06Cr25Ni20不锈钢表面氧化层去除方法的研究与应用

奥氏体耐热不锈钢06Cr25Ni20在不锈钢冷板连续退火酸洗线后表面形成的氧化层致密较难酸洗.本文通过影响表面氧化层的形成因素和酸洗因素控制,结合生产实际提出了控制加热温度和时间,氢氟酸浓度达到26 L/g后压下0.8 mm细度的碳化硅刷辊以提升酸洗效率,从而达到合格的钢板表面质量要求.     

内氧化层对高牌号无取向硅钢磁性的影响

通过金相法和磁声发射法（ＭＡＥ）研究了高牌号无取向硅钢脱碳退火时所产生的内氧化层，这种氧化层使钢板产生应力场，阻碍磁畴壁的位移，因而使铁损增加。     

热轧奥氏体不锈钢带钢酸洗工艺机理分析

 详细分析了热轧奥氏体不锈钢带钢的表面氧化皮形成机理、退火对氧化皮特性的影响机理、酸洗工艺机理。结论是：热轧奥氏体不锈钢带钢表面氧化皮外层主要以铁氧化物为主,内层主要以交替分布的Cr2O3和FeCr2O4层为主;退火后,氧化皮结构变得疏松多孔,且易脱落,贫铬层厚度增加,带钢更加容易酸洗;酸洗时,带钢表面的氧化皮主要通过机械剥离作用去除。分析结果对热轧奥氏体不锈钢带钢酸洗技术的改进具有一定的理论指导意义。     

缓蚀剂对推拉式酸洗工艺产品表面质量的改善

介绍了缓蚀剂的作用机理,并通过实验室研究和生产试验,研究了其对推拉式酸洗工艺产品表面质量的改善效果。结果表明,酸液中添加缓蚀剂后,试样表面颜色明亮,粗糙度较好,铁损量较小;酸洗时间越长,缓蚀剂的抑制作用越弱,带钢的铁损量越大。缓蚀剂可抑制过酸洗的发生,使铁损率下降0. 22%,直接提高产品成材率的同时,降低酸液消耗24%,经济社会效益显著。     

取向硅钢涂层对噪音特性的影响

取向硅钢片磁致伸缩是变压器噪音来源的主要因素,本文研究了取向硅钢片硅酸镁底层和磷酸盐涂层对磁致伸缩的影响。结果表明：取向硅钢表面的硅酸镁底层和磷酸盐涂层可降低取向硅钢的磁致伸缩;增加绝缘涂层的厚度可减少杂畴和90°畴,改善取向硅钢的噪音性能。     

热轧不锈钢板酸洗工艺

为去除热轧不锈钢板表面的氧化层与贫铬层,钝化基体,改善表面质量,在热轧退火后需进行酸洗处理。介绍了热轧不锈钢板表面氧化层和贫铬层的组成与结构特征及其对酸洗过程的影响,并对热轧不锈钢板的酸洗体系设计和酸洗工艺开发进行了阐述。中国热轧不锈钢板普遍采用前处理(机械除鳞、中性盐电解等)→硫酸(电解)预酸洗→硝酸-氢氟酸终酸洗的酸洗工艺,旨在通过前处理和预酸洗去除大部分的氧化层,在终酸洗阶段去除残余氧化层及贫铬层,同时实现基体钝化。目前,热轧不锈钢板的酸洗工艺存在酸洗效果不稳定、贫铬层去除不完全、局部腐蚀较为严重等问题,且会产生不同程度的环境污染问题。应该根据不同钢种不同退火工艺条件下的表面氧化层与贫铬层的性质与分布特征,研究开发相应的酸洗体系和酸洗工艺。热轧不锈钢板的环保型酸洗新工艺具有广阔的发展前景。     

激光刻痕对取向电工钢磁畴和铁损的影响

为了研究激光刻痕工艺参数对取向电工钢表面的磁畴形貌、刻痕线宽度和铁损的影响规律，开展了激光刻痕工艺试验。结果表明，激光刻痕后取向电工钢表面的磁畴宽度明显细化，且随着输入电流的增加，磁畴宽度先减小后增大；刻痕线宽度随着输入电流的增加而增大。对于本次试验样品，通过对比分析，确定最佳激光刻痕工艺参数为电流为 12 A，激光频率为 5 kHz，刻痕速度为 800 mm/s，该参数下铁损改善率可达 11.81%。     

BT303CuS2不锈钢表面氧化物结构的研究

易切削不锈钢BT303CuS2盘条热处理后表面氧化物结构较为复杂,与普通304不锈钢相比酸洗更加困难.为了探明其表面氧化物的结构及影响因素,通过试验的方法测量出不同的热处理温度、时间及炉内气氛状态下BT303CuS2钢表面氧化物种类及结构.试验结果表明,随着固溶处理时间的延长、固溶温度的提高或炉内气氛中氧含量的增加,表面氧化层逐渐增厚,并对后续酸洗工序造成了影响.     

