Influence of soaking time in deep cryogenic treatment on the microstructure and mechanical properties of low-alloy medium-carbon HY-TUF steel

The influence of soaking time in deep cryogenic treatment on the tensile and impact properties of low-alloy medium-carbon HY-TUF steel was investigated in this study. Microstructural studies based on phase distribution mapping by electron backscatter diffraction show that the deep cryogenic process causes a decrease in the content of retained austenite and an increase in the volume fraction of η-carbide with increasing soaking time up to 48 h. The decrease in the content of retained austenite from ~1.23vol% to 0.48vol% suggests an isothermal martensitic transformation at 77 K. The η-type precipitates formed in deep cryogenic-treated martensite over 48 h have the Hirotsu and Nagakura orientation relation with the martensitic matrix. Furthermore, a high coherency between η-carbide and the martensitic matrix is observed by high-resolution transmission electron microscopy. The variations in macrohardness, yield strength, ultimate tensile strength, and ductility with soaking time in the deep cryogenic process show a peak/plateau trend.

Analysis of the formation conditions and characteristics of interphase and random vanadium precipitation in a low-carbon steel during isothermal heat treatment

The characteristics of nanosized precipitates in steels depend on the heat-treatment parameters. The effects of characteristics of vanadium precipitates formed during isothermal heat treatment on the hardness of the ferrite matrix in low-carbon vanadium-alloyed steel were investigated through analysis of transmission electron microscopy images and microhardness measurements. The results show that, during isothermal holding in the temperature range from 675 to 750℃, only interphase precipitation occurs, whereas only random precipitation occurs in the ferrite matrix during holding at 600℃. Furthermore, during isothermal heat treatment between 600 and 675℃, both random and interphase precipitates occurred in the ferrite. Nanoscale vanadium carbides with different atomic ratios of vanadium(V) and carbon(C) were the dominant precipitates in the random and interphase precipitates. The sizes of random precipitation carbides were smaller than those of interphase ones. Also, the sample isothermally heat treated at 650℃ for 900s exhibited a higher hardness with a narrower hardness distribution.

Mathematical Model of Decarburization of Ultra Low Carbon Steel during RH Treatment

According to the balance of carbon and oxygen, a decarburization model for the RH treatment has been developed. in which the influence of the mass transfer of carbon and oxygen in the liquid steel and the stirring energy (ε) in the vacuum vessel on decarburization rate has been considered. The conclusion that the volumetric coefficients of the mass transfer of carbon is proportional to ε(1.5) is drawn. Industrical experiment proves this model is reliable. The influence of some factors on decarburization rate has been obtained. which can provide directions for RH treatment The decarburization behavior of steel with RH-OB treatment is also studied. The OB-or-not curve, the optimized OB time and OB amount are discussed.

Effect of Heat Treatments on Corrosion of Welded Low-Carbon Steel in Acid and Salt Environments

Effect of heat treatment on the corrosion of welded low-carbon steel in 0.3 M and 0.5 M of hydrochloric acid and sodium chloride environments at ambient temperature (25oC) has been investigated. Arc welded low-carbon steel sample of known composition were subjected to the corrosion reagents for 21 days (504 hours). pH and weight loss values were taken at interval of 3 days. Thereafter, weight loss method was used to measure therate of corrosion attack on the heat treated samples at ambient temperature. Results obtained showed that at low concentration, the annealed sample exhibits better corrosion characteristic as compared to the normalized and quenched samples. However, at higher concentration the normalized sample exercised better service performance over the annealed and quenched samples. Thequenched sample was found to have relatively low corrosion performance over the annealed and normalized samples at both low and high concentrations of the media.

Ecological and Low-carbon Technology in Urban Decentralized Treatment and Reclamation of Wastewater

China's water shortage situation is grim.Deep exploration of non-traditional water resources and relief of contradiction between China's economic development and water resources shortage is the only way to ensure the sustainable development of China.Urban sewage treatment and reclamation is a more stable and widely used method of non-traditional water resources development and utilization.However,urban centralized reclaimed water treatment faces many problems such as high transportation cost and difficulty in laying reusing pipe network.Relatively speaking,decentralized reclaimed water treatment technology has obvious advantages and is gradually getting more attention.In this research,three types of wastewater treatment process featured with urban decentralized low-carbon ecological technology have been mainly introduced.In addition,the operating data of relevant domestic and foreign engineering cases were analyzed from the perspectives of treatment effect,energy consumption level,applicable scale and occupied area,etc.This study considers that these three new sewage processes based on the principle of ecological engineering have the advantages of compact structure,small footprint,low water consumption,stable effluent quality,beautiful appearance and large applicable scale,and are worthy of researching and importing.

