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  本文關(guān)鍵詞：Q345H型鋼Z向性能的研究　出處：《山東大學(xué)》2016年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： H型鋼 Z向性能 帶狀組織 夾雜物

【摘要】：近年來具有高強度、塑性、抗疲勞強度和焊接性能的優(yōu)質(zhì)鋼越來越受到人們的青睞。H型鋼具有截面模量高、重量輕、容易組裝等特點,被廣泛應(yīng)用于高層建筑上。由于其受力環(huán)境比較復(fù)雜,因此還需要較好的Z向性能(即抗層狀撕裂性能)。目前我國廣泛使用的要求Z向性能的H型鋼大多是通過Z向鋼板焊接而成,焊接接頭金屬冷卻過程中發(fā)生收縮現(xiàn)象會產(chǎn)生很大的拉應(yīng)力,引起應(yīng)力集中,易形成微裂紋,發(fā)生層狀撕裂。因此研究影響鋼材Z向性能的因素,開發(fā)出具有較好Z向性能的熱軋H型鋼具有重要意義。本課題以萊鋼生產(chǎn)的精煉Q345B、未精煉Q345B和Q345ELH型鋼為研究對象,在精煉Q345B鋼翼緣和腹板、未精煉Q345B鋼翼緣和腹板、Q345EL鋼翼緣分別進行取樣,做厚度方向拉伸試驗測量其厚度方向力學(xué)性能,然后對其金相組織,斷口形貌和夾雜物等進行研究,總結(jié)出影響Q345H型鋼Z向性能的因素。研究發(fā)現(xiàn),試驗鋼中精煉Q345B鋼的Z向性能最好,Q345EL鋼次之,未精煉Q345B鋼的Z向性能最差。從微觀組織方面分析,影響Q345H型鋼Z向性能的主要因素是帶狀組織和晶粒度等級,帶狀組織越明顯,晶粒度等級越小,Z向性能越差。Q345EL和未精煉Q345B鋼組織均為鐵素體和珠光體組成的帶狀組織,而Q345EL鋼在冶煉的過程中添加了B、Nb等微量合金元素,晶粒得到細化, Z向性能相對較好。而經(jīng)鋼包精煉的Q345B鋼組織中沒有出現(xiàn)明顯的對Z向性能不利的帶狀組織,原因是它在軋制過程中應(yīng)用了控軋控冷技術(shù),帶狀組織消失,改善了鋼板的各向異性,Z向性能相對更好。從夾雜物方面分析,影響Q345H型鋼Z向性能的主要因素是夾雜物的含量、形狀和尺寸,夾雜物含量越多,尺寸越大,Z向性能越差。精煉Q345B和Q345EL鋼中的長條狀硫化物、硅酸鹽類夾雜物均明顯少于未精煉Q345B鋼,Z向性能相對較好。同一種型鋼中,翼緣和腹板部位的夾雜物種類一致,且含量基本相同,但是腹板部位的硫化物夾雜物的尺寸較大,作為裂紋源擴展的傾向性較大,Z向性能較差。斷口形貌分析發(fā)現(xiàn),五組試樣斷口均屬于韌性斷口。精煉Q345B鋼翼緣和腹板試樣斷口出現(xiàn)大量等軸韌窩,尺寸較小,韌坑較深,可以觀察到少量微小夾雜物。Q345EL鋼翼緣試樣斷口出現(xiàn)較多長條狀韌窩,尺寸較大、韌坑較淺,也可以觀察到少量微小夾雜物。未精煉Q345B鋼翼緣與腹板試樣斷口出現(xiàn)較多長條狀韌窩,尺寸較大、韌坑較淺,同時出現(xiàn)了一些解理面形貌,并且可明顯的觀察到較多長條狀夾雜物。韌窩尺寸越小、深度越深,斷面收縮率越大,材料的Z向性能越好。因此工業(yè)化生產(chǎn)具有優(yōu)良Z向性能的熱軋H型鋼時需應(yīng)用精煉技術(shù)降低其夾雜物的含量,尤其是硫化物、硅酸鹽等塑性夾雜物,同時采用控軋控冷工藝改善帶狀組織,細化晶粒,提高材料的Z向性能。
[Abstract]:In recent years, high quality steels with high strength, plasticity, fatigue strength and welding properties have been more and more favored by people. H section steel has the characteristics of high section modulus, light weight, easy assembly and so on. It is widely used in high-rise buildings, because of its stress environment is more complex. Therefore, we also need better Z performance (that is, layer tearing resistance). At present, the H-section steel which is widely used in our country, which requires Z-direction performance, is mostly welded by Z-direction steel plate. The shrinkage phenomenon of welded joint metal during cooling will produce great tensile stress, cause stress concentration, and easily form micro-cracks and lamellar tear. Therefore, the factors that affect the Z-direction properties of steel are studied. It is of great significance to develop hot rolled H-section steel with good Z-direction properties. In this paper, the refined Q345B, unrefined Q345B and Q345ELH sections produced by Laiwu Iron and Steel Co. The flange and web plate of refined Q345B steel, unrefined Q345B steel flange and web plate steel Q345EL steel flange were sampled, and the thickness direction mechanical properties were measured by tensile test in thickness direction. Then the metallographic structure, fracture morphology and inclusion of Q345H steel were studied, and the factors affecting the Z-direction properties of Q345H steel were summarized. It was found that the Z-direction property of Q345B steel was