China Wenzhou Zheheng Steel Industry Co.,Ltd Company News

Stainless steel flat welded flange side accessories are customized. The fixture must first reach the leak point. The main point is to create a closed cavity between the stainless steel flange of the valve body and the pipe joint. To prevent leakage between the valve body and the stainless steel flange due to pressure retention, a ring cavity is provided where the outer edge of the clamp and the stainless steel flange of the valve body overlap. The tooth contact clamp is used as a limiting device because the clamp on the small diameter stainless steel flange is easily moved to the small diameter stainless steel flange during the injection process. After the sealant has hardened during operation, check for stress relaxation and then perform a local re-injection to close the injection port.   Stainless steel flat welding flange installation procedure   1, welding current should not be too large, about 20% smaller than carbon steel electrode, arc can not be too long, interlayer cooling can not prevent heating flange cover corrosion corrosion must be fast.   2, the electrode must be dried before use. Perovskite type should be dried at 150°C for 1 hour, low hydrogen type should be dried at 200-250°C for 1 hour (do not repeat drying more than once. Do not increase the welding, the carbon content of the welding is to prevent the electrode coating from adhering to the oil and other dirt, so as not to affect the quality of the parts.   3. When welding stainless steel flange fittings, carbide precipitation and mechanical properties will occur due to repeated heating and corrosion resistance.   4. After welding, the flange of the hardenable American standard chromium stainless steel flange fittings is larger and easier to crack. Similar types of chrome-stainless steel electrodes (G202, when using G207) must be preheated to 300°C or higher after welding and gradually cooled to about 700°C after welding. If heat treatment of the weld is not possible, the rod (A107, A207) must be used for welding of stainless steel flanges.   5, stainless steel flange, appropriate amount of stable elements Ti, Nb, Mo, etc., to improve corrosion resistance and weldability, weldability is better than chromium stainless steel flange, when using the same type of chromium stainless steel flange electrode (G302, G307), preheat it to 200°C or higher, and tempered to about 800°C after welding. If not, it needs to be used.   6, stainless steel flange electrode (A107, A207), stainless steel flange fittings, welding flange electrode with excellent corrosion resistance and oxidation resistance is widely used in the manufacture of chemicals, fertilizers, petroleum, medical machinery.

1, before installation, be sure to carefully check the various standards of stainless steel elbow, check whether the diameter meets the requirements of use, eliminate the defects caused by the transportation process, and remove the dirt of stainless steel elbow, and prepare for installation.   2, when installing, the stainless steel elbow can be directly installed on the pipe according to the connection method, and installed according to the position used. Under normal circumstances, it can be installed in any position of the pipeline, but it needs to be easy to operate maintenance, pay attention to the media flow of the stainless steel elbow should be upstream below the longitudinal valve disc, and the stainless steel elbow can only be installed horizontally. Stainless steel elbow should pay attention to sealing when installing to prevent leakage and affect the normal operation of the pipeline.   3, stainless steel elbow valve packing gland bolts should be evenly tightened, should not be pressed into a distorted state, so as not to hurt hinder the movement of the valve stem or cause leakage.   4, stainless steel elbow ball valve, globe valve, gate valve when used, only fully open or fully closed, not allowed to adjust the flow, so as to avoid the sealing surface erosion, accelerated wear. The gate valve and the upper thread stop valve have reverse sealing devices, and the hand wheel is turned to the upper position to tighten, which can prevent the medium from leaking from the packing place.

