基于纳米铁碳析出物的钢综合强化机理

简要叙述了关于钢强化机理的研究现状,用化学相分析+X射线小角散射、RTO方法及高分辨透射电镜对薄板坯连铸连轧钛微合金化高强耐候钢中纳米粒子的属性进行了综合分析。发现钛微合金化高强耐候钢中尺寸<36 nm的粒子,除纳米TiC以外,还存在大量的纳米Fe3C,其体积分数为同尺寸TiC体积分数的4.4倍,析出强化作用比纳米TiC粒子大,不可忽略;提出了钢的综合强化机理,指出对不同种类、不同尺寸的纳米析出粒子,应分别根据位错切割和位错绕过机理计算出析出强化贡献,然后与固溶强化和细晶强化贡献加和,求得钢的屈服强度;讨论了细晶强化与位错强化不能加和的原因以及相变对钢强度影响的表现形式,对钛微合金化高强耐候钢屈服强度的理论计算与生产结果相符,实验钢σs=630～676 MPa,实际σs=630～680 MPa。简述了钢综合强化机理的应用情况,指出了有待进一步研究的科学问题。

铁钢界面铁水温降碳析出利用研究

研究了铁钢界面宝山基地铁水温降与碳析出的定量规律,结果显示,铁水温度降低100 K,碳的饱和溶解度平均减少0.265%,即1 t铁水析出碳约2.65 kg。采用高温试验方法,考察了不同含铁氧化物种类对降碳效果的影响;采用物料平衡热平衡计算分析了鱼雷罐车中加入废钢对铁水碳析出量的影响。结果表明,鱼雷罐里利用低碳轻薄料废钢,可稀释铁水饱和碳,减少碳析出,原来损失的吨铁4.42 kg标煤能源得以高效利用。该方法已在工业现场大规模应用。

利用除尘灰降低铁水碳析出的实验研究

为解决高炉到转炉转运过程中铁水的碳析出问题,采用钢铁厂含铁氧化物除尘灰作为氧化剂,并通过高温实验研究了除尘灰在降低铁水碳含量中的应用效果。考察的除尘灰有:转炉LT(Lurgi and Thyssen)除尘灰、转炉二次灰、电炉灰和高炉灰。分析了除尘灰种类、加入量、反应温度以及加料顺序对降碳效果的影响。实验研究结果表明,直接加入粉状除尘灰,氧化反应十分剧烈,并且会发生喷溅。压块后,能使除尘灰100%被利用。高炉灰碳含量过高,不能直接作为铁水降碳的氧化剂使用,其余3种灰的降碳效果依次为:转炉LT除尘灰>电炉灰>转炉二次灰。3种除尘灰加入量均为铁水质量的2%~5%时,LT除尘灰能使铁水中碳降低0.19%~0.59%,电炉灰和转炉二次灰分别为0.12%~0.47%和0.05%~0.12%。

HSLC和HSLA钢中的纳米铁碳析出物

用化学相分析、X射线小角散射测定的纳米粒子的质量衡算、高分辨透射电子显微镜观察和热力学分析及回火快冷技术研究了低碳高强度钢(HSLC钢)中尺寸小于20nm析出物的属性、质量分数、粒度分布及其对钢力学性能的影响,发现薄板坯连铸连轧低碳钢中存在大量尺寸小于18nm的铁碳析出物,它们主要是在A1温度以下形成的Fe-O-C和Fe-Ti-O-C析出物,这些纳米粒子对薄板坯连铸连轧低碳钢具有显著的沉淀强化作用,是HSLC钢强度高的主要原因之一.HSLA钢中也存在大量小于36nm的铁碳析出物.

