1　Introduction

Cu,as a beneficial alloying element in steel,modifies the dynamics of austenite decomposition upon cooling and improves the strength and tough-ness properties of steel resulting from the solid solution or precipitation.Cu can be added to steel as a corrosion-resistant element to enhance the cor-rosion resistance of steels[1-2].However,when Cu-containing steel is heated,Fe and other active elements are oxidized preferentially,causing the more-inert Cu accumulate on the scale/steel inter-face.As oxidation proceeds,the Cu in the interface is enriched and a Cu-rich phase is formed when this Cu exceeds the solid solubility limit of the Cu in steel.The melting point of Cu is 1 083 ℃,as this tem-perature is generally below the heating temperatures used in steel production,the Cu-rich phase is melted into a liquid,which subsequently penetrates into austenite grain boundaries on the metal surface.Such penetration causes a loss of ductility and,eventually,fracturing during the hot-rolling process.This phenom-enon is known as the surface hot shortness of Cu-containing steels[3-4].

The use of Cu in steel is severely limited because of the hot shortness phenomenon.Several intensive research studies have been conducted to solve this problem.The influences and mechanisms of various alloying elements,including Sn,Ni,P,S,B,Si,and Mn,on Cu-induced surface hot shortness have been investigated by Shibata et al.[5].Djurovic[6] and Chen et al.[7] conducted other studies on the subject from the aspects of surface enrichment of Cu,methods of assessing the hot shortness of Cu-containing steels,and the influences of process parameters.Suppres-sing or reducing the amount of the Cu-rich phase formed has been reported to be key in preventing hot shortness.Besides the oxidation rate of the steels,the amount of Cu-rich phase is related to the melting point and solid solubility of Cu in austenite and the amount of Cu occluded in the scale.

Addition of Ni to Cu-containing steels to suppress and reduce the formation of Cu-rich phases is a common practice at home and abroad to solve the problem of Cu-induced surface hot shortness.Ni can increase both the melting point of the Cu-rich phase and solid solubility of Cu in austenite and promote the formation of occlusions in scales.However,Ni addition also leads to higher production costs.A previous study has reported[8] that Al,a low-cost alloying element,significantly improves the solid solubility of Cu in steel.However,whether it can eliminate the Cu-induced hot shortness by inhibiting the formation of the Cu-rich phase has not been reported.In this paper,the effects of Al and Ni on the surface microstructures and morphologies of Cu-containing steel are studied via high-temperature oxidation experiments.Analysis of the effects of these elements on the reduction of Cu-rich phase formation is also performed.

一周后，他们也没能分出摁哪里接电话，摁哪里挂电话。我在他们的电话里，输入了120,110,119，还有我的号码，当我再一次让爸试着拨一个电话给我的时候，他气急把电话摔到地板上，扬言要带着妈回老家。

2　Materials and methods

2.1　Materials

Four steel samples containing various amounts of Al or Ni or both were used in this study.All of the samples were smelted by a vacuum induction furnace and cast into square ingots.Then,the ingots were rolled into steel plates with a thickness of 15 mm.The compositions of the four steels are listed in Table 1.

When the Cu content in a steel sample is held constant,the faster the oxidation rate,the more extensive the formation of a Cu-rich phase.Addition of various alloying elements to steel results in vari-ations in oxidation rates[10,16-19].Chen and Yuen[17],as well as Yin[19],confirmed that adding Ni to Cu-containing steel would obviously reduce its oxida-tion rate.After studying the isothermal oxidation of steel samples with (0.16-0.34) Cu-(0.017-0.084) Ni at 980,1 120,and 1 220 ℃,Chen and Yuen[17] found that Cu could decrease the oxidation kinetics of the steels at 980 ℃ and that this effect was more remarkable when Ni was simultaneously added to the samples.By comparison,this effect became weak at 1 120 ℃ and robust at 1 220 ℃.Al is an active metal element with a stronger affinity to O2 than Fe does,but its oxidation product,Al2O3,is dense enough to prevent inward diffusion of O2 and suppress oxidation.Fig.8[20] shows the weight increment per unit area of cast iron with various Al contents after oxidation for 5 h at 850,1 000,and 1 100 ℃.Al can be observed to promote oxidation when its content is low but inhibit oxidation when its content is higher than 3.0%.This result could be explained by the formation of an Al2O3 layer on the steel surface,which suppresses the diffusion of O2 and Fe and reduces the oxidation rate.Because the four test steels contained fairly low Al contents (about 0.5%),decreases in oxidation rate on account of the effect of Al were not observed.

