Thermal specification refers forging forging the selected thermodynamic parameters, including forging temperature, the degree of deformation, strain rate, stress state (forging method), the heating plus cooling rate. These parameters directly affect the microstructure and properties of metallic materials, and forgings malleable, reasonable choice of several thermodynamic parameters above, is to develop an important part of the forging process.

The hot welded cracks are also known as high-temperature crack or solidification cracking, usually produced in Weld, sometimes also occur in the heat-affected zone, the manifestations are: longitudinal cracks, transverse cracks, roots crack crater cracks and heat-affected zone cracking.

Under the harsh winter conditions of low-carbon steel welding, due to the cooling speed of welded joint fastly make the crack tends to increase, especially in the first weld Heavy structures susceptible to cracking, for which the process must take the following measures:

Nondestructive testing (NDT) is the process of inspecting, testing, or evaluating materials, components or assemblies for discontinuities, or differences in characteristics without destroying the serviceability of the part or system. In other words, when the inspection or test is completed the part can still be used.

High-frequency straight seam steel pipe is based on the principle of electromagnetic induction and the skin effect, proximity effect and eddy current thermal effect of charges, thereby locally heating the steel at the edge of the weld to a molten state, and realizing butt welding through intergranular bonding extrusion, thereby achieving The purpose of seam welding.

The characteristics of submerged arc welded steel pipes are: the production process of straight seam welded steel pipes is simple, high production efficiency, low cost, and fast development speed. The strength of spiral welded pipes is generally higher than that of straight seam welded pipes.

Surface pitting of submerged arc welded steel pipe welds refers to weld defects where the surface of the weld is partially lower than the normal surface of the weld. It is a common weld surface defect in submerged arc welding.

While welding process, thermal stress, the phase transformation stress, stress and other processing is over the yield limit (Yield strength), so that after cooling the weldment left failed to eliminate the stress.

Added to the liquid steel deoxidizing element, which is dissolved in a portion of the metal and the slag deoxidation oxygen into the product and consume oxygen, and the remaining part is absorbed by the liquid steel in order to meet the specifications of the finished steel element requirements.

According to the point of metal corrosion process can be divided into chemical corrosion and electrochemical corrosion.

Rockwell hardness of the surface is also very suitable for testing the hardness of the workpiece surface hardening, surface Rockwell hardness scale, there are three to choose from.

When welding steel pipe is firstly liquidation clean welded joints of oil, paint, water, rust, and then based on wall thickness open groove, thick open and thin open smaller (angle grinder)