加热气氛对一种C-Mn-Si-Al高强钢选择性氧化的影响

为了研究局部露点技术在含铝高强钢上应用的潜力,采用热浸镀工艺模拟器研究了加热过程的露点温度对一种C-Mn-Si-Al高强钢选择性氧化的影响。加热过程中的露点温度设置为-10、-20和-50℃,而在保温过程中的露点温度为-50℃。采用SEM/EDS表征了退火后试样表面的氧化形貌和元素质量分数,使用GDOES分析了退火试样表层的元素深度分布,采用XPS分析鉴定了试样表面的氧化物种类。试验结果表明,使用-10℃露点温度加热时,试样表面氧化轻微,铝元素出现明显内氧化现象。随着加热过程露点温度降低到-50℃,试样表面出现较多富含锰和铝的氧化物。因此,加热过程中较高的露点温度可以抑制合金元素向外表面的富集,减少试样表面的氧化物数量。     

加热工艺对含磷高强钢氧化行为的影响

 含磷高强钢具有良好的成形性能和较高的强度,被广泛用于汽车零件冲压成形。除了磷元素,含磷高强钢中通常还含有锰、硅等合金元素进行固溶强化,这些合金元素在退火过程中容易发生选择性氧化。采用镀锌模拟器研究了加热过程的露点温度对含磷高强钢在加热过程中的氧化行为。采用扫描电镜、辉光放电光谱仪以及光电子能谱仪分别分析了含磷高强钢的表面微观形貌、元素深度分布以及表面化合物种类。结果表明,加热过程的露点温度对合金元素在表面的氧化行为有显著影响,较高的加热过程露点温度可以显著抑制锰元素和硅元素在表面的选择性氧化行为,但是会加速磷元素在表面的偏析。进一步研究表明,磷元素在样品表面以磷酸盐形式存在。     

过时效工艺对C-Mn-Si高强钢表面选择性氧化的影响

 为了研究过时效过程露点调节技术在高强钢上的应用，采用热浸镀工艺模拟器研究了过时效工艺中气氛露点温度（－30、－10 ℃）和温度（250、350 ℃）对一种C-Mn-Si高强钢选择性氧化的影响，分别采用FE-SEM和EDS观察分析了试样表面形貌和化学成分，采用GDOES表征了试样表面的元素深度分布，采用XPS确定了氧化物种类。结果表明，高过时效温度（350 ℃）和高露点温度（－10 ℃），可显著抑制锰和硅在钢表面的选择性氧化，此时试样表面为无定型SiOx、无定型MnOx以及纯态锰。随着过时效温度和露点温度的降低，锰和硅在表面的富集明显增加，同时发现，露点温度对合金表面元素富集峰值的影响比过时效温度更显著。采用低过时效温度（250 ℃）和低露点温度（－30 ℃）时，试样表面出现大量富锰和硅的颗粒状氧化物，由晶态的Mn3O4和MnO2以及硅的非化学计量氧化物SiO1.49和SiO0.93组成。     

连退机组过时效段温度对DP钢组织及性能的影响

利用MULTIPAS多功能连续退火模拟机对590MPa级别DP钢在不同过时效温度情况下进行模拟退火实验,探索过时效温度对DP钢性能及组织的影响,确立了双相钢过时效段的温度控制范围。通过实验结果指导本钢的生产实践,保证了冷轧双相钢的稳定生产,使产品具有最佳的力学性能。     

退火工艺对Nb-V微合金化双相钢组织性能的影响

为了进一步提升双相钢性能、探究Nb-V元素复合添加对双相钢组织性能的影响,在实验室研发了Nb-V微合金化的冷轧双相钢。利用连退模拟试验机、扫描电镜等设备,系统地研究了退火温度和过时效温度对双相钢组织性能的影响。结果表明,抗拉强度和伸长率随着退火温度的升高变化不大,屈服强度在组织中铁素体含量明显减少后有显著提升;Nb、V元素的添加细化了组织,可以提高综合性能。随着过时效温度的升高,试验钢主要组织由起初低温时的淬火马氏体+回火马氏体变为高温时的粒状贝氏体,残余奥氏体比例也逐渐增大。高温过时效时,试验钢强度的降低主要由回火马氏体的软化造成;低温过时效时,V析出量的增加也对试验钢的强化起到了重要作用。     

