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Stainless steel has good overall performance and good surface characteristics and has a wide range of applications in all walks of life. Similarly, stainless steel pipe is no exception. Stainless steel pipe is a kind of steel with a hollow section, generally divided into stainless steel seamless pipe and welded pipe. They also have certain differences in processing methods and performance, the differences are as follows:

First, the difference in the production process

Stainless steel welded pipe is made of steel plate or strip after the unit and mold curling and forming welded, the tube wall generally has a weld; and a seamless tube is used as a round billet for perforation of raw materials, through the production process of cold rolling, cold drawing or hot extrusion made, there is no welding point on the tube.

Second, the difference in the appearance of steel pipe

Stainless steel welded pipe, the tolerance of its wall thickness is very small, and the wall thickness of the entire circumference is very uniform; the high precision of steel pipe, and high brightness of the inner and outer surface of the tube, can be arbitrarily sized; can do thin-walled tube. In contrast, the steel tube of seamless pipe has low accuracy, uneven wall thickness, low brightness of the inner and outer surface of the tube, high cost of sizing, and the inner and outer surfaces of the pockmark and black spot are not easy to remove. Therefore, the production of seamless pipe walls is usually thicker.

Third, the difference in performance and price

Seamless pipes are much higher than welded pipes in terms of corrosion resistance and pressure and high-temperature resistance. With the improvement of the production process of welded pipes, mechanical properties, and mechanical properties are slowly approaching seamless pipes. Seamless pipe is more complicated in the production process, and it is more expensive than welded pipe. Based on the characteristics and differences between seamless and welded stainless steel pipe, the application should be reasonably selected to achieve economical, beautiful, and reliable results: 1, used as a decorative tube, product tube, or prop tube, generally requires a good surface effect, usually choose stainless steel welded pipe; 2, for general lower pressure fluid transfer, such as the transfer of water, oil, gas, air and heating hot water or steam and other low-pressure systems, usually Choose stainless steel welded pipe; 3, for the pipeline used in industrial engineering and large equipment to transport fluids, as well as power stations, nuclear power plant boilers, require high-temperature and high-pressure, high-strength transport fluid pipeline, should be selected seamless stainless steel pipeline; 4, stainless steel welded pipe is generally used for liquid transport below 0.8MPa, a seamless pipe can be used to withstand the liquid transport above 0.8MPa. If the pressure requirements are not high, the use of welded pipe will be more economical.

Four, stainless steel seamless pipe advantages and disadvantages

Advantages: forming speed, high yield, can be made into a variety of cross-sectional forms to adapt to the needs of the conditions of use; cold rolling can make a large plastic deformation of steel, thereby increasing the yield point of steel. Hot rolling can destroy the casting organization of the ingot, refine the grain of the steel, and eliminate microstructural defects so that the steel organization is dense and the mechanical properties are improved. Disadvantages: 1, metal delamination – steel after cold rolling, the steel internal non-metallic inclusions (mainly sulfides and oxides, and silicates) are pressed into thin sheets, the phenomenon of delamination (sandwich). Delamination makes the steel along the thickness of the direction of the force performance greatly deteriorate, and there is a possibility of interlayer tearing when the weld expands. 2, uneven wall thickness – we are familiar with the metal has thermal expansion and contraction, due to rolling to the end of the cold-rolled steel pipe even if the length, and thickness are up to standard, the final cooling will still appear a certain negative difference, this The larger the negative difference, the worse the uniformity of the wall thickness. Therefore, the wall thickness, length, straightness, and ellipticity of cold-rolled seamless steel tubes can not be required to correct. 3, residual stress – due to uneven cooling, a variety of cross-sectional steel tubes have residual stress, the larger the cross-sectional size of the steel, the greater the residual stress, under the action of external forces has a certain impact on performance. Such as deformation, stability, fatigue resistance, etc. may have a detrimental effect. 4, poor surface finish – the inner surface of the steel pipe tensile marks are longitudinally distributed, showing a symmetrical or single linear fold, some through-length presence, and there is also a local presence.

