2.2 Factors causing welded pipe cracking
2.2.1 Influence of impurities inside welded pipes
To meet the requirements of the welded pipe flattening experiment, ensure the overall performance of the welded pipe, and prevent cracking or other defects, it is necessary to study the substances in the cross-section layer of the welded pipe, such as analyzing sulfides, and clarify the influence of sulfide form, content, and distribution on the experimental results. Additionally, a comprehensive inspection of impurities in the welded pipe should be conducted, and high-quality materials that meet relevant standards should be selected to avoid the influence of impurities on the experimental results.
 
2.2.2 Impact of welded pipe materials
Steel exhibits allotropy, meaning their crystal structure changes from one lattice to another with variations in temperature and pressure. The main allotropes of steel are α iron, β iron and γ iron. α iron is most prone to cracking, forming longitudinal cracks that seriously reduce the value and usability of the welded pipe. β iron and γ iron also exhibit cracking, but mainly form transverse cracks, which have a relatively minor impact on the usability of welded pipes. The overall crack degree of the welded pipe is inversely proportional to its value. In other words, the higher the crack degree, the lower the value of the welded pipe, and vice versa.

3. Measures for cracking issue

3.1 Improving welding level
Since the welding process directly impacts flattening test results and is a main cause of welded pipe cracking, attention must be paid to improving welding quality. First, operators should be trained in standardized operation steps to improve their professional level and ensure high-quality operation. Second, welding conditions, such as the amount of molten metal extruded and welding temperature, should be accurately controlled to prevent weld cracking due to external factors. Third, the existing welding process should be optimized, and the welding method improved according to the requirements for welders and performance indicators, ensuring the existing welding plan is optimal.
 
3.2 Doing a good job in impurity treatment
To reduce the impurity content in welded pipes, index analysis and control of each stage of welded pipe production should be executed well. Chemical treatment operations should be standardized, composition analysis of mineral processing at each stage should be thorough, and treatment plans for each subsequent stage should be based on the ore's chemical composition. Impurities such as oxides and sulfides should be treated as necessary. For example, during iron and steel making, changes in various elements are monitored in real-time to ensure the standardization and scientific accuracy of each step. By adopting processes such as molten iron pretreatment and refining outside the furnace, inclusions and harmful substances in the steel are removed, effectively reducing the impurity content during smelting. During steel forming, compounds should be analyzed and their characteristics utilized. Necessary treatment of harmful impurities should be carried out according to the steel's use requirements.
 
3.3 Control production process
Before conducting the flattening experiment on the welded pipe, first formulate and select the experiment plan. Strictly control the production process of the welded pipe according to the specific requirements of the flattening experiment performance to ensure that the physical and chemical performance indicators are optimized from the beginning of ore dressing, thereby avoiding cracking during the experiment. Strictly control the content of welded pipe components and formulate physical and chemical performance indicators based on composition analysis results of different materials to provide accurate target parameters for the experiment. Additionally, optimize the implementation details of the pressurization technology, and achieve the goal of improving the overall quality of the welded pipe by selecting advanced production equipment and processes.
 

4. Conclusion

The application of welded pipes is becoming increasingly extensive, and they occupy an important position in the steel market. Therefore, improving the quality of welded pipes is particularly important. Relevant institutions should increase research on welded pipe flattening tests. According to the operating specifications and objectives of the flattening experiment, the experiment should be carried out scientifically to study and control the factors that cause experimental cracking, ensuring the reliability and accuracy of the results. Based on the cracking observed in the experiment, technicians can accurately judge the quality of the welded pipe, determine whether it has defects, identify the causes of these defects, and control them in terms of raw materials, production, operation, and management. This lays a good foundation for producing high-quality welded pipes.