1) Having a longitudinal weld steel pipe, inside and outside welds using a submerged arc welded. 2) After expanding the overall mechanical handling, pipe internal stress is small and evenly distributed, which can effectively prevent stress corrosion cracking, high dimensional accuracy, easy on-site welding construction. 3) After the pre-finish welding the welding process, welding process is stable and high weld quality. 4) Weld production process is easy to implement and use of non-destructive testing in the field of non-destructive testing review. 5) Great specifications, can produce small-diameter, thick wall also produces large-diameter, thick-wall steel pipe.

Hot straight seam steel pipe manufacturers, the small caliber in the output of crude oil or heating pipes, in order to reduce the heat pipes to the soil, outside the pipe plus insulation composite layer. Commonly used insulation material is a rigid polyurethane foam, a temperature of -185 ~ 120 ℃. This material is soft texture, to increase its strength, insulation on the outside add a layer of high density polyethylene cladding layer, to form a composite structure, in order to prevent infiltration of groundwater within the insulation. Ordinary straight seam steel pipe for use in harsh environmental conditions, there will be severe corrosion, which will reduce the life of the steel pipe, anti-corrosion pipe insulation is relatively long service life, under normal circumstances can be used are 30-50 years or so, and the correct installation and use is also possible to make the pipe network maintenance costs low, corrosion pipe insulation can also set the alarm system, automatic leak detection pipe network failure, the exact knowledge of the fault location and automatically alarms. Pipe insulation is widely used in the construction and promotion, and production technology constantly improve and popularize. Pipe insulation has a good performance can promote their use in a good range, different parts of the structure and cooperate with each other in use, play an important role and value. Polyurethane foam has good mechanical properties and thermal insulation properties, usually can be temperature 120 ℃, by modification or other insulating material combinations can be temperature 180 ℃.

The basic principles of the outer coating selected city gas pipeline a, good insulation properties and mechanical properties; b, good resistance to cathodic disbanding performance; c, good resistance to water, gas permeability; d, good chemical resistance properties of soaking and aging; e, low temperature and high temperature performance; f, easy mending and mending; g, the price is reasonable.

Blank perforated temperature varies according to the raw material strange strange. Thermal expansion pipe but mostly in 1200 ℃, when the carbon content and other alloying elements more temperature slightly lower. The second key is to try to reduce the heating operation scale quantities. Especially in hot kneading elbow, straight seam steel pipe from leaving things life expectancy and kneading pipe surface quality, pleading even more severe. In the straight seam steel pipe production process, because the primary process is in a hot state, so the heating operation is resolution product quality is very important process. The heat with the furnace, according to their results, and reheating furnace is divided into two kinds; the former is used to billet heated from room temperature to the processing temperature; the latter is used in the process in the blank reheated to the required processing temperature. Heating will be wrong in the outer surface of the tube surface may exhibit cracks, folds and migraine pain and other waste reason. There are many kinds of heating furnace, but the primary use is a ring furnace. This furnace has an annular hearth, it can slowly change the direction of the diameter of the blank along the bottom of the load from the entrance, a reversal can be used at the outlet of the heating and soaking temperature to the rule kind of stove. This operation is the key blank is heated uniformly heated to a temperature suitable for processing. Because a great impact on the quality of the perforation, that is, when the temperature of the process piercing is an important condition affecting the quality, it is generally the temperature of the billet piercing working is to manipulate.

Disadvantages of high frequency electric resistance welding pipe(erw steel pipe) forming roller is following below: 1. Weakening crude molding deformation is the root of the pipe defects. Since the one-sided pursuit of the common roll to reduce the number of roll and roll changing times, thus reducing the horizontal row roll forming roll stand (breakdown stand), so that the original level by the amount of deformation of the deformation roll stand, more transferred to the discharge roller section and precision molding machine. Row roller segment consists of many efflux roll and some of the inner roller composed mainly efflux roll by applying pressure to the outer surface of the steel strip to deform the inner surface of the roll so that deformation of the inner strip. 2. The crude molding deformation is not sufficient, increase the precision molding machine, a number of mill. In the high-frequency welded pipe production, the effects of the deformed state edge of the strip on the welding quality greatly. The best steel tube curvature of the opening edge portion of the pipe and finished very close, and this deformation required to complete the rough shaping stage. The row roll forming technology since the horizontal roll stand reduction in crude forming stage is difficult to do, had to be deformed into the discharge roller segment and fine machine, but in the row roll segment, due to the structure of the device is also very difficult to guarantee, the result is the roundness of welded pipe difference after. 3. Pipe intrinsic product quality. Since the outer and inner roll cage roll steel strip uneven deformation, so that the degree of partial pipe material hardening increases, the residual stress is large and unevenly distributed. Although the dimensions of products can meet the requirements, but the relative performance of the material steel base material has changed greatly, pipe internal toughness, extensibility, resistance to stress corrosion and so has been compromised, which is used in cold regions casing great influence of high grade steel pipeline corrosion and requires media. 4. The lack of thrust, unstable welding speed. In ERW molding process, totally dependent on the drive roller thrust provided by the steel strip to overcome the deformation resistance and stable welding speed. Since the horizontal rack reduced, so that the deformation of the thrust to overcome, particularly in areas large strip thickness, high strength material, the phenomenon is prone to insufficient thrust of the strip forming velocity fluctuations. In order to compensate for the lack of thrust, stable welding speed is also required to increase the number of precision molding machine. 5. Equipment poor rigidity, and high strength thick-walled pipe production difficult. Early compared with the current row roll forming machine is used in many interior rollers, but after the increase in the number of rollers also have some problems.