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

Abstract

The invention discloses a machining method for improving the intergranular corrosion resistance of an FCC crystal structure alloy. The machining method comprises the following steps that (1) molten steel is made by performing smelting according to specified components, electromagnetic stirring continuous casting is performed, then water cooling is performed to enable the molten steel to be cooledbelow 200 DEG C, and continuous casting billets are prepared, wherein the billets comprise the components including, by mass percent, 0.02-0.1% of C, 16-19% of Cr, 8-13% of Ni, not greater than 3% ofMo, 0.2-0.8% of Si, 0.5-2% of Mn and the balance Fe; (2) cogging rough rolling is performed, wherein the deformation per pass is 4-10%, and the total deformation is 20-40%; (3) continuous precision rolling and water cooling are performed in sequence, wherein the deformation per pass is 5-8%, and the total deformation is greater than or equal to 60%; and (4) the billets are heated to 1050-1100 DEGC for solution treatment, and water quenching is performed. According to the machining method provided by the invention, not smaller than 40% of low sigma coincidence site lattice (CSL) grain boundaries are introduced into the FCC structure corrosion resistant alloy, the connectivity of the CSL grain boundaries is enhanced, grain boundary characteristics are optimized, and the sub-grain proportionis decreased so as to reduce the grain boundary energy and improve the alloy intergranular corrosion resistance; and the process is simple and easy to implement, the grain boundary optimizing effectis obvious, and the machining difficulty and production cost are remarkably 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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