共查询到20条相似文献,搜索用时 31 毫秒
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Fitsum Feyissa D. Ravi Kumar P. Nageswara Rao 《Journal of Materials Engineering and Performance》2018,27(4):1614-1627
In this work, microstructure, mechanical properties and formability of cryorolled and annealed AA5083 alloy sheets have been characterized and a comparison has been made with cold rolled and annealed sheets. Five-millimeter-thick sheets of this alloy were cryorolled in multiple passes to a final thickness of 1 mm (80% reduction with a true strain of 1.6). Effect of annealing time and temperature on hardness has been studied, and it has been found that a short annealing at 275 °C for 15 min after cryorolling would yield a good combination of strength and ductility. Microstructural investigations showed that the cryorolled and short annealed samples possess bimodal grain structure which is responsible for better mechanical properties than cold rolled sheets. From the experimentally determined forming limit diagrams, the limit strains of cryorolled sheets have been found to be almost equal to conventional cold rolled and annealed sheets in all modes of deformation. No major differences have been found in strain distribution also. This work clearly demonstrates that cryorolling of AA5083 alloy sheets followed by a short annealing with bimodal grain structure can be used for sheet metal forming applications with higher strength and toughness than conventional sheets without any reduction in formability. 相似文献
3.
Haitao Yan Hongyun Bi Xin Li Zhou Xu 《Journal of Materials Processing Technology》2009,209(5):2627-2631
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. 相似文献
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《Science & Technology of Welding & Joining》2013,18(4):384-388
AbstractThe formability of welded dual phase 590 (DP 590) steel sheets was investigated, using both friction stir welding and laser welding. Similar and dissimilar gauge sheets were joined using both processes. The laser welded sheets were produced under process conditions typical of industrial production of tailor welded blanks. The friction stir welded specimens were produced in a lab, where different tool rotational speeds and translation speeds were investigated in order to obtain good weld properties. The formability of the welded sheets was evaluated using a series of mechanical tests, including transverse tension and plane strain formability testing. Friction stir welded specimens performed about the same as laser welded specimens in transverse tension testing; however, hardness profiles showed that the laser welds had greater peak hardness than the friction stir welds. Therefore plane strain formability tests were performed with the welds oriented along the major strain direction. When this type of weld stretching was performed the friction stir welded sheets were shown to be ~20% more formable than the laser welded sheets. 相似文献
5.
Riichi Murayama Kazuo Fujisawa Masahiko Hirao Hidekazu Fukuoka 《NDT & E International》1997,30(6):377-382
An ultrasonic technique for evaluation of the formability of zinc-coated steel sheets has been developed. The technique is based on the dispersion relation, which correlates the velocity anisotropy of the S0-mode Lamb wave to the texture defined by orientation distribution coefficients. In cold rolled steel sheets, we have already developed the evaluation system and installed it on two continuous annealing production lines. In this paper, we describe how to remove the effect of the zinc-coated layer from the measured velocity and the evaluation results of the formability for zinc-coated steel sheets. The coating induced a decrease in the S0-mode Lamb wave velocity. The change in ultrasonic velocity due to the zinc-coated layer has been shown to be compensated by using a simple correction curve, which enables the correction for the effect of zinc coating from the known coating/substrate thickness ratio. The test results indicate that the monitoring of the formability for zinc-coated steel sheets as well as for cold rolled steel sheets is quite feasible. 相似文献
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Tetsuo Oya Nicolas Tiesler Seiichiro Kawanishi Jun Yanagimoto Toshihiko Koseki 《Journal of Materials Processing Technology》2010,210(14):1926-1933
In this study, the bending formability of multilayered steel sheets is evaluated by tensile tests, V-bending tests, and hemming tests. Enhanced formability was observed in these experiments, namely, the constituent high-strength materials were elongated beyond the original fracture strain limit. As a result of this effect, multilayered steel sheets were successfully formed in V-bending tests and even in hemming tests. Observations using a scanning electron microscope verified that no delamination occurred at interfaces. To represent the geometrical features of a multilayered steel sheet, a solid-element model under an isostrain condition was utilized in finite element modeling, where the rule of mixtures was adopted to obtain the flow curve of the constituent high-strength material, and a good agreement with experimental results was observed. Analyses using this finite element model were conducted to investigate the effect of the geometry on the springback of multilayered steel sheets undergoing V-bending. 相似文献
7.