The C,Si,Mn,P,S,and Cu contents of all four samples were relatively identical,and only their Al and Ni contents differed.For example,2# steel con-tained more Al than 1# steel to enable the study of the influence of Al on the formation and mor-phology of the Cu-rich phase at the scale/steel inter-face of Cu-containing steel.Similarly,only Ni was added to 3# steel and both Al and Ni were added to 4# steel to determine the effects of Ni alone and Al plus Ni,respectively,on Cu-containing steel.

2.2　Experimental methods

Samples measuring 30 mm×50 mm×15 mm were cut from the rolled plates and oxidized in a high-temperature box-type electrical resistance furnace.In brief,the samples were polished to eliminate surface scales,placed in the furnace,and then heated to the desired temperature,which was maintained for some time.Thereafter,the samples were cooled to room temperature in air.A protective atmosphere was not employed in this process.The heat process in which the furnace temperature was higher than 1 100 ℃ and sustained at least 100 min was designed to ensure sufficient Cu enrichment and Cu-rich phase formation and penetration.

(3) Changes in the rate of oxidation.During high-temperature oxidation,the faster the oxidation rate,the more extensive the Cu enrichment at the scale/steel interface and the higher the extent of liquid Cu-rich phase formation.

3　Results

3.1　Microstructures at the scale/steel interface

(4) Changes in the amount of Cu-rich phase occlusion in scales.Previous investigations[2-3,7,9] have demonstrated that some Cu-rich phases could be occluded in the scales and distributed in scale-like islands at high oxidation temperatures.In this circumstance,the scales can isolate the liquid Cu-rich phase from the steel matrix and prevent it from penetrating into austenite grain boundaries.When all other conditions are held constant,the higher the availability of Cu-containing occlusions,the lower the presence of the liquid Cu-rich phase at the interface[2].

(1) Changes in the melting point of the Cu-rich phase.The melting point of the Cu-rich phase changes when the alloying elements dissolve in the Cu-rich phase.As the melting point of the Cu-rich phase increases,the formation of the liquid phase is limited,thus its penetration into austenite grain boundaries decreases.

为了保证语料标注的质量,两位标注者同时对语料库进行标注,目的是进行标注结果的一致性检测.本工作采用Passoneau[15]提出的语料库指代标注可靠性计算方法,并根据Krippendorff[16]的alpha系数来表示两位标注者标注结果之间的一致性.该方法通过一个距离度量来表示指代链之间的相似度,然后通过alpha系数计算指代链之间的相似度距离来表示不同标注者标注结果之间的一致性.

Fig.1　Microstructures at the scale/steel interface of 1# steel after high-temperature oxidation

3.2　Influences of Al and Ni on microstructures at the scale/steel interface

The cross section metallographs of 2#,3#,and 4# steels after high-temperature oxidation are shown in Fig.3.The scale/internal oxidation layer interface of 2# steel,the sample to which only Al had been added,is uneven and features a low density of scale branches,which appear to preferentially grow laterally rather than inward.3# steel,the sample to which only Ni had been added,features a large quantity of occlusions in the scales near the inter-face,and these occlusions take the shape of thin strips with a dispersed distribution;scale branches in this sample are relatively scarce.The microstruc-tures of 4# steel,the sample to which Al and Ni had been added simultaneously,show a mixture of the features of 2# and 3# steels.That is,in this sample,a fairly even scale/internal oxidation layer interface,few scale branches,and large quantity of occlusions in the scales near the interface may be observed.

