Advantages Bright surface No decarburization No oxidation Minimized distortion Reproducibility Vacuum high temperature brazing Economical
TECHNICAL DATA VKNQ
Working Space 600x600x900 mm Charge Weight 500 Kgs max Rated Temp. 1,300 oC max Temp. Uniformity < + - 5 oK Quenching N2 Gas 6~10 bars Vacuum 10 -2 ~10 -5 mbars Manufactured by ALD (Germany)
PROCESS CONVECTIVE HEATING
Heat transfer takes place by radiation only in vacuum, which is ineffective at lower than 500 oC and develop large temperature difference between surface and core of work piece. Such temperature difference should make thermal stress, which might cause some distortion of work piece. By adding N2 gas of 2 bars for heat convector, homogeneous and rapid heating can be achieved.
PROCESS MARQUENCHING
In case of parts with large sections and complicated shapes, rapid quenching may lead to crack and/or serious distortion on work piece. By programmed controlling quenching above Ms point of material by using two thermocouples installed on surface and core of a dummy with charge, minimized distortion can be achieved.
PROCESS Reversible Direction
QUENCHING In quenching process, it is said that steel has to be quenched as fast and slowly as possible. The former is for enough cooling speed to obtain ideal micro structure, the latter is for prevent cracking and severe distortion of work. Our furnace makes both available by high pressure gas quenching, by programmable reversible cooling and by Marquenching
Concept Heat Treatment of HIGH ALLOYED TOOL STEELS
Hardening of high alloyed tool steels have to be carried out in way of vacuum process, in order to prevent any oxidation and decarburization. In our vacuum process, a dummy block of which diameter is equivalent to the control section of work piece to be hardened. Two thermocouples installed at both core and surface of the dummy can manage the temperature control of work piece at both surface and core throughout its hardening procedure. By this way we are able to ; - manage any thermal stress which may arise while heating work piece up and minimize any distortion. prevent insufficient austenitizing of core and over solution of carbides through austenitizing by controling austenitizing by core temperature. apply marquenching procedure in order to prevent cracking and minimize any distortion by both thermal and transforming stress in case of complicated shape work piece. Three high temperature temperings are to done as general rule. The first temper is for decomposing retained austenite which is unavoidable in high carbon and high-alloyed tool steels. By the second tempering we control hardness required. The third tempering is stress relieving to prevent any cracking and deforming through the subsequent process.
Hot work Alloyed Tool Steel
Though hot work alloyed tool steels have good hardenability and be enable to harden by gas quenching in vacuum process, as the size of mold become larger recently, early cracking problem has reported and quenching speed has been to be discussed. According to CCT curve left, bainite transforms in earlier stage than pearlite and it will accompany some amount of retained austenite in matrix. Carbides precipitated on boundary of austenite by tempering are considered the cause of early cracking. In our vacuum process, quenching nitrogen up to 10 bars can be used and can increase effective quenching speed by alternative direction quench program. Thus we will try to reduce bainite, intending long life mold making. We also recommend the late bainite transform type steels recently announced.
Cold Work Alloyed Tool Steels
Retained austenite may not be avoided by quenching this kind of steels because of high carbon and alloyed elements. Retained austenite often causes cracking or distortion of work piece in subsequent wire cut or grinding, subzero treatment or 2 times high temperature tempering are recommendable. By high temperature tempering, hardness specified shall be HRC55~58. When HRC60 is needed, austenitizing temperature must be applied 1070oC that is higher than usual one of 1030oC, in order to harden by second hardening. This process is not recommendable because it increases retained austenite. Further stress relieving is to be carried out for any subsequent machining process
High Speed Steels
High speed steel, as it shown in its name, has developed for cutting tools which can keep high hardness even if temperature of tools come up into red condition by high speed cutting. For this purpose, austenitizing must be carried out at 1200oC for high hardness. Tempering shall be carried out more than 3 times, as this steel has a lot of retained austenite after quenched. Thin cutting tools can be straightened taking an advantage of existing retained austenite after quenched while warm. High speed steel may be used in room temperature and instead high toughness is required. In this case, austenitizing shall be lower than usual. The pocess for high toughness is called as under hardening.
Vacuum high temperatureAdvantageous BRAZING
Oxide film on base metal bursts and be removed by vacuum and metal wall gets wet with alloy which enables good brazing. By heating the work piece to high temperature in vacuum, enough diffusion is available between metals and good bonding with no inclusion nor gas hole can be attained. Very narrow brazing gaps of less than 0.05mm makes bonding metals with high strength and good accuracy.
	Top