变形工艺对低碳钢奥氏体中析出物的影响

研究变形温度和变形量对微合金元素碳氮化物在形变奥氏体中析出的影响,观察了不同变形工艺下奥氏体中析出物形貌。研究表明:变形量越大,变形温度越低,实验钢奥氏体中析出物数量越多,析出物平均尺寸越小。

冷变形后微合金钢碳氮化物的析出与组织

通过固溶时效处理,研究冷变形、时效温度等因素对微合金元素V,Ti,Nb的碳氮化物沉淀析出行为和组织演变过程的影响。结果表明:预变形试验钢的时效动力学曲线和未变形试验钢的时效动力学曲线具有相似的形状,预变形后达到的硬度峰值高,所需的时效时间缩短。预变形对含钒钢和含钛钢的碳氮化物析出动力学的影响很小,组织发生了再结晶并生成铁素体组织。预变形促进了含铌钢的碳氮化物较快析出,阻止再结晶,保持粒状贝氏体组织。

TMCP工艺对低碳贝氏体钢铁素体中碳氮化物析出影响

采用物理化学相定量分析技术,较系统地研究了不同工艺条件下实验钢中微合金碳氮化合物在铁素体中的析出行为。研究结果对开发高强度钢板具有一定的参考价值。

TMCP工艺对低碳贝氏体钢铁素体中碳氮化物析出的影响

本文采用物理化学相定量分析技术,系统研究了不同工艺条件下实验钢中微合金碳氮化合物在铁素体中的析出行为。研究结果对开发高强度钢板具有一定的参考价值。

氧化铝蒸发母液析出碳碱新方法研究与应用

本文介绍了氧化铝工业生产过程中蒸发母液碳碱析出的新方法,它不同于传统的靠蒸发器强制效蒸发掉水分使碳碱结晶析出,而是采用化学方法在低蒸母液里加入片碱使Na OH浓度提高,促使碳酸钠结晶析出。该方法简单、有效、节能,效果显著。

热环境下建筑用高钢级管线钢中碳氮化物的析出行为

研究了建筑用高钢级管线钢在热环境下的碳氮化物析出问题。结果表明,800℃下平衡状态合金中的Nb和Ti元素含量较低。在析出物中,Nb C所占的质量分数最大,Al元素绝大部分熔化在合金中。Nb元素的存在能够限制Ti元素的析出,同时高含量的Nb还可以提高Al N和碳氮化物的析出温度。

氮化物形成元素对低碳含铌钢连铸板坯高温塑性和碳氮化物析出的影响

为了降低低碳含铌钢连铸坯的表面裂纹，在模拟钢坯表面通过立－弯式连铸机喷水冷却段和扇形段热循环的条件下，研究了碳氮化物的成分和形貌对连铸坯高温塑性的影响。现已表明，由于喷水重复冷却和与输送辊道紧密后再加热，引起的板坯表面温度变化，原始奥氏体晶界细小的铌的碳氮化物析出增多。高温微分热力学分析表明，钛的微合金化对钢凝固过程和δ／γ相变的过冷度有显著的影响，除钛元素外，氮化物形成元素诸如Ｚｒ。

CSP工艺试制汽车用高强度热轧板中的析出

利用透射电镜研究了珠钢CSP工艺试生产的汽车用高强度热轧板中的析出颗粒形貌与分布;利用AshbyOrowan的弥散强化模型讨论了析出物颗粒尺寸及体积分数与屈服强度的关系。结果表明,在ZJ510LB热轧板的铁素体晶界、晶内及位错上有大量细小的析出物,析出以TiC颗粒为主,细小弥散的析出颗粒产生的强化增量约40MPa,CSP工艺规程充分发挥了微合金元素的潜力。

退火温度对含铌微合金高强钢力学性能的影响

模拟含铌微合金高强钢的卷曲过程并在不同温度下进行退火处理试验。检测不同退火温度下试验钢的力学性能,结合OM、EBSD和TEM方法,研究退火温度对试验钢微观组织和力学性能的影响。结果表明,随着退火温度的升高,铁素体晶粒长大,铌-碳析出相粗化并发生溶解,试验钢断后伸长率逐渐增加。当退火温度由780℃升高到800℃时,试验钢的屈服强度和抗拉强度大幅度降低,而退火温度由800℃增加到820℃时,试验钢的屈服强度和抗拉强度下降幅度较小。

