黄河宁夏段泥沙和灌淤土团聚体速效氮磷分布特征

为明确黄河上游宁夏段泥沙输入对农田灌淤土团聚体和土壤培肥的影响特征,在干流动态采集了5月(春灌)、8月(夏灌)、10月(冬灌)的沉积泥沙,以灌淤土为对照,测定了其机械稳定性团聚体及其NO_(3)^(-)-N、NH_(4)^(+)-N、有效磷含量。结果表明,黄河宁夏段泥沙中<0.25 mm团聚体占70.8%~87.5%;>0.25 mm团聚体数量、平均重量直径和几何平均直径均为8月>10月>5月,泥沙团聚体稳定性显著低于灌淤土。泥沙团聚体无机氮以NO3--N为主,占78.9%~99.3%。泥沙1~2或0.5~1 mm团聚体有效磷含量较高。5、8月泥沙和灌淤土各粒径团聚体无机氮含量呈正相关,而在10月呈负相关。不同灌溉时期泥沙和灌淤土各粒径团聚体有效磷含量均呈负相关。因此,黄河宁夏段灌溉泥沙<0.25 mm微团聚体对灌淤土团粒结构影响较大,春灌时期不同粒径团聚体泥沙速效氮磷含量最高。

外源性碳磷输入对宁夏灌淤土磷素变化的影响

以宁夏引黄灌区水旱轮作种植模式为背景,以灌淤土为研究基础,采用室内培养法研究水旱轮作淹水培养90 d后灌淤土磷素的演变特征。结果表明,与对照相比外源性鸡粪、秸秆生物炭和磷肥添加均显著提高了灌淤土全磷、有效磷含量,增幅在6.4%~165.2%之间,输入外源性鸡粪与对照相比土壤Ca-P提升了88.4%,且随施磷水平增加无机磷(Pi)占土壤总磷比例提高。输入外源性秸秆生物炭显著增加土壤O-P含量,与施磷量的高低差异不显著,添加外源性鸡粪土壤全磷、有效磷含量较秸秆生物炭提升45.9%和45.4%。施用外源性鸡粪和秸秆生物炭前者较后者无机磷总量增加176.1 mg/kg,增幅34.5%,但无机磷占全磷相对比例后者较前者平均提高了8.5%,这可能与外源性鸡粪和秸秆生物炭对土壤全磷增量大小不同有关。

Numerical Simulation of Austenite Recrystallization in CSP Hot Rolled C-Mn Steel Strip

An integrated mathematical model is developed to predict the microstructure evolution of C-Mn steel during multipass hot rolling on the CSP production line, and the thermal evolution, the temperature distribution, the deformation, and the austenite recrystallization are simulated. The characteristics of austenite recrystallization of hot rolled C-Mn steel in the CSP process are also discussed. The simulation of the microstructure evolution of C-Mn steel ZJ510L during CSP multipass hot rolling indicates that dynamic recrystallization and metadynamic recrystallization may easily occur in the first few passes, where nonuniform recrystallization and inhomogeneous grain size microstructure may readily occur; during the last few passes, static recrystallization may occur dominantly, and the microstructure will become more homogeneous and partial recrystallization may occur at relatively low temperature.

Advances in Modern EAF Steelmaking Technology of China

Municipal waste disposal system by high temperature smelting has the following characteristics: ① The smelting temperature is as high as 1 700-1 800 ℃; ② The dioxin is hardly produced; ③ The secondary pollution can be avoided because of the absence of heavy metals in the flux; ④ The metals and flux after disposal can be reused for construction materials. If outdated, the idle or discarded medium and small blast furnaces can be reconstructed into a waste resource system with high temperature smelting technique, and it is possible to make full use of their existing functions to reduce the investment and exploit their social function of environmental protection. In addition, a new waste disposal system with high temperature smelting was designed based on the recycling municipal waste technology abroad.

薄板坯连铸连轧炼钢高效生产技术进步与展望

薄板坯连铸连轧技术发展近30年,已由最初的单坯轧制模式发展到现在的无头轧制,炼钢-连铸新技术的不断应用贯穿其整个发展历程,特别是高效化生产、铸坯无缺陷技术方面的不断进步,促进了薄板坯技术的发展。简要回顾了薄板坯连铸连轧产线的发展概况,介绍了薄板坯连铸连轧产线配套炼钢-连铸关键技术的发展情况,分析了各项关键技术的特点、难点以及某些关键装备研制方面取得的进展,在此基础上,提出了薄板坯连铸连轧产线炼钢-连铸技术的发展方向。

施肥措施对水旱轮作条件下灌淤土磷素形态的影响

【目的】研究水旱轮作条件下灌淤土磷素形态的变化特征,为宁夏引黄灌区作物施肥调控土壤磷素有效性提供科学依据。【方法】在水稻-玉米轮作体系下,设不施氮肥(T0)、常规施肥(T1)、优化施氮(T2)、70%优化施氮+30%有机肥氮(T3)、80%优化施氮+20%有机肥氮(T4)、秸秆还田+70%优化施氮+30%有机肥氮(T5)、秸秆还田+80%优化施氮+20%有机肥氮(T6)7个试验处理,通过田间小区定位试验研究了不同施肥措施对灌淤土全磷、速效磷和无机态磷含量的影响。【结果】在水旱轮作过程中,不同施肥措施对各季作物土壤全磷含量和旱地玉米速效磷含量影响不明显,但秸秆还田配施化肥和有机肥(T5、T6)能提高耕层土壤速效磷含量,水稻季和玉米季最高含量分别达56.4 mg kg^(-1)和40.4 mg kg^(-1)。由水田改为旱作后,不同施肥措施下土壤速效磷含量平均降低了7.6~18.1 mg kg^(-1)。水田条件下不同施肥措施对无机磷含量均有显著影响(铝结合态磷除外);旱作条件下不同施肥措施对铝结合态磷、铁结合态磷、闭蓄态磷含量均有显著影响,但对交换态磷、钙结合态磷含量影响不大。水田或旱作条件下,闭蓄态磷和钙结合态磷都是灌淤土无机磷的主要赋存形态。【结论】在宁夏引黄灌区水旱轮作体系下,有机无机肥配施秸秆还田是灌淤土磷素有效化调控的最有效手段,且在水稻季的调控效应最明显。