There are many kinds of connections between stainless steel pipes. For example:   1. Clamp type connection The working principle of the clamping connection is to insert the thin-wall stainless steel pipe into the socket of the clamping pipe fitting, and use the special clamping tool to clamp the stainless steel pipe in the pipe fitting, the section shape of the clamping is hexagonal, and there is an O-ring seal between the stainless steel pipe and the pipe fitting, so that it has the characteristics of anti-leakage, anti-drawing, anti-vibration and high-pressure resistance. This connection method is suitable for water, oil, gas and other pipeline connections.   2. Card type connection A connection in which the pipe is pressed to the fitting with a locking nut and a clamping ring for an open pipe. Features: The sealing surface of the sleeve pipe fitting is short, easy to install, no special tools are required, and can be disassembled. It is generally used in water and gas systems below 2632 specifications.   Socket connection Socket connection mode is divided into mechanical interface and non-mechanical interface. The mechanical interface is connected with the upper flange of the pipe end by pressing the rubber seal ring in the gap of the cast iron socket, so that the rubber ring is compressed and closely with the pipe wall to form a seal.   Threaded connection Threaded connection, also known as wire connection, it is through the internal and external threads to connect the pipe with the pipe, the pipe with the valve. This connection is mainly used for steel pipe, copper pipe and high pressure pipe connection.   Flange connection Flange connection is a connection method that fixes two pipes or pipe fittings on a flange, and then adds flange pads between the two flanges, and finally pulls the two flanges tightly together with bolts.   Welding connection Stainless steel pipe welding generally adopts argon arc welding to cover the bottom, manual arc welding to cover the surface, and the tube is filled with argon protection, so that the weld inside the tube does not produce oxidation. For stainless steel pipes with smaller diameters, argon arc welding can also be used directly to seal and cover the bottom. After the stainless steel pipe is welded, the weld surface should be pickled and passivated.

Stainless steel pipes are divided into ordinary carbon steel pipes, high-quality carbon structural steel pipes, alloy structural pipes, alloy steel pipes, bearing steel pipes, stainless steel pipes and bimetal composite pipes, coatings and coated pipes to save precious metals and meet special requirements. There are many kinds of stainless steel pipes, because of different uses, their technical requirements are different, and the production methods are also different. The current production of steel pipe diameter range 0.1-4500mm, wall thickness range 0.01 ~ 250mm. In order to distinguish its characteristics, the steel pipe is usually classified according to the following method.   Mode of production   Stainless steel pipe according to the production method is divided into seamless pipe and welded pipe two categories. Seamless steel pipes can also be divided into hot-rolled pipes, cold-rolled pipes, cold-drawn pipes and extruded pipes. Cold drawing and cold rolling are the secondary processing of steel pipe. The welded pipe is divided into straight seam welded pipe and spiral welded pipe.   Section shape   Stainless steel pipe according to the cross-section shape can be divided into round pipe and shaped pipe. The special-shaped pipe has rectangular pipe, diamond pipe, oval pipe, hexagonal pipe, eight pipe and a variety of cross-section asymmetric pipe. Shaped tubes are widely used in various structural parts, tools and mechanical parts. Compared with the round tube, the shaped tube generally has a larger moment of inertia and section modulus, and has a larger bending and torsional resistance, which can greatly reduce the weight of the structure and save steel.   Pipe end shape   Stainless steel pipe can be divided into light pipe and wire pipe (with rebar steel pipe) according to the state of the pipe end. Wire pipe can also be divided into ordinary wire pipe (conveying water, gas and other low pressure pipe, using ordinary cylindrical or conical pipe thread connection) and special thread pipe (oil, geological drilling pipe, for important wire pipe, using special thread connection), for some special pipe, in order to make up for the impact of thread on the strength of the pipe end, Tube end thickening (internal thickening, external thickening or internal and external thickening) is usually carried out before wire drawing.   Use classification   According to the use can be divided into oil well pipe (casing, tubing and drill pipe, etc.), pipeline pipe, boiler pipe, mechanical structure pipe, hydraulic support pipe, gas cylinder pipe, geological pipe, chemical pipe (high-pressure fertilizer pipe, oil cracking pipe) and ship pipe.