Effects of hot compression on carbide precipitation behavior of Ni-20Cr-18W-1Mo superalloy

The effect of hot compression on the grain boundary segregation and precipitation behavior of M6C carbide in theNi-20Cr-18W-1Mo superalloy was investigated by thermomechanical simulator, scanning electronic microscope （SEM） and X-raydiffraction （XRD）. Results indicate that the amount of M6C carbides obviously increases in the experimental alloy after hotcompression. Composition analyses reveal that secondary M6C carbides at grain boundaries are highly enriched in tungsten.Meanwhile, the secondary carbide size of compressive samples is 3？5 μm in 10% deformation degree, while the carbide size ofundeformed specimens is less than 1 μm under aging treatment at 900 and 1000 ℃. According to the thermodynamic calculationresults, the Gibbs free energy of γ-matrix and carbides decreases with increase of the compression temperature, and the W-rich M6Ccarbide is more stable than Cr-rich M23C6. Compared with the experimental results, it is found that compressive stress accelerates theW segregation rate in grain boundary region, and further rises the rapid growth of W-rich M6C as compared with the undeformedone.

Effect of carbon on high temperature compressive and creep properties of β-stabilized TiA l alloy

Carbon is an important alloying element in improving high temperature mechanical properties of various metallic materials.The effects of carbon on high temperature mechanical properties of aβ-stabilized Ti?45Al?3Fe?2Mo(molar fraction,%)alloy were studied through compressive and creep tests.The results show that the carbon addition(0.5%,molar fraction)obviously enhances the high temperature compressive strength and creep resistance of theβ-stabilized Ti?45Al?3Fe?2Mo alloy.A lot of nano-scaled Ti3AlC carbides precipitate in theβ-stabilized alloy and these carbides pin the dislocations,and greatly increase the high temperature properties.At the same time,the carbon addition decreases the amount of?phase,refines the lamellar spacing,and causes solution strengthening,which also contribute to the improvement of the high temperature properties.

基于非调质钢凝固特性的二次冷却控制

提出了基于非调质钢凝固特性的二次冷却控制方法.在凝固特性研究方面,运用高温共聚焦显微镜、场发射扫描电镜研究了冷速对第二相粒子析出规律的影响,并阐释了先共析铁素体的相变机制.结果表明,第二相粒子在1086℃开始析出,并在912℃达到峰值.当冷速在0.1~5℃·s^(-1)时,随着冷速增大,第二相粒子尺寸和数量均减小,且第二相粒子由晶界处的链状分布向晶体内的弥散分布过渡,提高冷速有助于削弱第二相粒子的钉扎作用,强化铸坯表层微观组织;在二冷配水优化方面,建立了考虑铸坯横向水量分布的凝固传热数学模型,提出了基于非调质钢凝固特性的二冷配水优化方案,即对出结晶器后的铸坯实施强冷,以满足控制第二相粒子析出的合理冷速和温度区间的要求.工业试验证实了技术方案的可行性.此外,研究表明,降低喷淋距离有助于改善连铸坯横向冷却不均匀性.本研究统筹考虑二冷水量与喷淋距离对非调质钢裂纹敏感性的影响,通过开展“纵‒横”凝固冷却控制研究对连铸二次冷却进行系统优化,提出的二冷优化方案有助于改善连铸坯的表面及皮下裂纹.