相变时间对CSP热轧TRIP钢组织和性能的影响

利用OM、SEM、XRD、EBSD和室温拉伸试验机等研究了CSP热轧TRIP钢中间缓冷时间及贝氏体等温时间对组织和力学性能的影响。结果表明,随着中间缓冷时间的延长,试验钢中的铁素体和残余奥氏体体积分数增加,贝氏体体积分数减少;抗拉强度基本不变,屈服强度逐渐降低,断后伸长率和强塑积变化不明显。中间缓冷时间为6 s时,可满足CSP产线的要求。对贝氏体相变时间的研究表明,当等温时间为15 min时,试验钢中的残余奥氏体主要分布于铁素体/铁素体界面、铁素体/贝氏体界面以及贝氏体中,体积分数约为7.1%,表现出良好的TRIP效应。其抗拉强度、屈服强度、断后伸长率和强塑积分别达到744.0 MPa、522.5 MPa、29.3%和21.8 GPa·%,力学性能最优。当等温时间延长至50 min时,试验钢中的贝氏体含量增加,残余奥氏体体积分数减少至2.7%,强塑积明显下降。

CSP热轧TRIP 600钢的连续冷却相变行为

利用Thermecmastor-Z型热模拟试验机、Formastor-F型相变仪,结合光学显微镜、扫描电子显微镜及显微硬度计等设备系统研究了CSP热轧TRIP 600钢的连续冷却相变行为,获得了试验钢的动态及静态CCT曲线,探讨了形变和冷速对其相变行为的影响。研究结果表明：随着冷速的增加,试验钢中铁素体转变温度逐渐降低,体积分数不断减少,其转变温度范围为480~716℃;珠光体含量则先增加后减少,转变温度范围为519~647℃。当冷速大于2℃/s时,试验钢中已出现贝氏体转变,其含量随冷速的增加先增大后减小,转变温度范围为451~533℃。试验钢经变形后,钢中铁素体、珠光体及贝氏体转变温度范围往左上方移动,分别为550~760、539~708和478~550℃,而且相同冷速下钢中组织更加细小。此外,变形也会提高奥氏体的机械稳定性,抑制马氏体转变,使得马氏体开始转变温度Ms由418℃降至360℃。

CSP热轧50CrV4弹簧钢等温相变行为

利用Thermecmastor-Z型热模拟试验机,结合金相显微镜（OM）、扫描电镜（SEM）、维氏硬度计等,系统研究了CSP热轧50CrV4弹簧带钢的等温相变行为。研究结果表明,试验钢在680～550℃等温时,奥氏体发生铁素体-珠光体相变;随着等温温度的降低,等温相变动力学先加快后减慢,铁素体晶粒和珠光体片层逐渐细化,显微硬度不断增加。当等温温度为620℃时,相变完成时间仅需96s。此外,根据Johnson-Mehl-Avrami（JMA）理论建立了试验钢的相变动力学模型,计算了JMA方程动力学参数,获得了50CrV4弹簧钢的TTT曲线,结果表明理论计算值与试验测量值吻合较好。

形变对共析钢连续冷却过程中珠光体相变的影响

为掌握形变对共析钢连续冷却过程中珠光体相变的影响,研究了共析钢在720~920℃温度范围内进行形变后,在连续冷却过程中奥氏体向珠光体相变的规律,建立了相变时的过冷度和珠光体片层间距的相互关系,并预测了试验钢的力学性能。结果表明:形变储存能促进共析钢在50℃/s高冷速下发生珠光体相变,形成片层间距为129~187 nm的超细片层珠光体,抗拉强度达到近1000 MPa,且随着形变温度提高,形变储存能减小,珠光体相变温度降低,珠光体片层间距减小,屈服强度和抗拉强度提高。

Effect of Annealing Temperature on Recrystallization Behavior of Cold Rolled Ti-Microalloyed Steel

In order to develop cold rolled Ti-microalloyed steel strips, the effects of annealing temperature on recrys-tallization behavior of experimental steel were researched by optical microscopy （OM）, transmission electron micros-copy （TEM） and Vickers hardness test. The annealing treatment could be divided into three distinct stages： recovery, recrystallization and grain growth. Reerystallization took place from 933 to 1033 K, during which a large number of recrystallized grains appear and hardness drops sharply. The morphology and size of TiN particles nearly remained unchanged at different stages of processing. With increasing annealing temperature, nanometer precipitates coarsened and the dislocation density was significantly reduced. In comparison with annealing time, annealing temperature was more crucial for recrystallization of cold rolled Ti microalloyed steel. It could be concluded that the pinning force of nanometer particles on dislocations increased the recrystallization temperature. At higher annealing temperature, re crystallization took place because of precipitates coarsening caused by Ostwald ripening.