The characteristics and heat treat process of precision steel tube

Because of the precision steel tube inside and outside wall without oxidation layer, under high pressure without leakage, high precision, high finish, cold bending deformation, flaring, flattening without cracks etc, it is mainly used to produce pneumatic or hydraulic components products, such as a cylinder or cylinder, can be a seamless steel pipe, welded pipe.Vacuum annealing of high quality spring steel, tool steel, precision steel wire, stainless steel and titanium alloy material, make bright annealing treated by vacuum.The lower annealing temperature is, insist on the higher the degree of vacuum.In order to prevent the evaporation of chromium and accelerate the heat conduction, generally USES the carrier heating method (insulation), and pay attention to stainless steel and titanium alloy is unfavorable use nitrogen and argon gas should be adopted.

Vacuum quenching vacuum quenching furnace according to the cooling method is divided into two types of oil quenching and quenching, according to the location number can be divided into single room and double room, 904 mountain feared chao cycle type furnace.Vacuum oil quenching furnace are double room, room after electric heating element, tank down to the bottom of the front room.Artifacts after heating, heat preservation before moving room, closed the door after forward chamber inert gas, into the oil.Oil quenching easy cause surface deterioration.In short, because of the large surface activity under the action of high temperature and oil film can markedly thin-layer carburizing, in addition, carbon black and oil on the surface adhesion to simplify the heat treatment process is very adverse.Vacuum quenching technology development is the main of the development of high performance, the single gas cooling quenching furnace.The double chamber furnace can also be used for gas quenching (in the front room jet cooling), but the operation of the double location type difficult in the mass production of furnace, is also in the workpiece deformation caused by the high temperature moving or changing artifacts bearing quenching distortion increase.In a single location - cooling quenching furnace is after completion of the heat preservation in heating indoor jet cooling.Oil is better than cold air cooled cold speed is fast, and lower than the traditional quenching method of molten salt, isothermal, graded and quenching.Therefore, continuously improve spray cold chamber pressure, increase traffic, and the molecular weight smaller than nitrogen and argon, inert gas helium and hydrogen is the mainstream of the development of vacuum quenching technology today.The cooling capacity close to the pressure of oil cooling.The mid - 80 - a super high pressure gas quenching, the cooling capacity is equal to or slightly higher than the oil quenching, has entered the industrial utility.Close to the water quench cooling capacity, was still in its infancy.Industrial developed country has progress to high pressure gas quenching as the main body, and some chinese-made gas quenching metal vapor pressure (theoretical value) and the relationship between the temperature is at ordinary pressure gas quenching (2% 26 times; 10 pa) phase.

Vacuum carburizing for vacuum carburizing and quenching process curve.In a vacuum heating surface to the carburizing temperature and heat preservation after purification, activation, bubbled into thin carburizing enriched gas (see the controlled atmosphere heat treatment), about 1330 pa (10 t0rr) infiltration under negative pressure, and then stop gas diffusion (buck).Precision steel tube after carburizing quenching A quenching method, namely the first power, nitrogen cooling artifacts to point A below, make the internal phase change, and then stop gas, open the pump, heating up to Ac1, ~ Accm.Quenched method can be used air-cooled or oil cooling.After the latter for the austenitizing before moving room, nitrogen filled to atmospheric pressure, into the oil.Vacuum carburizing temperature is higher than ordinary gas carburizing, 920 ~ 1040  is often used as shown in the infiltration and diffusion can be divided into two stages, also can use pulsed ventilation and gas, many sections of the ooze a expansion and white, more effective.Owing to the high temperature, especially surface clean, active, vacuum carburizing layer forming speed is faster than ordinary gas, liquid and solid carburizing and carbonitriding layer to 1 mm, just 5 h at 927 , 1033  and only 1 h.