用铬提高钢锭模的寿命

以前曾指出过,用含锰量较高(1～1.4％),含硅1％左右的高炉生铁浇注成的钢锭模在使用中表现出高的寿命。聚集在珠光体中的锰可增加共析碳化物的稳定性,因而在使用过程中减慢基体的铁素体化,从而减少铸铁的生长并增加寿命,同时增加对形成网状热裂及热疲劳裂纹的抵抗能力。但是,要得到高的含锰量,尤其在生产条件下(如马钢或切列波维奇克冶金厂要求校正加入的铁合金量),要涉及到繁重的作业,技术工艺和经济效益低的问题。铬作为强碳化物形成元素,加少量就能保证组织的必需的珠光体化。

铸铁钢锭模在使用中组织的变化

钢锭模的使用性能一般是由其在反复高温加热中组织的变化程度而定。但资料中只介绍了钢锭模破损后组织的质的变化。根据这些数据很难购钢锭模使用中破损过程的程度。因此,研究钢锭模在使用初期沿模壁厚度组织的质和量变化情况是有意义的。本研究是用重6吨无底方形钢锭模,它由下列化学成分的铸铁铸成:C4.3％,Si1.13％,Mn0.83％,S0.05％,P0.065％,Ti0.05％。试验钢锭模在组合铸型中浇注,铸型由粘土砂芯和粘土衬砖底板及周围有金属型壁或金属涂层组成。金属用下注法浇注,用光学高温计测出注温为1453K,注后6.

SH760小客车激冷合金铸铁凸轮轴

凸轮轴是内燃机上的重要零件。过去国内各厂生产的凸轮轴,自从采用铸造工艺以后,虽然比锻造工艺生产的凸轮轴节约工时和材料,但它在使用寿命问题上,始终存在着明显的缺陷。例如SH760轿车的凸轮轴,除上海汽车厂生产的凸轮轴能保证一定的寿命外,其它几家配件厂生产的SH760凸轮轴,寿命都是很低的。装车后。

Seepage laws of two kinds of disastrous gas in complete stress-strain process of coal

The similarities and differences in seepage flow evolution laws of CH4 and CO2 during complete stress- strain process of samples were comparatively analyzed. The results show that the seepage flow evolution laws of CH4 and CO2 are extremely similar during the stress-strain process, showing that the character- istic first decreased and then increased. A mathematical model was also established according to the rela- tionship of seepage velocity and axial strain. However, due to the strong adsorption ability of CO2, the coal samples generated a more serious ''Klinkenberg effect'' under the condition of CO2. Owing to this, the CO2 seepage flow resulted into occurrence of ''stagnation'' phenomenon during the late linear elastic stage II. In the strain consolidation stage III, the increment rate of CH4 seepage velocity was significantly greater than that of CO2. In the stress descent stage IV, when the axial load reached the peak pressure of coal, the increment rates of CH4 seepage velocity presented a turning point. But the changing rate of CO2 seepage velocity still remained slow and a turning point was presented at one time after the peak of thestrain pressure, which showed an obvious feature of hysteresis.

Experimental study on influence of coal structural anisotropy to gas permeation

Based on ＂true triaxial coal rock permeability of coal sample test system , the permeability under different gas pressure to coal specimen in bedding plane and the vertical bedding directions are tested. The results show that coal structural anisotropy has a greater impact on gas permeability properties, differences in experimental coal permeability are roughly one order of magnitude. In view of the differences of the gas flow characteristics in the coal bedding plane and vertical bedding, established series and parallel choked flow model of coal sample gas seepage, and made a theoretical analysis to the influences of the bedding structure to gas permeability properties.

耐磨硼铸铁及硼磷铸铁

前言机器部件的磨损是很值得重视的问题,我国每年年计划中易损配件的生产数量要等于或超过主机的产量,因此而造成的经济损失及自然资源的浪费是相当大的。设法减少这种损失,是有意义的。在耐磨损材料中,合金灰铸铁广泛用于发动机、农机、矿山等机器制造业中。提高合金铸铁的耐磨性是靠加入合金元素,使铸铁金相组织中产生一种硬化相。