一种新型高强度低温热成型钢
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">日前</span>热成形钢的发展趋势<span style="color: black;">重点</span>集中在<span style="color: black;">加强</span>延性上，<span style="color: black;">同期</span>，新钢种的设计<span style="color: black;">亦</span>克服了表面过度氧化，避免了冲压模具冷却系统的<span style="color: black;">繁杂</span>性。这种新型钢及相应的成形技术被<span style="color: black;">叫作</span>为低温热成形或热冲压技术，克服了传统热成形钢的缺点。本文<span style="color: black;">科研</span>了<span style="color: black;">区别</span>退火温度后的微观结构特性和力学<span style="color: black;">行径</span>。结果<span style="color: black;">显示</span>，其微观结构和力学特性与退火温度有很大的关系。这些结果<span style="color: black;">显示</span>，当罩退退火温度在570-630℃之间时，钢的抗拉强度超过1400MPa，总伸长率为9%。在690℃以上，拉伸强度和总伸长率<span style="color: black;">显著</span>下降。这些恶化的力学性能<span style="color: black;">能够</span>归因于先前的奥氏体粒尺寸和板条马氏体分数的<span style="color: black;">增多</span>。</p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">Keywords: </span><span style="color: black;">Low temperature hot forming; Medium-Mn; Microstructure; Mechanical characteristics</span></p>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">1.Introduction</h1>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;"><span style="color: black;">日前</span>，<span style="color: black;">因为</span>汽车车身轻量化和<span style="color: black;">加强</span>被动安全性的<span style="color: black;">需要</span>，<span style="color: black;">促进</span>汽车行业<span style="color: black;">连续</span><span style="color: black;">研发</span>新的材料和制造工艺。热冲压是一种结合了成型和淬火工艺，用以生产超高强度汽车结构件的创新且有效<span style="color: black;">办法</span>，如汽车A柱、B柱、车顶梁、保险杠等 。在热冲压生产过程中，将硼钢放到800-950℃的加热炉中保温3-10分钟，使其充分奥氏体化，<span style="color: black;">而后</span><span style="color: black;">快速</span>转移到模具中，成形和淬火<span style="color: black;">同期</span>进行，并<span style="color: black;">最后</span><span style="color: black;">得到</span><span style="color: black;">拥有</span>超高抗拉强度的全马氏体组织构件。22MnB5（抗拉强度在1300MPa以上）是近几十年来在热冲压生产中最常用的硼钢。近年来，一种抗拉强度超过1800 MPa的新型热冲压钢被<span style="color: black;">研发</span>出来，用以取代部分传统的热冲压钢。</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">热成形钢在模具中淬火冷却成形<span style="color: black;">得到</span>全马氏体结构是其重大特点。 然而较高的热处理温度<span style="color: black;">引起</span>氧化皮严重，<span style="color: black;">同期</span>需要较高的冷却能力，<span style="color: black;">引起</span>模具设计制<span style="color: black;">导致</span>本较高，影响传统热成形钢的应用，近年来低温热冲压成形技术<span style="color: black;">逐步</span><span style="color: black;">作为</span><span style="color: black;">科研</span>热点，中锰<span style="color: black;">成份</span>可降低奥氏体化温度，<span style="color: black;">同期</span>对冷却能力<span style="color: black;">需求</span>低，<span style="color: black;">最后</span>性能优异.</span></p>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">2.Material and test process</h1>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">本论文<span style="color: black;">科研</span>的钢<span style="color: black;">成份</span>为，wt%: C, 0.1-0.13; Si, 0.25; Mn, 4.50-5.50; Cr, 0.15-0.55; S, 0.0017; P, 0.006; B, 0.0010-0.0040; and Fe, balance. <span style="color: black;">最后</span>冷轧板厚度为1.5mm。利用相图计算软件计算的 Ae1 和 Ae3 分别为 451°C 和737°C。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-axegupay5k/f4b55cfc4ea74ad9ab4cf0b50117dd91~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1728801734&x-signature=OPUb4Yg7S7Y4MIb%2FgAz0fg7Hf1g%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">10°C/s热膨胀测定的 Ac1 和 Ac3 分别为 652 °C 和 781°C, <span style="color: black;">因此呢</span>低温热成形采用800℃-7min来完成完全奥氏体化。热成形前在570-720°C范围内退火。