There are thousands of varieties of steel used in various industries. Each steel has a different trade name due to different properties, chemical composition or alloy type and content. Although fracture toughness values greatly facilitate the selection of each steel, these parameters are difficult to apply to all steels. The main reasons are:   1. Because a certain amount of some or more alloying elements need to be added in the smelting of steel, different microstructure can be obtained after simple heat treatment, thus changing the original properties of steel; 2. Because the defects generated in the process of steelmaking and pouring, especially concentrated defects (such as pores, inclusions, etc.) are extremely sensitive during rolling, and different changes occur between different furnace times of the same chemical composition steel, and even in different parts of the same billet, thus affecting the quality of the steel. Because the toughness of steel mainly depends on the microstructure and the dispersion of defects (strictly prevent concentrated defects), rather than the chemical composition. Therefore, toughness will change greatly after heat treatment. In order to deeply explore the properties of steel and the causes of fracture, it is also necessary to master the relationship between physical metallurgy and microstructure and steel toughness.   The influence of processing technology   It is known from practice that the impact performance of water-quenched steel is better than that of annealed or normalized steel, because the rapid cooling prevents the formation of cementite at grain boundaries and promotes the finer of ferrite grains. Many steels are sold in the hot rolled state, and rolling conditions have a great influence on impact properties. The lower final rolling temperature will reduce the impact transition temperature, increase the cooling rate and promote the ferrite grain to become finer, thus improving the toughness of the steel. Because the cooling rate of thick plate is slower than that of thin plate, the ferrite grain is thicker than that of thin plate. Therefore, under the same heat treatment conditions, thick plates are more brittle than thin plates. Therefore, normalizing treatment is commonly used after hot rolling to improve the properties of steel plates. Hot rolling can also produce anisotropic steels and directional ductile steels with various mixed structures, pearlite bands and inclusion grain boundaries in the same rolling direction. The pearlite band and elongated inclusions are coarse dispersed into scales, which have great influence on the notch toughness at low temperature in Charpy transition temperature range.   The impact of carbon content in 0.3% ~ 0.8%   The carbon content of hypoeutectoid steel is 0.3% ~ 0.8%, and the proeutectoid ferrite is a continuous phase and first forms at the austenitic grain boundary. Pearlite is formed in austenite grains and accounts for 35% ~ *** of the microstructure. In addition, a variety of aggregation structures are formed within each austenite grain, making pearlite polycrystalline. Because the pearlite strength is higher than the pre-eutectoid ferrite, the flow of ferrite is limited, so that the yield strength and strain hardening rate of steel increase with the increase of the carbon content of pearlite. The limiting effect is enhanced with the increase of the number of hardened blocks and the refinement of the preeutectoid grain size of pearlite. When there is a large amount of pearlite in the steel, micro-cleavage cracks can be formed at low temperatures and/or high strain rates during deformation. Although there are some internal aggregate tissue sections, the fracture channel is initially along the cleavage plane. Therefore, there are some preferred orientations in the ferrite grains between the ferrite plates and in the adjacent aggregation structures.   Stainless steel fracture   Stainless steel is mainly composed of iron-chromium, iron-chromium-nickel alloys and other elements that improve mechanical properties and corrosion resistance. Stainless steel corrosion resistance is due to the formation of chromium oxide on the metal surface to prevent further oxidation - an impermeable layer. Therefore, stainless steel in an oxidizing atmosphere can prevent corrosion and strengthen the chromium oxide layer. However, in reducing atmosphere, the chromium oxide layer is damaged. The corrosion resistance increases with the increase of chromium and nickel content. Nickel can improve the passivation of iron. The addition of carbon is to improve the mechanical properties and ensure the stability of austenitic stainless steel properties. In general, stainless steel is classified by microstructures. Martensitic stainless steel It is an iron-chromium alloy that can be austenitized and post-heat treated to produce martensite. Typically 12% chromium and 0.15% carbon. Ferritic stainless steel. Chromium content about 14% ~ 18%, carbon 0.12%. Because chromium is a stabilizer of ferrite, the austenitic phase is completely suppressed by more than 13% chromium and is therefore a complete ferrite phase. Austenitic stainless steel. Nickel is a strong stabilizer of austenite, so at room temperature, below room temperature or high temperature, nickel content of 8%, chromium content of 18% (type 300) can make the austenite phase very stable. Austenitic stainless steels are similar to ferritic forms and cannot be hardened by martensitic transformation. The characteristics of ferritic and martensitic stainless steels, such as grain size, are similar to those of other ferritic and martensitic steels of the same class.