Compared with other traditional pipes, seamless steel pipes are lighter in material, higher in strength, more durable, can withstand higher internal pressures, are flexible in production and use, and can adapt to complex or harsh geological conditions.
There are some differences in performance between seamless steel pipes and traditional pipes, which are mainly reflected in the following aspects:
1. Full-size continuity
Seamless steel pipes are manufactured through processes such as
hot rolling or
cold drawing, so they have full-scale continuity and no welded joints. Traditional pipes (such as welded steel pipes) usually require welded joints, which may have welding weaknesses and risk of breakage.
2. Compression resistance
Because seamless steel pipes have no welded joints, the overall structure is stronger and more consistent, and has higher compression resistance. The welded joints of traditional pipes may have weaknesses. For applications that are subject to high pressure or impact loads, seamless steel pipes may be more suitable.
3. Surface finish
The inner and outer surfaces of seamless steel pipes are relatively smooth and have been treated with anti-rust treatment, which can effectively reduce the adhesion of corrosion and obstructive substances and improve the efficiency of fluid transportation. However, the surface of traditional pipes may have uneven conditions such as welding burrs and oxide layers, which will have a certain impact on fluid transportation and the accumulation of obstructions.
4. Corrosion resistance
Seamless steel pipes can be made of different materials according to the use environment and requirements, and have good corrosion resistance. For example, stainless steel seamless steel pipes have strong corrosion resistance in humid or corrosive environments. Traditional pipes (such as ordinary steel pipes) may require anti-corrosion treatment to improve corrosion resistance.
5. Production process and cost
The production process of seamless steel pipes is relatively complex, including hot rolling, cold drawing, hot expansion and other steps, so its production cost is relatively high. The production process of traditional pipes (such as welded steel pipes) is relatively simple and the cost is low.
Disadvantages and limitations:
1. There are relatively big defects in the use of steel pipes, mainly because the internal and external anti-corrosion treatment is troublesome. First of all, the issue of external anti-corrosion is very critical. The quality of external anti-corrosion directly affects its service life. At present, the main external anti-corrosion methods for domestic steel pipes are: concealment method. All steel pipes require reinforced ribs or special reinforced external anti-corrosion, and cathodic protection is promoted in some areas.
Concealed external anti-corrosion methods usually use petroleum asphalt, epoxy coal tar asphalt and other coatings. The latter is not easy to solidify at low temperatures, and there are many concerns about on-site weld construction. This chlorosulfonated polyethylene has been used before. Due to too much solvent, pinholes are easily generated, the breakdown resistance is unqualified, and some areas are obviously not used. For cathodic protection, its anti-corrosion effect is better, but due to the use of sacrificial anodes, the anodes must be replaced regularly in future operations, which increases operating costs and workload.
In addition to inner wall treatment issues, there are three commonly used supply methods for seamless steel pipes: anti-corrosion coating, resin mortar, and cement mortar. There are two problems in all three methods: The first is the bonding strength problem between the anti-corrosion layer and the steel pipe, which has been mentioned above using cement mortar. Whether it is anti-corrosion coating or resin mortar, the inner and outer surfaces of the steel pipe are required to be completely rust-free before construction, but it is difficult to achieve perfection.
Therefore, the rusty part will become the source of delamination and peeling in the future, causing corrosion and scaling; secondly, most steel pipes are butt welded on site, and anti-corrosion is carried out after welding. This can only be done manually. The quality is difficult to control, and for pipes with smaller diameters, since personnel cannot enter the construction, anti-corrosion is no longer available. It also creates hidden dangers for future weld damage. According to the analysis of many steel pipe explosion accidents, it is mainly caused by weld corrosion caused by poor weld quality.
2. The overall cost of seamless steel pipe supply is relatively high.
3. Poor hydraulic function and high energy consumption. The in-pipe roughness coefficient of steel pipes is between 0.013-0.014. Therefore, for pipelines with the same water delivery volume and equal diameters, the resistance along the way will be high. It is necessary to increase the lift of the pump and increase the initial investment. At the same time, the operating costs will be due to consumption. The power is large and greatly increased.
4. The pipeline has the disadvantage of poor bearing capacity for water hammer.
Seamless steel pipe production process:
The production methods of ms seamless pipes are roughly divided into cross-rolling method (Mannesmann method) and extrusion method.
1. The cross-rolling method (Mannesmann method) is to first use a cross-rolling roller to pierce the pipe, and then use a rolling mill to extend it. This method has fast production speed, but requires high processability of the tube blank. It is mainly suitable for the production of carbon steel and low alloy steel tubes.
2. The extrusion rule is to use a piercing machine to pierce the tube blank or steel ingot, and then use an extruder to extrude it into a steel pipe. This method is less efficient than the cross-rolling method and is suitable for the production of high-strength alloy steel pipes.
Both the cross-rolling method and the extrusion method must first heat the tube blank or steel ingot, and the steel pipe produced is called a hot-rolled pipe. Steel pipes produced by hot processing can sometimes be cold processed as needed. There are two methods of cold working: one is the cold drawing method, which is to draw the steel pipe through a drawing die to make the steel pipe gradually thinner and elongated; the other method is the cold rolling method, which was invented by the Mannesmann brothers. The hot rolling mill is used in cold processing. Cold processing of seamless steel pipes can improve the dimensional accuracy and processing finish of the steel pipes, and improve the mechanical properties of the material.
In short, it is necessary to select appropriate pipe materials according to specific application scenarios and needs, and comprehensively consider factors such as performance, cost, corrosion resistance, and pressure requirements for evaluation and selection.