退火工艺对Nb-V微合金化双相钢组织性能的影响

为了进一步提升双相钢性能、探究Nb-V元素复合添加对双相钢组织性能的影响,在实验室研发了Nb-V微合金化的冷轧双相钢。利用连退模拟试验机、扫描电镜等设备,系统地研究了退火温度和过时效温度对双相钢组织性能的影响。结果表明,抗拉强度和伸长率随着退火温度的升高变化不大,屈服强度在组织中铁素体含量明显减少后有显著提升;Nb、V元素的添加细化了组织,可以提高综合性能。随着过时效温度的升高,试验钢主要组织由起初低温时的淬火马氏体+回火马氏体变为高温时的粒状贝氏体,残余奥氏体比例也逐渐增大。高温过时效时,试验钢强度的降低主要由回火马氏体的软化造成;低温过时效时,V析出量的增加也对试验钢的强化起到了重要作用。     

过时效和平整对冷轧双相钢板强度、塑性及烘烤硬化性的影响

以低碳Si-Mn系冷轧双相钢为研究对象，探讨了过时效和平整工艺对双相钢板力学性能的影响。发现：过时效温度高于350℃左右时屈服强度和屈强比大幅度提高并出现屈服平台；平整对双相钢力学性能的影响也与过时效温度有关。平整和过时效均对双相钢的BH值有较大影响。过时效温度过高或者双相钢的BH值很低，不施加任何平整和预拉伸的情况下，双相钢的BH值很小。300℃以下温度过时效后进行平整和预拉伸有利于获得较高的BH值。     

连续退火工艺对冷轧马氏体钢板力学性能的影响

 冷轧马氏体钢采用水淬退火机组生产,可以节约合金元素,同时获得高强度,符合汽车用钢高强度和减重节能的要求。以冷轧低碳马氏体钢为研究对象,研究了连续退火工艺对马氏体钢板力学性能的影响,发现淬火温度、缓冷速度和回火温度均对马氏体钢的强度有很大影响。在奥氏体缓慢分解的较高温度区间开始淬火有利于马氏体钢强度的稳定。回火降低马氏体钢的抗拉强度,对屈服强度有提高的作用,在200~300℃之间回火,冷弯性能基本不变或有所提高,未发现在240℃以上过时效出现显著的冷弯性能下降的现象。     

超高强度冷轧双相钢组织与性能

在Gleeble-3500热模拟试验机上进行冷轧超高强度双相钢的连续退火工艺研究,利用光学显微镜、扫描电镜、透射电镜和拉伸试验研究了连续退火过程中各个参数对1000MPa级冷轧双相钢组织性能的影响.结果表明:试验用钢在退火温度800℃下保温80s,可以得到抗拉强度为1030MPa、延伸率为14%超高强双相钢;随着退火温度的升高,屈服强度和抗拉强度降低.当退火温度为830℃时,显微组织中粒状的非马氏体组织明显增多.过时效温度低于300℃时,屈服强度和抗拉强度变化不大;当过时效温度超过300℃时,抗拉强度急剧下降,屈服强度先降低后升高,在过时效温度为360℃时开始出现屈服平台.     

镀锌DP780漏镀缺陷的成因分析与预防措施

为了解决热镀锌线生产高强度双相钢产品出现的表面漏镀问题,通过对缺陷的宏观与微观形貌以及成分进行分析,同时对漏镀的形成机理进行分析,确定影响表面漏镀的主要原因是双相钢中含有硅、锰等元素较多,容易发生选择性氧化,氧化物阻碍铁元素和锌液的铝热反应,形成漏镀。根据分析结果,采取提高炉区加热段露点和降低氢气含量的方法对漏镀进行预防。结果表明,同时提高炉区加热段露点和降低氢气含量能有效解决表面漏镀问题,取得了较好的实用效果,为进一步开发拓展更高级别镀锌双相钢提供了技术基础和理论依据。     

Galvanizability of Complex Phase High Strength Steel

Complex phase (CP) steels have very high ultimate tensile strengths, resulting from the use of specific alloying elements, which improve the hardenability but cause difficulties when applying a zinc coating by means of continuous hot‐dip galvanizing. The galvanizability of a cold rolled 1000MPa complex phase steel was investigated by monitoring the surface chemistry before dipping and evaluating the quality of the zinc coatings applied by a laboratory hot‐dipping simulator. Two steel compositions with different Cr levels were used. The influence of the most important production parameters, the annealing temperature and the dew point of the annealing atmosphere, was investigated. Both steel compositions were galvanizable, but both the surface appearance and zinc coating adhesion were improved when low Cr contents were used. At a low dew point of ‐30°C, Cr, Mn and Si segregated to the surface and the presence of Mn₂SiO₄ could be demonstrated. At high dew point of +10°C, less oxides were present at the steel surface. There was no effect of the annealing temperature on the coatability.     

