Views: 0 Author: Site Editor Publish Time: 2021-04-30 Origin: Site
Hydrogenation reactor is one of the key equipment in the petrochemical industry. The material is mainly used for 12Cr2Mo1 forged steel flanges with high temperature creep resistance and oxidation resistance. Because it operates under high temperature, high pressure, and hydrogen conditions, the quality requirements for steel are very strict. Not only must meet the requirements of strength, resistance and hydrogen corrosion, but also have good welding and forming functions. CrMo steel will show the appearance of embrittlement when it is operated in the temperature range of 350 to 575 ℃ for a long time.
The temper brittleness of the data will lead to deterioration of resistance and brittle fracture. Therefore, the demand for temper embrittlement resistance of steel should also be satisfied. The study believes that the temper brittleness of steel is closely related to the content of P, Sn, As, Sb and other remaining elements, which will segregate in the austenite grain boundary and cause the grain boundary to weaken. After discussing the production process of 12Cr2Mo1 forged steel flanges at home and abroad, and drawing up a reasonable production process, a company successfully announced 12Cr2Mo1 cylinder forgings for hydrogenation reactors. The detailed production process is as follows: Exercise: In order to improve the inductive mechanical function of steel, the content of P, S, Sn, As, Sb, Cu and other remaining elements and H, O, N gas elements should be strictly controlled during the steelmaking process, and the content of gas elements should be reduced. Tendency to temper embrittlement. The remaining elements such as Sn, As, and Sb have lower affinity with O than Fe, and cannot be effectively removed in the steelmaking process.
Therefore, low-remaining element, low-sulfur, and low-phosphorus scrap steel and feedstock should be used for electric furnace training. Essence: Use C powder to disperse and deoxidize as much as possible in the refining process. Disperse deoxidizers should be added in batches. Stick to a reducing atmosphere and use less silicon-aluminum-calcium-barium powder for deoxidation to improve the purity of molten steel. In addition, the high-basicity refined slag is used for the white slag operation to complete the desulfurization. After the alloy is added, the refined white slag is required to persist for more than 20 minutes. Participate in the trace alloying element Nb to refine the grains and optimize the composition before the refined steel tapping.
When VCD vacuum carbon deoxygenation, when the vacuum degree is less than 66.7Pa, the disposal time is more than 15min. It is necessary to investigate the slag splashing situation at any time. Once there are signs of splashing, reverse aeration to reduce the vacuum. Heat treatment after casting and forging: Casting on a 185MN hydraulic press, using 75t steel ingots, forging weight 47.98t, and steel ingot utilization rate of 64%. It is formed by four-fire casting, the casting temperature is 1250～750℃, and the total casting ratio of the deformation process is 6.4. Normalizing + tempering is used for heat treatment after forging. The more ideal arrangement for the 12Cr2Mo1 forged steel flange is the bainite arrangement, which has good strong resistance, arrangement stability, heat resistance and fatigue resistance, and has very good resistance to tempering than the martensite arrangement or ferrite + pearlite Talent.
Through SEM, EDS and other test methods, the size, morphology and quantity of inclusions in steel were studied, and it was found that most of the inclusions in steel were deoxidized products and oxidation products of alloy materials and refractory materials, mainly aluminosilicate composite inclusions. . The test shows that the purity of the 12Cr2Mo1 forged steel flange is relatively high, and the inclusions larger than 10μm are about 0.47%. The grade of non-metallic inclusions meets the standard requirements, A+C≤2.0, B+D+Ds≤2.5, A+B+C+D+Ds≤4.0. In summary, the selection of 12Cr2Mo1 forgings produced by the process of EBT electric furnace → LF essence → VCD vacuum treatment → VC vacuum casting → ingot hot delivery → heating → casting → post-forging heat treatment can meet the requirements of quality and function.