首页> 外文OA文献 >The austenitisation and decarburisation of high silicon spring steels
【2h】

The austenitisation and decarburisation of high silicon spring steels

机译:高硅弹簧钢的奥氏体化和脱碳

代理获取
本网站仅为用户提供外文OA文献查询和代理获取服务,本网站没有原文。下单后我们将采用程序或人工为您竭诚获取高质量的原文,但由于OA文献来源多样且变更频繁,仍可能出现获取不到、文献不完整或与标题不符等情况,如果获取不到我们将提供退款服务。请知悉。

摘要

The 1970’s saw the demand for more fuel efficient vehicles. This necessitated lighter automobiles, and was partly attained by lowering the weight of the coil springs used for the suspensions of these vehicles. Substantial weight reductions were achieved with new steels such as SUP7, with their elevated carbon and silicon contents allowing the springs to operate at higher stresses. However, these steels are prone to decarburisation during spring manufacture, which sharply reduces the sag resistance and the fatigue strength of the springs. The literature pertaining to the decarburisation of high silicon spring steels is limited, despite the subsequent reduced sag and fatigue properties. The research detailed in this thesis was therefore undertaken to investigate the decarburisation of spring steels with 0 to 3wt.% silicon for a range of temperatures and heat treatment atmospheres. The austenitisation of these steels was also investigated to provide complementary information. Austenitisation and decarburisation heat treatments were undertaken with 0, 1 and 3wt.% silicon experimental steels, and the commercially available 2wt.% silicon SUP7 and SUP7NV steels. These five steels have similar carbon, manganese and chromium contents. Two dimensional austenite growth occurred for the different steels, with the austenite grain shape inherited from the initial ferrite grain structure. The austenitisation accelerated with increasing temperature, with the higher silicon steels exhibiting faster transformation kinetics at comparable intercritical fractional superheat temperatures due to the higher Ac₁ and Ac₃ temperatures. The austenite growth was controlled by the substitutional diffusion of the alloy elements at low intercritical temperatures, and by carbon diffusion through the austenite at higher temperatures. This resulted in the faster transformation of ferrite/spheroidal cementite initial microstructures than pearlitic microstructures at low intercritical temperatures, and the opposite at higher temperatures. Austenite nucleated earlier in ferrite/spheroidal cementite initial microstructures when the cementite particles were located predominantly on the ferrite grain boundaries of the initial structures rather than within the ferrite grains. The austenite growth eventually became faster for the latter structure. An increasing silicon content up to 2wt.% increased the rate of carbon removal at comparable temperatures. Multiple linear regression analysis demonstrated that the mass of carbon removed during decarburisation increased with silicon contents up to 2wt.%, with temperature, and with PH₂O/PH₂ ratios of 0.01 to 0.25, while manganese decreased the decarburisation. However, slower decarburisation resulted for the 3% Silicon steel, especially at higher temperatures and lower PH₂O/PH₂ ratios, where a dense oxide layer strongly inhibited carbon removal. The decarburisation of the 1% Silicon, SUP7 and SUP7NV steels was fastest at their respective Ac₃ temperatures. Columnar free ferrite grain structures were obtained for the 0% Silicon and SUP7 steels, compared with equiaxed grains for the 1% Silicon, SUP7NV and 3% Silicon steels. The decarburisation of SUP7 was fastest when the specimen was heated in the furnace with the heat treatment atmosphere already established, while slower decarburisation resulted when the specimens were annealed in inert atmospheres prior to the introduction of the decarburisation atmosphere. Different initial SUP7 microstructures influenced the carbon release kinetics as the specimens heated to temperature. Prolonged decarburisation of SUP7 and SUP7NV at 900°C yielded decreasing free ferrite depths after 4hr, despite continued carbon removal from the steel. This research contributes to the understanding of the austenitisation and decarburisation of spring steels. The information obtained is directly applicable to automobile coil spring production, but is also pertinent to the austenitisation and decarburisation of steel.
机译:1970年代看到了对更省油车辆的需求。这需要较轻的汽车,并且部分地通过减轻用于这些车辆的悬架的螺旋弹簧的重量来实现。新型钢(例如SUP7)的重量大大减轻,其碳和硅含量的提高使弹簧可以在更高的应力下工作。但是,这些钢在弹簧制造过程中易于脱碳,这大大降低了弹簧的抗流挂性和疲劳强度。尽管随后降低了垂度和疲劳性能,但有关高硅弹簧钢脱碳的文献有限。因此,本文进行了详细的研究,以研究在一定温度和热处理气氛下含0至3wt。%硅的弹簧钢的脱碳作用。还对这些钢的奥氏体化进行了研究,以提供补充信息。奥氏体化和脱碳热处理是用0、1和3wt。%的硅实验钢以及市售的2wt。%的SUP7和SUP7NV钢进行的。这五种钢具有相似的碳,锰和铬含量。不同钢发生二维奥氏体生长,奥氏体晶粒形状继承自最初的铁素体晶粒结构。随着温度的升高,奥氏体化加速,由于较高的Ac₁和Ac₃温度,较高的硅钢在相当的临界分数过热温度下表现出更快的转变动力学。奥氏体的生长是通过在低临界温度下合金元素的取代扩散和在较高温度下通过奥氏体的碳扩散来控制的。这导致在较低的临界温度下,铁素体/球状渗碳体的初始微观结构比珠光体的显微组织转变更快,而在较高的临界温度下则相反。当渗碳体颗粒主要位于初始结构的铁素体晶界上而不是在铁素体晶粒内时,奥氏体在铁素体/球状渗碳体的初始显微组织中形核早。对于后一种结构,奥氏体的生长最终变得更快。在可比较的温度下,将硅含量提高到2wt。%可以提高除碳率。多元线性回归分析表明,脱碳过程中除去的碳质量随温度上升以及硅的含量高达2wt。%,PH 2 O / PH 2比为0.01至0.25而增加,而锰降低了脱碳。但是,对于3%的硅钢,脱碳速度较慢,尤其是在较高的温度和较低的PH 2 O / PH 2比值下,致密的氧化层强烈抑制了碳的去除。 1%的硅,SUP7和SUP7NV钢在各自的Ac₃温度下脱碳最快。与1%硅,SUP7NV和3%硅钢的等轴晶相比,0%硅和SUP7钢获得了柱状自由铁素体晶粒结构。在已经建立了热处理气氛的情况下在炉中加热样品时,SUP7的脱碳速度最快,而在引入脱碳气氛之前将样品在惰性气氛中退火时,SUP7的脱碳速度较慢。当样品加热到一定温度时,不同的初始SUP7微观结构会影响碳释放动力学。尽管继续从钢中去除碳,但在900°C下SUP7和SUP7NV长时间脱碳仍会导致自由铁素体深度减小。这项研究有助于理解弹簧钢的奥氏体化和脱碳。获得的信息直接适用于汽车螺旋弹簧的生产,但也与钢的奥氏体化和脱碳有关。

著录项

  • 作者

    Mardon Chris;

  • 作者单位
  • 年度 1998
  • 总页数
  • 原文格式 PDF
  • 正文语种 en
  • 中图分类

相似文献

  • 外文文献
  • 中文文献
  • 专利

客服邮箱:kefu@zhangqiaokeyan.com

京公网安备:11010802029741号 ICP备案号:京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有
  • 客服微信

  • 服务号