Novel mechanism for the modification of Al_2O_3-based inclusions in ultra-low carbon Al-killed steel considering the effects of magnesium and calcium

Many researchers have explored the inclusion modification mechanism to improve non-metallic inclusion modifications in steelmaking. In this study, two types of industrial trials on inclusion modifications in liquid steel were conducted using ultra-low-carbon Al-killed steel with different Mg and Ca contents to verify the effects of Ca and Mg contents on the modification mechanism of Al_2O_3-based inclusions during secondary refining. The results showed that Al_2O_3-based inclusions can be modified into liquid calcium aluminate or a multi-component inclusion with the addition of a suitable amount of Ca. In addition, [Mg] in liquid steel can further reduce CaO in liquid calcium aluminate to drive its evolution into CaO–MgO–Al_2O_3 multi-component inclusions. Thermodynamic analysis confirmed that the reaction between [Mg] and CaO in liquid calcium aluminate occurs when the MgO content of liquid calcium aluminate is less than 3 wt% and the temperature is higher than 1843 K.

Study on the serialization and applications of low carbon ductile iron

Both the production process and the chemical composition of Sx were studied, and the serialization of low carbon ductile iron was also discussed. It was indicated that Sx modifier was sensitive to the carbon equivalent (CE) of molten iron and to some alloying elements too. When the CE of molten iron and the contents of alloying elements were changed, the content of Sx must be revised with the change correspondingly. Low carbon ductile iron can be stably changed into the one that non-carbon acicular ferrite and retained austenite (about 25%-28%) by quasi-casting bainitic process of using Sx-2 modifier treated Si-Mn-Cr-Cu-alloyed low carbon molten iron. The austenitic low carbon as-cast ductile iron could be obtained by the Ni-Si-Cr 35 5 2 percent alloys molten iron with less than 2% carbon treated by type Sx-3 modifier. The high-toughness ferritic low carbon as-cast ductile iron which contained more than 85 % ferrite in matrix could be got after the molten iron treated by type Sx-4 modifier, and it’s elongation was more than 10 %.

Influence of Equal Channel Angular Pressing on Tribological Properties of Low Carbon Steel (Fe-0,09C-0,64Si-,26Mn)

This paper presents the results of equal channel angular pressing (ECAP) and subsequent heat treatment (HT) as a method to improve the wear resistance of metallic materials in friction sliding. The effect of ECAP and HT on the microstructure and mechanical properties of low carbon steel is investigated in this work. The mechanisms of wear resistance of steel with ultrafine and nanostructures produced by equal-channel angular pressing is analyzed. The results show that ECAP at room temperature and annealing at 350&degC and 450&degC can be used as a technology of reducing wear in friction sliding.

城镇净水厂提标改造的主要问题及对策

城镇净水厂作为城市基础设施的重要组成部分,提供人们日常生活所需用水。由于部分水厂建成年代久远,净水工艺落后,难以处理水源中出现的新兴污染物,特别是《生活饮用水卫生标准》(GB5749-2022)发布实施,对于出厂水水质提出了更高要求。为优化处理工艺,提高运行管理成效,保障人民群众饮用水安全达标,已成为净水厂当前面临的重要任务。

绿色建筑施工废弃物堆放对周围环境的污染与低碳化处理措施研究

针对绿色建筑施工废弃物堆放对周围环境的污染展开分析,并设计了合理的低碳化处理措施。在确定研究目标背景概况后,根据废弃物产生和堆放情况,考虑监测点之间的距离,合理布设监测采样点,并借助相关仪器完成样本检测,获取堆放场污染时空分布特征。以特征分析结果为基础,提出提升垃圾利用率、使用装配式材料等低碳化处理措施。经过低碳化检测效果可知,利用研究制定的低碳化治理措施开展废弃物低碳化处理后,能够有效降低堆放场的污染物污染浓度,且可以实现废弃物的再利用。