Figs.1-3 demonstrate that,in contrast to 1# steel,2#,3#,and 4# steels present scale branches with a lower density and shallower depth.The map scan-ning results further indicate that the Cu-rich phase located at the boundaries of the scale branches is caused by the melting of the enrichment layer and its penetration into austenite at high temperature.The amount of Cu-rich phase formed after high-temperature oxidation in 2#,3# and 4# steels is less than that in 1# steel,and this finding proves that Al and Ni can reduce the formation of a Cu-rich phase at the scale/steel interface.

(2) Changes in the solid solubility of Cu in austenite.When the total content of Cu in a certain steel sample is held constant,the higher solid solubility of Cu in austenite means less precipitation of the Cu-rich phase and less penetration of this phase into austenite grain boundaries.

4　Discussion

The above experiment results indicate that addition of Al or Ni helps reduce the formation of a liquid Cu-rich phase at the scale/steel interface of Cu-containing steels during high-temperature oxida-tion.A large number of experiments and studies[9-14] have been done on the effects of alloying elements on the formation of a Cu-rich phase and hot shortness.The effects of alloying elements on the formation and penetration of the liquid Cu-rich phase can be analyzed in the following aspects:

The SEM scanning results of the cross section of 1# steel are presented in Fig.2.The white area in Fig.2(b) reveals Cu enrichment and formation of a Cu-rich phase.Comparing Figs.1 and 2(b),the Cu-rich phase can be observed to be mainly located in occlusions near the interface and the boundaries of scale branches.According to the mechanism of Cu-induced hot shortness,the scale branches and Cu-rich phase in the branch boundaries result from selective oxidation,Cu enrichment,melting,and penetrating during high-temperature treatment.

The sizes and distributions of oxide particles in the internal oxidation layers of 1#- 4# steels are dis-played in Fig.4.In general,the internal oxide particles of all four steel samples are spherical and feature a dispersed distribution.2# steel,the sample to which only Al had been added,clearly includes oxide particles larger than those found in 1# steel,which shows oxide particles as large as those in 3# steel,the sample to which only Ni had been added.The sizes of the oxide particles of 4# steel,the sample to which Al and Ni had been added simul-taneously,are between those of 2# steel and 3# steel.

2.1.2 密度对红花花丝产量的影响 从表2看出，种植密度与红花花丝产量之间呈较好的二次抛物线关系，种植密度（x，万株/hm2）与花丝产量（y，kg/hm2）的回归方程为y=-7.038 3x2+128.6x+87.559，其复相关系数R2=0.998 6。由回归方程求偏导数，并令其为零，得到获得最高产量的种植密度为9.13万株/hm2。

高度专业化的知识特性。知识服务需要提供者具备高度专业化的知识和技能,这些知识和技能往往是客户所不具备的,或者是客户满足自我知识需求的成本太高，或者客户无法通过自身努力获取这些高度专业化的知识和技能，因此知识服务提供者以其专业化，可在人力资本市场上明码标价。服务的高附加值特性。知识服务是通过自身的知识创新,在满足客户需求的过程中,帮助客户实现创新,是一种高智力型难以复制的创新服务,因此具有高附加值，此附加值是知识服务提供者将专业化服务与客户需求巧妙对接的创造性产物。

After high-temperature oxidation,optical microscopy and scanning electron microscopy (SEM) were used to observe the compositions of the oxidation layers,microstructures at the scale/steel interfaces,and morphologies and distributions of Cu-rich phases in the samples.

运动控制系统分为直流部分、交流部分和伺服电机控制三部分，由于主要研究电机转速的控制，也有书籍称其为调速技术。该课程的综合性强，与实际应用联系紧密，对知识的融会贯通能力和实践动手能力都有很高的要求。在实际教学过程中发现，如果学生不能将前期分散学习的各科基础知识综合地应用到该专业主干课程的学习中，将给运动控制系统课程的学习带来很大困难，这也使得该课程成为自动化专业比较难教和难学的一门课程。因此，如何改革传统的教学方式，提高运动控制系统课程的教学质量，是一项很有意义的教学尝试。

Fig.1 illustrates the cross-sectional metallograph of 1# steel after high-temperature oxidation.An internal oxidation layer forms between the scales and substrate,and a number of spherical oxide particles are distributed in a disperse manner in the internal oxidation layer,which is characterized by a rough interface with scales.Occasionally,the scales penetrate into the internal oxidation layer like branches,but the lengths of these scales do not exceed the thickness of the internal oxidation layer.Some particle-containing cakes are broken from the internal oxidation layer and embedded with scales at the interface.These cakes are occlusions.