Conclusion

Seamless pipe due to the complexity of the production process, the wall thickness uniformity is poor, the inner and outer wall surface roughness is poor, the actual operation is easy to make the chloride ion (or sulfur ion) substances (such as organic matter) bonded in the stainless steel pipe wall, the formation of a local anoxic acidic environment, so that the inner wall passivation film dissolved lose the protective effect on the metal, the metal directly in contact with the medium in the acidic environment, as the anode lost electrons and formed with water Hydroxide, hydroxide in the hydroxide is replaced by chlorine and dissolved in water, reducing the anodic passivation effect. Bond as a cathode to capture the hydrogen ions generated by the inner wall to form hydrogen gas, and with the inner wall of the metal reaction products together with the outward discharge, with the depth of the reaction, the wall of the metal is constantly corroded to form hole corrosion, the hole will gradually deepen and increase. When the temperature rises to 50 degrees above the pitting corrosion accelerates, the higher the temperature pitting corrosion faster. In large stress, conditions will also occur under the stress corrosion and stress corrosion expansion characteristics. In addition, the seamless tube in the welding process will produce a variety of instability, not easy to weld, and weld impermeable.

Five, stainless steel welded steel pipe advantages

Stainless steel welded steel pipe – uniform wall thickness of stainless steel strip in the gas protection without the addition of solder fusion welding once rolled into shape.

Advantages: 1. uniform wall thickness – the parent material for the forming strip, wall thickness consistency, high surface finish, to achieve industrial clean surface level 2B. 2. low residual stress – forming the steel tube using a high temperature higher than 1040 degrees for bright annealing stainless steel tube stress relief. 3. High weld strength – welding using melt welding, the material composition remains unchanged after high-temperature heat treatment of the weld and the parent material has the same intergranular structure, the weld is flattened, reverse bending, flaring and other damage experiments, the weld will not crack or cracks, burrs, and other problems. In addition to this, eddy current testing and water pressure or gas test should be done to ensure the quality of the tube. 4. Good consistency – good consistency of the outer diameter, wall thickness, length, and straightness of the tube, and high processing accuracy.

The Copper alloy has excellent electrical and thermal conductivity as well as good strength, toughness, and fatigue resistance, and is therefore widely used, for example, in various continuous casting molds, blast furnace slag holes, oxygen nozzles for converters, and so on. Among them, the C17200 copper alloy has very good strength and electrical conductivity and is popular for its easy processing and non-magnetic properties. C17200 copper alloy is widely used in contact components such as conductive brushes and rolled rings because of its very good elastic properties. However, because of the low hardness of these alloys, they are susceptible to adhesion and abrasive wear, so it is essential to improve their tribological properties by preparing surface modification layers. This can be achieved by introducing other alloying elements into the surface to create intermetallic compound-modified layers.

Chemical composition of C17200 copper alloy

Beryllium Be:1.90-2.15

Cobalt Co:0.35-0.65

Nickel Ni:0.20-0.25

Copper Cu: remainder

Silicon Si:<0.15

Iron Fe:<0.15

Aluminum Al:<0.15

Comparison standard: AISIC17200

Intermetallic compounds exhibit good properties such as high strength, low density, good oxidation resistance, and high-temperature performance. Recently, intermetallic compounds have gained much attention as good wear-resistant materials such as Ti-Al intermetallic compounds, Ni-Al intermetallic compounds, Ni-Ti compounds, Mo-Si compounds, and Fe-Al compounds.

Main performance index

Tensile strength(Mpa):1105

Specific gravity(g/cm3):8.3

Yield strength(0.2%)Mpa:1035

Softening temperature(℃):930

Elongation(%):1

Modulus of elasticity(Gpa):128

Hardness(HRC):38-44

Thermal conductivity(W/m.k20℃):105

Electrical conductivity(IACS%):18

Titanium nitride films have excellent chemical and physical properties and exhibit good tribological and mechanical properties, such as good electrical conductivity, chemical stability, chemical inertness, biocompatibility, high thermal conductivity, wear and corrosion resistance, and fairly high hardness.

Characteristics and Applications of C17200 copper alloy

After heat treatment (solution treatment and aging treatment), it has a high strength limit, elastic limit, yield limit, and fatigue limit which are comparable to special steel, and also has high electrical conductivity, thermal conductivity, high hardness, corrosion resistance, wear resistance, good casting performance, non-magnetic and non-sparking characteristics. It is widely used in mold-making, machinery, electronics, and other industries.