带钢表面氧化缺陷的产生与预防

主要介绍了氧化铁皮类缺陷对带钢表面质量的影响。分析了化学成分、终轧和卷取温度等因素对氧化铁皮结构的影响,指出了轧辊表面状况对带钢氧化铁皮及表面质量的间接影响,提出了从轧制温度、轧制负荷、轧制节奏、轧制润滑等方面控制轧辊表面氧化膜的措施。介绍了通过控制FeO的先共析反应和共析反应来获得"减酸洗钢"和"免酸洗钢"的方法。     

表面缺陷对取向硅钢磁畴形态的影响

取向硅钢的磁畴形态与其损耗密切相关，研究其内部的磁畴结构对于理解铁损的产生具有重要意义。利用粉纹法观察了带有涂层、激光刻痕处理以及存在表面缺陷的硅钢片磁畴。结果表明，施加较小的垂直磁场更容易观察硅钢的原始磁畴形态，有利于显示清晰的磁畴图像和晶界；如果硅钢片表面存在冲裁小孔，原有的180°畴在小孔附近会变为迷宫畴，且附加应力和退磁场作用会使小孔周围磁畴细化，使用微磁学模拟的方法定性验证了这一变化；如果硅钢表面存在划痕，划痕两端的180°畴会变为迷宫畴，随着划痕方向的不同，磁畴形态也不同。最后，比较了圆盘剪裁切与线切割后硅钢片边缘的磁畴形态，讨论了其磁畴形态不同的原因。     

Internal oxidation of hot-rolled ultra-high strength steel and its effect on the surface quality of cold-rolled sheets

In this study,the scale and internal oxidation of hot-rolled ultra-high strength steel sheets were characterized.It was found that both the formation of the scale and the internal oxidation of Si and Mn depended on the coiling temperature and position of the steel sample on the strip coil.At a relatively high coiling temperature,a large amount of internal oxidation was observed on the samples cut from the middle of the coil.The depth of the internal oxidation zone exceeded 10 μm and a thin iron layer covering the scale was observed in some cases.Pickling and cold-rolling experiments were conducted on selected samples.Scale pickling was found to be greatly delayed by the formation of an iron layer,which frequently resulted in under-pickled defects.In addition,pickling of the entire internal oxidation zone was difficult,except at the grain boundaries,where the degree of internal Si and Mn oxidation was enriched.The surface of the cold-rolled steel sheet was ruined by the remaining oxidation zone in the subsurface of the pickled steel.The internal oxidation of hot-rolled ultra-high strength steel must be precisely controlled to improve the subsequent surface quality of cold-rolled steel.     

Oxidation of porous nanocrystalline titanium nitride. III. Oxidation mechanism

The air oxidation mechanism of nanocrystalline TiN at 500 to 900 °C is examined. It is shown that at t ≤ 800 °C the oxidation of titanium nitride is controlled by the diffusion of oxygen and at t > 800 °C the interdiffusion of titanium ions is observed. The oxidation properties of porous TiN are determined by the chemical interaction of oxygen and the reaction surface, which includes the external surface of samples and the internal surface of the pores into which oxygen penetrates. The time and temperature dependence of the weight increment complies with the porous material oxidation model. Active initial oxidation is due to the interaction of oxygen and large internal surface. Short-term self-heating of porous samples is also possible. At t ≤ 800 °C, the pores are obliterated with oxides with time, the internal reaction surface reduces, an external oxide film is formed, the oxygen diffusion and weight increment slow down, and the process stabilizes. With temperature increase, these processes are activated and lead to a smaller weight increment at the final stage (2 to 4 h) at 800 °C as compared with 600 °C. At t > 800 °C the pore obliteration rate increases, but due to the interaction of oxygen and titanium ions that diffuse into the external scale surface, weight increment continuously increases with both time and oxidation temperature. The phase composition of the scale also affects the oxidation mechanism of porous TiN. Oxynitride of terminal composition plays a protective role; the transformation of anatase into rutile is accompanied by a decrease in the oxygen diffusion rate; Ti₂O₃ formed in pores accelerates their obliteration. __________ Translated from Poroshkovaya Metallurgiya, Vol. 46, No. 3–4 (454), pp. 95–104, 2007.     

