高碳盘条力学性能不合原因分析

借助金相检验、化学分析和扫描电子显微镜及能谱仪分析了高碳盘条力学性能不合格的原因.分析结果表明.高碳盘条抗拉强度不合格的主要原因是控轧控冷时造成的索氏体比例较小,中心偏析造成的网状碳化物和马氏体、夹杂物的大小对抗拉强度的影响并不显著.     

回火马氏体中合金碳化物的3D原子探针表征Ⅲ.粗化

Nb-V微合金钢在1200℃固溶0.5 h后淬火,在650℃回火4 h,利用SEM和HRTEM观察显微组织,合金碳化物的形貌特征和精细结构,用三维原子探针(3DAP)研究合金碳化物中元素分布规律.结果表明,淬火微合金钢在650℃回火4 h后,马氏体板条内位错和板条界面因回复而消失,粗化的合金碳化物分布在原马氏体板条界面和板条内部.同时,伴随着合金元素的再分配,早期析出的圆盘状碳化物沿厚度方向生长,出现一个与基体(M_(bcc))和原碳化物(P_(inner))成半共格关系的新生过渡相(P_(outer)).非碳化物形成元素Si和Al主要分布在碳化物/基体界面处;V和Mn主要分布在碳化物内层,而Mo和Nb分布在整个碳化物区域.粗化的碳化物是一种具有核心和外壳结构的合金碳化物,内层主要是V-Mn-Mo-Nb的碳化物,而外层主要是Mo-Nb的碳化物.     

Carbide characterization in low-temperature tempered steels

The nature of the initial carbides formed during the early stages of the tempering of steels is still a matter of debate. Conventionally, the main transition carbide is described as epsilon carbide, with a composition of approximately Fe_2.4C. However, earlier one-dimensional atom probe (1DAP) results indicated the existence of carbon-rich regions having much lower carbon contents, with maxima of around 10 at%. There was some uncertainty about the interpretation of the 1DAP results, because of possible problems with alignment of the aperture and with trajectory aberration effects. We have therefore re-visited this topic, using the three-dimensional (3D) atom probe, and studying both a model Fe–Ni–C alloy and a well-known engineering steel (AISI4340). We demonstrate that, for both materials, low-temperature (20–150 °C) aging produces carbon-rich regions with average peak carbon contents of up to 10%. We show for the first time the three-dimensional structure of these carbon-rich regions, and demonstrate that fine-scale faulting exists within them.     

回火温度对热轧低碳贝氏体钢显微组织和力学性能的影响

对低碳贝氏体钢进行了热轧和不同温度回火处理后,采用光学显微镜和多功能材料试验机研究了回火温度对其显微组织及力学性能的影响.结果表明:不同回火温度下试验钢的显微组织主要为由板条贝氏体、粒状贝氏体、准多边形铁素体等组成的混合组织,回火温度不同,各种组织所占的比例有很大不同;回火温度对低碳贝氏体钢的屈服强度有明显影响,但对抗拉强度的影响相对较小,随着回火温度的提高,屈强比明显增加.     

9Cr2Mo冷轧辊用钢的激光淬火试验

采用硬度测试、显微组织和断口分析,对经激光淬火处理后的9Cr2Mo冷轧辊用钢进行了研究.结果表明,与常规淬火相比,9Cr2Mo钢激光淬火后硬度明显提高,但激光淬火搭接区出现硬度值陡降,其原因为搭接区的马氏体组织回火分解;常规淬火处理后的9Cr2Mo钢内有条、块状碳化物,断口为脆性解理断裂特征;而激光淬火后,条块状碳化物溶解或部分溶解,未完全溶解的碳化物细化成球形颗粒,其断口为浅韧窝+脆性准解理的断裂特征.     

20Cr钢奥氏体渗氮中温回火的初步研究

将20Cr钢盔过640℃奥氏体渗氮后油淬,然后于220℃用不同时间回火。利用光学金相显微镜、显微硬度计、电子探针及X射线衍射分析：仪初步探索其中温回火转变过程。同时磨损试验证实’在适当的工艺参数条件下’该工艺对材料的耐磨性有显著提高。     

盘条焊接操作方法的改进

高碳钢丝拉拔过程容易产生断丝,通过试验总结出盘条焊接操作新方法。(1)端头准备:用砂轮机将切头处毛刺去除干净,并进行长度为2 mm的45°倒角处理;(2)对焊:在材质相同的条件下依据被焊接材料的尺寸、规格选择不同的电流,以保证合适的焊接温度;(3)焊缝隆起清除:在环境温度下自然冷却至80℃以下,焊缝处打磨后的直径应不小于盘条原始直径的95%。给出焊接回火的4步操作法。采用新的焊接方法,提高了盘条焊接质量,盘条的断面收缩率在10%～20%,抗拉强度达到母材抗拉强度的85%～95%,拉丝的断头次数由原来的每百吨2.50次下降到1.16次。     

利用萤光染色跟踪水份在润麦时进入小麦颗粒的路径

本文映示了小麦润麦过程中水分在小麦颗粒中扩散的路径．通过将杜伦麦、软麦在含有萤光试剂的溶液中浸泡12,24,48h之后，萤光切片图像显示出色剂．首先是通过麦胚进入麦粒，再由珠心层传送到麦粒的另一端，同时由糊粉层进入到胚乳．色剂沿背部一侧传送要比腹沟一侧快．皮部吸水速度快，而种皮有抵制水份进入胚乳的作用．从微观观测看出，细胞壁(膜)的三维网状结构形成了水份传送的渠道．色剂在细胞壁里的运动是毛细作用，而在胚乳细胞内的运动则是渗透作用．色剂在细胞壁里的运动要快于在胚乳细胞内的运动．色剂在杜伦麦(硬麦)及软麦里的运动模式是相同的，但是色剂进入软麦的速度要比进入杜伦麦快．     

Valence electron structure of cementite phase and its interface and the tempering phenomenon

Tempering is an important phenomenon in ferrous alloys. Most steels, especially alloying steels, are used after quenching and tempering. To design the composition of quenching and tempering steels, control the tempering process more effectively, improve the properties after tempering and realize the potentials of steels, the essence of tempering process and the properties of tempering products have to be understood. In this paper, the phase structure factors and interface conjunction factors of common alloying elements in cementite and its interface are calculated out. The relationships between these valence electron structure parameters and (i) the phenomena of martensite decomposition, (ii) transformation, gathering and growth of the carbides and (iii) the mechanical properties of tempering products are built up. The nature of the effect of alloying elements on tempering process and properties of tempering products is uncovered on the level of valence electron structure. One new theoretical foundation     

S-136高级镜面塑料模具钢实物质量剖析

通过对我厂试制的S-136镜面塑料模具钢性能和组织与日本生产的模具钢实物对比研究，说明我厂生产的模具钢化学成分，钢材纯洁度，试样淬回火显微组织与日本材料处于相当水平。但在实验室同样热处理条件下，我厂试样冲击韧性只需稍加改善便可。