宝钢搪瓷用钢的开发与应用 总被引:2,自引:0,他引:2
简要介绍宝钢开发的冷轧和热轧搪瓷钢板的成分和工艺流程,阐述搪瓷钢板在成形性能、抗鳞爆性能以及强度等方面的要求,举例说明搪瓷钢的应用.结果表明,宝钢冷轧和热轧搪瓷钢能够满足不同搪瓷制品的生产需要. 相似文献
8.
The increasing use of high strength steels in a variety of mechanical engineering applications has illuminated problems associated with galling in sheet metal forming operations. Galling is a tribological phenomenon associated with transfer of material from the steel sheet to the tool surface during forming resulting in seizure of the tool/steel sheet contact and extensive scratching of the steel sheet surface. As a result, a number of concepts have been developed in order to reduce the tendency of galling in sheet metal forming, including the development of new dry lubricants, new forming tool steel grades and improved surface engineering treatments such as the deposition of low friction CVD- and PVD-coatings. In the present study the potential performance of three commercial PVD coatings, including CrN, (Ti,Al)N and a CrC/C DLC-based coating, in the forming of hot and cold rolled high strength steel as well as electro and hot-dip galvanized high strength steel has been evaluated using pin-on-disc testing under lubricated contact conditions. Post-test examination of the tribosurfaces using FEG-SEM and EDS analyses was performed in order to evaluate the mechanisms controlling the tendency to material transfer and wear. The results show that in contact with the hot and cold rolled steel the material pick-up tendency of the PVD coatings tend to increase in the order CrC/C-CrN-(Ti,Al)N while in contact with the two galvanized steel sheets, the CrC/C and the (Ti,Al)N coating show a significantly lower material pick-up tendency as compared with the CrN coating. Further, the substrate hardness has a strong influence on the wear of the PVD coatings and consequently on the friction characteristics and galling tendency of the coating/substrate composite. Low substrate hardness, resulting in a low load bearing capacity, increases the tendency to cracking and subsequently chipping of the brittle coating. 相似文献
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Warm and Hot Stamping of Ultra High Tensile Strength Steel Sheets Using Resistance Heating 总被引:5,自引:0,他引:5
A warm and hot stamping process of ultra high tensile strength steel sheets using resistance heating was developed to improve springback and formability. In this process, the decrease in temperature of the sheet before the forming is prevented by directly heating the sheets set into the dies by means of the electrical resistance, the so-called Joule heat. Since the heating time up to 800°C is only 2 seconds, the resistance heating is rapid enough to synchronise with a press. The effects of the heating temperature on the springback and formability of ultra high tensile strength steel sheets were examined. The springback in hat-shaped bending of the high tensile strength steel sheets was eliminated by heating the sheet. In addition, the ultra sheet having a tensile strength of 980MPa was successfully drawn by the heating. The heating temperature is optimum around 600°C due to the small springback and oxidation and the increase in hardness. 相似文献
11.
S. K. Paul U. Ahmed G. M. Megahed 《Journal of Materials Engineering and Performance》2011,20(7):1163-1170
Low-carbon Al-killed hot rolled strips for direct forming, cold rolling, and galvanizing applications are produced from the
similar chemistry at Ezz Flat Steel (EFS) through thin slab casting and rolling (TSCR) technology. The desired mechanical
and microstructural properties in hot bands for different applications are achieved through control of hot rolling parameters,
which in turn control the precipitation and growth of AlN. Nitrogen in solid solution strongly influences the yield strength
(YS), ductility, strain aging index (SAI), and other formability properties of steel. The equilibrium solubility of AlN in
austenite at different temperatures and its isothermal precipitation have been studied. To achieve the formability properties
for direct forming, soluble nitrogen is fixed as AlN by coiling the strip at higher temperatures. For stringent cold forming,
boron was added below the stoichiometric ratio with nitrogen, which improved the formability properties dramatically. The
requirements of hot band for processing into cold rolled and annealed deep drawing sheets are high SAI and fine-grain microstructure.
