Causes of surface cracking of spiral steel are analyzed

　　Generally speaking, hydraulic (pneumatic) part in planning the use of mechanical performance, data are assumed to be uniform, successive, isotropic, according to the analysis of this approach is safe and that the plan will sometimes spiral steel pipe unexpected trouble cracking attack.

　　Study found that the use of brittle cracking and also member of the relevant temperature. After discussions we found that when the temperature drops below a certain temperature, brittle materials will change the situation, the impact absorbed energy decreased, this representation is called cold crisp, high-strength metal resources guessed low stress brittle episodes cracking process, the data arrangement is far from uniform, isotropic. Arrangements have cracks, there will be inclusions, porosity and other drawbacks can be funded look into guessed microcracks. Therefore, even when the program based on the operating temperature of the member to choose a suitable cold brittle temperature change information.

　　Spiral pipe frequency and circuit capacitance, inductance is inversely proportional to the square root, perhaps proportional to the square root of voltage, current, just change the circuit capacitance, inductance, or voltage, you can change the size of the current frequency, and then arrived at the welding temperature control intention. On low-carbon steel welding temperature control in the 1250 ~ 1460 ℃, can meet the pipe wall thickness 3 ~ 5mm penetration requirements. In addition, the welding temperature welding speed can also go through the scheduling to end.

　　When the spiral steel pipe cold drawn, hot rolled tube cracks and other shortcomings or high-precision drawing fuel tank is made after cracking in the process of applying attack, almost no plastic deformation episodes are usually brittle cracking. Brittle cracking is a result of a variety of reasons. Such as: the separation of the grain boundary thereof, regardless of their strength is stronger than the matrix strength or weak, are all reasons for the onset of cracks; the grain boundary segregation of inclusions is cracking reason; the other, even in far less than the yield limit alternating loading, will also cause the onset of fatigue crack appearance.

　　Spiral Pipe welding temperature affected the primary frequency eddy current heating power, the impact of high frequency eddy current thermal power by the primary current frequency, the eddy current heating power and current proportional to the square of the frequency of agitation; and the current frequency of agitation by agitation and voltage, current and capacitance , inductance effects.

　　When the lack of spiral steel pipe heat input, the weld edge is heated up to a temperature of less than weld metal arrangements still adhere to solid form incomplete fusion or penetration; when the lack of heat input, the weld edge is heated beyond the soldering temperature seizures burnt or droplet weld constitute Cave.