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一般认为钢的变脆例如蓝脆和回火脆都与钢中的扩散和沉淀有关系。本文尝试用内耗测量的方法研究碳与氮在α-铁及碳素钢中的扩散、脱溶和沉淀,从而进一步地了解钢的变脆的机构。实验的结果指出,碳在α-铁中的扩散不受自身浓度、合金元素和沉淀历史的影响。氮的情形与碳显著不同,合金元素使氮的扩散变慢,在沉淀初期使氮的扩散加速。 较有系统地研究了碳、氮在加工后的α-铁中脱溶时所引起的内耗峰(当振动频率约为每秒1周时出现在250℃左右),发现了高温淬火在含碳或氮较多的试样中所产生的内应力也可以引起这个内耗峰。实验指出:①这个脱溶内耗峰的出现条件与钢的蓝脆的出现条件相同,都是一种应变时效或淬火时效的现象;②与这个内耗峰有关的碳、氮是处于原子的状态。这些联系使我们认为钢的蓝脆是一种应变脱溶或淬火脱溶的过程,是由于原子状态的碳或氮聚集于钢中的内应力区域或晶体缺陷(例如原子脱节)中所引起来的。关于这方面的深入研究正在继续进行中。 根据本实验及以前关于钢铁中碳氮的扩散、脱溶和沉淀所得的结果,对于钢的回火脆的机构也提出了一种初步的看法。回火脆是一种回火沉淀的过程,引起回火脆的沉淀似乎是氮化物而不是碳化物。
It is generally believed that steel brittle such as blue brittle and temper brittleness are associated with the diffusion and precipitation in steel. In this paper, we attempt to study the diffusion, desolvation and precipitation of carbon and nitrogen in α-iron and carbon steel by means of internal friction measurement, so as to further understand the brittle mechanism of steel. The experimental results indicate that carbon diffusion in α-iron is not affected by its own concentration, alloying elements and precipitation history. Nitrogen is significantly different from carbon in that alloying elements slow the diffusion of nitrogen and accelerate the diffusion of nitrogen during the initial stages of precipitation. The internal friction peaks caused by the desolventizing of carbon and nitrogen in the processed α-iron (about 250 ℃ when the vibration frequency is about 1 second per second) were systematically studied. It was found that the high-temperature quenching in carbon Or nitrogen in the sample generated by the internal stress can also cause this internal friction peak. The experiment shows that: ① The appearance condition of the internal friction peak is the same as that of the steel blue brittleness, which is a phenomenon of strain aging or quenching aging; ② The carbon and nitrogen related to the internal friction peak are in the atomic state. These connections make us believe that the blue-brittleness of steel is a process of strain dissolution or quenching and desorption due to the aggregation of atomic states of carbon or nitrogen in the internal stress region of steel or crystal defects (eg, atomic dislocations) of. In-depth research on this area is continuing. According to this experiment and the previous results on the diffusion, desolvation and precipitation of carbon and nitrogen in steel, a preliminary view was also given to the tempering mechanism of steel. Temper embrittlement is a tempering process that causes tempering brittle deposits that appear to be nitrides rather than carbides.