Hot bending method for stainless steel pipe fittings

Stainless steel pipe fittings in heating condition, to bend called hot bending. The bending of the stainless steel pipe fittings and can be divided into sand filling without buckling of hot bending and buckling is not filling sand hot bending.
Without buckling filling sand hot bending under applicable to D400mm stainless steel pipe fittings, the bending radius R > 3.5 D,. Its main operations include line filling sand heating, cooling and heat treatment, etc.
(1) stainless steel pipe’s line pipe crossing is usually marked with white chalk or white paint mark. L, when a is in the bend, the fixed with two block string (bolt) ask, D, < l50mm stainless steel pipe fittings, L1 should be not less than 500 mm, D > l50mm stainless steel pipe fittings, L1 should be not less than 600 mm, L the length of the stainless steel pipe fittings heating bending part.
(2) the sand filling,  tube filling sand within the purpose is to prevent the stainless steel pipe fittings elliptic or buckling when bending. At the same time, in the sand heating can save big when the quantity of heat, can extend the time of bend pipe.
Sand should be clean screen and drying, to particle size also to have certain requirements. Before filling sand, stainless steel pipe fittings at one end of the plug with length to diameter 1.2 ~ 2 times. About 25 of taper conical dry wood heart can also use the steel seal or use the steel plate welding seal), and then sucked straight stainless steel pipe fittings, with one end of the cork on the ground, with a special filling sand and sand filling equipment or manual with funnel will move into the tube. Each pack sand filling height 300 ~ 400 mm, with iron bars or vibrators outside the tube walls of beat vibration, the packed sand strong. After filling sand, in the top of the stainless steel pipe fittings to also want to break into a cork, and cork must come into contact with the tube of the sand.
(3) stainless steel pipe fittings of commonly used heating pipe, heating furnace, heating gu, used for carbon SuoGang with coke or anthracite, the brass and alloy steel pipe, appropriate USES charcoal for aluminum tube with coke. Bituminous coal tender material it is forbidden to use it, for the bituminous coal contain harmful impurities such as sulfur, phosphorus, heating will penetrate into pipe fittings surface of metal in the organization, and make the pipes become fragile.
Heating pipe, should be assorted child need ah song over the toe in the flame of uniform, do not turn the pipe when heated evenly. Depending on the types of pipes and heating temperature, the carbon steel pipe is 950 ~ 1000 ℃ (i.e., to pink or orange), of low alloy steel pipe is 1050 ℃, the nickel and chromium stainless steel tube is 1100 ~ 200 ℃, the copper pipe is 400 ~ 500 ℃, the aluminium tube is 300 ~ 400 ℃ when the stainless steel pipe fittings and the sand are all reach the heating temperature, should immediately remove the pipe bending.
(4) Platform has two kinds of concrete and cast iron. Fixed platform soil has a steel bolt, sample or model. Better stainless steel pipe fittings of heating on the platform quickly, end between steel bolt, the other end is in 3 ~ 5 seven hand dumpling or electric car hinge for wire rope tied bent stainless steel pipe fittings, smooth stretch bending speed should be uniform. Tended to be slightly stainless steel pipe fittings for cooling after bending springback straightened (3 ~ 5 °), so when bend bend more than sample 3 ~ 5 °, or taken into account when making sample.
(5) the cooling of the stainless steel pipe fittings and desanding tube bending, buried in the hot sand or asbestos dust, best to make it slow cooling. After being the pipe cooling, will empty tube sand, remove residual burning in the sand, with compressed air blowing off again, finally check its curved shape and any other defects.
(6) stainless steel pipe fittings after heat treatment of carbon steel pipe bending generally don’t need to heat treatment, but for the higher working pressure pipe bending best annealing treatment, in order to eliminate the internal stress generated when the bend. Annealing method is generally around the bend heated to 600 ℃, slow cooling in the air again can. For alloy steel tube, should for normalizing and tempering treatment, in order to improve the microstructure and stress relief.

Source: Zhejiang Yaang Pipe Industry Co., Limited (www.yaang.com)

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