Research and application of automatic control system of argon blowing at ladle shroud

Argon blowing at the ladle shroud requires the best flow control strategy to effectively avoid the secondary oxidation of molten steel, slag entrapment and heat loss during the casting of the tundish, and at the same time, give full play to the role of bubbles to remove inclusions. Therefore, an automatic control system for argon blowing at the ladle shroud was proposed. The data collected by S7-300PLC and software programming were used to adjust the argon blowing flow online in real time according to factors such as pouring and continuous pouring. On this basis, PID control algorithm and closed loop control mechanism were used for real time adjustment. The flow control valve ensures theminimum deviation between the actual value of the flow and the set value. The production data of this system in the first quarter of 2021 in a special steel plant show that the proportion of furnaces with an acid soluble aluminum (Als) loss percentage of less than 10% of each steel grade has increased by 5.52%, and the proportion of furnaces with an Als loss percentage of more than 60% has increased from 1% decrease to 0. The actual application results show that the use of the system improves the surface quality of the continuous casting slab and the performance of the final product.     

蜗杆副的跑合工艺

叙述了蜗杆副跑合的目的、作用以及跑合过程的特点和跑合中应重视的几个问题。     

建设工程质量保证体系存在的问题及对策

结合建筑业市场管理体制的改革及其发展态势，就建筑工程质量保证体系存在的问题作了阐述，从加强勘察设计资格的管理，完善监理法规等方面，提出了健全和完善质保体系的措施。     

螺纹钢牙筋长度不足的原因及解决办法

分析了影响螺纹钢牙筋长度的原因，根据铣床的工作原理，利用刀头夹持长度与凸轮工作轨面半径的几何关系，推导出计算各种不同规格螺纹钢牙筋的工艺参数，解决了螺纹钢牙筋长度不足之问题。     

P／MCs新型复合材料制备、结构及阻尼性能

采用特殊的渗流法所制备的新型Ｐ／ＭＣｓ复合材料，由高分子聚合物与蜂窝状铝架组成，它具有优异的阻尼性能，并简述了结构对阻尼的影响     

适合航天电子系统应用的DC－DC变换器

讨论了航天ＤＣ－ＤＣ混合集成电路的拓朴结构。通过对几种电路的性能比较，提出了适合航天应用的ＤＣ－ＤＣ变换器的最佳拓朴结构。论述了ＰＷＭ－ＬＩＮ变换器的控制方法，该方法对于确保二次稳压ＤＣ－ＤＣ变换器较高的效率具有重要意义，亦可大大提高混合集成电路的成品率。     

聚电解质溶液分子热力学模型

<正>链状聚电解质由于是长链大分子又有很高的电荷密度,其溶液即使在极低的浓度下仍具有很强的负偏差,与Debye-Huckel理论预测的结果相去甚远。工程上使用的Manning模型认为聚离子的电荷密度有一临界值,当超过临界值时,反离子即凝聚在聚离子表面使其实际电荷密度降至临界值。Nagvekar等在该模型的基础上引入NRTL方程,以计及短程相互作用的贡献。Manning等的方法虽然有一定的物理意义,但临界值的确定缺乏可靠的根据。     

树脂悬浮光度法测定微量银

在ｐＨ６．９的缓冲溶液中，银与硫代米Ｃｈｉ酮（ＴＭＫ）形成的螯合物在树脂甘油相中悬浮富集，用光度法测定银在波长４６１ｎｍ处有最大吸收，银在０～６μｇ／１０ｍＬ范围内遵守比尔定律，可用于样品中微量银的测定。     

一种碳－碳复合材料长寿命防氧化涂层的失效机制

用液相法联合ＣＶＤ法和硅化法制备了一种碳－碳复合材料复合梯度涂层，在此基础上对这种涂层在氧化过程中的失效机制进行了研究．结果表明：氧化层与液相层界面反应生成的气相产物是涂层失效的根本原因界面上气泡的不均匀形核、长大和破裂导致涂层表面出现孔洞．孔洞处气泡优先形核、长大和破裂并发展成为缺陷而使涂层失效     

Densification of plasma deposited silicon nitride films by hydrogen dilution

The effects of hydrogen dilution on the bonding characteristics, composition, and properties of SiN films deposited from a SiH₄/NH₃ mixture by r.f. plasma enhanced chemical vapor deposition were studied. The addition of relatively small amounts of hydrogen increased the Si/N ratio resulting in a corresponding increase in the Si---H/N---H bonding ratio. At higher hydrogen dilutions, the Si/N ratio decreased towards stoichiometric with significant changes in the hydrogen bonding characteristics. Changes in the physical properties are discussed in terms of the measured changes in bonding structure. Changes normally associated with changes in bulk film density were found to be well correlated to the Si---N bond density. The effects of substrate temperature and NH₃/SiH₄ ratio on films deposited under conditions of high hydrogen dilution were similar to those widely reported in the literature for plasma-enhanced chemical vapor deposition films deposited without hydrogen. Films deposited by remote plasma using hydrogen as the excitation exhibited high Si---N bond densities and low hydrogen. Experiments are planned to clarify the mechanism responsible for the observed changes in film properties.