Although the relatively cool cooldown of this type of weld encountered in 10 seconds was somewhat longer, the longer time was determined for experimental repeatability and the need to simulate a high heat input weld, because the purpose of this study was to evaluate the ability of the parent material to exhibit good performance over a given large heat input range.
ERW pipe welding in the pipeline industry, shorten the construction time and reduce the related costs of voice getting higher and higher. One way to reduce costs is to shorten the welding time or by using higher welding speeds and / or fewer beads. However, the former method may increase the welding defect rate, and the latter method may result in an increase in heat input. Unfortunately, it is often observed that high heat input soldering can cause performance degradation in the HAZ. Therefore, we want to optimize the steel's ability to withstand a wide range of welding conditions. The main cause of deterioration is the large original austenite grain size and the coarse discrete particles produced by some chemical reactions, such as the presence of carbonitrides of Ti and Nb in welded steel pipe.
As the first step in improving the tolerance performance of X70 pipeline steel to different conditions, we produced a series of steel tubes of different chemical compositions and attempted to determine their tolerance performance for control of the weld thermal cycle for various alloy chemistries. The 7-lot API 5L X70 Ti-Nb microalloyed steel was selected to have different Ti-Nb contents and a Ti / Nb ratio range was determined. We also note that the carbon content in each sample is also different. All of these materials were automatically welded using a typical in-situ girth welding process, then the microstructures of the weld and heat-affected specimens were tested and the toughness of these areas was tested by mechanical testing. In addition, the heat-affected zone was also simulated using a gleeble thermomechanical simulator. The purpose is to give the same heating to all the specimens and to create a larger test and observation area, which is usually small for real welds. In order to simulate the thermal cycle of a coarse heat-affected zone during GMAW welding, the welded steel pipe was heated at 250 °C / s and held at a peak temperature of 1425 ° C for one second to stabilize the temperature and avoid The stream is then cooled and the cooling time from 800-500 °C is 0 sec. Use a 12mm space. The temperature range of 800-500 °C (t8-5) is generally considered to be the governing factor determining the microstructure and properties of the heat affected zone, as the transformation typically occurs at this temperature. Cooling at 800-500 °C for 10 seconds represents the measured cooling rate in the non-reheatable heat-affected zone of the fusion line near the multi-channel GMAW weld.
What are the precautions for storing seamless steel pipes?
1. Choose a suitable venue and warehouse; 2. Reasonable stacking, advanced first; 3. Packaging and protective layers of protective materials; 4. Keep warehouse clean and strengthen material maintenance.
Significance of Proximity Effect on the Production of High-frequency Longitudinal Welded Pipes
In addition to the skin effect, the proximity effect is another feature of current. When alternating currents of equal magnitude and opposite directions pass through two adjacent conductors, the current will flow through the adjacent inner surface layers of the two conductors, and when the two conductors pass When alternating currents of the same size and direction, the current will flow through the outer surface layers of the two conductors. The proximity effect of the current makes the current in the conductors further uneven. It is this unevenness that makes the high-frequency welded pipe(ERW).
Summary of Advantages and Disadvantages of High-Frequency Welded Pipe Forming Methods
Advantages and disadvantages of high-frequency welded pipe forming methods