<span style="color: black;">每一个</span>退火参数都要垂直于滚动方向切割三个拉伸样品。室温下在仪器5985拉伸<span style="color: black;">实验</span>机上<span style="color: black;">测绘</span>了力学性能，十字头位移为2mm/min，标距长度为50mm，宽度为12.5mm。在平行于轧制方向的电解抛光后，采用电子背散射衍射(EBSD)对其截面进行了微观结构分析。EBSD观察是在JSM 7001FFE-SEM进行的。<span style="color: black;">首要</span>对EBSD样品进行机械抛光，<span style="color: black;">而后</span>在室温下在10%高氯酸和85%酒精的混合溶液中进行电子抛光，应用电位为25V。</span></p>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">3.Results and discussion</h1>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">3.1Mechanical properties before and after low temperature hot forming</h1>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-6w9my0ksvp/920e31c4eafa4257a42ac920b60ad215~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1728801734&x-signature=G55mJ0qURLVEfOjEQROsZ9xi1z0%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">图2描述了<span style="color: black;">区别</span>的罩退退火温度和随后的低温热形成的力学性能。这些结果<span style="color: black;">显示</span>，当退火温度在570-630C之间，退火时间为8h时，退火钢的抗拉强度约为800MPa。结果<span style="color: black;">显示</span>，在低温热成形状态下，当加热温度超过1100MPa时，其力学性能略有下降。当浴缸退火温度在570-630C之间时，低温热成形后的钢的抗拉强度超过1400MPa。然而，当退火温度超过690C时，低温热成形钢的抗拉强度和屈服强度降低到1300MPa<span style="color: black;">上下</span>。.</span></p>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">3.2Microstructure evolution</h1>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-6w9my0ksvp/a4f1c10189cd4a0491392baaf1c3e015~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1728801734&x-signature=8Dpp9uKNWjQfc%2BFMJ4AM2Flx1VA%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">图3<span style="color: black;">表示</span>了模拟罩退退火后钢的微观结构。630℃以下退火<span style="color: black;">要求</span>下的钢的微观结构由以下的铁氧体和碳化物<span style="color: black;">构成</span>。<span style="color: black;">另外</span>，<span style="color: black;">因为</span>优良的淬火耐火性，在模拟罩式退火炉冷却过程中<span style="color: black;">能够</span>形成马氏体。马氏体分数随退火温度的<span style="color: black;">上升</span>而<span style="color: black;">逐步</span><span style="color: black;">增多</span>。在720℃下退火后，形<span style="color: black;">成为了</span>一个几乎完全的马氏体结构。 退火参数对<span style="color: black;">实验</span>钢微观组织的影响如图4所示。钢在800℃下奥氏体化，在淬火前等温保持8 min。<span style="color: black;">能够</span>看出，经过完全奥氏体化后的微观结构由板条马氏体和<span style="color: black;">海量</span>马氏体<span style="color: black;">构成</span>。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-6w9my0ksvp/91d190f7e1cc41ac91ba7888dba36fba~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1728801734&x-signature=RIGQe7xuTbRxKPB%2FIzbPwpvzSWw%3D" style="width: 50%; margin-bottom: 20px;"></div>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">为了<span style="color: black;">仔细</span>分析<span style="color: black;">区别</span>退火<span style="color: black;">要求</span>下微观结构的变化，<span style="color: black;">咱们</span>进行了EBSD分析。<span style="color: black;">表示</span>了EBSD逆极图(IPF)和重建的晶界图。随着罩退退火温度的<span style="color: black;">上升</span>，板条马氏体的比例和奥氏体粒径增大。原奥氏体晶粒的平均粒度由5.9μm增加到9.6μm。在720℃退火的马氏体板条的长度和宽度均大于600℃。未溶解的碳化物和细铁素体结构<span style="color: black;">供给</span>了<span style="color: black;">海量</span>的成核点，<span style="color: black;">因此呢</span>奥氏体的粒径<span style="color: black;">少于</span>初始结构为粗马氏体的样品。<span style="color: black;">针对</span>马氏体钢，强度<span style="color: black;">是由于</span>原始奥氏体颗粒中三个子结构的尺寸决定的，<span style="color: black;">因此呢</span>，退火温度是与材料热冲压应用<span style="color: black;">相关</span>的关键<span style="color: black;">原因</span>。它<span style="color: black;">能够</span>总结在曲线中，较高的退火温度的样品似乎遇到了强度的下降。</span></p>
