9Cr-ODS钢的烧结收缩动力学曲线特征

以N2气雾化的9CrW铁基合金粉末和纳米Y2O3粉末为原料,采用放电等离子烧结(SPS)工艺制备9Cr-ODS钢。通过SPS温度和位移测量单元研究烧结压力、升温速率和Y2O3含量对烧结过程中9Cr-ODS钢烧结收缩动力学曲线的影响,并对其显微组织和力学性能进行观察和测试。结果表明,增加烧结压力能够使9CrW铁基合金粉末在较低的温度下完成烧结收缩过程。升温速率增大时,收缩曲线向高温区移动,剧烈收缩温度、最大收缩速率和密度均有所提高。Y2O3的加入可阻碍收缩致密化过程,导致曲线的最大收缩速率降低,并且力学性能测试结果表明Y2O3的加入可提高材料的拉伸性能,通过添加质量分数为0.35%的Y2O3可使得材料的抗拉强度和屈服强度分别提高到1 653 MPa和1 405 MPa。

放电等离子烧结制备9Cr-ODS钢的组织与力学性能

采用放电等离子烧结（Spark plasma sintering,SPS）工艺制备了成分为Fe-9Cr-1.5W-0.4Mn-0.2V-0.1Ta-0.3Ti-0.3Y2O3（质量分数,%）的9Cr-ODS钢。利用扫描电镜（SEM）、透射电镜（TEM）、电子背散射衍射（EBSD）、高分辨透射电镜（HRTEM）对ODS钢的宏观烧结特征、晶粒形貌、析出相形貌等进行表征。利用万能拉伸试验机测量不同温度下样品的力学性能。结果表明：通过放电等离子体烧结工艺可以制备出具有超细晶粒的ODS钢,950℃/5 min时烧结效果最好,致密度达到97.7%。950℃/5 min烧结后样品的晶粒呈现粉末颗粒表面晶粒粗大（〉1μm）而内部晶粒细小（纳米级）的现象,样品内的析出相以高密度、纳米尺寸、弥散分布的纳米团簇为主,其分布密度可以达到5.1×10^22个/m^3,同时还发现了少量化学计量比的Y2Ti2O7。放电等离子体950℃/5 min烧结样品的常温和650℃拉伸强度分别达1040 MPa和407 MPa。

热等静压成型温度对雾化合金粉制备的9Cr-ODS合金钢组织及拉伸性能的影响

以雾化合金粉为原料采用热等静压成型制备了9Cr-ODS合金钢。首先,使用扫描电镜(SEM)和能谱仪(EDS)分析了雾化法制备的合金粉的表面形貌和化学成分。利用电子背散射衍射(EBSD)、透射电镜(TEM)、小角X射线散射(SAXS)等研究了9Cr-ODS合金钢的晶粒形貌及平均尺寸、析出相的形貌及分布密度。结果表明:随着热等静压温度的升高,9Cr-ODS合金钢样品的晶粒逐渐长大,抗拉强度逐渐降低;900℃成型制备的9Cr-ODS合金钢的平均晶粒尺寸为0.62μm,其强度高于其他两个成型温度制备的样品。9Cr-ODS合金钢中各类型析出相的分布密度随着成型温度的升高而降低,尺寸则呈现长大的趋势。测试温度越高样品的抗拉强度越低,700℃测量时3个样品的抗拉强度比较接近。测试温度的升高会使样品的伸长率升高,但900℃成型制备的样品的伸长率在700℃测量时出现下降的现象。

Formation of FeMo_2B_2 phase in boron containing 9Cr-1.5Mo ferritic steels

The segregation and diffusion of boron during heat treatments were studied. The influence of boron contents, aging time and applied stress on FeMo2B2 formation was also studied. Finally, the effects of boron contents and FeMo2B2 formation on the high temperature strength were studied. Boron atoms were segregated to prior austenite grain boundary during normalizing treatment. And these boron atoms were slowly diffused into the grain interior during tempering and aging at 700 ℃. The FeMo2B2 phase was only formed after 1,000 h aging at 700 ℃ in alloy containing 196 ppm boron. The formation of FeMo2B2 phase is accelerated by the applied stress. It was expected that the formation of FeMo2B2 is closely related to the redistribution of boron atoms. The tensile strengths at 700 ℃ are increased with the increase of boron contents. However, the formation of FeMo2B2 phase results in lower tensile strength.

