本文關(guān)鍵詞：退火工藝對Q195冷軋鋼板組織及屈強(qiáng)比的影響　出處：《山東大學(xué)》2017年碩士論文　論文類型：學(xué)位論文

  更多相關(guān)文章： 碳素結(jié)構(gòu)鋼 夾雜物 退火工藝 顯微組織 屈強(qiáng)比

【摘要】：Q195冷軋鋼板因其具有優(yōu)良的塑、韌性和加工性能,被廣泛應(yīng)用于輕工、機(jī)械、交通運(yùn)輸?shù)刃袠I(yè),在我國低碳薄鋼板中占據(jù)較大市場份額。但在進(jìn)行Q195冷軋鋼板生產(chǎn)時(shí),普遍存在屈強(qiáng)比偏高問題。屈強(qiáng)比(YieldRatio=ReL/Rm)是衡量材料冷變形和均勻延伸能力的重要指標(biāo)。屈強(qiáng)比高的鋼板由開始發(fā)生塑性變形到最終斷裂的形變?nèi)萘啃?嚴(yán)重影響了鋼板的成型性能和結(jié)構(gòu)設(shè)計(jì)安全性。因此,研究屈強(qiáng)比影響因素對鋼板屈強(qiáng)比控制和開發(fā)低屈強(qiáng)比鋼材具有重要意義。本課題以泰鋼1780產(chǎn)線(板寬1780mm)和950產(chǎn)線(板寬950mm)生產(chǎn)的Q195鋼板為研究對象,采用組織表征和力學(xué)性能分析相結(jié)合的方法,首先探討了導(dǎo)致Q195鋼板屈強(qiáng)比偏高的主要原因,再系統(tǒng)研究了退火工藝對Q195冷軋鋼板微觀組織及屈強(qiáng)比的影響,以此探究退火工藝是否可以解決Q195鋼板屈強(qiáng)比過高的問題。對泰鋼Q195鋼板的力學(xué)性能進(jìn)行分析可知,其屈強(qiáng)比為0.68～0.83,高于普通碳素鋼屈強(qiáng)比要求(0.60～0.65),主要因?yàn)榍䦶?qiáng)度偏高(281～338MPa)。進(jìn)行組織觀察和夾雜物分析可知,1780產(chǎn)線Q195鋼板屈強(qiáng)比偏高的原因主要為:熱軋鋼板組織在厚度方向上不均勻,心部組織細(xì)小,表層組織粗大;鋼中難變形的A1203及其復(fù)合夾雜物含量過高且細(xì)小彌散。950產(chǎn)線Q195鋼板屈強(qiáng)比偏高的原因主要為:熱軋及退火鋼板組織均勻但過于細(xì)小;鋼中難變形的A1203及其復(fù)合夾雜物含量過高且細(xì)小彌散。細(xì)小彌散的夾雜物造成了彌散強(qiáng)化和細(xì)晶強(qiáng)化,提高了鋼板的屈強(qiáng)比。對Q195冷軋鋼板進(jìn)行了模擬罩式退火,研究了退火溫度和保溫時(shí)間對Q195冷軋鋼板顯微組織及屈強(qiáng)比的影響。研究結(jié)果表明,在3小時(shí)恒時(shí)退火時(shí),1780產(chǎn)線Q195冷軋鋼板在610℃時(shí)完成再結(jié)晶;隨著退火溫度從610℃升高到760℃,鋼板組織均勻性得到提高,但晶粒沒有明顯長大,因此屈服強(qiáng)度未明顯降低,屈強(qiáng)比依然偏高。950產(chǎn)線壓下率為58.5%和86.1%的Q195冷軋鋼板分別在580℃和550℃時(shí)完成再結(jié)晶,大壓下率鋼板的再結(jié)晶溫度更低,且再結(jié)晶晶粒越細(xì)小;隨著退火溫度由640℃升高至760℃,950產(chǎn)線Q195冷軋鋼板組織均勻性得到提高,晶粒略微長大,故屈服強(qiáng)度隨之降低,屈強(qiáng)比由0.92降至0.84,但仍高于普碳鋼屈強(qiáng)比要求。在670℃和730℃恒溫退火時(shí),兩條產(chǎn)線的Q195冷軋鋼均在5min內(nèi)完成了再結(jié)晶,說明冷變形金屬在高于再結(jié)晶臨界溫度條件下,再結(jié)晶過程可以迅速完成。保溫時(shí)間在30min內(nèi),硬度下降較明顯,而保溫時(shí)間由30min延長至7h過程中,硬度降低較小,晶粒尺寸僅略微長大。綜上所述,兩條產(chǎn)線生產(chǎn)的Q195鋼板都無法單純通過調(diào)整退火工藝來改善因夾雜物過多而造成的晶粒細(xì)小問題,降低屈強(qiáng)比的效果不明顯。兩條產(chǎn)線都需要優(yōu)化冶煉除雜工藝,提高鋼水純凈度;1780產(chǎn)線還需要在熱軋過程進(jìn)行工藝優(yōu)化,提高熱軋組織均勻性。
[Abstract]:Q195 cold-rolled steel sheet is widely used in light industry, machinery, transportation and other industries because of its excellent plasticity, toughness and processability. It occupies a large market share in China's low carbon steel sheet. But in the production of Q195 cold rolled steel plate, there is a widespread problem of high ratio of flexion to strength. The ratio of flexion and strength (YieldRatio=ReL/Rm) is an important index to measure the cold deformation and the uniform extension ability of the material. The deformation capacity of the steel plate with high bending strength from the beginning of plastic deformation to the final fracture is small, which seriously affects the forming and structural design safety of the steel plate. Therefore, it is of great significance to study the influence factors of the flexion ratio for steel plate bending strength ratio control and the development of low yield strength ratio steel. This topic in Taigang 1780 production lines (board width 1780mm) and the 950 production line (width 950mm) Q195 steel production as the research object, using the method of tissue characterization and mechanical properties analysis unifies, first discusses the cause of Q195 plate yield ratio of the main reasons for the high, and then studied the annealing process on the yield and effect of high ratio of Q195 cold rolled steel microstructure, in order to explore whether the annealing process can solve the Q195 