On strengthening mechanisms in commercial Nb-Ti hot strip steels
On strengthening mechanisms in commercial Nb-Ti hot strip steels
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DOI：
10.1007/s11661-001-0133-7
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发表时间：
2001-05
期刊：
影响因子：
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通讯作者：
S. S. Campos-S.;H. Kestenbach;Eduardo Morales
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文献类型：
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作者：
S. S. Campos-S.;H. Kestenbach;Eduardo Morales
SS CAMPOS、EV MORALES 和 H.-J。 KESTENBACH 其中，pct Mn、pct Si 和 pct Nf 是铁素体中溶解的锰、硅和游离氮的重量百分比，细碳氮化物颗粒的沉淀硬化具有，d 是铁素体晶粒尺寸（以毫米为单位）。由于长期以来被认为是微合金添加的重要机制，Nf 被认为可以忽略不计。微合金钢的屈服强化。[1]过去，一些强度预测来自方程[1]与拉伸相比重要的评论文章都强调了表三中显着的测试结果。计算的强化效果只能从非常精细的强度中预期，而测量的强度之间的差异通常归因于一些二碳氮化物颗粒，这些颗粒在铁素体相中显着析出半共聚强化机制，例如碳氮化物。[2, 3]这种析出应该是同步[8]或亚结构强化。[9]重要的一点在热轧带材产品中特别有效，表III中的177的非常大的附加强化结合了更短的轧制时间、更高的精轧MPa（就Nb-Ti钢而言），其温度降低，并且在正火后轧制69MPa后加速冷却速率。如前所述，也不应导致大量微合金元素发生麦化，不会降低铌钢的屈服强度，在卷取之前保留在溶液中。 [4]然而，作者在该钢的成核碳氮化物颗粒中没有发现铁素体和额外的强化贡献，其保持在 60 MPa 左右，该水平非常接近 69 实验室最近对 Nb-Ti 钢在正火后表现出的商业 Nb-Ti MPa 的研究中的水平。使用在工业透射电子显微镜 (TEM) 下加工的微合金钢在热带钢轧机上进行试验条件。 [5]长期以来，人们一直争论要研究轧制热机制中强度损失的额外强化的可能来源。为了检查碳氮化物沉淀，带材在正火过程中容易受到损害，可以认为每种钢中总共检查了 20 个铁素体晶粒。强烈表明存在这种细小的碳氮化物。在所有颗粒中都发现了细小的碳氮化物沉淀，这些颗粒在奥氏体化过程中会失去其凝聚力（图 2），但方向关系是根据与周围铁素体晶格的 ence 确定的。 [6]值得注意的是，没有电子衍射[5, 8]表明这些颗粒在奥氏体中商业热剥离中观察到强度核损失。此外，碳氮化物分布与正火后的钢一样。[5]另一方面，图 2 中所示的屈服强度似乎与在之前的钢中观察到的含 0.02% Nb 和 0.06% Ti 的钢磨损非常相似。 [5]在这种情况下，已经相当低（332 MPa），这表明也许定量金相学和热机械加工条件的应用对沉淀强化的Orowan-Ashby模型不是非常有效。表明强化贡献约为 60 至 80 MPa，现在从优质 Nb-Ti 微合金化热轧带钢中奥氏体中形成的碳氮化物颗粒的另一个商用 MPa 获得了新结果，其与表中所示强度 534 MPa 的附加强化达到屈服协议，并且根据预期，Nb 钢以及 Nb-Ti 钢在正火期间失去部分强度后失去了 III。一种铌钢，正火处理。仅达到 310 MPa 并保持......
SS CAMPOS, EV MORALES, and H.-J. KESTENBACH where pct Mn, pct Si, and pct Nf are the weight percentages of manganese, silicon, and free nitrogen dissolved in ferrite, Precipitation hardening by fine carbonitride particles has and d is the ferrite grain size in millimeters. Due to the long been recognized as an important mechanism for the microalloy addition, Nf was assumed to be negligible. Yield strengthening of microalloyed steels.[1] In the past, several strength predictions from Eq.[1] are compared to tensile important review articles have emphasized that a significant test results in Table III. The difference between calculated strengthening effect could only be expected from very fine and measured strength is usually attributed to some addicarbonitride particles, which had precipitated semicoher- tional strengthening mechanism such as carbonitride precipiently in the ferrite phase.[2, 3] Such precipitation should be tation [8] or substructure strengthening.[9] The important point particularly effective in the case of hot strip products, where in Table III is the very large additional strengthening of 177 a combination of shorter rolling times, higher finish rolling MPa in the case of the Nb-Ti steel, which was reduced to temperatures, and accelerated cooling rates after rolling 69 MPa after normalizing. As mentioned previously, norshould cause a larger amount of microalloy elements to malizing did not reduce the yield strength of the Nb steel, remain in solution prior to coiling.[4] However, no ferrite- and the additional strengthening contribution in this steel nucleated carbonitride particles were found in the authors’ remained at around 60 MPa, a level very close to the 69 laboratory during a recent study of a commercial Nb-Ti MPa exhibited by the Nb-Ti steel after normalizing. microalloyed steel, which had been processed under indus- Transmission electron microscopy (TEM) was used to trial conditions on a hot strip mill.[5] It has been argued for investigate the possible sources of additional strengthening a long time that the loss of strength, which the as-rolled hot mechanisms. In order to check for carbonitride precipitation, strip tends to suffer during normalizing, can be taken as a a total of 20 ferrite grains were examined in each steel. strong indication for the presence of such fine carbonitride Fine carbonitride precipitation was identified in all of them particles, which, during austenitizing, would lose their coher-(Figure 2), but orientation relationships determined from ence with the surrounding ferrite lattice.[6] Significantly, no electron diffraction [5, 8] showed that these particles had nucleloss of strength was observed for the commercial hot strip ated in austenite. In addition, carbonitride distributions as steel after normalizing.[5] On the other hand, the yield shown in Figure 2 appeared to be very similar to the disstrength of this 0.02 pct Nb and 0.06 pct Ti containing steel tributions observed in the previous steel.[5] In that case, had been rather low (332 MPa), suggesting that perhaps quantitative metallography and the application of the the thermomechanical processing conditions had not been Orowan–Ashby model of precipitation strengthening had very effective. indicated a strengthening contribution of about 60 to 80 New results were now obtained from another commercial MPa for carbonitride particles formed in austenite, in good Nb-Ti microalloyed hot strip steel, which reached a yield agreement with the additional strengthening shown in Table strength of 534 MPa and, according to expectations, lost III for the Nb steel and also for the Nb-Ti steel after part of that strength during normalizing. A Nb steel, which normalizing. only reached 310 MPa and maintained …