Effect of Temperature on Scale Morphology of Fe-1.5Si Alloy

Because of the effect of silicon on the formation of oxide scale, red scale is the main surface defect of hot-rolled Fe-Si plate, making the scale difficult for descaling compared with carbon steel. Thermogravimetric analyzer (TGA) is used to simulate isothermal oxidation process of Fe-1.5Si alloy for 60 min under air condition, and the temperature range is from 700 to 1200 °C. Electron probe microanalysis (EPMA) is used to observe cross-sectional scale morphology and analyze elemental distribution of the scale. Relational graph of temperature, scale thickness and scale structure is obtained. It is found that scale structure (outer Fe oxide layer+inner FeO/Fe₂SiO₄ layer+internal Si oxide precipitates) is almost unchanged with temperature except at 1000 and 1200 °C. At 1000 °C internal Si oxide precipitates cannot be found at the subsurface of the alloy, and at 1200 °C FeO/Fe₂ SiO₄ not only forms a layer as usual but also penetrates into the outer Fe oxide layer deeply.     

Effect of soaking temperature and annealing atmosphere on magnetic properties of semi-processed nonoriented electrical steel containing 0.4 % silicon

In order to investigate the effect of soaking temperature and annealing atmosphere on magnetic properties of the semi-processed nonoriented electrical steel containing 0.4 % silicon, customer annealing was carried out at a temperature ranging from 730 to 950 and in different annealing atmospheres. As the soaking temperature increases from 730 to 950 in the dry N2 atmosphere, the core loss at 1.5 Tesla decreases continuously, whereas the permeability at 1.5 Tesla increases up to 890 and then decreases significantly at 950 °C. Among DX atmospheres having a dew point of -23 °C, the air to LPG ratio of 19.5 is found to reveal the best magnetic properties due to the lowest carbon content. At a dew point of +5 °C and an air to LPG ratio of 18.5 the best magnetic properties are to be achieved regarding both carbon content and internal oxidation layer.     

FeMnAlC TWIP钢加热过程中的氧化行为GD-OES研究

摘要：以成分（质量分数）为Fe-16%Mn-1.5%Al-0.6%C-0.11%Cr的TWIP钢为研究对象，采用模拟试验研究了加热过程中的氧化行为，使用GD-OES分析了加热温度和加热气氛中O2含量对表面元素深度分布的影响。结果表明，当TWIP钢在N2-0.05%（体积分数）O2的气氛中加热至550~700℃时，表面会形成Fe-Mn氧化层，次表层会形成贫锰层、脱碳层及内氧化层，各层厚度随加热温度升高而增大。在氧化性气氛中加热时，Al元素优先在次表层形成内氧化，少量的Cr元素在氧化层/基体界面上形成外氧化，表面氧化层中基本不含Al和Cr。当加热温度为650℃时，气氛中O2体积分数在0.025%~0.2%之间变化对氧化层厚度影响较小，均可获得厚度介于400~500nm的氧化层。由此可见，为获得TWIP钢合适的预氧化层厚度，同时减少预氧化层/基板界面位置的氧化物，直火加热出口温度控制比空燃比控制更重要。     

GD-OES study on oxidation behavior of FeMnAlC TWIP steel sheets during heating

The oxidation behavior of Fe-16%Mn-1.5%Al-0.6%C-0.11%Cr TWIP steel sheet during heating process was studied by simulation experiments. The effects of heating temperature and O2 content in heating atmosphere on the depth distribution of surface elements were analyzed by GD-OES. When TWIP steel sheet is heated to 550-700℃ in the atmosphere of N2-0.05 vol%O2, an oxide layer composed of Fe, Mn and O covers the surface, a Mn depleted zone, a decarburized zone and an internal oxidation zone will be formed in the subsurface layer. The thicknesses of the oxide layer and the subsurface zones increase with heating temperature increasing. When being heated in an oxidizing atmosphere, Al preferentially forms internal oxidation in the subsurface layer, and a small amount of Cr forms external oxidation at the oxide layer/matrix interface. The surface oxide layer basically contains no Al and Cr. When the heating temperature is 650℃, the change of O2 volume fraction in the atmosphere between 0.025%-0.20% has little effect on the thickness of the oxide layer, and the oxide layer with a thickness of 400-500nm can be obtained. In order to obtain the appropriate thickness of the pre oxide layer of TWIP steel and reduce the oxide at the interface between the pre oxide layer and matrix interface, the temperature control of the direct fire heating outlet is more important than the air-fuel ratio control.     

