1. Hot-rolled can significantly reduce consumption, reduce costs Where it can be hot-rolled billet should be hot-rolled metal, because metal hot deformation resistance than cold-rolled low, can significantly reduce energy consumption during rolling. 2. The hot rolling process can improve the performance of metals and alloys Because coarse grains of hot-rolled state can cast broken, microcracks healing and reduce or eliminate casting defects, converting low ductility cast structure into a higher plastic deformation of tissue. 3. The hot rolling may be a large reduction rolling Within a certain temperature range, with increasing temperature, increasing the plasticity of metals, can use a larger amount of deformation of rolling, it can also reduce metal crack defects, improving the rate of finished metal. 4. The hot rolling usually large ingot rolling Since the hot-rolled metal has high plasticity and less distortion resistance. It may be larger ingots, both to improve productivity, yield and rolling speed, but also for the continuous rolling process automation to create the conditions.

Pipeline transportation with the growth in oil and gas production and developed, has become the main mode of transport onshore oil and gas transport pipeline in recent years, solid materials, such as coal, ore pipeline transport, is also a great the development of pipeline transport advantages are: (1) transport capacity, a foreign coal pipeline diameter 720 mm, and a year to transport 20 million tons of coal, equivalent to almost one-directional transmission capacity of a single-track railway; (2) small amount of traffic engineering, small footprint, pipeline transportation just laying pipelines, construction of pumping stations, construction of railways is much smaller than the earthwork and the plains are mostly buried under, does not occupy farmland; (3) energy consumption in various modes of transport is the lowest; (4) safe, reliable, non-polluting, low cost; (5) the climate, and all-weather transport, high reliability and delivery of goods (6) pipeline can take shortcuts., short distance transport; (7) can be closed transport, less wear and tear. The disadvantage of pipeline transportation are: (1) specific and strong, can only transport oil, natural gas and solid slurry (such as coal), but in the field it occupies, with a fixed and reliable market; (2) pipeline from input the magnitude of the amount of the highest traffic among small, so in the early field development, the use of pipeline transportation difficulties, but also to road, rail, sea and land transportation as a transition. (3) the construction of pipelines, gas stations and oil storage device has to spend huge investment. In addition, the pipeline route through a set dressing, unregulated traffic room, small transport elasticity, flexibility is poor.

Types of erw welding are following below: Spot welding Spot welding (Spot Welding) welding member is assembled into lap joints, and pressed between two cylindrical electrodes, the use of a hot-melt resistance of the base metal, resistance welding solder joint formation. Mainly used for spot welding sheet metal welding. Seam welding Seam welding (Seam Welding) and spot welding process is similar, but with a disk-shaped rotating wheel columnar electrode or electrodes, the weldment assembled into lap or butt joints, and the electrodes disposed between the two rollers, the welding pressure rollers and rotating member, continuous or intermittent power transmission, resistance welding method for forming a continuous weld. Butt welding Butt (Butt Welding) is to make the weldment along the entire contact surface resistance welding method of welding. Projection welding Projection welding (Projection Welding) is a variant form of spot welding; on a workpiece has preformed bumps, when the projection welding, one can form one or more of the nugget at the joint.

From the principle of eddy currents can be seen in eddy current testing has the following characteristics: (1) Eddy current testing is only applicable to the conductive material, if a non-conductive material, it can not induce a swirling current, it can not make use of eddy current testing. (2) Eddy current testing is particularly suitable for detection of surface and near-surface conductive material. (3) Eddy current testing does not need coupling agent. Electromagnetic Field in Eddy Current Testing substance is excited by an electromagnetic wave and particle nature are volatile, so between the probe (coil) can be coupled with the workpiece without having to spread, it can be non-contact detection. This is better than ultrasonic testing. Because ultrasound is a mechanical wave, can only propagate in the substance. So ultrasonic inspection coupling agent must be added between the probe and the workpiece. (4) Eddy current testing for fast and automated testing. (5) Eddy current testing can be applied to the detection of the high temperature metal, because the metal having conductivity at high temperatures. (6) Eddy current testing is also suitable for detecting shaped material, as long as the coil into various shapes can be detected.

SAW(Submerged Arc Welding) Submerged arc welding is an arc welding under flux layer combustion method. Welding arc between the wire and the weldment burning heat of the arc and arc welding wire ends near the base metal and solder melted wire continuously fed, and proceeds along a certain trajectory, an arc weld pool solidified metal is removed to weld the molten solder is solidified into a shell covering the surface of the weld slag, slag of molten pool and weld metal for protection against arcing and the pool by the outside air intrusion. For the submerged arc welding equipment, there are two. One is the constant wire submerged arc welding machine, wire feed speed according to the set speed constant, maintaining a relatively stable arc arc is to rely on self-regulation. Another is the shift wire submerged arc welding machine, which is the use of arc voltage as a feedback signal, after changing the wire feed speed control system, so as to maintain a relatively stable arc. Further, in order to ensure that the most suitable welding process in a stable position and reliable welding process, SAW also need more complex auxiliary equipment compatible with the welder, commonly used auxiliary equipment: weldments displacement equipment, welding machine operator (ie welding head displacement device), welding jig and weld equipment. Since the SAW current, deep penetration, the groove form and size requirements are: a thickness of not less than 12mm plate beveling, in 12 ~ 20mm thickness can be used between the side welding, welding opposite gouging, more than when asked to open groove 20mm, but its blunt edge requires 5 ~ 6mm. Welding current based on the wire diameter, the thickness of the weldment, and the flux model is selected. Because of the large submerged arc welding current, welding the first layer prone to burn, often using the following welding process: SMAW welding back permanently submerged plate, lock bottom butt joint submerged arc welding, flux pad SAW. HFW(High-frequency Welding) In high-frequency current heating of the workpiece, and then applying pressure welding joints (see figure) is formed. A high-frequency current is concentrated along the surface of a conductor and flow along the path of least inductance over principle, the current will be concentrated heating of the workpiece surface to be welded, the thermoplastic state is reached or a partially molten state, extruding the molten metal on the workpiece and pressing the metal oxide, they form a welded joint. High-frequency welding common frequency range of 60 to 500 kHz. High frequency resistance welding high frequency welding points welding two kinds of high-frequency induction. ① High Frequency Resistance Welding: the contact with the wheel or as a sub-electrode high-frequency currents in the workpiece, suitable for continuous longitudinal seam welded pipe and spiral lap seam welding, boiler tube and fin heat exchanger spiral welded fin, can pipe external diameter of 1200 mm and a wall thickness of 16 mm, beam welding abdominal electrode thickness 9.5 mm, high productivity. ② High-frequency induction welding: a small diameter tube and the wall thickness of the workpiece by the induction heating coil can be welded to an outer diameter of 9 mm and 1 mm thin-walled tube. Commonly used in small diameter longitudinal pipe and brass seam welding, girth welding can also be used, but the power consumption is greater than the high-frequency resistance welding. The main parameters affecting the high-frequency welding quality is high-frequency power frequency, power, workpiece forming angle, welding speed and pressure from the squeeze, the electrode (or induction coil) and squeeze rollers. Major equipment has a high-frequency power supply, the workpiece forming apparatus and extrusion machinery. Stable high-frequency welding quality, high productivity and low cost. For high-efficiency automatic production line, the production of advanced methods slit tube.