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本文研究的白斑组织是船用大马力柴油机离心浇注汽缸套在生产中存在的主要异常组织之一。通过对白斑的空间形态、大小及分布的宏观和微观分析,认为它在空间是一些不同方位的不规则曲面板状物,其金相组织是不含共晶片状石墨的细片状珠光体,与周围正常组织相比较,除碳元素外的其它合金元素没有发生偏析,自斑在高温时应是合金中析出的初生奥氏体相。影响白斑形态、大小和分布的主要因素有合金化学成分、铸模冷却速度以及铸模转速。选择结晶温度范围较窄的合金、适当提高冷却速度和铸模转速对消除和限制白斑组织都有明显的作用。根据白斑的强度以及白斑与周围基体的结合强度都高于周围基体本体的强度,同时从带有白斑组织的汽缸套多年来使用情况出发,在目前生产中应允许在缸套内工作面上存在一些细小分散的白斑组织。
The white spot tissue studied in this paper is one of the main anomalies in the production of centrifugal cast-in cylinder liner for marine high-powered diesel engine. According to the macroscopic and microscopic analysis of the spatial morphology, size and distribution of the white spot, it is considered that it is irregularly shaped plates with different azimuths in space. Its microstructure is fine lamellar pearlite without eutectic flake graphite, Compared with the surrounding normal tissue, alloying elements other than carbon have not segregated, since the plaque at high temperature should be alloy precipitated primary austenite phase. The main factors that affect the morphology, size and distribution of leukoplakia are the chemical composition of the alloy, the cooling speed of the mold and the rotational speed of the mold. Select a narrow range of crystallization temperature alloy, the appropriate increase in cooling rate and mold speed to eliminate and limit the white tissue has a significant role. According to the intensity of the white spot and the bonding strength between the white spot and the surrounding substrate are higher than the strength of the surrounding substrate body, starting from the use of the cylinder liner with white spot tissue for many years, the present production should allow the presence of Some scattered fine white tissue.