problem of high yield ratio of steel plate. The analysis on the mechanical properties of Taishan steel Q195 plate, the yield ratio is 0.68 ~ 0.83 higher than that of ordinary carbon steel, yield ratio requirements (0.60 ~ 0.65), mainly because of the high yield strength (281 ~ 338MPa). By metallographical analysis, 1780 production line of steel Q195 high yield ratio of the main reason for the organization: hot rolled steel plate is not uniform in the thickness direction, heart tissue surface fine and coarse microstructure; steel deformed A1203 and its composite inclusion content is too high and fine dispersion. The main reason for the high yield ratio of Q195 steel plate on the 950 production line is that the hot rolled and annealed steel plate is homogeneous but too small, and the A1203 and its complex inclusions in the steel are difficult to deform. The fine dispersion of inclusions resulted in dispersion strengthening and fine grain strengthening, and increased the ratio of flexion to strength of the steel plate. The simulated annealing of Q195 cold rolled steel sheet was carried out. The effects of annealing temperature and holding time on the microstructure and yield ratio of Q195 cold rolled steel sheet were studied. The results show that in the 3 hours of constant time during annealing, 1780 Q195 production line of cold rolled steel plate at 610 DEG C to complete recrystallization; with the increase of the annealing temperature from 610 degrees to 760 degrees, the microstructure uniformity is improved, but the grain size does not grow significantly, so the yield strength has been significantly reduced, yield ratio is still high. The 950 line pressure rate of Q195 cold rolled steel plate 58.5% and 86.1% are completed in 580 degrees and 550 degrees when the recrystallization rate under the pressure plate, the recrystallization temperature is lower, and the recrystallization grain size; with the increase of the annealing temperature from 640 DEG to 760 DEG C, Q195 cold rolled steel production line 950 uniformity to improve the grain grow up slightly, the yield strength decreases, yield ratio decreased from 0.92 to 0.84, but still higher than the carbon yield ratio requirements. The recrystallization of Q195 cold rolled steel produced by two production lines was completed in 5min at 670 and 730 degrees constant temperature, indicating that the recrystallization process of cold formed metal can be completed at a higher critical temperature than that of recrystallization. When the holding time is in 30min, the hardness decreases obviously. While the heat preservation time is extended from 30min to 7h, the hardness decreases less, and the grain size is only slightly grown. To sum up, the Q195 steel plates produced by two production lines can not only improve the grain size problem caused by too much inclusions by adjusting the annealing process, but the effect of decreasing the ratio of yield to strength is not obvious. The two production lines need to optimize the smelting and impurity removal process and improve the purity of molten steel. The 1780 production line also needs to optimize the process in hot rolling process and improve the homogeneity of hot rolled structure.
【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】：2017
【分類號】：TG142.1;TG335.5;TG162.83

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