Chrome-Moly steel, or Chromoly steel, is a type of low alloy heat resistant steel, also known as medium temperature hydrogen resistant steel, which has better mechanical properties and hydrogen resistant properties at room temperature and high temperature. The main alloying elements in steel are molybdenum, chromium, vanadium, silicon, boron, etc., among which Cr(≤ 1O %) and Mo can significantly improve the high-temperature strength limit and creep limit, making it have good hydrogen corrosion resistance and high-temperature resistance.
Chrome-moly steel plate is widely used in oil refining, chemical and other hydrogen-containing units and high-temperature equipment are one of the commonly used steel pressure vessels. Chrome-Moly steel pipe includes rounds, square and rectangular tubes, and are often used in the manufacture of high-temperature and high-pressure resistant valves, bike frames, screwdriver tips, etc.
The Property of Chrome-moly Tubing
- Heat Resistance
The addition of Cr, Mo, Al, and other elements can effectively improve the performance and strength of steel tubing against high-temperature oxidation. Chromium mainly exists in the cementite (FeC), which increases the decomposition temperature of carbide and prevents the graphitization, thus improving the heat resistance of steel. Molybdenum strengthens ferrite solution and improves carbide stability, which is beneficial to steel high-temperature strength. The addition of vanadium can keep the fine grain structure at higher temperatures and improve the thermal stability and strength of the steel.
- Hydrogen Corrosion Resistance
Elements such as chrome-moly improve the stability of carbides, prevent their decomposition and reduce the possibility of carbon and hydrogen precipitation reaction to produce methane. The addition of V can keep the fine grain structure of steel at higher temperatures and greatly increase the stability of steel to hydrogen under high temperature and pressure.
- Temper Brittleness
Chrome-moly steel at 370℃ -595 ℃ temperature for a long time will lead to the decline in impact toughness, which is the temperature range of hydrogen equipment for a long time.
The results show that tempering embrittlement tendency is the most serious in Chromoly steel commonly used in pressure vessels. P, Sb, Sn, As, Si, Mn and other elements have a great influence on temper brittleness. The embrittlement is reversible that can be removed by proper heat treatment. The dehydrogenation treatment and post-welding heat treatment can not only eliminate the residual stress but also improve the mechanical properties and hydrogen corrosion resistance of Chromoly steel tubing.
Wiho metals is a professional supplier, manufacturer, stockiest of Chromoly steel. We mainly supply 42CrMo4 steel tubing, 4130 steel bar, 4130 steel tubing for pressure vessels, bike frames and other structural applications. For more information, call us today!
