连铸大圆坯包晶反应区域影响因素分析

通过理论计算和生产实践分析了合金元素和冷却速度对包晶反应的影响,结果表明:Si、Mn、S使包晶点左移,P、Al使包晶点右移,在圆管坯成分范围内,P、Si、Al影响较小,Mn、S影响较大;连铸冷却使包晶反应点向左移动,圆管坯冷却条件下,冷速使包晶点移动0.03%。实际生产中,C含量应避免0.08%～0.11%区间,避开包晶反应强烈区,同时选择恰当的结晶器保护渣,能够减少裂纹缺陷的发生。     

经济型热轧TRIP钢的成分对组织和性能的影响

研究了不添加任何贵重合金元素的经济型热轧TRIP钢.在实验室用真空感应炉冶炼了不同碳、硅、锰含量的试验钢,经控制轧制和随后二阶段控制冷却获得3 mm厚的热轧TRIP钢薄板,分析研究了经济型热轧TRIP钢中碳、硅、锰等元素对组织和性能的影响.试验结果表明:在不添加任何贵重合金元素的情况下,通过合适的轧制与冷却工艺可使碳的质量分数为0.09%时获得TRIP效应;增加碳、锰含量可以提高钢的抗拉强度;锰含量对性能的影响规律与碳含量有关;硅可以在不影响伸长率的情况下提高钢的强度.仅通过控制钢中的碳、硅、锰含量,在相应的轧制和冷却条件下可获得600 MPa级和800 MPa级热轧TRIP钢,其强塑积分别达到21833 MPa·%和24650 MPa·%.     

Fe-C合金包晶相变收缩的研究方法概述

在实际生产中,ω(C)=0.10%左右的钢种因包晶相变收缩剧烈,导致铸坯出现裂纹较其它碳含量的钢种严重.分析了铸坯裂纹与包晶相变收缩之间的关系,介绍了几种研究Fe-C合金包晶相变收缩的方法以及相应的研究进展.     

碳和锰的变化对包晶钢凝固模式和表面裂纹敏感性的影响

本文研究了在3种钢凝固过程中,化学成分、碳和锰含量以及冷却速率对凝固模式和相演变的影响,其中两个是亚包晶组成,另外一个是过包晶组成。并且推断了与裂纹敏感性有关的δ相和γ相力学性能差别以及凝固过程中的收缩。 碳或锰的轻微变化,当其变化数量级达到0．04％时,即可促进凝固过程中相演变的明显变化。试验观察到亚包晶钢接近包晶点,当冷却速率较高时可观察到锰的微观偏析,而且在凝固末端时,较高的冷却速率可促进过包晶凝固模式的发生。另一方面,凝固模式和所研究钢种的化学成分与裂纹敏感性无关,δ相和γ相力学性能差是导致两个固相分数区裂纹敏感性的原因。 而且与发生过包晶钢凝固模式的钢相比,对于亚包晶凝固模式的钢来说,包晶转变发生在固相分数较高区。因此,残留的液相能够补充包晶转变发生时固一液坯壳的收缩。所以在亚包晶钢中不仅可观察到由δ相和γ相力学性能差产生的裂纹敏感性,而且还可观察到液体不能补充与包晶转变有关的收缩。     

SWRH82B冶炼过程中钢水碳含量对硅锰收得率影响分析

在生产SWRH82B过程中，电炉出钢后依次加入碳粉和硅锰合金，通过对实际生产过程中不同碳含量炉次中硅锰合金收得率进行分析，得出LF进站钢水中碳含量对后续硅锰合金收得率具有较大影响。钢液碳含量0.2%～0.7%不同炉次下，合金中Mn收得率从78%～87%波动，合金中硅收得率从65%～85%波动。结合冶金热力学基础理论，在不同碳含量条件下对合金在渣铁间的平衡进行分析，钢液碳含量升高可明显降低合金在渣铁间的分配比，这表明在电炉出钢过程中需要提高并精准控制碳粉的加入量，稳定钢包中钢液碳含量，可降低硅锰合金的消耗。     