热镀锌线上炉内带钢表面选择性氧化的影响因素分析

对热镀锌线上带钢表面合金元素选择性氧化的几个主要影响因素进行分析,阐述了合金元素的选择性氧化不仅与露点有关,还与热处理的退火气氛和合金元素的组成成分有关,另外热处理过程的退火时间和保温时间也会影响合金元素的选择性氧化,从而影响镀锌的粘附性,进而影响带钢的镀锌性能.     

低合金耐硫酸露点腐蚀钢的性能和应用

耐硫酸露点腐蚀钢是用于热交换部件的低合金钢。该钢主要分为两类:(1)以0.2%~0.5%Cu-＞0.010%S为基础,添加少量P、Sn、As、Sb、Se、Te等元素;(2)以Cu-Cr或Cu-Cr-Ni为基础的钢类,用于高温(130~160℃)、高浓度硫酸(80%~90%)的腐蚀环境。介绍了硫酸露点腐蚀环境的特点并讨论了合金元素对该低合金钢耐硫酸露点腐蚀的作用机制和国内外现有主要低合金耐硫酸露点钢的化学成分、力学性能和耐蚀性能。     

Effect of the presence of alloying elements in interstitial-free and low-carbon steels on their surface composition after annealing in reducing atmospheres (dew point=−30 °C)

The X-ray photoelectron spectroscopy (XPS) method is used to study the outer surfaces of interstitial-free (IF) and low-carbon (LC) steels with different alloying element contents (P, Ti, Nb, and Mn) after annealing at temperatures of 805 °C and 705 °C, respectively, for 40 seconds in reducing atmospheres (dew point=−30 °C). The work discussed seeks to establish possible relationships between the bulk composition of the IF and LC steels and the contents of segregated alloying element observed by XPS on the surface of the annealed steels, as well as to establish the influence of the presence of a thin iron oxide film on the steel surface on the segregation and oxidation of the alloying elements. Despite the low Mn and Si bulk steel contents and the shortness of the annealing cycle, considerable enrichment of these elements on the surface is seen, mainly as manganese and silicon oxides. The formation of a MnO layer on the annealed steel surface seems to be related to the reduction of iron oxides and the increase in the metallic Fe content. Despite its low content in LC steels, carbon also seems to diffuse towards the annealed steel surface to reduce iron oxides.     

Galvanizing and Galvannealing Behavior of CMnSiCr Dual-Phase Steels

Alloying elements, such as Mn, Mo, Si, and Cr, are commonly used to enhance the strength of advanced high-strength steels. Those elements also play an important role in the hot-dip galvanizing (GI) and galvannealing (GA) process. In this study, two kinds of CMnSiCr dual-phase steels were galvanized and galvannealed using a hot-dip simulator to investigate the effect of the alloying elements on the microstructure of the GI and GA coatings. The results showed that the dual-phase steels had good galvanizability because no bare spots were observed and the Fe-Zn phases were readily formed at the interface. However, the alloying reaction during the GA process was significantly hindered. XPS analysis showed that external oxidation occurred under an extremely low dew point [213 K to 203 K (?60 °C to ?70 °C)] atmosphere during the annealing prior to hot dipping. However, most of the oxides were reduced during the GI process. After the GI process, the Al was present as solid solutes in the Fe-Zn phase, suggesting that the Fe-Zn phase was formed from the transformation of the Fe-Al inhibition alloy. Meanwhile, the solubility of Si in the ζ phase was extremely low. With continued GA reaction, the ζ phase transformed into the δ phase, which contained approximately 1.0 at.pct Si. The Si also diffused into the Zn layer during the GA reaction. Hence, the ζ phase did not homogeneously nucleate at the steel substrate/Zn coating interface, but was found at the area away from the interface. Therefore, the Fe-Zn phases on the CMnSiCr dual-phase steels were relatively non-uniform compared to those on interstitial-free steel.     

先进高强钢选择性氧化及抗粉化性能

介绍了生产先进高强钢热浸镀锌板的重要性,论述了生产过程中出现选择性氧化的原因及合金化板产生粉化的原因.具体分析了保护气氛的露点、保护气氛的组成、退火温度及时间、合金元素的种类和含量对高强钢选择氧化的影响.并分析了合金化工艺及锌液成分对合金化镀层相结构及抗粉化性能的影响.