高氮不锈轴承钢碳化物分布与高温断裂机制

 通过高温拉伸试验研究高氮不锈轴承钢高温断裂行为,探究了170 ℃和470 ℃回火态钢中碳化物分布特征,分析了高温拉伸断裂及组织演变和碳化物分布规律。研究发现,回火温度从170 ℃升高至470 ℃,高氮钢中大于0.8 μm的碳化物明显增加,高氮钢中M₂₃C₆强化增量提高了2.59 MPa,固溶强化增量下降了118.82 MPa,470 ℃回火态钢的室温抗拉强度降低、拉伸断口表现为准解理和少量撕裂韧窝;拉伸温度升高至300 ℃,试样断口表现为等轴型韧窝特征,170 ℃和470 ℃回火态试样起裂源断裂碳化物尺寸分别为2.8~3.6 μm和5.5~6.7 μm;450 ℃拉伸断口表现为塑孔韧窝特征,170 ℃和470 ℃回火态试样起裂源断裂碳化物尺寸分别为2.7~3.4 μm和5.8~6.4 μm。拉伸温度从300 ℃提高至450 ℃,钢的固溶强化和位错强化作用减弱,金属原子间结合能下降,碳化物与基体不连续应力分布加剧变形不协调性,碳化物承担较高应力而发生断裂。单纯热作用下钢中0.5~0.8 μm尺寸碳化物数量比例增加;在热力耦合作用下,钢中应力所导致的位错增殖为碳元素扩散提供通道,钢中碳化物在晶界和位错线上形核析出0.2~0.8 μm碳化物。裂纹沿着与拉伸方向45°角的最大剪力方向快速扩展而断裂,最终形成锯齿状的断口,小尺寸碳化物增多阻碍位错滑移导致塑性降低;钢中大尺寸碳化物不均匀分布在碳化物间形成大变形塑孔而增加钢的塑性。     

含铈304不锈钢夹杂物改性及耐腐蚀性能优化

 通过在304不锈钢中加入不同含量的铈,研究了铈处理前后钢中夹杂物的变化,并借助于腐蚀失重试验及电化学试验,分析了不同含量的铈处理后钢中夹杂物性质变化对304不锈钢耐腐蚀性能的影响。研究结果表明,未加铈的不锈钢中主要为MnS夹杂及复合氧化物夹杂,夹杂物的平均尺寸为8.6 μm,而钢的自腐蚀电位仅为-348.52 mV。加入稀土铈后,夹杂物逐渐改性成球状或椭球状的含铈夹杂物,平均尺寸有所降低,而不锈钢耐腐蚀性则有所提高。当铈质量分数达到0.012%时,钢中MnS夹杂全部改性成球状含铈夹杂,不锈钢自腐蚀电位高达-311.25 mV,耐腐蚀性能最好。继续增加稀土铈含量,钢中夹杂物的形状变得不规则,尺寸也有所增加,导致不锈钢耐腐蚀性能降低。     

铁矿石品位与焦比、铁水产量关系的研究

为进一步了解铁矿石品位与焦比、铁水产量的关系,用拉姆计算法对铁矿石品位变化1％对焦比的影响进行计算,对国内某炼铁厂2 500 m3高炉实际生产数据进行统计及理论计算.研究结果表明随着矿石品位的增加,矿石品位对焦比的影响越来越小,铁水产量随铁矿石品位呈线性增长关系.计算得出入炉铁矿石品位为56.4％时,矿石品位增加∶焦比减少∶铁水产量增加=1∶1.6∶1.77,与实际统计得到的1∶1.74∶2.39较为相近,计算结果有效,但与经验关系1∶2∶3有所不同.提供了一种能用于生产高炉分析矿石品位与焦比、铁水产量关系的计算方法,为细化高炉操提供指导.     