硅锰合金炉外降碳可能性的探讨

前言中低碳锰铁是炼钢中重要的脱氧剂和合金添加剂,而硅锰合金是冶炼中低碳锰铁用的还原剂,为满足中低碳锰铁对碳含量的要求,一般要求硅锰合金中含碳量小于1.3%。但是在硅锰合金冶炼中,由于碳和硅存在一定关系,即硅高碳低,硅低碳高,因而要使碳低就得冶炼含硅较高的硅锰合金,     

硅锰合金增氮制备氮化硅锰

在实验室条件下,设计9种温度制度制备氮化硅锰合金,并利用差热分析仪研究升温速率、保温温度、保温时间和降温速率对硅锰合金增氮效果的影响。结果表明,硅锰合金样品的增氮量(质量分数)为5.45%~37.92%,其均值为19.33%;影响硅锰合金增氮的主要因素是升温速率、保温温度和保温时间。硅锰合金增氮的最佳升温速率、最佳温度区间和保温时间分别为5℃/min、1 100~1 400℃、4h。在最佳温度区间1 100~1 400℃、保温4h的条件下,硅锰合金的增氮量最大,此时,硅锰合金的氮的质量分数为32.8%。使用XRD分析仪分析可得,其主要物相是Si_3N_4、MnSiN_2和Fe_2Si。硅锰合金增氮过程是固态和液态硅锰合金与氮气反应的过程,其中液态硅锰合金与氮气发生反应时增氮速度较快。     

硅锰母合金对烧结钢性能和组织的影响

通过添加硅锰母合金,将硅、锰这两种对氧亲和力较高的元素加入到烧结钢中,以改善烧结钢的力学性能。结果表明,当硅含量为1.1%~1.7%,锰含量为2.7%,碳含量为0.35%时,烧结钢的强度可以超过800MPa。但添加硅锰母合金对冲击韧性有不利影响。两种不同成分的母合金相比较,硅、锰含量高的母合金对烧结钢的力学性能影响较显著。     

冶炼特殊需求的中碳锰铁合金工艺研究

根据冶金学原理,探讨了中碳锰铁中锰含量的控制方法。中碳锰铁主要元素为锰、铁、硅、磷、碳、硫等,其中硅、磷、硫三种元素占的比例不超过5%,而锰和铁含量占95%以上的比例。如果合理控制合金中铁的含量,就能有效控制合金中的锰含量,从而生产出不同锰含量的中碳锰铁合金。文章研究了如何控制和优化合金中锰、铁含量比例,从而生产出符合炼钢企业需要的产品。     

高硅锰硅合金还原脱磷的工业试验

介绍了对高硅锰硅合金进行炉外还原脱磷的原理及方法。结果表明,使用CaSiCaF2CaO作脱磷剂,采用倒包法和喷吹法高硅锰硅合金的平均脱磷率分别为3154%和4132%。脱磷同时,也降低了合金中碳含量。     

直流焦耳处理对Co718Fe49Nb08Si75B15玻璃包覆非晶丝非对称巨磁阻抗效应的影响

 研究了Co718Fe49Nb08Si75B15玻璃包覆非晶丝经直流焦耳处理后的非对称巨磁阻抗效应。结果表明，随着处理电流的增加，阻抗最大变化率随之增大，并在处理电流为70 mA时达到最大值。在15 MHz的驱动电流下，阻抗最大变化率为335%，线性区域的灵敏度达1%/(A·m-1)。进一步提高处理电流，导致阻抗最大变化率减小。对钴基玻璃包覆非晶丝的AGMI性能特征用表面阻抗张量进行了讨论。     

Reason for the Beneficial Effect of Sulfur Additions on the Hypoperitectic Reaction in a 0.1?Pct Carbon and the Sulfur Content Needed to Establish the Effect

It has been shown that the addition of 0.3?pct sulfur to the 0.1?pct carbon, 0.9?pct manganese, and 0.3?pct silicon peritectic steel does not exhibit a rippled shell because of the accommodation of the buckling strains by the presence of a significant amount of low-melting point liquid when solid austenite and ferrite are formed. A similar solidification path will exist for sulfur contents down to approximately 0.1?pct for this alloy. A significant amount of low melting liquid will be present down to that sulfur concentration. The exact point for the disappearance of the peritectic effect still must be determined experimentally, but it certainly is in the range of 0.1 to 0.15?pct sulfur. For other peritectic alloys, the approximate sulfur content at which the effect of the peritectic reaction will disappear can be determined similarly to the method used in this study.     

