热轧工艺对高铝铁素体耐热不锈钢组织性能的影响

电站锅炉的连接件需具有优良的抗高温氧化性、冲击韧性和塑性，主要采用铁素体耐热不锈钢0.1C-18Cr-1Al-1Si制造，热轧工艺对其塑韧性能有至关重要的影响。采用热轧试验，研究了不同热轧工艺对铁素体耐热不锈钢0.1C-18Cr-1Al-1Si组织性能的影响规律。结果表明，热轧温度为700 ℃时，0.1C-18Cr-1Al-1Si热轧板的再结晶最充分；横纵轧和纵轧不同轧制方式下0.1C-18Cr-1Al-1Si板材小角度晶界比例均较高，边部小角度晶界出现频率更高；采用横纵轧工艺可以明显减轻0.1C-18Cr-1Al-1Si板材力学性能的各向异性。     

铁素体耐热不锈钢0.1C-18Cr-1Al-1Si铸造合金析出相研究

采用相图计算、透射电子显微镜分析等手段,研究了铁素体耐热不锈钢0.1C-18Cr-1Al-1Si铸造合金析出相种类、析出规律和形貌。结果表明:0.1C-18Cr-1Al-1Si在平衡状态下平衡相由铁素体相、α-Cr相、AlN相、M_7C_3相、M_(23)C_6相等组成;随着温度降低,M_(23)C_6相中C含量先升高后降低,Fe含量逐渐降低,Cr含量逐渐升高;M_(23)C_6相具有复杂面心结构,M_7C_3晶体结构为正交结构;AlN为密排六方结构,密排面为(0001),密排面的面间距d=0.476 nm。     

热变形及冷却条件对0.1%C-2%Si钢双相组织形成的影响

研究了热变形及冷却条件对0.1％C-2％Si钢双相组织形成的影响。结果表明:终轧温度与冷却速度影响钢的双相组织形成及最终马氏体与铁素体双相组织相对量;通过控轧、控冷,0.1％C-2％Si钢可获得理想的铁素体加～20％马氏体热轧双相组织。     

热处理对0.1C-18Cr-1Al-1Si铁素体耐热钢力学性能的影响

采用热处理试验、力学性能测试、扫描电镜观察等方法,研究了不同热处理制度对铁素体耐热不锈钢0.1C-18Cr-1Al-1Si力学性能的影响。结果表明:随着退火温度的提高,钢的屈服强度和抗拉强度先增高后保持不变,伸长率和90℃下的冲击功先增高后降低且在850℃退火达到最大值,断裂类型也从脆性断裂转变为韧性断裂再转变为脆性断裂;随着退火时间的延长,钢的屈服强度、抗拉强度、90℃下的冲击功逐渐增高,伸长率逐渐降低;退火温度和退火时间对硬度、20℃冲击功的影响不大;850℃/15 min退火后经不同温度的回火和不同条件的冷却,钢的强度和伸长率变化不大。     

终轧温度对PQ600钢组织及性能的影响

设计了高温、中温和低温3种终轧温度,在现场进行了工业试验,研究不同终轧温度对PQ600高强工程机械用钢组织和性能的影响,确定了钢的热轧工艺参数。结果表明:降低终轧温度可以提高未结晶区的变形量,细化铁素体晶粒,充分发挥细晶强化作用;高温终轧的金相组织是铁素体和珠光体的混合物,铁素体组织均匀性较差,中温终轧和低温终轧的组织是铁素体和珠光体,铁素体晶粒比较规则,而且低温终轧的均匀性比中温终轧好。高温终轧的铁素体晶界明显存在M3C型复合条状或短棒状的碳化物。     

42CrMo钢轧制工艺优化

针对某轧钢厂生产的Φ100 mm以下规格42Cr Mo钢热轧态硬度超标现象,研究了常规轧制工艺和控轧控冷工艺,分析了不同工艺参数对42Cr Mo钢金相组织与硬度的影响。通过优化工艺参数,将终轧温度控制在830~850℃,轧后保温罩冷却速率控制在0.1~0.2℃·s-1,出保温罩温度控制在400~500℃。结果表明:采用常规轧制工艺,42Cr Mo钢的硬度值普遍在290~330 HBW之间,金相组织主要为贝氏体;采用控轧控冷工艺,42Cr Mo钢的硬度值可控制在220~260 HBW之间,金相组织为铁素体与珠光体;通过优化在线轧制工艺参数,42Cr Mo钢热轧态硬度满足了标准要求,降低了生产成本,提高了钢材的市场竞争力。     