In the next sections,we discuss the effects of Al and Ni on the formation of the liquid Cu-rich phase at the scale/steel interface from these four aspects.The alloying elements in the test steel were oxidized in a high-temperature oxidation experiment.Accord-ing to the Ellingham diagram[15],the critical O2 partial pressures of NiO,CuO,and Cu2O,which are the oxidation products of Ni and Cu,are larger than that of FeO;by comparison,the critical O2 partial pressure of Al2O3,the oxidation product of Al,is not.Therefore,under a high-temperature oxidizing atmosphere,the Fe on the surface of Cu-containing steel samples to which Ni had been added is preferentially oxidized but the inert Cu and Ni remain and become enriched at the scale/steel interface.Due to the unlimited mutual solubility of Cu and Ni,as shown in Fig.5,the melting point of the Cu-rich phase also increases to dissolve some Ni.In Cu-containing steel to which Al had been added,however,the O2 on the surface layer first oxidizes Al and then reacts with Fe.Thus,Al2O3 and Cu are observed.The isothermal section diag-ram of the Cu-Al-O ternary system at 1 000 ℃ is shown in Fig.6.Al2O3 is immiscible with Cu,which means no Al2O3 is present in the Cu-rich phase.In other words,adding Al to Cu-containing steel makes no difference to the melting point of the Cu-rich phase.

Ohtani et al.[8] and Akamatsu et al.[10] studied the effects of Al and Ni on the solid solubility of Cu in austenite.Ohtani et al.[8] found that when the Al content in Cu-containing steel was lower than 2.0%,the solid solubility of Cu in austenite slightly decreased;by contrast,when the Al content was high,the solid solubility of Cu in austenite increased sharply with the Al content.The results of Akamatsu et al.[10] showed that Ni could enhance the solid solubility of Cu in austenite and that the larger the wNi/wCu,the more significant the increase in solid solubility.

官地电厂中控室发出1号机组停机令，1号机组自动停机过程中，机组转速降至90%时2号高压油泵自动启动开始运行，2号高压油泵运行76 s后因未知故障突然停止运行，自动切换至1号高压油泵运行，1号高压油泵运行60 s后同样因未知故障突然停止运行。为了避免由于节点松动、信号误报等偶发性的原因引起高压油泵停止运行，导致可能发生发电机推力轴承瓦损坏的重大事故，运行人员在CCS系统上手动启动1号机2号高压油泵，以检查2号高压油泵能否工作，结果2号高压油泵启动后运行正常，直到机组停机。

The solid solubilities of Cu in the austenite of the four steel samples were calculated using Thermo-Calc software,and the results are shown in Fig.7.Figs.7(a) and 7(b) reveal that addition of a cer-tain amount of Al,approximately 0.5%,slightly decreases the solid solubility of Cu regardless of the presence or absence of Ni.Ni clearly raises the solid solubility of Cu in austenite with or without Al,as shown in Figs.7(c) and 7(d).The calculation results above are in accordance with the research of Ohtani et al.[8] and Akamatsu et al.[10].The Cu-rich phase usually forms at the scale/steel interface.The composition of the steel surface differs from that of its matrix after high-temperature oxidation and changes as oxidation proceeds;these findings should be considered when calculating the effects of Al and Ni on the solid solubilities of Cu in austenite.Specifically,in Cu-containing steel to which Al is added,as oxidation proceeds,the Al near the interface is gradually oxidized into Al2O3 and precipitated from austenite;thus,the ability of Al to decrease the solid solubility of Cu will weaken.In Cu-containing steel to which Ni is added,Ni will continuously accumulate on the interface,similar to Cu.As the diffusion coefficient of Ni in austenite is lower than that of Cu,the diffusion velocity of the former toward the steel matrix will be slower than that of the latter,leading to a larger wNi/wCu ratio and,according to Akamatsu et al.[10],a propor-tionate increase in the solid solubility of Cu in austenite.