The influence of the ferrite to austenite transformation on the formation of sulfidesx

Steel solidifies either by a primary precipitation of δ-Fe or by a primary precipitation of γ-Fe. In the former case the steel can either go through a peritectic reaction or a solid state transformation to form y-Fe during cooling. The influence of the rate of solidification and/or the transformation sequence on the sulfide precipitation in steels was studied in unidirectionally solidified Fe-Ni-S and Fe-Ni-Mn-S alloys. Nickel was used to govern the solidification sequence. It was shown that the solid state transformation could give rise to iron sulfide films according to a metatectic reaction. It was also shown that the peritectic reaction favored the formation of iron sulfide films. These films solidified at a very low temperature. During cooling the films contracted and small sulfide particles were formed. If the alloy contained manganese the composition of the films was changed during cooling from nearly pure iron sulfide to nearly pure manganese sulfide due to diffusion of manganese from the matrix.     

Kinetics of peritectic reaction and transformation in Fe-C alloys

In situ dynamic observation of the progress of a peritectic reaction and transformation of Fe-(0.14 pct C)- and Fe-(0.42 pct C)-peritectic Fe-C alloys has been successfully made with a combination of a confocal scanning laser microscope and an infrared image furnace. The peritectic reaction is characterized by the formation of the γ-austenite phase at the junction of the liquid and the grain boundary of δ-ferrite crystals and subsequent propagation of the three-phase point, liquid/γ/δ, along the liquid/δ boundary, whereas the peritectic transformation occurs by the thickening of the intervening γ toward both the liquid side and the δ side. The rates of the peritectic reaction for the two peritectic alloys are found to be much faster than the rate that would be controlled by carbon diffusion, suggesting that either massive transformation to γ or solidification as γ controls the rate. This is also the case for the Fe-0.14%C transformation in the hypoperitectic alloy. However, the rate of the peritectic transformation in the Fe-0.42%C alloy is determined by carbon diffusion. This article is based on a presentation made in the “Geoffrey Belton Memorial Symposium,” held in January 2000, in Sydney, Australia, under the joint sponsorship of ISS and TMS.     

The Influence of Peritectic Reaction/Transformation on Crack Susceptibility in the Continuous Casting of Steels

The work presented here examines the surface cracks that can form during the continuous casting of near peritectic steels due to the volume changes during the peritectic reaction/transformation. The investigated samples were collected during plant trials from two different steel grades. The role and mode of the peritectic reaction/transformation are found to depend on the composition of the alloy, resulting in different types of surface cracks. The effect of the local variation in the cooling rate on the formation of the different types of cracks present in each steel grade, which can be due, for example, to the formation of oscillation marks, is demonstrated. The enhanced severity of the surface and internal oxidation, both of which depend on the alloy composition and consequent peritectic reaction, is highlighted. Experimental and theoretical studies show that different types of surface cracks can occur in peritectic steels depending upon the alloy composition and cooling rate, both of which define the fraction of the remaining liquid upon completion of the peritectic reaction/transformation.     

Kinetics of the peritectic phase transformation: In-situ measurements and phase field modeling

An experimental study has been conducted into the role of cooling rate on the kinetics of the peritectic phase transformation in a Fe-C alloy. The interfacial growth velocities of the peritectic phase transformation were measured in situ for cooling rates of 100, 50, and 10 K/min. In-situ observations were obtained using high-temperature laser scanning confocal microscopy (HTLSCM) in a concentric solidification configuration. The experimentally measured interface velocities of the liquid/austenite (L/γ) and austenite/delta-ferrite (γ/δ) interphase boundaries were observed to increase with higher cooling rates. A unique finding of this study was that as the cooling rate increased, there was a transition point where the L/γ interface propagated at a higher velocity than the γ/δ interface, contrary to the findings of previous researchers. Phase field modeling was conducted using a commercial multicomponent, multiphase package. Good correlation was obtained between model predictions and experimental observations in absolute values of interface velocities and the effect of cooling rate. Analysis of the simulated microsegregation in front of the L/γ and γ/δ interfaces as a function of cooling rate revealed the importance of solute pileup. This microsegregation plays a pivotal role in the propagation of interfaces; thus, earlier modeling work in which complete diffusion in the liquid phase was assumed cannot fully describe the rate of propagation of the L/γ and δ/γ interfaces during the course of the peritectic transformation.     