高品质热轧双相钢的开发

为了提高热轧双相钢的品质,研究了化学成分、轧制工艺、冷却工艺和不同季节水温等参数对热轧双相钢组织和性能的影响。结果表明,无Si成分设计显著提高了热轧双相钢的表面质量;较低的终轧温度和中间保温温度有利于获得更为细小的铁素体组织和弥散的马氏体组织;低的卷取温度（280 ℃）可以获得铁素体+马氏体双相组织;冷却水水温的降低显著提高马氏体含量并提高双相钢的强度。基于上述研究,邯钢实现了系列热轧双相钢的稳定生产,双相钢制作的汽车车轮性能良好。     

包覆叠轧TA7钛合金薄板的组织与力学性能

为了解决TA7钛合金板材冷加工困难的状况,对TA7钛合金薄板采用包覆叠轧工艺进行热轧直接成品轧制,可以有效简化工艺、降低成本。分析两种不同加工工艺下板材的组织、织构与性能。结果表明:采用包覆叠轧工艺可以使TA7钛合金板材获得较好的组织,具备较好的综合力学性能。     

热轧后补热对超级铁素体不锈钢中σ-相析出行为的影响

研究了热轧后补热工艺对27.6Cr-3.7Mo-2Ni超级铁素体不锈钢中σ-相析出行为的影响.结果 表明:热轧组织冷却过程中易形成σ-相、Laves相等脆性中间相.热轧后经1150℃短时间补热可以消除热轧变形组织,形成完全再结晶组织,有效减弱σ-相析出动力学,为热轧后冷却提供了更宽的时间窗口.     

温轧对6061铝合金铸轧板材显微组织和力学性能的影响

文主要是研究温轧对双辊铸轧6061铝合金板材进行处理,观察不同温轧温度及累积压下量对铸轧板材的影响。采用光学显微镜(OM),扫描电镜(SEM),X射线衍射仪(XRD),显微硬度仪和万能拉伸机等设备,观察了铸轧板材及温轧板材的显微组织,获得了材料的硬度、强度和延伸率等力学性能。研究表明,铸轧6061合金中主要含有耐热相Al0.7Fe3Si0.3、Al9Fe0.84Mn2.16Si及少量强化相Mg₂Si。合金中第二相随温轧道次的递增逐渐由网格状、片状转变为沿轧制方向的线条状,最终变为细小的颗粒状。经过温轧后,产生新的析出相Al0.5Fe3Si0.5且Mg₂Si析出相增多。铸轧板材温轧后,硬度随压下量的增大呈线性递增,且当温轧温度为370℃时,硬度曲线斜率最大为2.42114。此时细小的AlFeSi类析出相及Mg₂Si强化相均匀弥散分布于合金中,板材的硬度最大,可达84.28 HV,抗拉强度、屈服强度和延伸率分别为209.34 MPa、79.09 MPa和20.11％。     

Microstructure,texture and grain boundaries character distribution evolution of ferritic stainless steel during rolling process

In order to better understand the texture, microstructure and grain boundaries character distribution evolution of ferritic stainless steel, the texture, microstructure and grain boundaries character distribution of ferritic stainless steel (hot rolled sheet, cold rolled sheet and annealing sheet) with 11 wt%Cr content were studied using X-ray diffraction and electron back scattered diffraction technique. The texture of the hot and cold rolled sheets has a through-thickness texture gradient. In the center layer of the hot and cold rolling sheet, α-fiber texture was observed which was attributed to ideal plane strain deformation. Close to the surface a Gross orientation was detected which was attributed to shear deformation. During annealing, the γ-fiber was formed attributed to recrystallization process. The microstructure of the hot and cold rolled sheets was non-homogeneous through the sheet thickness, while, the microstructure of annealing sheets was homogeneous through the sheet thickness. Grain boundaries character distribution results show that there are many low angle grain boundaries in hot and cold rolled sheets and many high angle grain boundaries and coincidence site lattice after annealing. The above results indicated that the changes in texture are closely related to the grain boundaries type.     