高级氧化技术在医院污水低碳无害化处理中的研究与应用

医院污水中存在抗生素、内分泌干扰物等新污染物,这些污染物很难通过常规的生化处理方法有效去除。同时,在重点传染病频发的情况下,对医院污水中病原微生物的消杀能力也有待提高。近年来,国内外学者采用高级氧化技术有效降解医院污水中的抗生素等药物类污染物,同时灭活病原体。然而,高级氧化技术成本高、能耗大和可能产生有毒有害副产物的缺点,限制了其在实际工程中的广泛应用。本文对国内外关于高级氧化技术处理医院污水的研究现状进行了综述。首先介绍了芬顿氧化、活化过硫酸盐、过氧乙酸氧化、臭氧氧化和电化学等高级氧化技术的原理和应用。此外,还对基于电化学的协同催化氧化技术进行了介绍,针对实际医院污水的低碳无害化高级氧化处理工艺与装备进行了总结。最后,对我国目前医院污水低碳无害化处理过程中存在的问题进行了分析,并展望了未来的研究方向。

低碳水处理与资源化技术:厌氧膜生物反应器(AnMBR)的特性、应用与新技术简介

厌氧膜生物反应器(AnMBR)集成了厌氧生物处理的高效率和膜技术的精准选择性,开创了污水处理技术的新篇章。在当前全球环境保护意识和资源循环利用需求日益加强的背景下,AnMBR技术不仅响应了追求低碳水处理的趋势,还在资源回收利用方面展示了广阔的发展前景。本文详细探讨了AnMBR的原理、操作优势以及其在当下的应用实践,并阐述了AnMBR技术在推广过程中面临的技术挑战和最新的科研进展。即便AnMBR在商业化应用中仍存有挑战,但得益于科学研究的不断深入和技术创新的推动,这些挑战正被一一克服。基于AnMBR的新技术开发与应用为实现废水资源化利用与推动循环经济方面提供了有力支持。AnMBR技术在提高污水处理效率、减少碳排放,以及促进能源和资源的可持续利用方面取得了突破性进展,预示着水处理技术正在向更加绿色、高效的方向发展,对未来水资源管理与环境保护具有深远意义。

低碳城市与创新型城市减碳技术选择机制

低碳城市试点政策与创新型城市试点政策是实现“双碳”目标与促进经济高质量发展的重要政策工具。探究不同试点政策下企业碳减排技术的选择,对节约企业生产成本、提升企业减排成效具有重要的现实意义。基于此,该研究以利润最大化为目标,在碳减排技术只包括源头治理技术和末端处置技术,且不考虑其他外部政策因素冲击的假设条件下,构建基于希克斯中性技术的生产函数,分析三类试点政策下企业的减碳技术选择机制。进一步,基于2000—2019年中国75个试点城市的3766家企业的面板数据,运用Hansen门槛面板模型,验证了这一技术选择机制的科学性。研究发现,源头治理技术与末端处置技术在不同试点政策中的选择依据是末端处置技术投入占产出的比例。具体而言:①如果这一比例处于(0,0.5)区间,在低碳城市试点政策下,企业选用成本较低的末端处置技术;在创新型城市试点政策下,企业缺乏投入碳减排技术的意愿;在双试点政策下,企业既运用末端处置技术又投入源头治理技术减碳,并且前一技术见效快,投入更多。②如果这一比例处于(0.5,1)区间,此时,末端处置技术成本已经超过产出的50%,那么三类试点政策下的企业均选择成本较低的源头治理技术减碳。③异质性分析结果表明,在生产成本的约束下,非国有企业、老企业和高碳行业的企业缺乏增加减碳技术投入的积极性。因此,各级政府应引导这三类企业进入碳交易市场,并通过政策补贴、高新技术企业孵化以及碳减排源头治理技术推广的方式激发这三类企业低碳技术创新的主动性,最终以最小的碳减排成本实现碳排放总量的下降。

