without can be being used 100 thousand times only when deep cold treatment, and use liquid nitrogen classics - after deep cold treatment of 4h of 196 ℃ × again 400 temper, service life rises. (2) punch sunken model: Production uses a result to make clear, the yield after deep cold treatment rises duple much. (3) silicon steel piece cold die: To reduce the brittleness after mould deep cold treatment and internal stress, will deep cold treatment and in lukewarm temper closes suitably, ameliorable mould is fought ruinous reach other integral performance, the blade of the mould grinds life to raise 3 times above, stability is in 5 ― 70 thousand strong second. 4 last word (1) in process of high-speed steel deep cold treatment, as a result of body of rudimental austenite Xiang Ma and the separate out that exceed fine carbide, tenacity of hardness, wearability, concussion, red rigid gets rising. (2) in the heat treatment that uses in steel of high speed mould as deep cold treatment of a kind of new technology, can improve the service life of the mould significantly, have very great economic value. CNC Milling