(1) The chemical composition of steel is one of the most important factors affecting hardenability. All alloying elements that cause the "c" curve to shift to the right or left in steel have a great influence on the hardenability. The element that shifts the "c" curve to the right will increase the hardenability of the steel; the element that shifts the "c" curve to the left will reduce the hardenability of the steel. For example, 45 steel and 40Cr steel have similar carbon content. However, since the former does not contain chromium, the latter contains about 1% of chromium. Under the same heat treatment conditions, their hardenability is obviously different. 45 steel only It can be hardened by 3.5-9.5 mm, while 40Cr steel can be hardened by 25-32 mm.
(2) The cooling characteristics and cooling rate of the heat treatment cooling medium also have a great influence on the hardenability of the steel. When the cooling rate is fast, the hardenability is improved, and the cooling rate is lowered, and the hardenability is lowered. For example, 45 steel is cooled in water and cooled in oil, and its hardenability is different. When it is cooled in water, it can be hardened by 11-20 mm, and when cooled in oil, it can be hardened by 3.5-9.5 mm.
(3) The shape and size of the parts, heating temperature, cooling method, etc., affect the hardenability of the steel to varying degrees. The shape size is small, the heating temperature is high, and the continuous cooling can improve the hardenability to some extent. However, the shape size is large, the heating temperature is low, and the isothermal cooling can reduce the hardenability.
(4) The way of heating also affects the hardenability, which is very important in practical operation, and we tend to ignore this. The heating effect is different because of the different heating methods. For example, the use of a box type electric furnace is more serious than the oxidation and decarburization of the salt bath furnace, and the hardenability is lowered.
Ball valve is evolved from the plug valve, its opening and closing parts as a ball, using the ball to rotate 90 degrees around the axis of the stem to achieve the purpose of opening and closing, the difference is that the cock body is a ball, with a circular through hole or channel through its axis. The ratio of the sphere to the passageway should be such that when the ball is rotated 90 degrees, the inlet and outlet should be completely spherical, thus cutting off the flow.
The role of ball valve in the pipeline is mainly used to cut off, distribute and change the direction of media flow, designed into the V-shaped opening ball valve also has good flow regulation function.
Ball valve is not only simple in structure, good sealing performance, but also in a certain nominal range of small volume, light weight, less material consumption, small installation size, and driving torque is small, easy to operate, easy to realize rapid opening and closing, is one of the fastest developing valve varieties in recent decades. Especially in the United States, Japan, Germany, France, Italy, West, Britain and other industrial developed countries, ball valves are widely used, the variety and number of use is still continuing to expand, and to high temperature, high pressure, large mouth, high sealing, long life, excellent regulatory performance and a valve multifunctional direction, its reliability and other performance indicators have reached a higher level, And has partially replaced Gate Valve, Globe Valve, Regulating Valve.
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