薄带厚度对Fe-C合金气-固脱碳反应的影响

为了研究薄带厚度对Fe-C合金薄带气-固脱碳反应的影响,实验采用初始碳质量分数为4.20%,厚度分别为0.6、1.0、1.5和2.0mm的Fe-C合金薄带作为原料,在Ar-H2-H2O弱氧化气氛条件下进行气-固脱碳反应。结果表明,不同厚度薄带的脱碳速率均随着脱碳时间的延长而降低,薄带越薄脱碳速率越快,碳在薄带内部向反应界面的扩散是整个脱碳反应的限制性环节;通过对实验数据的拟合得到脱碳时间、薄带厚度和脱碳量三者的经验公式,同时对脱碳规律进行了数学的描述,得出不同厚度薄带的脱碳反应均近似于一级反应。提出了可明显改善脱碳效果的分段加热脱碳法,采用该种方法,厚度为1.5mm的薄带在50min内其碳的质量分数可由初始的4.20%脱除到0.39%。     

冷却速率对δ-TRIP钢包晶相变的影响

在钢的凝固过程中冷却速率对钢的相变具有不可忽视的影响。本研究采用Thermo-calc热力学软件,模拟计算了含Al 3.52%（质量分数）的δ铁素体相变诱导塑性（δ-TRIP）钢的相转变过程,并分别使用差示扫描量热法（DSC)和Ohnaka微观偏析模型,分析了不同冷却速率对3.52%Al δ-TRIP钢凝固过程中的包晶相变温度,以及溶质元素偏析的影响。结果表明,冷却速率越小,DSC试验所得的相变温度越接近Thermo-calc计算的热力学平衡值。随着冷却速率从10、30增加到50 ℃·min–1,L→L+δ的转变温度降低,L+δ→L+δ+γ和L+δ+γ→δ+γ的转变温度先降低后升高,前者主要受过冷度的影响,后者主要受元素偏析的影响。冷却速率对C、Mn、S的偏析影响很小,对Si、P、Al的偏析影响较大,并且随着冷却速率的增加,Si、P、Al偏析程度增加。Si和P的偏析会小幅度延缓包晶反应的进程;Al对改变包晶反应进程作用明显,随着冷却速率的增加,包晶反应区域逐渐下移,且下移趋势渐缓。      

2 mm铁碳合金薄带固态脱碳试验

 为了探究2 mm厚的铁碳合金薄带固相脱碳规律。试验以Ar-H2-H2O为脱碳气氛,在可控气氛管式炉内对Fe-C合金薄带进行脱碳。把初始碳质量分数为4.15%和3.20%的2 mm铁碳合金薄带分别放入加热场中,然后控制不同加热温度和脱碳时间进行脱碳研究。结果表明,碳向反应界面的扩散是脱碳反应的限制性环节,脱碳温度的升高和脱碳保温时间的延长均有利于脱碳,初始碳质量分数不同的铁碳合金薄带前期脱碳速率相同。由于薄带较厚,恒温脱碳不能达到脱碳要求,从而提出了分段加热脱碳法,脱碳效果良好,初始碳质量分数为4.15%的铁碳合金薄带70 min可脱到0.28%,初始碳质量分数为3.20%的铁碳合金薄带50 min可脱到0.23%。     

Thermodynamics of the fcc Fe-Mn-C and Fe-Si-C alloys

The activity of carbon in austenitic Fe-Mn-C and Fe-Si-C alloys has been studied by equilibration with controlled CH₄-H₂ atmospheres at temperatures in the range 848° to 1147°C and for composition up to about 60 pct Mn and 7 pct Si. The activity coefficient of carbon is diminished by manganese and is increased by silicon. Activity coefficients and derived values of the partial molar free energy, enthalpy, and entropy of solution of graphite in the alloy are expressed in mathematical form. The heat of solution of graphite, which is positive in the Fe-C binary alloys, decreases with increasing manganese and increases with increasing silicon concentrations. The partial molar entropy is independent of manganese, but is decreased by silicon. TSUGUYASU WADA, formerly of the Research Staff, Massachusetts Institute of Technology, Cambridge, Mass. HARUE WADA, formerly of the Research Staff, MIT, Cambridge.