低温对含盐食品污水深度处理性能与微生物群落的影响

固体碳源被广泛应用于污水深度处理,但是低温条件下对含盐食品污水的处理性能还缺乏评估,微生物特性也需要揭示。以聚丁二酸丁二醇酯为固体碳源,考察了不同温度条件下的脱氮性能、微生物群落结构以及基因富集特征。结果表明:常温(25~28℃)条件下的固体碳源反应器出水可以满足《污水综合排放标准》一级标准。低温(5~9℃)对脱氮性能抑制显著,NH_(4)^(+)-N、NO_(3)^(-)-N去除率仅为30.17%、73.51%,并且运行初期存在出水有机物超标的风险。固体碳源体系中unclassified_Comamonadaceae、Acidovorax分别是主要的硝化、反硝化菌属,但容易受低温影响而丰度降低。此外,温度降低还会导致硝化基因(amoA、amoB、amoC)和反硝化基因(narG、narH、narI)丰度降低。

低热-NaOH联合处理破解浓缩活性污泥释放碳源的试验研究

以低热-NaOH联合处理破解剩余活性污泥,考察NaOH投加量、加热温度、反应时间对污泥破解释放碳源的影响,通过总氮去除率分析污泥破解液代替生物脱氮外加碳源的效率,并研究该方法对污泥减量化的效果。结果表明:SCOD溶出率随NaOH投加量、加热温度和反应时间的增加而增大;当NaOH投加量为3.0g/L、加热温度为70℃、反应时间为24h时剩余活性污泥的破解效果最佳,污泥上清液中SCOD浓度可达1.829×10^(4)mg/L,总氮、氨氮、硝酸盐氮和总磷浓度分别达到943、419、487、204mg/L;污泥破解前后固体残渣中TSS含量由61.70 g/L下降至29.25g/L,VSS含量由31.95g/L下降至6.95g/L,生物减量化效果非常显著;污泥破解前后中值粒度D50分别为30.2、8.7μm,污泥破解过程中产生了大量的粒径为0.15μm左右的超细颗粒;扫描电镜结果显示污泥絮体和微生物细胞被破坏;在反硝化试验中,以最佳破解条件下释放的污泥破解液作为反硝化试验的补充碳源,结果显示COD利用率为83.4%,总氮的去除率为60.1%,脱氮的效果显著。低热-NaOH联合处理可在较低能耗下实现剩余活性污泥的碳源充分释放,且污泥减量化和资源化的效果优异,可为优化热碱法预处理剩余活性污泥提供依据。

“双碳”目标下工业污水低碳化处理技术研究

随着“双碳”目标的提出,各行业、领域在工业污水处理中普遍扩大了对低碳化处理技术的配置比例,旨在减少碳排放量。本文阐述了“双碳”目标下工业污水低碳化处理的必要性,并在剖析相关技术的基础上,结合某工业污水工程项目,分别从项目概况、工艺流程、低碳化特征、运行效果方面对其处理情况进行了具体探讨。

低碳韧性理念下半地下式污水处理厂设计

太仓城东水质净化厂建设规模为15万m^(3)/d,采用半地下式建设形式,是国内规模领先的振动式MBR应用案例(7.5万m^(3)/d)。污水处理采用初沉池-AAO生反池-MBR膜池工艺,出水主要执行《苏州特别排放限值标准》。污泥经离心浓缩脱水处理后(含水率<80%)外运处置。针对污水处理厂建设形式、总平面布置、竖向布置、污水处理、污泥处理等工艺设计要点进行了探讨,并综合考虑了低碳、韧性、多功能融合和生态绿色等设计理念和措施。

污染土壤修复工厂现状及发展研究

污染土壤修复工厂具有缩短修复周期、加快土地流转、降低处置成本等优点,适用于大型退役工业区的土壤修复。本文通过梳理现有政策对修复工厂模式的发展要求,分析了土壤修复工厂建设布置、选址和管理要求;结合国内现有实际案例,总结其发展现状和特性,发现修复工厂多位于经济发达及工业污染严重区域、多采用固化稳定化技术和氧化技术且具有明确的末端处置途径。目前,我国土壤修复工厂模式还存在成熟范例少、转运手续复杂等问题,但其仍具有广阔的发展前景,能够为土壤污染问题提供切实可行的解决方案。