Behavior of direct reduced iron and hot briquetted iron in the upper blast furnace shaft: Part II. A model of oxidation

The high-temperature properties of the ferrous burden in the cohesive zone of the blast furnace (BF) are a function of its history in the upper shaft. It is considered that charging direct reduced iron (DRI) and hot briquetted iron (HBI) into the BF increases its efficiency and productivity. However, oxidation of DRI and HBI can occur in the low-temperature zone in the BF, which may affect their softening and melting properties. This work was designed to estimate the oxidation degree of DRI/HBI in the upper BF shaft. In this article, a model of oxidation was developed, which predicted that DRI and HBI can be oxidized up to 10 and 2 pct, respectively. The model was then put forth to a laboratory-simulated test and industrial simulated blast furnace (SBF) test for its verification. The results of SBF tests indicated that the oxidation of DRI/HBI occurs in a temperature range of 700 °C to 950 °C with the gas compositions used for the tests. The morphology of iron in DRI is expected to exhibit Fe-FeO-Fe layers in varying thickness at the beginning of the cohesive zone. The oxidation in HBI briquettes is primarily limited to its external surface. These results indicate that the impact of oxidation of DRI/HBI on the cohesive zone will not be significant.     

On the Transition of Internal to External Selective Oxidation on CMnSi TRIP Steel

The selective oxidation of a CMnSi transformation-induced plasticity (TRIP) steel during intercritical annealing (IA) in a N₂ + 10 pct H₂ gas atmosphere with a dew point (DP) in the range from 213 K to 278 K (?60 °C to +5 °C) was investigated by transmission electron microscopy. The decarburization during IA resulted in a fully ferritic matrix at the TRIP steel surface. Annealing in high DP gas atmospheres resulted in a reduction of the oxide layer thickness at the surface and an increase of the depth of the subsurface internal oxidation. The experimental results were compared to the calculations of the DP for the transition from internal to external oxidation based on the Wagner model. The evolution of the surface oxide composition during annealing was analyzed thermodynamically by means of the chemical potential diagram for the surface oxides. In the high DP atmosphere conditions, mainly, Mn-rich xMnO·SiO₂ (1 < x < 2) oxides were formed at the surface, while Si-rich xMnO·SiO₂ (x < 1) oxides were formed by internal oxidation. The use of a high DP gas atmosphere is therefore advantageous to induce internal selective oxidation and reduce the amount of surface oxides. It also leads to the formation of Mn-rich xMnO·SiO₂ (1 < x < 2) oxides.     

Behavior of direct reduced iron and hot briquetted iron in the upper blast furnace shaft: Part I. Fundamentals of kinetics and mechanism of oxidation

It is considered that the use of prereduced ferrous materials and sources of metallic iron such as direct reduced iron (DRI) or hot briquetted iron (HBI) improves the productivity of the blast furnace (BF). However, oxidation of DRI/HBI can occur in the upper zone of the BF, which may increase the content of the reducing gases but may not decrease the coke rate substantially. The behavior of DRI and HBI was investigated by measuring the rate of oxidation of the materials in CO₂ gas in a temperature range of 400 °C to 900 °C. In addition, the microstructure of “as-received” and oxidized materials was examined. The iron oxide phases formed due to oxidation were determined using X-ray diffraction (XRD) and a vibrating sample magnetometer. The results of isothermal experiments indicated that the kinetics of oxidation of metallic iron is slow at 400 °C. In DRI samples, the initial rate is controlled by the limited mixed control of chemical kinetics at the iron/iron oxide interface and pore mass transfer, whereas gas diffusion in pores is the rate governing step during the final stages of oxidation. The oxidation of wustite from iron is found to be faster than the oxidation of the former to magnetite. The structure of DRI after oxidation resembled a “reverse topochemical-oxide on the surface metal in the center” structure at 600 °C to 700 °C. The final iron oxide phase formed in DRI after oxidation was magnetite and not hematite. The oxidation of HBI was limited to the surface of the samples at lower temperatures; at 900 °C, moderate oxidation was observed and a topochemical iron oxide layer was formed.