Phase precipitation behavior and tensile properties of as-cast Ni-based superalloy during heat treatment

The phase precipitation behavior and tensile properties of an as-cast Ni-based alloy,IN617B alloy,after solution heat treatment and long-term aging treatment were investigated.Ti(C,N),M6C and M23C6 are the primary precipitates in as-cast microstructure.After solution heat treatment,most of carbides dissolve into the matrix except a few fine Ti(C,N)within grains.During long-term aging at 700°C,the phase precipitation behaviors of the alloy are characterized as follows:(1)M23C6 carbides at grain boundaries(GBs)transform from film-like shape to cellular shape and gradually coarsen due to the decrease of the surface energy and element aggregation to GBs;(2)M23C6 carbides within grains have a bar-like morphology with a preferential growth direction[110]and have a cube-on-cube coherent orientation relationship with the matrixγ;(3)γ?particles inhibit the coarsening of M23C6 within grains by constraining the diffusion of formation elements.Furthermore,the tensile strength of the alloy obviously increases,but the ductility significantly decreases after the aging for 5000 h.The alloy has a relatively stable microstructure which guarantees the excellent tensile properties during long-term aging.

Carbide precipitation and microstructure refinement of Cr-Co-Mo-Ni bearing steel during hot deformation

The dynamic recrystallization and carbides precipitation of the Cr-Co-Mo-Ni bearing steel were investigated by hot compression tests performed at temperatures ranging from 850 ℃to 1080 ℃ with strain rate of 1-20 s-1. The activation energy（Q） for the tested steel is calculated to be around 682.99 k J/mol at a deformation strain of 0.6. Microstructural analysis by SEM shows that the dynamic recrystallization（DRX） behavior is dependent sensitively on the deformation strain, temperature and strain rate, while an exponential relationship between DRX grain size and Z parameter is obtained from the computational formula. Moreover, the M6C-type carbides（〈1 μm） act as the main prohibitor of grain coarsening, and the polynomial regression relationship between them is worked out. With electron backscatter diffraction（EBSD） observation, DRX is the main nucleation mechanism responsible for the formation of new grains during hot compression. In conclusion, the interaction between DRX affected by hot deformation parameters and carbides precipitation determines the ultimate grain size refinement.

Robust MOF-253-derived N-doped carbon confinement of Pt single nanocrystal electrocatalysts for oxygen evolution reaction

Although carbon-supported platinum(Pt/C) is still considered the most active electrocatalyst for hydrogen evolution reaction(HER) and oxygen reduction reaction(ORR), its applications in metal–air batteries as a cathode catalyst, or for oxygen generation via water splitting electrolysis as an anode catalyst is mainly constrained by the insufficient kinetic activity and stability in the oxygen evolution reaction(OER). Here, MOF-253-derived nitrogen-doped carbon(N/C)-confined Pt single nanocrystals(Pt@N/C) have been synthesized and shown to be efficient catalysts for the OER. Even with low Pt mass loading of 6.1 wt%(Pt@N/C-10), the catalyst exhibits greatly improved activity and long-time stability as an efficient OER catalyst. Such high catalytic performance is attributed to the core-shell structure relationship, in which the active N-doped-C shell not only provides a protective shield to avoid rapid Pt nanocrystal oxidation at high potentials and inhibits the Pt migration and agglomeration, but also improves the conductivity and charge transfer kinetics.

Effects of Cu content on microstructures and compressive mechanical properties of CNTs/Al-Cu composites

The carbon nanotubes(CNTs) reinforced Al-Cu matrix composites were prepared by hot pressing sintering and hot rolling, and the effects of Cu content on the interfacial reaction between Al and CNTs, the precipitation behavior of Cu-containing precipitates, and the resultant mechanical properties of the composites were systematically investigated. The results showed that the increase of Cu content can not only increase the number and size of Cu-containing precipitate generated during the composite fabrication processes, but also promote the interfacial reaction between CNTs and Al matrix, leading to the intensified conversion of CNTs into Al_(4)C_(3). As a result, the composite containing 1 wt.% Cu possesses the highest strength, elastic modulus and hardness among all composites, due to the maintenance of the original structure of CNTs. Moreover, the increase of Cu content can change the dominant strengthening mechanisms for the enhanced strength of the fabricated composites.