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几年前,氮就被用作为热处理的保护气氛,尤其是廉价液氮的供给大大扩大了它的应用。其特点是:经济、安全、操作简便。附表为各种热处理方法选用氮基气氛的例子。按照热处理的方法可以使用几种气氛,再按炉子的形式,工件的材质等选定最合适的气氛。根据气体的成分,气氛可分为几个类型。(1)N_2—H_2型:N_2—H_2型是使用混合气体或传统的氨分解气体。为了防止氧化,氧势必须比各金属的氧化还原线(例如 Fe/FeO)低,如图1所示.这时候氧势由 H_2O 和 H_2的分压比控制,氮基气氛比同样氧势的发生气用的 H_2要少,因而较为有利。(2)N_2—CH_4型:CH_4从天然气获得。它在800℃以下极少热分解,在1100℃的炉内分解缓慢,还有不发生污斑的优
A few years ago, nitrogen was used as a protective atmosphere for heat treatment, especially the supply of cheap liquid nitrogen which greatly expanded its application. Its characteristics are: economic, security, easy to operate. Schedule for a variety of heat treatment method using nitrogen-based atmosphere example. In accordance with the method of heat treatment can use several atmospheres, and then by the form of the furnace, the workpiece material selection, such as the most appropriate atmosphere. Depending on the composition of the gas, the atmosphere can be divided into several types. (1) N_2-H_2 type: N_2-H_2 type is the use of mixed gas or traditional ammonia decomposition gas. In order to prevent oxidation, the oxygen potential must be lower than the redox lines (eg Fe / FeO) of each metal as shown in Figure 1. At this time, the oxygen potential is controlled by the partial pressure ratio of H 2 O and H 2 and the nitrogen-based atmosphere is lower than that of the same oxygen potential H 2 occurs less gas, which is more favorable. (2) Type N_2-CH_4: CH_4 is obtained from natural gas. It is extremely thermally decomposed below 800 ° C, slowly decomposes in the furnace at 1100 ° C, and has excellent stain resistance