Views: 0 Author: Site Editor Publish Time: 2021-06-30 Origin: Site
Seamless stainless steel pipes are widely used in high pressure, low temperature and corrosion resistant piping systems. Mechanical properties, technological properties and corrosion resistance are three important indexes to measure the quality of steel pipes, and are also important guarantees to ensure the safe navigation of ships. In a practical shipboard application, a stainless steel chemical ship was found to have leaks in the deck cargo piping system after its first voyage. After pressure testing, more than 10 similar holes were found to leak. According to the production flow chart of stainless steel seamless tube, the round billet is made by perforation, cold drawing/cold rolling, solid solution, straightening and pickling. The process of pipe making is complementary to each other, especially the quality control of raw materials and intermediate products, which is an important guarantee to ensure that the finished pipe's chemical composition, surface quality, mechanical properties, process performance and corrosion resistance meet the specifications and requirements.
Seamless steel pipe :
1. Control the quality of raw materials
The main raw materials used in the production of seamless steel pipe are continuous casting round billet and rolled (forged) round steel. To ensure the billet quality is the first step to ensure the quality of steel pipe. It mainly includes the level of steelmaking, pouring and cooling processes and forming. Quality. The first is to improve steelmaking. It is necessary to reduce harmful elements and gases (nitrogen, hydrogen and oxygen), improve the uniformity and purity of compositions, reduce non-metallic inclusions and change their distribution patterns. When the billet composition is not uniform and severe segregation occurs, the rolled steel tube will show serious banded structure, which reduces the mechanical and corrosion properties of the steel tube, or even fails. Non-metallic inclusions (such as sulfides and oxides, silicate) are pressed into thin sheets, which not only affects the performance of the steel tube, but also causes the steel tube to break during production.
2. Ensure the accuracy and uniformity of the temperature control of the hot furnace
Heating furnaces for manufacturing seamless steel tubes include billet heating furnaces and steel tube heat treatment furnaces. The accuracy and uniformity of temperature control are two important indexes to judge the quality of heating equipment, and it is also an important guarantee for the heating process. Therefore, manufacturers should strictly comply with the service life and calibration period of the thermocouple and the furnace temperature uniformity test.
3. Optimize inspection process and equipment
The inspection of intermediate products is the key to control the quality of finished stainless steel seamless pipe, especially the surface quality of the inner wall. We must pay attention to the source. First of all, we must establish reasonable and effective inspection and processing procedures to ensure that existing problems can be found and those found can be effectively solved. Take the sewage pipe for example. Usually, sandblasting or pickling/passivation is used to remove the indicated oxides and reach the inspection state. To determine whether defects are removed, a combination of color checking, reheating, and pickling, if necessary, is required. In this way, you can effectively ensure that defective intermediate products do not flow into the next process.