不同镍含量奥氏体基低密度热轧钢的组织与力学性能

研究了3种Fe-18Mn-10Al-1C-(0, 3, 5)Ni-0.08V-0.03Nb(wt%)奥氏体基低密度双相钢在热轧后的组织和力学性能。结果表明,热轧后,试验钢的组织由拉长的奥氏体、条带状B2相及沿再结晶奥氏体晶粒晶界处的块状B2颗粒组成。此外,在奥氏体晶粒和B2颗粒中分别形成了纳米级κ-碳化物和DO₃相。5Ni钢屈服强度高达1352 MPa,这主要是由于奥氏体晶界存在大量纳米级别的B2颗粒以及VC相产生析出强化效果。随着Ni含量的增加,钢的强度与硬度均增加,5Ni钢屈服强度比0Ni钢高116 MPa,归因于5Ni钢中更多的B2相含量(16.9%)。但含Ni钢在强度增加的同时,极大损失了塑性,导致钢的伸长率极低,分析其原因为条带状B2相主要分布在奥氏体晶界处,试样在变形过程中裂纹更易沿晶界断裂,断口有分层现象。     

EF08高合金钢热轧工艺研究

通过相图、轧制理论以及对热轧带钢金相组织的观察,对比分析了EF08钢、410S铁素体不锈钢和304奥氏体不锈钢热轧过程中的变形抗力和动态回复再结晶能力。结果表明：EF08钢奥氏体区在900~1 200 ℃,热轧过程处于奥氏体相区,其动态回复再结晶能力较410S铁素体不锈钢和304奥氏体不锈钢强;EF08钢的粗轧过程轧制特性与304奥氏体不锈钢相近,精轧后几道次与410S铁素体不锈钢类似。     

00Cr12NiNbTi不锈钢热轧中析出行为

对00Cr12N iNbTi铁素体不锈钢进行加热、粗轧、精轧及卷取过程的模拟实验,应用扫描电镜、透射电镜、化学相分析及热模拟等方法对试样中析出物进行了定性定量分析。结果表明:加热到1140℃,保温0、45和90 m in后,粒子主要为TiN,Ti的固溶率为66.3%,N的固溶率为1.3%;从粗轧到精轧,微米级的小颗粒减少,大颗粒增多,颗粒平均尺寸由1.8μm增大到3.2μm,有聚集长大现象;在热轧过程中微米级粒子形貌为方形或球形,基本保持稳定;纳米级的(Nb,Ti)C颗粒在精轧阶段开始析出,卷取保温及缓冷至室温过程中大量析出,多分布于晶界及晶内处,在较高温度下卷取会析出较多的纳米级(Nb,Ti)C颗粒。     

Influence of Finish Rolling Temperature on Microstructure and Mechanical Properties of a 19Cr1.5Mo0.5W Ferritic Stainless Steel

A 444-type heat-resistant ferritic stainless steel containing 0.05 wt% Ce(rare earth element) and 2 wt%(Mo+W) was adopted as an experimental material to study the effect of finish rolling temperature on microstructure and texture evolution as well as on mechanical properties and formability.The rolling processes contain hot rolling at two different finish rolling temperatures(860℃ and 770℃) and annealing,cold rolling and subsequent annealing.It was found that the microstructures after hot rolling and annealing could be refined by lowering finish rolling temperature.The resultant microstructures after cold rolling and annealing were hereditarily refined.Lowering finish rolling temperature can weaken α-fiber texture in hotrolled or cold-rolled ferritic stainless steel strip,while γ-fiber texture in the final product was homogeneously strengthened.Additionally,enhanced mechanical property and formability in terms of strength and average plastic strain ratio could be obtained via decreasing finish rolling temperature.     

终轧温度对含钛铌超低碳铁素体不锈钢显微组织、织构和力学性能的影响

实验室研究了终轧温度对钛、铌复合添加的16%Cr超低碳氮铁素体不锈钢的显微组织、织构和力学性能的影响。结果表明,当终轧温度从940℃降低到800℃时,热轧退火钢板和冷轧退火钢板的铁素体晶粒尺寸均减小,因此采用低温终轧有利于细化铁素体晶粒。降低终轧温度,热轧退火后钢板中形成的γ纤维明显增强且比较均匀。由于织构具有遗传性,在冷轧退火钢板中也形成了均匀的γ再结晶织构。采用较低的终轧温度既有利于提高成型性又有利于改善材料的各向异性。     

Dynamic Precipitation of Laves Phase and Grain Boundary Features in Warm Deformed FeCrAl Alloy:Effect of Zr