含钇E36船板钢夹杂物改性

为了研究钇对E36船板钢中夹杂物成分和形貌的影响,对钇处理后E36船板钢中典型夹杂物进行热力学计算,并通过扫描电镜及能谱仪对钇处理前后E36船板钢中夹杂物进行检测分析,观察典型夹杂物形态和尺寸。结果表明,未添加稀土钇的E36船板钢主要为长条状MnS夹杂物;添加稀土钇后,钢中夹杂物主要为球状或类球状的含钇复合夹杂物。当钢中钇质量分数为0.007 8%时,夹杂物主要为球状或类球状的Y₂O₂S夹杂物和Y₂O₃夹杂物;当钢中钇质量分数增加至0.037 7%时,夹杂物改性为球状或类球状Y₂O₂S夹杂物、YS夹杂物和Y₂O₃夹杂物。     

圆坯连铸中间包温度场的数值模拟

对原型、U型和Y型挡墙中间包温度场进行了数值模拟。模拟结果表明：原型中间包挡墙形式不合理,中部和边部水口的温差较大;U型挡墙中间包温度场虽较原型有一定程度的改善,但也存在一定的问题;Y型挡墙中间包较原型和U型温度场分布更加均匀,温降更小,是较合理的挡墙形式。     

不同挡墙挡坝组合对两流中间包内流场的影响

在相似理论的基础上,通过水力学模拟对两流板坯连铸中间包3种不同挡墙挡坝组合形式下包内流场进行研究.试验结果表明:方案1(挡墙-挡坝-端挡坝方案)挡墙与挡坝间距不合理,端挡坝未起到控流作用致使中间包内流体平均停留时间、峰值时间短,死区比例较大(27.9%);方案2(挡坝-挡墙-端挡坝方案)显著改善了中间包内流场状况,全混流区及活塞流区比例增加,死区减小为21%;方案3(双墙双坝方案)由于增加一组挡墙延长了流体流动的路径,流体在中间包内的停留时间明显增加,死区比例最小(16.7%),同时微观电导率波动值也最小(0.025 ms/cm),为3种方案之最优.     

Hot Working Characteristics of Corrosion-Resistant Alloys G3 and 825

  The G3 and 825 alloys, with excellent combination of mechanical properties and corrosion resistance, can be used in hot, and acid environments. Thermal simulation tests were conducted on the alloys G3 and 825 in the THERMECMASTOR Z simulator, at temperature between 1030 and 1300 ℃, with strain rate from 1 to 50 s-1 and strain ε=08. The variations of flow stress with deformation temperature and strain rate were presented. Change of alloy structure with hot deformation and effect of strain rate on alloy dynamic recrystallization have been studied through microstructure observation by OM, SEM and TEM. Moreover, hot plasticity characteristics of alloy were analyzed by temperature reduction of area curves. The results showed that available hot working temperature for G3, G3 Z and 825 was 1100 to 1240 ℃, 1130 to 1220 ℃ and 1050 to 1240 ℃, respectively. The reliable information on hot working in the alloy pilot production in steelwork is given.     

Production of Nitrogen-Bearing Stainless Steel by Injecting Nitrogen Gas

 To replace nickel-based stainless steel, a nitrogen-bearing stainless steel was produced to lower the production cost stemming from the shortage of nickel recourses. Thermodynamic model to calculate the saturated nitrogen content in the stainless steel was developed and the model was validated by experimental measurements performed with a high temperature induction furnace. Nitrogen gas under constant pressure was injected into the molten steel with a top lance. Thus, the nitrogen was transferred to the molten stainless steel. The effects of chemical composition, temperature, superficial active elements and nitrogen flow rate on the transfer of nitrogen to the steel were investigated and discussed. The results showed that the dissolution rate of nitrogen in the molten steel increases with a higher temperature and larger nitrogen flow rate but decreases significantly with an increase in the content of surface-active elements. Alloying elements such as chromium and manganese having a negative interaction coefficient can increase the dissolution of nitrogen in the molten steel. It was also proposed that the primary factor affecting the final saturated nitrogen content is temperature rather than the dissolved oxygen content.     

村田No.7-Ⅱ型自动络筒机单锭控制板的国产化开发

针对村田No.7 Ⅱ型自动络筒机单锭板存在的问题,分析其电路和元器件功能,阐明四种典型单锭板国产化的设计原理和方法,并介绍了产品使用方法及特点。     

低频水力振动器的参数确定与试验研究

对地层施加振动处理是消除地层堵塞增加油水井产量的有效方法。理论研究和应用实践表明，施加的振动能量越大、振动频率越低，其处理深度越大，获得效果和经济效益就越高。文章介绍了一种可实现低频率大振幅振动的水力振动器．并对振动条件所满足的数学模型做了详细的推导，为参数设计提供了可靠的计算公式，结合室内模拟试验所取得的经验对参数设计做了相应的修改，为低频水力振动器的设计提供依据。