乌兹别克斯坦9度区某超高层建筑结构设计与优化

对于9度设防地区的超高层建筑,其结构设计基本由地震作用控制,因此抗震设计尤为重要。建筑消能减震技术可在提高结构地震安全储备的同时,降低整体工程造价,是结构优化设计的有效措施。对位于9度区的超高层建筑进行了结构方案选型对比、结构方案优化、减震设计方案比选、剪力墙内嵌钢板优化。结果显示,钢骨混凝土框架⁃核心筒方案相对于钢框架⁃支撑方案具备更高的成本优势;框架⁃核心筒方案可通过精细化设计作进一步优化;在此基础上,对钢骨混凝土框架⁃核心筒方案采用两种消能减震方案进行比选,结果表明,采用黏滞阻尼器方案的结构抗震性能明显优于采用黏滞阻尼墙方案;最后通过增大剪力墙竖向分布钢筋配筋率,对低区核心筒墙肢中的内嵌钢板进行了优化。

Effect of Rare Earth Elements on Austenite Growth Dynamics of Steel 9Cr2Mo

The growth dynamics of austenite grain was investigated in steel 9Cr2 Mo with different rare earth(RE)element addition.The results show that austenite grains of steel 9Cr2 Mo can be refined and their growth can be restrained by adding a certain amount of RE.According to the results,the n and Q were calculated and the mechanism of the refinement of austenite grains was discussed.

Microstructure of Steel 5Cr21Mn9Ni4N Alloyed by Rare Earth

The microstructure, composition and shape of precipitated phase under as-cast and finished product state of 5Cr21Mn9Ni4N steel with different rare earth （RE） amount were studied. Mechanical properties of 5Cr21Mn9Ni4N steels withont RE addition and with RE added by 0. 2% in mass percent were tested respectively. The results indicate that the solid solution amount of RE is about 10^-6 -10^-5 order of magnitude in 5Cr21Mn9Ni4N steel. Dendrite of as-cast condition is refined obviously and dimension of interstitial phase is shortened when RE is added by 0.10%-0.20%. But the microstructure will be coarser if surplus RE is added. Precipitated phase under finished product state distributes evenly in nearly same size with RE added by 0. 2% which leads to a largely improved high temperature mechanical property.

Deformation behaviors of 21-6-9 stainless steel tube numerical control bending under different friction conditions

For contact dominated numerical control(NC) bending process of tube, the effect of friction on bending deformation behaviors should be focused on to achieve precision bending forming. A three dimensional(3D) elastic-plastic finite element(FE) model of NC bending process was established under ABAQUS/Explicit platform, and its reliability was validated by the experiment. Then, numerical study on bending deformation behaviors under different frictions between tube and various dies was explored from multiple aspects such as wrinkling, wall thickness change and cross section deformation. The results show that the large friction of wiper die-tube reduces the wrinkling wave ratio η and cross section deformation degree ΔD and increases the wall thinning degree Δt. The large friction of mandrel-tube causes large η, Δt and ΔD, and the onset of wrinkling near clamp die. The large friction of pressure die-tube reduces Δt and ΔD, and the friction on this interface has little effect on η. The large friction of bending die-tube reduces η and ΔD, and the friction on this interface has little effect on Δt. The reasonable friction coefficients on wiper die-tube, mandrel-tube, pressure die-tube and bending die-tube of 21-6-9(0Cr21Ni6Mn9N) stainless steel tube in NC bending are 0.05-0.15, 0.05-0.15, 0.25-0.35 and 0.25-0.35, respectively. The results can provide a guideline for applying the friction conditions to establish the robust bending environment for stable and precise bending deformation of tube bending.

Study on wear resistant cast B-containing 1Cr18Ni9Ti stainless steel

The developed 1Cr18Ni9Ti austenitic stainless steel containing 1.63 wt.%B have been characterized by X-ray diffraction(XRD),electron probe microanalyzer(EPMA),optical microscopy(OM),scanning electron microscopy(SEM),energy dispersive X-ray spectroscopy(EDS)and Vickers microhardness measurement.The microstructural evolution and property of high boron stainless steel after solution treatment at the temperature of 1050℃are also investigated.The results show that the main compositions of borides are Fe,Cr and B,and with small amount of Ni,Mn and C elements.Silicon is insoluble in the borides.The hardness of borides is over 1,500 HV.It has been found that borides do not decompose during solution treatment,but part of borides dissolves into the matrix. The effect of increasing the solubility of boron element in the austenitic matrix favours the hardness enhancement by 8.54%.High boron stainless steel has excellent wear resistance in corrosive environment.Lifetime of transfer pipe made of high boron-containing stainless steel is 1.5-1.8 times longer than that of boron-free 1Cr18Ni9Ti stainless steel.