1.3统计学科学处理本次实验采取统计学软件SPSS 22.0对患者的数据进行统计学科学处理,其中计数资料采取(n,%)进行表示,用卡方进行表示,而计量资料采取(±s)进行表示,用t进行检验,且对科学处理后的结果进行研究与分析。

我心想，她很可能要倚老卖老了。珊德拉夫人说，我说你年轻，是因为我看到你在运动和感觉热的时候，脸上还会出现一些红润。而真正的老人，是不会出现这种血脉涌动的红润的。除非他患了高血压。

Fig.8　Effect of Al content on the oxidation rate of cast iron

The mechanism of formation of Cu-rich occlu-sions can be described as follows:When steel is heated at a high temperature,portions of the sample without Cu enrichment are oxidized rapidly due to selective oxidation while Cu-rich portions oxidize more slowly.This difference in oxidation rates causes a rough scale/steel interface to form,and Cu-rich portions are embossed into the scales.At high oxidation temperatures,internal oxidation occurs extensively and bridges form laterally along the austenite grain boundaries,causing the embos-sing Cu-rich portions entrapped by the scale and form occlusions[7,16].Two conditions are required to form occlusions:a rough scale/steel interface and internal oxidation.A rough interface is obtained through selective oxidation[21-22],and internal oxida-tion occurs as a consequence of differences in dif-fusion between O2 and other active element,such as Si and Mn,the oxidation activation energies of which are lower than that of Fe[23-24].As such,any factor that may impact these two requirements will influence the formation of occlusions.

The ability of Ni to promote the formation of occlu-sions when added to Cu-containing steel has been proven by many previous researchers[7,9,16-17,19,25] and confirmed by our experiment,as shown in Fig.3.Ni promotes the formation of occlusions because,like Cu,it has a higher oxidation activation energy than Fe.During high-temperature oxidization,inert Ni and Cu are enriched at the scale/steel interface without oxidizing.Portions of the samples that are rich in Ni and Cu reveal slow oxidation rates,while those with low Ni and Cu contents have rapid oxi-dation rates,leading to a rougher interface[19,26].Ac-cording to research by Webler et al.[11] and Fisher[22],Ni enrichment increases the concentration of O2 at the scale/steel interface and increases in O2 concentration help improve internal oxidation[11,22,27].Al is an active metal element,and the free energy of Al2O3 is lower than that of some ordinary oxides,such as SiO2 and MnO[15].As such,Al can react with O2 to produce Al2O3 at a much lower O2 concentration that required by other oxides.When the steel is oxidized at high temperature,O2 in the air diffuses into the steel matrix through its surface.The O2 concentration in the steel is reduced with increasing depth from the surface and increased with in-creasing oxidation time.As for the Al-added Cu-containing steel,with the oxidation proceeding,the O2 concentration in steel matrix reaches to the limitation of reacting with Al first,and reacts with Al to produce the core of Al2O3.Because Al2O3 has a high diffusion coefficient,which is two orders of magnitude higher than those of Si and Al,as shown in Fig.9[28],the Al2O3 cores can easily grow into large internal oxidation particles,as shown in Fig.4.As the particle size of the cores increases,bridging and connecting easily occur[9],thereby promoting the formation of occlusions.

