Processing method for improving intergranular corrosion resistance of alloy with fcc crystal structure

Abstract

A processing method for improving the intergranular corrosion resistance of an alloy with an FCC crystal structure, including the following steps: (1) melting according to set ingredients to produce molten steel, electromagnetic stirring and continuous casting, and then water cooling to below 200°C to produce a continuous casting billet, The ingredients contain C 0.02~0.1%, Cr 16~19%, Ni 8~13%, Mo≤3%, Si 0.2~0.8%, Mn 0.5~2%, and the balance is Fe in mass percentage; (2) Preform opening Rough rolling, the deformation amount in each pass is 4-10%, and the total deformation amount is 20-40%; (3) Continuous finishing rolling, the deformation amount in each pass is 5-8%, the total deformation amount is ≥ 60%, water cooling; (4) Heating to Solid solution treatment at 1050~1100℃ and water quenching. The present invention introduces ≥40% low ∑ heavy site lattice grain boundaries (CSL) into the corrosion-resistant alloy with FCC structure, enhances the penetration of the CSL grain boundaries, optimizes the grain boundary characteristics, reduces the sub-grain ratio, and reduces the grain boundary energy. , improve the intergranular corrosion resistance of the alloy; the process is simple and easy to implement, the grain boundary optimization effect is obvious, and the processing difficulty and production cost are significantly reduced.

Description

technical field [0001] The invention belongs to the technical field of iron and steel alloy materials, and in particular relates to a processing method for improving the intergranular corrosion resistance of an alloy with an FCC crystal structure. Background technique [0002] The intergranular corrosion resistance of FCC structural corrosion-resistant alloys (such as austenitic stainless steel 304, 316, etc.) is one of the most important service evaluation indicators, and has been widely concerned by users and researchers; intergranular corrosion is a local Corrosion is the serious damage from the metal surface along the intergranular under a certain corrosive medium, while the degree of damage inside the grain is relatively low; therefore, the bonding force between the grains is greatly weakened, and the entire grain often comes off completely. situation, or along the intergranular cracks, eventually causing serious engineering accidents. [0003] The phenomenon of interg...

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Problems solved by technology

[0002] The intergranular corrosion resistance of FCC structural corrosion-resistant alloys (such as austenitic stainless steel 304, 316, etc.) is one of the most important service evaluation indicators, and has been widely concerned by users and researchers; intergranular corrosion is a local Corrosion is the serious damage from the metal surface along the intergranular under a certain corrosive medium, while the degree of damage inside the grain is relatively low; therefore, the bonding force between the grains is greatly weakened, and the entire grain often comes off completely. situation, or along the intergranular cracks, resulting in serious engineering accidents

[0003] The phenomenon of intergranular corrosion was first discovered in the welding of austenitic stainless steel. Austenitic stainless steel should be solution treated before leaving the factory. After solution treatment at about 1100 ° C, austenite can dissolve more carbon; However, during use, such as welding or heat treatment, during heating or slow cooling at a temperature of 400-850 ° C, the solid solution of carbon in austenite will decrease, and supersaturated carbon will be precipitated from austenite. Chromium carbide and chromium are formed between grains, resulting in a decrease in chromium content near the grain boundary. When the chromium content is lower than 12%, a chromium-depleted area is produced; at this time, the chromium-depleted area acts as an anode, and the grain acts as a cathode. The micro-batteries are formed by the particles, and the intergranular corrosion accelerates, causing serious damage to the austenitic stainless steel in the corrosive medium.

[0004] Scholars at home and abroad have conducted a lot of research on the influence of grain size, shape, orientation on intergranular corrosion resistance and heat treatment after deformation to optimize grain boundary distribution characteristics and improve intergranular corrosion resistance. The Boundary Project introduces low Σheavy site matrix grain boundaries, optimizes the grain boundary characteristic distribution (GBCD) to improve the intergranular corrosion resistance of the alloy, and has achieved good results. Many technological measures have been proposed; among them, the grain boundary optimization is mainly through Multiple cold deformation and heat treatment, that is, deformation heat treatment process, such as: patent CN105177262A discloses a method for increasing the proportion of special grain boundaries in precipitation-strengthened austenitic heat-resistant steel, and optimizes the grain boundary by solid solution, cold rolling and annealing. increase the deformation at room temperature, increase the strain storage energy, and promote the occurrence of recrystallization in precipitation-strengthened austenitic steels, thereby increasing the proportion of special grain boundaries in precipitation-strengthened high-Cr and high-Ni austenitic heat-resistant steels, optimizing corrosion resistance and Anti-irradiation swelling ability; however, the related processes reported so far are more focused on mechanism research and laboratory research, and are difficult to apply to actual production, especially for medium-thick plates of FCC structure corrosion-resistant alloys, the distribution of grain boundaries in the thickness direction It is very complicated, and it is obviously not enough to adopt multiple deformation heat treatment processes

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