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The difference between cast valve and forged valve

Casting valves are valves made by casting. Generally, the pressure grades of cast valves are relatively low (such as PN16, PN25, PN40, but there are also high-pressure ones, which can reach 1500Lb, 2500Lb), and most of their calibers are above DN50. Forged valves are forged and are generally used in high-grade pipelines with relatively small diameters, generally below DN50. Casting 1. Casting: It is the process of smelting metal into a liquid that meets certain requirements and pouring it into a mold, cooling, solidifying, and cleaning to obtain castings (parts or blanks) with predetermined shapes, sizes and properties. The basic […]

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Study on processing technology of 316L stainless steel flange

Aiming at the problems of the flange parts in the first piece trial cutting process, such as the parts precision is not up to standard, the efficiency is low, and it is impossible to batch. The main reasons for the above problems are analyzed. At the same time, it is proposed that the optimization of processing technology and the design of special fixture are the main ways to solve the problems. The practice shows that the improved processing technology can improve the processing efficiency of parts by about 75%, and the qualified rate of products can reach 100%, which provides […]

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Crevice corrosion behavior of several super stainless steels in simulated flue……

Flue gas desulfurization (FGD) is an important means for thermal power plants and iron and steel industry to effectively control SO2 emission, and is one of the key areas of environmental protection industry. In the past 10 years, FGD industry has developed rapidly, its equipment localization rate has reached more than 90%, the industry market is huge, and the prospect is attractive. FGD equipment system is very complex, the corrosion environment is very harsh, and the metal components often have serious corrosion problems. In this environment, the flue gas temperature changes greatly, and the critical temperature fluctuates, which is easy […]

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From the accident of Jiaxing thermal power plant: measures to prevent steam pi……

The steam pipe burst in the boiler operation room of Jiaxing thermal power plant. According to preliminary investigation, the main steam pipe of boiler 1 in Fuxin thermal power plant burst at the branch pipe of temperature and pressure reduction station. The accident happened in the boiler operation room. There was a lot of steam, no open smoke and no open fire. Explosion causes of high pressure steam pipeline Unreasonable pipeline design Insufficient pipeline flexibility Due to the unreasonable structure of the pipeline, the connection form of the pipe fitting and the valve or the inconsistent screw system, the pipeline […]

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Effect of crack on elbow strength of main steam pipeline

Crack is a common defect on the main steam pipeline. Because it causes local discontinuity of the pipeline, the crack position often produces relatively large stress concentration [1]. The crack itself has the characteristics of propagation, so its influence on the safe operation of the main steam pipeline has certain uncertainty. Whether the crack propagates or not is related to the load, temperature and medium characteristics of the main steam pipe. Some shape and size cracks are safe under certain conditions, but their safety will change with time [2-5]. As for the main steam pipeline and its accessories, in addition […]

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How to prevent back oxidation of stainless steel pipe during welding?

During the welding of stainless steel pipe in petrochemical construction, the surface of weld bead and heat affected zone are easy to be oxidized and discolored. In order to ensure the corrosion resistance of stainless steel, pickling and passivation treatment is carried out on the weld after welding to form a dense oxide film on its surface, but the inner wall of stainless steel pipe is unable to be pickled and passivated, which seriously reduces the corrosion resistance of the inner wall of stainless steel pipe. However, general welding process and construction measures are difficult to ensure the welding quality […]

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Explosion accident analysis of UNS S32205 duplex stainless steel pressure pipe……

Based on the analysis of a deflagration accident of a UNS S32205 duplex stainless steel pressure pipeline, the nondestructive testing, composition analysis, hardness testing, ferrite content testing, metallographic examination and mechanical property test were carried out on the UNS S32205 elbow. The influence of ferrite content of duplex stainless steel plate on the steel performance was studied. It was pointed out that hot forming was not considered in the design of 50% ferrite and 50% austenite respectively Or the effect of welding hot working on the decrease of microstructure and properties caused by the increase of ferrite content. It is suitable […]

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Causes of flange gasket failure and precautions

Generally, there are four types of leakage phenomenon of flange gasket: interface leakage, penetration leakage, diffusion leakage and damage leakage. Combined with many years of engineering construction, maintenance and manufacturing experience, the author thinks that the main reasons for seal failure are as follows: uneven distribution of compression force, stress relaxation, unsuitable surface roughness of sealing surface and temperature change. Uneven distribution of pressing force The uneven distribution of the pressing force will cause the gap of the flange gasket, which will cause the leakage. The uneven compaction force is caused by many factors. 1. It is man-made factor, asymmetric […]

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Detection and judgment of bending crack in angle bar

The angle bar in the transmission line tower needs the processing technology of opening angle, closing angle, bending and so on. In the production process, due to improper processing, the angle bar has cracks, and it is detected by ultrasonic according to the standard provisions. When the straight probe is used for detection, the detection direction of the straight probe sound beam is single, which is easy to form missed detection; when the oblique probe is used for detection of the diagonal steel edge, the ultrasonic wave produces the phenomenon of end angle reflection, and it is difficult to judge […]

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Effect of external potential on stress corrosion behavior of 316L stainless st……

316L austenitic stainless steel is a kind of ultra-low carbon stainless steel with carbon content less than 0.03%. Its material properties are equivalent to 00Cr17Ni14Mo2 steel in China [1,2]. 316L stainless steel, as the main material of PWR primary pipe and core components [3], has excellent mechanical properties and corrosion resistance, and is widely used in nuclear power field. 316L stainless steel flange is prone to stress corrosion cracking under the condition of stress and corrosive medium at the same time. This kind of corrosion is mainly caused by the destruction of the passivation film on the surface of 316L […]

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