Argon

Lean alloy steel is often used in special pressure-bearing equipment. The alloying elements often added include manganese, silicon, chromium, nickel, molybdenum, vanadium, boron and rare earth elements. Most of silicon and manganese melt into ferrite, only a small amount into cementite, which are commonly used strengthening elements in lean alloy steel. The amount of chromium and nickel is generally small, and the main role of chromium and nickel is to increase the undercooling degree of austenite and refine the microstructure. Part of chromium is dissolved in ferrite and some in cementite, which can improve the stability of cementite. Molybdenum is dissolved in ferrite slightly, and has the effect of solid solution strengthening. It is a strong carbide forming element, which can improve the high temperature strength of steel and improve the temper brittleness.

Shell and tube air separation heat exchanger is the most representative wall heat exchanger. It has a long history of application and is still dominant in all heat exchangers. Shell and tube heat exchanger is mainly composed of shell, tube bundle, tube sheet and head. Most of the shell is round, and there are parallel tube bundles inside. Both ends of the tube bundle are fixed on the tube plate. In shell and tube heat exchanger, there are two kinds of fluids for heat exchange. One kind of fluid flows in the tube, and its stroke is called tube side. The other flows outside the tube and its stroke is called shell side. The wall of tube bundle is the heat transfer surface. In order to improve the heat transfer coefficient of the fluid outside the tube, a certain number of transverse baffles are usually installed in the shell. The baffle can not only prevent the short circuit of the fluid and increase the velocity of the fluid, but also force the fluid to flow through the tube bundle man