Warm compression deformation of Fe-13.5％Cr-4.7％Al-2.0％Mo-0.70％Nb-0.40Ta (wt％) (FeCrAl) and Fe-13.5％Cr-4.7％Al-2.0％Mo-0.45％Nb-0.40Ta-0.11Zr (wt％) (FeCrAl-Zr) ferritic stainless steel was performed by a thermal simulation machine Gleeble 3800 at 600 ℃ and strain rates of 0.01-10 s-1.Before deformation,all the samples were solution-annealed for 2 h at 1150 ℃ for FeCrAl alloy and 1250 ℃ for FeCrAl-Zr alloy.The strain rate has little or no effect on peak stress,and the precipitates in matrix or grain boundary precipitates (GBPs) have no difference in the samples deformed at the strain rate 0.01 s-1 and 1 s-1 both in FeCrAl and FeCrAl-Zr alloys.The addition of Zr increased the proportion of low-angle grain boundaries (LAGBs).The Laves phase in FeCrAl alloy precipitated uniform in the matrix,while in FeCrAl-Zr alloy Laves phase precipitated at grain boundary and formed GBP.The LAGBs and ∑3 coincident site lattice (CSL) grain boundary both increased in FeCrAl-Zr alloy,which possessed some beneficial properties such as high-temperature creep resistance to the Fe-Cr-Al alloy.More interesting,twins were created by warm deformation,which was difficult in typical bcc ferrite alloy.These results could be expected to provide guidance for subsequent warm working processes for the alloy.     

Effect of Al-Si coating layer on the penetration and microstructures of ferritic stainless steel, 409L GTA welds

In this study, commercial 409L ferritic stainless steels and Al-8 wt% Si alloy-coated 409L ferritic stainless steels were subjected to gas tungsten arc welding and the effect of the coated layer on the penetration properties and microstructure were investigated. Full penetration was obtained with a welding current greater than 90 A and a welding speed lower than 0.52 m/min. At the full penetration condition, the bead width of Al-8 wt% Si alloy-coated 409L ferritic stainless steels was narrower than that of commercial 409L ferritic stainless steels. In these samples, a narrow and deep weld pool was considered to have formed under gas tungsten arc welding due to Marangoni convection with existing oxides in the Al-Si coating layer. The grain size of both materials was the largest in the fusion zone and decreased from near the heat-affected zone to the base metal. Especially, the grain size of the heat affected zone and the fusion zone of Al-8 wt% Si alloy-coated 409L ferritic stainless steels were small compared to those of commercial 409L ferritic stainless steels. The hardness was maximized in the fusion zone and decreased from the bond line to the base metal. The maximum hardness in the fusion zone was attributed to the re-precipitation of the TiN and Ti(C, N), which were present in the base metal with the finer grain size during the melting and solidification processes. However, the maximum hardness of Al-8 wt% Si alloy-coated 409L ferritic stainless steels was relatively high due to the formation of oxides such as Al₂O₃ and SiO₂ that originated from the dissolved elements from the coating layer.     

Microstructure and Mechanical Properties of Nb- and Nb+ Ti-Stabilised 18Cr-2Mo Ferritic Stainless Steels

To explore the optimum use of stabilised elements and study the influences of stabilisation in 18 Cr-2 Mo grades,the Nb and Nb+Ti microalloying investigation focused on the relationships of the microstructure and mechanical properties of the microalloyed 18 Cr-2 Mo ferritic stainless steel thick plates.Thermo-Calc calculation was performed to predict the equilibrium phase diagrams.Afterwards,the microstructure,i.e.grain size and precipitation,of as-annealed specimens was analysed by means of optical microscopy,scanning electron microscopy and transmission electron microscopy,X-ray diffraction and energydispersive spectroscopy.Also,electron backscatter diffraction mapping was constructed to characterise grain boundary.The mechanical properties,including tensile strength and impact toughness,were tested to correlate with the microstructure.The results show that the grain sizes of Nb-stabilised steel are comparatively smaller,which is related to the fine precipitation at the grain boundaries and beneficial to the impact toughness.The increase in its strength is not apparent due to the inhomogeneous grain sizes.The grain boundary characters are similar,which is not the main factor related to their mechanical properties.When Ti is added,TiN forms above the liquidus,and large TiN particles evidently impair impact toughness.