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The influence of nickel on the mechanical properties of austenitic stainless steel, especially chromium nickel austenitic stainless steel, is mainly determined by the influence of nickel on the stability of austenite. Within the range of nickel content that may undergo martensitic transformation in steel, as the nickel content increases, the strength of the steel decreases and the plasticity increases. Chromium nickel austenitic stainless steel with stable austenite structure has excellent toughness (including extremely low temperature toughness), which can be used as low-temperature steel, It is well known that for chromium manganese austenitic stainless steel with stable austenite structure, the addition of nickel can further improve its toughness.
Nickel can also significantly reduce the cold work hardening tendency of austenitic stainless steel, mainly due to the increased stability of austenite, which reduces or even eliminates the martensitic transformation during cold work. At the same time, the cold work hardening effect of austenite itself is not very obvious, and the influence of stainless steel cold work hardening tendency. Nickel reduces the cold work hardening rate of austenitic stainless steel, and reduces the room temperature and low-temperature strength of steel, improving plasticity, The increase in nickel content is beneficial for the cold working formability of austenitic stainless steel, and increasing nickel content can also reduce or even eliminate the corrosion of 18-8 and 17-14-2 types of chromium nickel austenitic stainless steel δ Ferrite can improve its hot working performance, but, δ The reduction of ferrite is unfavorable for the weldability of these steel grades, which increases the tendency of welding hot cracking wire. In addition, nickel can significantly improve the hot working performance of chromium manganese nitrogen (chromium manganese nickel nitrogen) austenitic stainless steel, thereby significantly improving the yield of steel. In austenitic stainless steel, the addition of nickel and the increase of nickel content lead to an increase in the thermodynamic stability of the steel, Therefore, austenitic stainless steel has better rust resistance and resistance to oxidizing media, and as the nickel content increases, the performance of reducing media is further improved.
It is worth pointing out that nickel is still the only important element to improve the resistance of austenitic stainless steel to transgranular stress corrosion in many media. The impact of nickel on the corrosion resistance of austenitic stainless steel in various acid media should be noted that under certain conditions of high temperature and high pressure water, the increase in nickel content leads to an increase in the sensitivity of steel and alloys to intergranular stress corrosion, However, this adverse effect can be alleviated or suppressed by the increase in chromium content in steel and alloys. With the increase in nickel content in magnetic card austenitic stainless steel, the critical carbon content for intergranular corrosion decreases, which means that the sensitivity of steel to intergranular corrosion increases. As for the resistance to point corrosion and crevice corrosion of austenitic stainless steel, the effect of nickel is not significant. In addition, nickel also improves the high-temperature oxidation resistance of austenitic stainless steel, This is mainly due to the improvement of the composition, structure, and performance of the chromium oxide film by nickel, and the higher the nickel content, the more harmful it is. This is mainly due to the low melting point of nickel sulfide at the grain boundaries in the steel.