<div style="color: black; text-align: left; margin-bottom: 10px;"><img src="https://p3-sign.toutiaoimg.com/tos-cn-i-6w9my0ksvp/4f7a0851235040ab85b119fb4a053cae~noop.image?_iz=58558&from=article.pc_detail&lk3s=953192f4&x-expires=1728801734&x-signature=luILu74SXQzTNO8qPV8VJSIdQYc%3D" style="width: 50%; margin-bottom: 20px;"></div>
<h1 style="color: black; text-align: left; margin-bottom: 10px;">4.Conclusions</h1>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">从本文中得出的<span style="color: black;">重点</span>结论如下： 当罩退温度在570-630C之间时，低温热成形后的钢的抗拉强度超过1400MPa。然而，当罩式退火温度超过690C时，低温热成形钢的抗拉强度和屈服强度降低到1300MPa<span style="color: black;">上下</span>。 随着浴退火温度的<span style="color: black;">上升</span>，板条马氏体的比例和奥氏体粒径增大。先验奥氏体的平均粒度由5.9μm<span style="color: black;">增多</span>到9.6μm。较高的退火温度的样品似乎遇到了强度的下降。</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><strong style="color: blue;"><span style="color: black;">References</span></strong></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">1. Z. Q. Zhang, C. H. Liu, S. F. Meng, X. J Li and X. H. Zhao, Investigation of Heat Transfer in Hot Stamping of Boron Steel,</span><span style="color: black;"> Metall. Mater. Trans. B</span><span style="color: black;">.</span><strong style="color: blue;"><span style="color: black;"> 47, </span></strong><span style="color: black;">824(2016).</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">2. S.Q. Zhang, D. Feng, Y. H. Huang, S. Z. Wei, H. Mohrbacher and Y. Zhang, Constitutive Modeling of High-Temperature Flow Behavior of an Nb Micro-alloyed Hot Stamping Steel,</span><span style="color: black;">J. Mater. Eng. Perform.</span><strong style="color: blue;"><span style="color: black;">25, 948</span></strong><span style="color: black;">(2016).</span></p>
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<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">5. S. S. Li and H. W. Luo, Medium-Mn steels for hot forming application in the automotive industry, </span><span style="color: black;">International Journal of Minerals, Metallurgy and Materials,</span><strong style="color: blue;"><span style="color: black;">28, 741</span></strong><span style="color: black;">(2021)</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><span style="color: black;">6. C. Y. Wang, X. D. Li, S Han, L. Zhang, Y. Chang, W.Q. Cao, H. Dong, Warm Stamping Technology of the Medium Manganese,</span><span style="color: black;">Steel research international</span><span style="color: black;">, </span><strong style="color: blue;"><span style="color: black;">12, </span></strong><span style="color: black;">(2018).</span></p>
<p style="font-size: 16px; color: black; line-height: 40px; text-align: left; margin-bottom: 15px;"><strong style="color: blue;"><span style="color: black;">注：本文由首钢集团<span style="color: black;">科研</span>院供稿，热成形产业联盟整理发布，版权归原作者所有。<span style="color: black;">这里</span>声明禁止<span style="color: black;">媒介</span>、<span style="color: black;">公司</span>或个人在未经授权的<span style="color: black;">状况</span>下违法转载和<span style="color: black;">运用</span>。热成形产业联盟是服务于工业企业的垂直行业<span style="color: black;">媒介</span>，关注「热成形产业联盟」公众号<span style="color: black;">认识</span><span style="color: black;">更加多</span>专家<span style="color: black;">诠释</span>、技术热点、<span style="color: black;">新闻</span>及活动<span style="color: black;">关联</span>信息，投稿合作：13501964098 联盟秘书处。</span></strong></p>
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