It has no sand holes, air holes, balanced hardness, dense organization, high strength, good thermal conductivity, good electrical conductivity, corrosion resistance, excellent wear resistance, good processing performance, stable performance under high-pressure conditions, non-magnetic, and good anti-adhesive properties.

NI200 is a pure nickel material that differs from ordinary nickel-based alloys in terms of chemical composition. Other elements such as chromium, molybdenum, titanium, and iron are added to ordinary nickel-based alloys to improve their corrosion resistance and high-temperature performance. NI200 nickel-based alloy is commonly used in chemical, electric power, nuclear industry, aerospace, and other fields due to its high purity and excellent chemical stability, and electrochemical properties.

This paper reviews the research progress of NI200 pure nickel and its alloys, focusing on the organizational structure, physical and mechanical properties, corrosion behavior, and application fields of pure nickel and nickel-based alloys. It also discusses the current problems and future development trends of it.

It has a face-centered cubic structure and has excellent mechanical properties and high-temperature stability. In addition, the addition of other elements, such as chromium, molybdenum, and titanium, to nickel-based alloys can improve their oxidation resistance and corrosion resistance. Therefore, in engineering applications, nickel-based alloys are usually composites composed of multiple elements.

Corrosion behavior of NI200 nickel-based alloy

It has good corrosion resistance to oxygen, water vapor, hydrochloric acid, sulfuric acid, and other media. However, there are still problems of corrosion in strong acids and etching media. When studying corrosion behavior, factors such as chemical composition, crystal structure, and cracking of the material need to be taken into account to develop suitable corrosion prevention measures.

NI200 nickel-based alloy application areas

It is widely used in the aerospace, chemical, nuclear, and power industries. In the manufacture of turbine components, aero engines, high-temperature furnaces, etc., the high-temperature resistance of nickel-based alloys is fully utilized. In addition, in the nuclear industry, NI200 pure nickel material is also widely used on the internal components of nuclear reactors.

It still has some problems in practical application, such as material corrosion, welding problems, etc. Future research directions include composite modification of the material, new surface treatment technology, and advanced manufacturing processes. Through these efforts, its performance will be further improved and its application areas will be expanded.

This paper reviews the research progress of NI200 pure nickel and its alloys in terms of tissue structure, physical and mechanical properties, corrosion behavior, and application areas. However, there are still problems in the practical application of this material, which need further research and improvement.

Hastelloy C22 and titanium alloy are both high-quality metal materials, widely used in industry, aerospace, and other fields. So, which is better in terms of electrical conductivity, Hastelloy C22 or titanium alloy? The following will be a detailed comparison of their electrical conductivity.

First of all, it is important to understand that electrical conductivity is an important physical property of a material, which describes the ability of charge to be transferred within the material, depending on factors such as the structure and chemical composition of the material, etc. Hastelloy C22 and titanium alloys are slightly different in terms of chemical composition, structure, etc., so their electrical conductivity will also be different.

Hastelloy C22 is a nickel-based alloy consisting mainly of nickel, molybdenum, chromium, and iron, and has excellent corrosion resistance and high-temperature properties. Comparatively speaking, Hastelloy C22 is not as conductive as titanium alloys. This is because the composition of Hastelloy C22 contains some relatively high elements, such as molybdenum and chromium, which will have some influence on the electrical conductivity of the material.

Titanium alloy is a metal material with titanium as the main component, which has good corrosion resistance and high specific strength, among other characteristics. Compared with Hastelloy C22, titanium alloy has better electrical conductivity. This is because the titanium element in the titanium alloy has good electrical conductivity and the structure of the material is relatively simple and is not affected by other elements. Therefore, titanium alloys are more commonly used in some application scenarios that require high electrical conductivity, such as aerospace and electronic equipment.

It should be noted that Hastelloy C22 and titanium alloys have their own advantages and limitations in terms of applications. Hastelloy C22 has excellent corrosion resistance and high-temperature performance, and is widely used in some strong corrosive environments; while titanium alloys have good strength and toughness, and also have a wide range of application prospects in aerospace, medical devices, and other fields.

