Properties of A387 Gr.91 Cr Mo Alloy Steel Plate

　　A387 Gr.91 alloy plate is widely used in refining, chemical and hydrogenation equipment in various hydrogenation units and reforming units. It has excellent hydrogen corrosion resistance and good high temperature strength. It is a high temperature and high pressure vessel shell and seal. The preferred material for the head. It is a heat-strength steel and hydrogen-resistant steel widely used in the world. The addition of alloying elements such as Cr and Mo to low carbon steel greatly improves the overall performance of A387 Gr.91 steel plates. A387 Grade 91 alloy plate has good high temperature mechanical properties, high temperature oxidation resistance, corrosion resistance, good toughness, process performance and weldability, so it is widely used in the manufacture of petrochemical, coal conversion, nuclear power, steam turbine blocks. Large-scale equipment with harsh conditions and complex corrosive media, such as thermal power.

　　Properties of A387 Gr.91 Cr Mo Alloy Steel Plate

　　1, Heat Resistance

　　Metal materials resist high temperature oxidation, called heat resistance or oxidation resistance. It requires that the metallurgical structure of the steel is stable under medium and high temperature conditions, otherwise graphitization may occur.

　　If the carbon steel is above 425°C and the C-0.5Mo steel is used at 475°C or above for a long time, the cementite in the steel will resolve the carbon atoms by themselves, resulting in graphitization, and the brittleness of the metal material increases sharply. In addition, heat-resistant steels also require steels with high temperature endurance and creep limits. The chromium-molybdenum steel containing heat stable and strong carbide forming elements Cr, Mo, V can increase the decomposition temperature of cementite and prevent the occurrence of graphitization, thereby increasing the high temperature endurance limit and creep limit of the steel.

　　2, Antioxidant

　　The phenomenon that the metal material is reduced in plasticity due to absorption of hydrogen and the performance is deteriorated is called hydrogen damage, and may also be called hydrogen embrittlement. The hydrogen produced by the pickling, electrolysis or corrosion reaction, the hydrogen remaining inside the solidification of the metal, and the hydrogen in the medium environment may be absorbed by the material and diffused to the inside to cause hydrogen embrittlement. Hydrogen damage can lead to various forms of material failure, such as hydrogen bubbling, hydrogen-induced brittle cracking, high temperature hydrogen corrosion, and the like. For the hydrogen container in the petrochemical industry, chrome molybdenum steel is mainly used to prevent high temperature hydrogen corrosion.

　　3, Temper Brittleness

　　The temper brittleness mentioned here refers to the phenomenon that the impact toughness (increased ductile-brittle transition temperature) caused by the long-term operation of the steel in a certain temperature range.

　　The temper brittleness of Cr-Mo steel is in the temperature range of 370 ° C ~ 595 ° C. When the temperature is close to the upper limit of this temperature range, the embrittlement rate is high. When the temperature is lower than this lower limit, the embrittlement is slow.

　　The hydrogen pressure vessel such as a hydrogenation reactor in the refining industry is operating in this temperature range for a long period of time, and this phenomenon has attracted great attention. The difference between the embrittled material and the non-embrittled material is only reflected in the difference between the notched impact toughness and the ductile-brittle transition temperature, and the tensile properties are not significantly different. The degree of temper embrittlement is generally manifested by an increase in the ductile-brittle transition temperature. Temper embrittlement has only a slight impact on the impact energy of the upper platform.

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