Effect of Rare Earth Elements on Quenching Crack Resistance of Steel 9Cr2Mo

The effect of rare earth elements on quenching crack resistance of steel 9Cr2Mo was investigated by means of scanning electron microscopy (SEM) and optical microscopy. Experimental results show that, by adding RE elements to steel 9Cr2Mo, the number of quenching for crack initiation is increased. Meanwhile the propagation of quenching cracks is postponed and the paths of crack propagation are changed. Therefore, quenching crack resistance can be improved by adding RE elements to steel 9Cr2Mo.

Cyclic oxidation behavior of Fe-9Cr-1Mo steel in water vapor atmosphere

The cyclic oxidation behavior of Fe-9Cr-1Mo steel (9Cr-1Mo) in 10%H2O+90%Ar (volume fraction) atmosphere at 600, 650 and 700 ℃ for various time was studied. The oxidation mechanism of 9Cr-1Mo steel in 10%H2O+90%Ar atmosphere was discussed. The thermal stress was evaluated in two oxide layers to illustrate the spallation of the oxide layer. The experimental results indicate that there exists a duplex oxide scale with an outer layer of Fe2O3 and an inner layer of mixed (Fe, Cr)3O4 formed on 9Cr-1Mo steel during cyclic oxidation. Some cracks generated in both inner and outer oxide layers. Parts of oxide scales spalled from substrate during the cyclic oxidation. A higher tensile stress in the oxide layer is formed at the early oxidation stage than at the later oxidation stage during heating. This tensile stress results in the formation of cracks in the oxide layer.

FORMATION OF PRECIPITATED AUSTENITE IN 9%Ni STEEL AND ITS PERFORMANCE AT CRYOGENIC TEMPERATURE

The formation of precipitated austenite in 9% Ni steel exposed at the temperature of α+γ re- gion and its influence on impact tonghness at cryogenic temperature have been studied. Austenite-rich and ferrite-rich bands are formed during soaking because of the re-distribu- tion of elements of C,N and Ni.The former phase is enriched of Ni,Mn,C and N,while the latter one is relatively pure.Part of the austenite formed at intermediate temperatures trans- forms into martensite when the steel is cooled down to room temperature.The complex struc- ture which consists of fine martensite and austenite exhibits a moderate strength and high enough cryogenic toughness.The austenite enriched of C,N and Ni is still stable at the cryogenic temperature.The tearing ridges on the impact fracture surface is densely occupied by the precipitated austenite,elongated along the tearing direction.One of the important cause of the excellent eryogenic properties is that the precipitated austenite absorbs the impurities and thus purifies the matrix of the steel.

Effect of Rare Earth on Thermal Shock Resistance of Steel 9Cr2Mo

The effect of rare earth elements on thermal shock resistance of cold roller steel 9Cr2Mo was investigated by means of X-ray diffractometry and optical microscopy. Experimental results show that the process of carbide precipitation of heat effect zone is restrained by adding RE elements in steel 9Cr2Mo. Therefore, thermal shock resistance of this steel can be improved.

INFLUENCE OF PHASE COMPOSITION ON PITTING CORROSION RESISTANCE OF SPUTTERED COATING OF 1Cr18Ni9Ti STAINLESS STEEL

A series of single bcc,bcc plus fcc duplex and single fcc microcrystalline coatings of 1Cr18Ni9Ti stainless steel were prepared by using sputtering technique.The resistance against pitting corrosion was studied by measurements of pitting corrosion potentials and electrochemical noise during initiation of corrosion pits.The results show that the sputtered coatings with single bcc phase or single fcc structure are more resistant to pitting corrosion than those with bcc plus fcc duplex phase structure.

Prospects for 12Cr martensitic creep resistant steels for 650℃steam power plant

In the last three decades new stronger modified 9%Cr steels have been introduced in new power plants with steam parameters up to 300 bar(1 bar =10~5 Pa) and 600℃. In order to further increase the steam parameters of steel based power plants up to a target value of 650℃/ 325 bar it is necessary to double the creep strength compared with todays strongest 9%Cr steels,and at the same time the resistance against steam oxidation must be improved by adding 12%Cr to the steel. However,so far all attempts to make stronger 12%Cr steels have been unsuccessful because the high chromium content introduced severe microstructure instabilities in the tested steels.Recently,it was found that the microstructure instabilities in 11%- 12%Cr steels can be explained by the precipitation of coarse Cr(V,Nb)N Z-phases, which dissolve fine(V,Nb)N nitrides. A new possibility to use the Z-phase for strengthening of 12%Cr steels has been identified,and the development of stable strong martensitic 12%Cr steels based on this concept is expected to allow the construction of 325 bar/ 650℃steam power plants all based on steel.

