【摘要】：優(yōu)質(zhì)碳素結(jié)構(gòu)鋼SPCC冷軋鋼板因其具有良好的深沖性能、較低的屈服強度、良好的延展性和光潔平整的表面狀態(tài)在汽車、農(nóng)用機械、電子產(chǎn)品、儀器儀表及家電領(lǐng)域得到了越來越廣泛的應(yīng)用。薄板材的性能嚴(yán)重影響著成品的工藝性能,因而優(yōu)質(zhì)的沖壓板材是獲得性能優(yōu)異、表面光潔成品的保證。因此生產(chǎn)較低屈強比、力學(xué)性能優(yōu)異的薄鋼板對于企業(yè)具有重要意義。本課題選取泰山鋼鐵集團生產(chǎn)的兩種不同規(guī)格的冷軋板作為研究對象。分別對其進行4小時熱處理,溫度區(qū)間為440℃-760℃,步長為40℃。通過金相顯微鏡分析恒時熱處理的金相組織,利用維氏硬度計測量不同溫度熱處理后試樣的硬度。根據(jù)金相顯微組織和硬度值選取較為合適的熱處理溫度;隨后對其進行恒溫不同保溫時間的熱處理,通過金相顯微組織和硬度觀察分析保溫時間的影響。從恒溫和恒時熱處理結(jié)果中選定較為合適的幾組熱處理工藝制度,對950產(chǎn)線和1780產(chǎn)線的冷軋板進行熱處理,測定其力學(xué)性能,并利用SEM掃描電子顯微鏡對其拉伸斷口形貌進行觀察。隨后通過SEM配合能譜儀對金相試樣中的夾雜物形貌及其成分、分布等觀察分析。為獲得較低屈強比、力學(xué)性能良好的SPCC鋼板提出改善工藝。研究發(fā)現(xiàn)泰鋼生產(chǎn)的兩種規(guī)格的冷軋薄鋼板均存在屈強比過高,沖壓變形抗力過大的問題。分析其金相顯微組織發(fā)現(xiàn)退火后的晶粒過于細(xì)小,晶粒度等級在9-10,晶粒度等級過高。恒時熱處理結(jié)果顯示,950產(chǎn)線和1780產(chǎn)線的SPCC鋼板再結(jié)晶的溫度在520℃左右,在520℃以下退火時,SPCC冷軋薄鋼板金相組織中呈現(xiàn)纖維狀的拉長晶粒,在520℃退火后金相組織中開始出現(xiàn)無畸變的新晶粒,隨著退火溫度的升高,無畸變的新晶粒開始增多并逐漸吞噬變形組織進行長大,在680℃時材料的再結(jié)晶過程基本完成,晶粒較為均勻。晶粒度隨著溫度升高而呈現(xiàn)降低的趨勢。680℃和720℃恒溫?zé)崽幚砗蟀l(fā)現(xiàn),SPCC鋼板退火后的晶粒度和硬度隨著保溫時間的增加呈現(xiàn)緩慢波動變化,總體來說保溫時間相比于退火溫度對SPCC鋼板組織性能的影響較小。拉伸斷口形貌分析顯示宏觀斷口均為無金屬光澤的暗灰色,屬于韌性斷口。在微觀斷口形貌上,隨著溫度的升高,950產(chǎn)線拉伸斷口的韌窩尺寸和數(shù)量逐漸減小,韌窩的尺寸由均勻性向差異性發(fā)展,韌窩的深度變得越來越淺。1780產(chǎn)線680℃4小時退火后的拉伸斷口韌窩的大小相對均勻,720℃4小時退火后拉伸斷口平均尺寸跟680℃時相差不大,但韌窩尺寸大小不均,溫度在760℃時,韌窩尺寸增大,平均韌窩尺寸在12μm左右且大小更加不均勻。拉伸斷口中的韌窩越均勻,韌窩深度較深且尺寸越小,材料的力學(xué)性能越好。從夾雜物方面分析來看,夾雜物對SPCC冷軋薄鋼板力學(xué)性能的影響主要表現(xiàn)在夾雜物的含量、尺寸和分布上,夾雜物的含量越多,尺寸越大,則其韌性越差。950和1780產(chǎn)線的夾雜物總體來說尺寸較為均勻,大尺寸的環(huán)狀外來夾雜物相對較少。夾雜物以鏈狀的Al2O3和長條狀的MnS以及不變形的硅酸鹽居多,Al2O3和MnS常以復(fù)合的蝌蚪狀存在于基體之中。1780產(chǎn)線的夾雜物相比950產(chǎn)線數(shù)量更少,因而其延伸率更高,塑性相對更好。
[Abstract]:The high-quality carbon structural steel SPCC cold-rolled steel plate has been widely used in the fields of automobile, agricultural machinery, electronic products, instruments and electrical appliances because of its excellent deep drawing performance, lower yield strength, good ductility and smooth and smooth surface state. The performance of the thin plate greatly influences the process performance of the finished product, so the high-quality stamped sheet material is a guarantee of excellent performance and smooth surface finish. Therefore, the thin steel sheet with low yield ratio and excellent mechanical property is of great significance to the enterprise. In this paper, two kinds of graphite plates with different specifications produced by Taishan Iron and Steel Group are selected as the research object. The heat treatment is carried out for 4 hours respectively, and the temperature range is 440-760 DEG C and the step length is 40 DEG C. The hardness of the specimen after heat treatment at different temperatures was measured by means of the Vickers hardness meter by means of the metallographic structure of the heat treatment at constant time by means of a metallographic microscope. The proper heat treatment temperature is selected according to the metallographic microstructure and the hardness value, and then the heat treatment of the constant temperature and different heat preservation time is carried out, and the influence of the thermal insulation time is analyzed through the metallographic microstructure and the hardness observation. A suitable group of heat treatment process systems were selected from the results of constant-temperature and constant-time heat treatment. The mechanical properties of 950 and 1780 wire-producing plates were measured and their tensile fracture morphology was observed by means of SEM. The morphology, composition and distribution of the inclusions in the metallographic sample were then analyzed by means of the SEM. In ord to obtain a SPCC steel plate with a lower yield ratio and a good mechanical property, an improvement process is proposed. It has been found that the two kinds of cold-rolled steel sheets produced by Tae Steel have the problems of high yield ratio and excessive punching deformation resistance. The results show that the grain size is too small, the grain size is 9-10, and the grain size is too high. The results of the constant-time heat treatment show that the recrystallization temperature of the SPCC steel sheet at the 950-and 1780-producing lines is about 520.degree. C., and in the annealing at 520.degree. C., a fibrous elongated crystal grain is present in the metallographic structure of the SPCC cold-rolled steel sheet, and a new crystal grain with no distortion is started in the gold-phase structure after annealing at 520 DEG C, With the increase of the annealing temperature, the new crystal grain with no distortion started to increase and the deformed tissue was gradually engulfed to grow. The recrystallization process of the material was basically completed at 680 鈩，

本文編號：2512550