Fig.9　Diffusion coefficients of Al,Si,and Mn elements in austenite (γ)

We have analyzed the effects of Al and Ni on the formation of a liquid Cu-rich phase at the scale/steel interface in terms of the melting point of the Cu-rich phase,the solid solubility of Cu in austenite,the rate of oxidation,and the amount of Cu-rich occlusions in the above sections.The analysis results reveal that,since Al is more active than Fe,Al exerts its effects via its oxidation product Al2O3;by comparison,Ni,which is less active than Fe,exerts its effects via its elemental form.When Al and Ni are added to Cu-containing steel at the same time,they exert their effects individually and influence the formation of the liquid Cu-rich phase collectively because no reac-tion or dissolution takes place between Al2O3 and Ni.Specifically,the morphology at the interface of Cu-containing steel to which Al and Ni had been added,for example,4# steel,presents the chara-cteristics of both Al-only-containing Cu-containing steel (for example,2# steel) and Ni-only-containing Cu-containing steel (for example,3# steel),as shown in Figs.3 and 4.Al and Ni can both promote the production of occlusions in the liquid Cu-rich phase.Furthermore,Al (Al2O3) does not increase the melting point of Cu-rich phase,while Ni does.From these two aspects,addition of Al and Ni simultaneously can be considered to reduce the formation of a liquid Cu-rich phase at the steel/scale interface.While Ni increases the solid solubil-ity of Cu in austenite and suppresses oxidation,the influence of Al in this regard depends on its content in the steel.Hence,to minimize the liquid Cu-rich phase at the steel/scale interface,the content of Al in steels should be controlled and the ratio of Al and Ni must be optimized.More work on these efforts is recommended in future research.

5　Conclusions

In this paper,the effects of Al and Ni on the surface microstructures and morphologies of Cu-containing steel after high-temperature oxidation were studied.Al and Ni were found to reduce the formation of a liquid Cu-rich phase at the steel/scale interface.Analyses of the melting point of the Cu-rich phase,the solid solubility of Cu in auste-nite,the rate of oxidation,and the amount of Cu-rich phase occlusion were performed,and the fol-lowing conclusions are drawn:

(1) Al added to Cu-containing steel is preferen-tially oxidized to Al2O3,which is immiscible with Cu.Thus,Al exerts no influence on the melting point of the Cu-rich phase.By contrast,Ni dissolves in Cu infinitely,and the melting point of the former is higher than that of the latter.Thus,when Ni is added to Cu-containing steel,the melting point of the Cu-rich phase is increased.

(2) Al decreases the solid solubility of Cu in austenite when its content in Cu-containing steel is less than 2.0%;by contrast,Ni increases the solid solubility of Cu in austenite.As oxidation proceeds,the effects of Al and Ni weaken and strengthen,respectively,because of their individual oxidation properties.

(3) Both Al and Ni can promote the formation of Cu-rich occlusions.In this case,Al and Ni boost internal oxidation.Ni also promotes the formation of a rough scale/steel interface.

References

[1]　OKIDA H,SEKINO S,HOSOI Y,et al.Copper containing structural steels[M]∥LEMAY I,SCHETKY L M,WILEY J,et al.Copper in iron and steel.New York:John Wiley and Sons Inc.,1982:83-133.

[2]　WANG W.Review on studies of reducing Cu-induced surface hot shortness in steel[J].Baosteel Technical Research,2015,9(2):3-13.

[3]　COUTSOURADIS D,LEROY V,GREDAY T,et al.Review of hot shortness problems in copper-containing steel[J].ATB Metallurgie,1983,23(3):1-24.

[4]　SHIBATA K.Surface hot shortness due to Cu(+Sn) and its suppression by physical metallurgy[C]∥Current Advances in Materials and Processes:Report of the ISIJ Meeting.Tokyo:ISIJ,2003:1391-1394.

[5]　SHIBATA K,SOEK J S,KAGA M,et al.Suppression of surface hot shortness due to Cu in recycled steels[J].Materials Transactions,2002,43(22):292-300.

[6]　DJUROVIC M,PEROVIC B,KOVACEVIC K,et al.The effect of residuals on the susceptibility to surface cracking and hot deformability of plain carbon steels[J].Materials and Technology,2002,36(3/4):107-113.

[7]　CHEN R Y and YUEN W Y D.Copper enrichment behaviours of copper-containing steels in simulated thin-slab casting processes[J].ISIJ International,2005,45(6):807-816.

[8]　OHTANI H,SUDA H and ISHIDA K.Solid/liquid equilibria in Fe-Cu based ternary systems[J].Transactions of the Iron & Steel Institute of Japan,1997,37(3):207-216.