In summary, Hastelloy C22 and titanium alloys are slightly different in terms of electrical conductivity, with titanium alloys having better electrical conductivity. However, when selecting materials, other factors such as corrosion resistance and mechanical properties need to be taken into account to choose the most suitable material to ensure the stable operation of equipment and systems.

As the flagship nickel alloy in our impressive range of materials on offer, the INCONEL 625 alloy is a marvel in the INCONEL alloy range. Its many positive properties mean that it has many different industrial applications, making it a particularly versatile alloy.

This high-performance material is often praised for its excellent corrosion resistance, even in the harshest environments and at the highest temperatures. But this is not its only characteristic; this alloy has been carefully crafted to provide a wealth of physical and mechanical properties that help solve common design engineering problems.

Over the years, the Inconel 625 alloy has been developed to further enhance these properties. Since the 1960s, when it was first introduced as a material for steam pipes, it has been refined to improve its creep resistance and weldability, thus increasing its number of industrial applications.

Defining mechanical properties of INCONEL 625

1. There are many factors to consider in the selection of materials. It is important to assess the physical and mechanical properties of an alloy to see how these properties match the intended end use.

Physical properties are measurable characteristics, such as the electrical conductivity or melting point of an alloy. These properties are a fact of the alloy’s composition and are useful points to consider.

However, the mechanical properties of an alloy are more useful for design engineers to compare the properties of different metal alloys to meet their requirements. Mechanical properties are an indication of how a material will perform under different forces. These include strength (tensile, fracture, fatigue, etc.), ductility, and wear resistance.

Mechanical properties can be affected by the way an alloy is processed, which is why some nickel alloys are hot or cold-worked to obtain the right balance of mechanical properties. Balance is necessary when selecting a material – some materials perform well under certain conditions and in certain properties, but are weaker in others. It is therefore important to choose the right alloy for the right strength and range of application.

Key mechanical properties of INCONEL 625 CrNiFe alloy

2. Although numerous tests have been carried out on nickel alloys to determine their mechanical properties, one of the most important is the tensile strength test. This property is related to the amount of load that the metal can withstand before fracture. The metal passes through a number of important strength points before it finally fractures. The material will first begin to deform and stretch until it reaches the point where it retains that deformation (as opposed to returning to its original shape). This is the yield strength. When the material reaches the load at which it will eventually break, this is the tensile strength. The more a material can resist permanent deformation in shape, the harder it is called an alloy.

INCONEL 625 has a high level of strength and hardness. By cold-working the alloy, it is possible to increase the tensile strength of the material at intermediate-temperature operating conditions. When exposed to intermediate temperatures, some hardening occurs within the alloy.

Another key test carried out on alloys is to determine their strength, i.e. to observe their fatigue strength. This is how much repetitive stress a metal can withstand, although it depends very much on the level of stress the metal is subjected to, and the frequency and duration of the applied stress. INCONEL 625 exhibits good fatigue strength at room temperature, as well as solid-state properties at high temperatures – which vary depending on whether the metal has been solution treated or annealed.

As an example of its exceptional fatigue strength, the endurance limit for INCONEL 625 alloy was found to be 90,000 psi for smooth bars in 108 cycles at room temperature using cold-rolled annealed plates in full reverse bending. the toughness of a material is usually measured by impact testing to see how well an alloy can absorb an impact without breaking. This is usually done over a range of temperatures. Ductility is also tested to see how much a material can stretch without breaking and how much it retains its new shape after the force is removed. Both toughness and ductility are compromised at very low temperatures when the material is more prone to cracking. However, INCONEL 625 alloy retains its excellent toughness and ductility at temperatures as low as -320 °F.

3. To give INCONEL 625 alloy the best mechanical properties, it is usually hot-worked, cold-worked, or annealed at temperatures below 1200°F. For hotter temperatures, it has the best properties when annealed or solution treated. Typically, if parts with optimum creep or fracture resistance are required, the material is usually solution treated.

It does need to be machined by hand by experts to maintain these impressive mechanical properties. As this material has been developed to be very strong at high temperatures, care must be taken when hot working it. It can easily be manufactured by thermoforming, but it requires very powerful equipment to do so. However, the material can be cold formed by standard processes, which has a beneficial effect on the mechanical properties of the alloy, for example, by increasing the tensile strength as described above.