The magnetic properties and hysteresis of LaFeSi based magnetic refrigeration materials with different sizes and magnetic field rates were studied.It is found that both thermal hysteresis and magnetic hysteresis increase with the increase of sample size due to the low response of large-size samples to thermal effects.The double peaks of the upfield magnetic entropy change can be observed in the magnetic entropy change curve of the 2 mm×2 mm×2 mm sample.This phenomenon can be solved by calculating the magnetic entropy change and the average magnetic entropy of the reduced magnetic field.From small to large,the values of magnetic entropy change ΔSM are-22.29 J/(kg·K),-24.97 J/(kg·K)and-20.36 J/(kg·K),respectively,indicating that the size has little effect on the magnetic entropy change.In addition,the hysteresis increases first and then decreases with the increase of temperature,and reaches the maximum value near TC,which is similar to the curve of magnetic entropy change.There is a correlation between hysteresis and magnetic entropy change.However,the maximum magnetic entropy change values at differ-ent magnetic field rates are not significantly different,and there is no obvious correlation with the magnetic field rate.The size of the sample and the magnetic field rate have an effect on the hysteresis,but have little effect on the magnetic entropy change.This study deepens our understanding of the influencing factors of hysteresis,and provides a solid experimental and theoretical basis for the development of magnetic refrigeration technology.
材质为ZG270-500的大型铸钢泵盖是船用挖泥泵上的关键零部件之一.采用模数理论设计大型铸钢泵盖的铸造工艺,制定铸造工艺方案,分析其存在问题.针对泵盖产品壁厚不均,热节较为分散,补缩困难,易产生缩孔、缩松等铸造缺陷,采取在热节部位加冒口、在冒口下的铸件上增加补贴,并采用假箱造型工艺进行工艺改进,优选最佳方案,并利用CASTsoft铸造模拟软件进行凝固模拟,以保证铸件无缩孔、缩松等铸造缺陷.实际生产大型铸钢泵盖铸件达到技术条件要求.
简要介绍了消失模铸造工艺的特点及生产工艺流程,根据其特点进一步介绍了消失模铸造厂的工程设计要点,将白区与黑区分开布置,在满足消防要求的同时,降低了消防投入.为以后消失模铸造项目的设计提供借鉴和参考.
针对汽车用大型铝合金压铸件的生产,基于提高生产效率、确保产品质量和保护环境的理念,介绍了 一体化大型压铸件车间设计要点,包括关键工艺设备选型及工艺布置,物流、人流,节能和合理用能,环境保护,职业安全卫生等几个方面.通过合理的压铸车间工艺规划和环保措施,可以在提高生产效率的同时,保护环境和提升工作人员的职业健康水平.
镁合金由于其自身优异的性能,发展潜力巨大,在诸多领域受到广泛的需求.在镁合金中添加稀土元素,合金的强度、蠕变性能等提升显著.本文总结了铸造高强Mg-Gd合金的研究进展,从合金体系、组分、热处理工艺、合金的强度以及强化机制方面,分析了不同合金元素对重力铸造Mg-Gd合金的影响作用,可以为铸造Mg-Gd合金的设计和优化提供参考依据.