Study of High Temperature Deformation and Recrystallization in W9Mo3Cr4V Steel

The behavior of high temperature deformation and recrystallization of W9Mo3Cr4V steel have been studied in this paper. Dynamic precipitation during deformation has also been investigated. In W9Mo3Cr4V steel, stress strain curves exhibit many features. The deformation structures and the effects of deformation parameters on dynamic recrystallization are more complicated than those in low alloy steels. For W9Mo3Cr4V steel, there is a large number of residual carbides on the matrix at high temperature. Also, many second carbides precipitate from the matrix during high temperature deformation. These two kinds of carbides (especially the latter) make the behavior of deformation and dynamic recrystallization in W9Mo3Cr4V steel different from those in low alloy steels. ABSTRACT:The behavior of high temperature deformation and recrystallization of W9Mo3Cr4V steel have been studied in this paper. Dynamic precipitation during deformation has also been investigated. In W9Mo3Cr4V steel, stress strain curves exhibit many features. The deformation structures and the effects of deformation parameters on dynamic recrystallization are more complicated than those in low alloy steels. For W9Mo3Cr4V steel, there is a large number of residual carbides on the matrix at high temperature. Also, many second carbides precipitate from the matrix during high temperature deformation. These two kinds of carbides (especially the latter) make the behavior of deformation and dynamic recrystallization in W9Mo3Cr4V steel different from those in low alloy steels.

High-Temperature Oxidation Behavior of 5Cr21Mn9Ni4N Steel Micro-Alloyed by Rare Earth

The oxidation resistance of 5Cr21Mn9Ni4N steel micro-alloying by RE at 700 - 900 ℃ was investigated. The results indicate that oxidation exponent n and oxidation activation energy are increased, and oxidation velocity constant kp is decreased when 0.2% RE is added in 5Cr21Mn9Ni4N steel. The addition of RE elements does not alter phase constitution of oxidation scale, however it improves the configuration of oxidation scale, and increases thermal stability and adhesivity of oxidation scale, which results in the raise of oxidation resistance of 5Cr21Mn9Ni4N steel at high temperature. The oxidation scale constitutes of refractory steel transfer from manganic oxide mostly to ferric oxide mostly with the increase of temperature, which leads to descend of compactness and desquamation resistance of oxidation scale. The mass increase of ferric oxide in the oxidation scale and the looseness of oxidation scale are the main reason to descend the oxidation resistance of refractory steel.

Hot Corrosion Behavior of Sol-Gel Nano Structured Zirconia Coated 9Cr1Mo Ferritic Steel in Alkali Metal Chlorides and Sulphates Deposit Systems at High Temperatures

Fused salt accelerated hot corrosion is quite common in gas turbines, fossil fuelled devices, waste inclinators, pyrochemical systems, etc. Presence of fused salt on metal surface dissolves their existing oxide layer. This results in an increase in oxidation rate of the metal. Since, zirconia coating is well recognized for corrosion protection under high temperature oxidative environment, we have developed zirconia coating on 9Cr1Mo ferritic steel and their oxidation performance was evaluated in LiCl-NaCl and Na2SO4-K2SO4 salts deposit system in air atmosphere at 650?C and 850?C, respectively. Before coating development, zirconium based sol was synthesized using zirconium (IV) propoxide as a precursor. Oxidation test results indicated that the zirconia coated specimens shows more than two times higher corrosion resistance in LiCl-NaCl and three time higher corrosion resistance in Na2SO4-K2SO4 salt deposit, respectively.

INFLUENCE OF RARE EARTH ON INTERGRANULAR CRACKING OF 9% Ni CAST STEEL

The intergranular cracking of 9% Ni cast steel seems mainly to relate to the segregation of contaminates H,S and P along boundaries.An addition of rare earth may eliminate the seg- regation of these contaminates along grain boundaries and improve the binding force among boundaries,so as to reduce remarkably the intergranular cracking.

EFFECT OF AGING ON HYDROGEN EMBRITTLEMENT SUSCEPTIBILITY OF STEEL Cr21Ni6Mn9N

Effects of 650℃ aging for 1—1000 h on structure and hydrogen embrittlement susceptibility (HES)of steel Cr21Ni6Mn9N have been investigated.The results show that M_(23)C_6 type carbide precipitates at grain boundaries and Cr-depletive region appears beside them during aging.The precipitates grow and connect each other as the aging time prolongs.Meanwhile, the degree of Cr-depletion aggravates first and then recovers gradually while the aging time is very long,i.e.,1000 h.The HES of the steel increases with increasing aging time but does not reduce with the recovery of Cr content at the Cr-depletive region.That implies that the ex- isting of carbides at grain boundaries might be the main reason which promotes the HES of steel during aging.