the best in the test steel. Q345EL steel followed by unrefined Q345B steel in Z direction properties. From the microstructure analysis, the main factors affecting the Z direction properties of Q345H steel are strip structure and grain size grade. The more obvious the strip structure is, the smaller the grain size grade is, the worse the Z direction property. Q345EL and the unrefined Q345B steel structure are both ferrite and pearlite. However, in the process of smelting Q345EL steel, some trace alloying elements, such as Bnb, were added, and the grain size was refined. The Z direction property is relatively good, but there is no obvious strip structure which is unfavorable to the Z direction property in the Q345B steel structure refined by ladle, because it has applied the controlled rolling and cooling control technology in the rolling process. The disappearance of strip structure improves the anisotropic zigzag property of steel plate. From the analysis of inclusions, the main factors affecting the Z-direction properties of Q345H steel are the content, shape and size of inclusions. The larger the size of the inclusions, the worse the Z direction properties of the steel. In the refined Q345B and Q345EL steels, the silicate inclusions are obviously lower than those of the unrefined Q345B steels. The long stripe sulfides in the refined Q345B and Q345EL steels are obviously lower than those of the unrefined steels. The type of inclusions in flange and web are the same, and the content is basically the same, but the size of sulfide inclusion in web is larger. The fracture morphology analysis shows that the fracture surface of five groups of specimens belongs to ductile fracture. A large number of equiaxed dimples appear in the flange of refined Q345B steel and the fracture surface of web specimen. The size is small and the toughness is deep. A small amount of micro-inclusions. Q345EL steel flange specimen fracture surface appears more long stripe dimples, larger size, shallow toughness. A small amount of small inclusions can also be observed. The fracture surface of unrefined Q345B steel flange and web specimen has more long dimples, larger size, shallow toughness, and some cleavage surface morphology. The smaller the dimple size, the deeper the depth and the greater the section shrinkage. The better the Z direction property of the material is, the better the content of inclusions, especially the plastic inclusions such as sulphide, silicate and so on, should be reduced by refining technology when producing hot rolled H-section steel with good Z-direction properties. At the same time, the controlled rolling and cooling process was used to improve the strip structure, refine the grain and improve the Z direction properties of the material.
【學(xué)位授予單位】：山東大學(xué)
【學(xué)位級別】：碩士
【學(xué)位授予年份】：2016
【分類號】：TG142.1

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相關(guān)碩士學(xué)位論文 前1條

1 王佳艷;Q345H型鋼Z向性能的研究[D];山東大學(xué);2016年

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本文編號：1381836