April 21, 2022 Quality Control of Galvanized Seamless Pipe

Galvanized seamless pipes are widely used in high pressure, low temperature and corrosion resistant environments.

Galvanized seamless pipes are widely used in high pressure, low temperature and corrosion resistant environments. Mechanical properties, process properties and corrosion resistance are three important indicators to measure the quality of steel pipes, and are also an important guarantee for the safety of ship navigation. The seamless pipe sizes is expressed by outer diameter * wall thickness in millimeters. So how to control the quality of galvanized seamless pipe?

According to the production flow chart of galvanized seamless pipe, the round billet is made into seamless steel pipe through the main processes such as perforation, cold drawing/cold rolling, solution, straightening, pickling, etc. Each pipe making process complements each other, especially the temperature control of the hot furnace. The accuracy and uniformity of the finished steel pipe is an important guarantee to ensure that the chemical composition, surface quality, mechanical properties, process performance and corrosion resistance of the finished steel pipe meet the specifications and standards. Let’s take a brief look at this process.

The heating furnaces used in the manufacture of galvanized seamless pipes include billet heating furnaces and steel pipe heat treatment furnaces. The accuracy and uniformity of temperature control are two important indicators for judging the quality of heating equipment and an important guarantee for the heating process. Therefore, the manufacturer should strictly follow the service life and calibration cycle of the thermocouple, and check the uniformity of the furnace temperature.

The formulation of the heating process for galvanized seamless pipes should consider the inherent characteristics of the heating furnace equipment, the type and quantity of billets or steel pipes, and strictly control the heating rate, holding time and cooling rate to avoid cracks, overheating or overburning. Taking the heating of the billet in the perforation stage as an example, considering the low thermal conductivity of stainless steel (that is, slow heat transfer), the large expansion coefficient at room temperature, the preheating time in the furnace is long, and the heating speed at the initial stage of heating is slow to prevent hot cracks; When the temperature exceeds a certain temperature (generally around 850 ° C), the thermal conductivity and plasticity of the galvanized seamless pipe increase rapidly. At the same time, if the stainless steel stays in the high temperature section for too long, α phase, that is, ferrite, will be produced. When the α phase exceeds a certain proportion, the metal thermoplasticity will drop sharply. In severe cases, it will lead to perforation failure, and high temperature and long-term heat preservation will also make the internal grains of the galvanized seamless pipe coarse. Therefore, in the soaking stage, it is necessary to heat quickly and soak for a short time.

In addition, attention should be paid to controlling the adjustment of the atmosphere in the furnace and maintaining a weak oxidizing atmosphere, which can not only reduce the degree of oxidation on the surface of the galvanized seamless pipe, but also prevent surface carburization.

Nansteel Manufacturing Co.,Ltd is a company specializing in the production of carbon steel pipes, stainless steel pipes, structural profiles and pipe fittings. Its products are widely used in nuclear power plants, thermal power plants, atomic power plants, oil and natural gas, petrochemical, fertilizer, chemical and pharmaceutical fields. With strong technical strength and years of spontaneous service, we provide customers with high-quality products with economies of scale. For more, please visit: www.nan-steel.com

Contact:
Chase Liu chase@nan-steel.com
https://www.nan-steel.com/
+86 731 8878 7783

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