Higher finish rolling and low coiling temperatures are used to achieve these. Fully processed cold rolled sheets from these
hot strips at customer’s end have shown good formability properties. Coil break marks observed in some coils during uncoiling
were found to be associated with yielding phenomenon. The spike height (difference between upper and lower yield stresses)
and yield point elongation (YPE) were found to be the key material parameters for the break marks. Factors affecting these
parameters have been studied and the coiling temperature optimized to overcome the problem. 相似文献
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The relationship between the texture and mechanical properties of 6xxx aluminum alloy sheets processed via cross rolling was
investigated. The microstructures of the conventional rolled and cross rolled sheets after annealing were analyzed using optical
micrographs (OM). The texture distribution across the thickness in the Al-Mg-Si-Cu alloy, conventional rolled sheets, and
cross rolled sheets both before and after annealing was investigated via X-ray texture measurements. The texture was analyzed
in three layers from the surface to the center of the sheet. The β-fiber texture of the conventional rolled sheet was typical
of the texture obtained using aluminumoll ring. After annealing, the typical β-fiber orientations were changed to recrystallization
textures: cube{001}〈100〉 and normal direction (ND)-rotated cubes. However, the texture of the cross rolled sheet was composed
of an asymmetrical, rolling direction (RD)-rotated cubes. After annealing, the asymmetrical orientations in the cross rolled
sheet were changed to a randomized texture. The average R-value of the annealed cross rolled sheets was higher than that of
the conventional rolled sheets. The limit dome height (LDH) test results demonstrated that cross rolling is effective in improving
the formability of the Al-Mg-Si-Cu alloy sheets. 相似文献
13.
Qinglai Zhang Hailing Guo Fugui Xiao Lin Gao A.B. Bondarev Weidong Han 《Journal of Materials Processing Technology》2009,209(15-16):5514-5520
Single point incremental forming of the magnesium alloy AZ31 sheets, which were fabricated by hot extrusion, slab + hot/cold rolling, strip-casting rolling and cross-rolling, respectively, was investigated at elevated temperatures. The results show that the anisotropy of the sheets fabricated by casting slab + hot/cold rolling and cross-rolling is not remarkable, and the formability is improved significantly. The circular, square and rotary cone parts were performed with satisfactory surface quality and without any microcracks successfully, and which is superior to those of the extruded sheet and the one-way rolled sheet. Therefore, anisotropy of the sheets has remarkable effects on the surface quality of the formed parts, and the effect becomes weakened with increasing temperature. It is proposed that cross-rolling sheet is much more suitable for warm SPIF process. 相似文献
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通过对一批国产的和进口的低碳钢板材进行拉伸和胀形试验,研究了这种具有各向异性的轧制板材的冲压成形性能。结果表明,对于各向异性材料,冲压成形时破裂较易在应变比小的方位发生;等双拉应力状态与等双拉应变状态一般是不对应的,但在极值方位θ=45°处相互对应;而不同方位的硬化指数n值与破裂方位关系不明显。 相似文献
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系统研究了超纯铁素体不锈钢(w(Cr)=17%)沿钢板厚度方向各层织构的演变规律和不同精轧温度对织构演变及成形性能的影响规律。采用X射线衍射仪分析了宏观织构演变。研究表明: 热轧及退火后, 钢板表层以剪切织构为主, 中心层由?和?纤维织构组成; 冷轧后, 各层均由较强的?纤维织构和较弱的?纤维织构组成; 冷轧退火后各层均形成?纤维再结晶织构。与高温精轧相比, 低温精轧有利于冷轧退火板?纤维再结晶织构的强化、偏离{111}<112>组分的程度降低, 从而显著改善冷轧退火板的成形性能。 相似文献
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A. Chattopadhyay V. Subramanya Sarma A. Haldar 《Surface & coatings technology》2009,203(22):3465-3471