[9]　WEBLER B A and SRIDHAR S.Effects of 0.1wt.% man-ganese,aluminum,and silicon on oxidation and copper-rich liquid phase formation in an iron- 0.3wt.% copper-0.15wt.% nickel alloy[J].Oxidation of Metals,2009,71(1/2):21- 42.

[10]　AKAMATSU S,SENUMA T,TAKADA Y,et al.Effect of nickel and tin additions on formation of liquid phase in copper bearing steels during high temperature oxidation[J].Materials Science and Technology,1999,15(11):1301-1307.

[11]　WEBLER B A and SRIDHAR S.The effect of silicon on the high temperature oxidation behavior of low-carbon steels containing the residual elements copper and nickel[J].ISIJ International,2007,47(9):1245-1254.

[12]　DONG H J,ZHANG H,CHE M J,et al.Effects of Si on Cu enrichment at copper-containing steel surface after high temperature oxidation[J].Iron and Steel,2010,45(2):86-89.

[13]　SEO S J,ASAKURA K and SHIBATA K.Effects of 0.4%Si and 0.02%P additions on surface hot shortness in 0.1%C- 0.5%Mn steels containing 0.5%Cu[J].ISIJ International,1997,37(3):240-249.

[14]　NAGASAKI C,KAGA M,SHIBATA K,et al.Effect of boron on copper induced surface hot shortness of 0.1% carbon steel[J].ISIJ International,2002,42(S):57-61.

[15]　HUANG X H.Principles of steel metallurgy[M].Beijing:Metallurgical Industry Press,1981:242.

[16]　FUKAGAWA T and FUJIKAWA H.Effect of small amounts of Ni on liquid-Cu embrittlement in hot-rolled mild steel after high-temperature oxidation[J].Oxidation of Metals,1999,52(3/4):177-194.

[17]　CHEN R Y and YUEN W Y D.Isothermal and step isothermal oxidation of copper-containing steels in air at 980-1 220 ℃[J].Oxidation of Metals,2005,63(3/4):145-168.

[18]　CHEN R Y and YUEN W Y D.Review of the high-temperature oxidation of iron and carbon steels in air or oxygen[J].Oxidation of Metals,2003,59(5/6):433- 468.

[19]　YIN L,BALAJI S and SRIDHAR S.Effects of nickel on the oxide/metal interface morphology and oxidation rate during high-temperature oxidation of Fe-Cu-Ni alloys[J].Metallurgical and Materials Transactions B,2010,41(3):598-611.

[20]　PIWOWARSKY E and SÖHNCHEN E.Über den Einfluss von Aluminium auf Gusseisen[J].Metallwirtschaft,1933,12:417- 421.

[21]　MORRIS L A and SMELTZER W W.The kinetics of wustite scale formation on iron-nickel alloys[J].Acta Metallurgica,1967,15(10):1591-1596.

[22]　FISHER G L.The effect of nickel on the high-temperature oxidation characteristics of copper-bearing steels[J].Journal of the Iron and Steel Institute,1969,207(7):1010-1016.

[23]　YI M Z and LIN J S.Overview on the internal oxidation of steels[J].Journal of Xi’an University of Technology,1988,4(1):131-139.

[24]　YI M Z and LIN J S.Theoretical analysis and application of the kinetics of internal oxidation of steels[J].Hot Working Technology,1989(5):3-8.

[25]　CHEN R Y and YUEN W Y D.Examination of oxide scales of hot rolled steel products[J].ISIJ International,2005,45(1):52-59.

[26]　WEBLER B,YIN L and SRIDHAR S.Effects of small additions of copper and copper+nickel on the oxidation behavior of iron[J].Metallurgical and Materials Transactions B,2008,39(5):725-737.

[27]　BÖHM G and KAHLWEIT M.Über die innere Oxydation von Metallegierungen[J].Acta Metallurgica,1964,12(5):641-648.

[28]　MORI T,ICHINOSE H and MORROKA A.Tekkoubinran Ⅲ[M].3rd edn.Tokyo:Iron Steel Inst.J.,1981:3-17.