Galvanized hot rolled steel sheets are inferior to cold rolled sheets because of the segregation of carbides at the surface/sub-surface region. In order to change the distribution of the carbides at the surface/sub-surface region, continuous annealing/reheating operation is carried out at different temperatures prior to the galvanizing operation. The reheating temperature maintained in continuous annealing line is the main factor which redistributes the carbides at the surface/sub-surface region. At intercritical annealing temperature all the carbides get dissolved into the matrix and the surface became suitable for galvanizing reaction. The reducing atmosphere also plays an important role to remove all the room temperature oxides present at the surface. Thus, a combination of proper temperature and reducing atmosphere leads to the proper galvanizing on the hot rolled steel surface. 相似文献
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采用Nd:YAG激光对强度为800MPa,厚度为1.2mm的TRIP钢板进行焊接.研究焊接速度对焊缝外观和截面成形的影响及接头的组织特点、硬度、强度和成形能力.激光功率相同,焊接速度较低时焊缝易产生气孔,速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝组织主要由马氏体构成,从焊缝、热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝中出现马氏体,接头的塑性和韧性降低,板材的冲压成形能力下降. 相似文献
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Sangjoon Park Chang Gil Lee Heung Nam Han Sung-Joon Kim Kwansoo Chung 《Metals and Materials International》2008,14(1):47-57
Based on the imperative social demand for lighter vehicles, lightweight materials such as aluminum alloys are expected to
replace conventional steels in many automotive applications. In automotive parts manufacturing, most of the components produced
in conventional stamping operations are geometrically complex as the blanks are subjected to both stretching and drawing deformations.
However, aluminum alloys have intrinsic drawbacks, such as the inferior formability of these materials, although the effects
of the weight reduction in terms of performance are highly promising. In an effort to improve the formability of aluminum
alloy sheets, the surface friction stir process is proposed in this study. This process locally modifies the surface of automotive
aluminum alloy sheets via stirring and advancing on the surface of the sheet, similar to the Friction Stir Welding (FSW) process
that utilizes a probe without a pin. When the surface of the sheet is modified locally by stirring, dynamic recrystallization
due to the severe shear deformation along with heat resulting from the friction occur due to changes in the micro-structure
and mechanical properties in the stirred zone, while the dislocation density and grain size refinement are curtailed. In this
work, the drawability performance of AA5052-H32 sheets (thickness 1.5 mm) that were welded using the surface friction stir
process was experimentally and numerically investigated in cylindrical cup drawing tests. When applied to AA5052-H32 automotive
sheets, the surface friction stir process improved the drawability of the entire aluminum alloy sheet. For numerical simulations,
the non-quadratic anisotropic yield function Yld2000-2d was employed along with isotropic hardening, while the formability
was evaluated by utilizing theoretical forming limit diagrams (FLD) based on Hill's bifurcation and M-K theories. 相似文献
19.
采用CO2激光对抗拉强度为600MPa,厚度1.4mm的DP钢进行焊接.研究焊接速度对焊缝外观和截面成形的影响、接头的组织特点、硬度、强度和成形能力.结果表明,激光功率相同,焊接速度较低时焊缝易产生气孔,焊接速度较高时易发生飞溅;焊接速度对焊缝熔深及熔宽也有影响.焊缝区组织主要由马氏体构成,从焊缝、焊接热影响区到母材,组织中马氏体含量下降,接头的最高硬度出现在焊缝或热影响区.在平行于焊缝方向,焊接接头的抗拉强度高于母材,垂直于焊缝方向,接头的抗拉强度与母材相当.由于焊缝出现马氏体组织,接头的塑性和韧性降低,板材的冲压成形能力下降. 相似文献
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