本文選題：水電用鋼 + 低合金高強(qiáng)鋼　； 參考：《西南交通大學(xué)》2017年碩士論文

【摘要】：某水電站是中國(guó)在建的最大水電站工程之一,為了保證大水流量下的正常運(yùn)行,其壓力鋼管采用強(qiáng)度級(jí)別為800MPa的新型國(guó)產(chǎn)高強(qiáng)結(jié)構(gòu)鋼。本文針對(duì)國(guó)產(chǎn)新型800MPa級(jí)低合金高強(qiáng)度結(jié)構(gòu)鋼的常用焊接方法——焊條電弧焊、富氬氣體保護(hù)焊以及埋弧焊工藝進(jìn)行了一系列研究。首先對(duì)比了 780CF鋼800CF鋼埋弧焊的接頭組織和性能,兩者接頭焊縫區(qū)都為韌塑性較好的針狀鐵素體和粒狀貝氏體組織,熱影響區(qū)為貝氏體組織,其中粗晶區(qū)和部分相變區(qū)為接頭薄弱區(qū)域。針對(duì)780CF鋼,采用不同焊接方法、不同焊材及不同線能量下的接頭性能進(jìn)行試驗(yàn)分析。埋弧焊由于焊劑覆蓋,在相同線能量下,冷卻速度較小,晶粒較焊條電弧焊和富氬氣體保護(hù)焊稍粗大,但原子擴(kuò)散更充分,強(qiáng)化質(zhì)點(diǎn)和第二相的強(qiáng)化效果較好。在都能達(dá)到標(biāo)準(zhǔn)要求的前提下,埋弧焊焊接效率更高,焊接過(guò)程更穩(wěn)定,自動(dòng)化程度高,因此采用埋弧焊作為壓力鋼管的主要焊接方式。對(duì)比不同焊材的接頭性能,從焊材化學(xué)成分及接頭組織等方面進(jìn)行分析對(duì)比,選出綜合性能較優(yōu)焊材。對(duì)不同焊接方法設(shè)定了大、小兩種線能量,兩種線能量下都能得到符合標(biāo)準(zhǔn)GB/T 50766-2012《水利水電工程壓力鋼管制作安裝及驗(yàn)收規(guī)范》的接頭。大線能量下接頭加熱溫度較高,晶粒較粗大,但同時(shí)原子擴(kuò)散能力增強(qiáng),有利于強(qiáng)化質(zhì)點(diǎn)的形成和均勻分布,增強(qiáng)接頭強(qiáng)度和韌塑性。且大線能量下生產(chǎn)效率更高。因此推薦焊條電弧焊線能量范圍在25～35KJ/cm之間;富氬氣體保護(hù)焊線能量范圍25～35KJ/cm之間;埋弧焊線能量范圍28～35KJ/cm之間。針對(duì)多層多道焊中相鄰的兩條焊道進(jìn)行分析,未變?cè)贌岽志^(qū)和亞臨界再熱粗晶區(qū)的性能變化不大,與一次粗晶區(qū)相似;過(guò)臨界再熱粗晶區(qū)晶粒細(xì)化,強(qiáng)度及韌塑性提高;臨界再熱粗晶區(qū)形成了晶粒大小和成分不均勻的組織,韌塑性下降,但相比于一次部分相變區(qū)性能仍較好。因此焊道間相互作用使焊接溫度場(chǎng)重合區(qū)域性能較優(yōu),接頭薄弱區(qū)域仍為一次粗晶區(qū)和一次部分相變區(qū)。
[Abstract]:A hydropower station is one of the largest hydropower projects under construction in China. In order to ensure the normal operation under the heavy water flow, the steel pipe with strength grade 800MPa is adopted as a new type of domestic high strength structural steel. In this paper, the common welding methods of 800MPa low alloy high strength structural steel, such as electrode arc welding, argon rich gas shielded welding and submerged arc welding, are studied in this paper. The microstructure and properties of submerged arc welding (SAW) of 780CF steel 800CF steel were compared at first. The weld zone of both joints was acicular ferrite and granular bainite structure with good ductility and ductility, and the heat affected zone was bainite structure. The coarse-grained region and partial phase transition zone are the weak zone of the joint. The joint properties of 780CF steel under different welding methods, different welding materials and different wire energy were tested and analyzed. Because of flux covering, the cooling rate of submerged arc welding is smaller than that of electrode arc welding and argon-rich gas arc welding, but the atomic diffusion is more sufficient, and the strengthening effect of particle and second phase is better than that of electrode arc welding and argon rich gas welding. On the premise of meeting the standard requirement, submerged arc welding is more efficient, the welding process is more stable, and the degree of automation is high. Therefore, submerged arc welding is used as the main welding method of pressure steel pipe. The joint properties of different welding materials were compared and analyzed from the aspects of chemical composition and joint structure. For different welding methods, two kinds of line energy, large and small, can be obtained under two kinds of line energy. The joints can be obtained according to the standard GB/T 50766-2012 "Specification for production, installation and acceptance of penstock for water conservancy and hydropower engineering". The higher heating temperature and larger grain size of the joints with large wire energy, however, the enhancement of the atomic diffusion ability is beneficial to the formation and uniform distribution of particles and the strengthening of the strength and ductility of the joints. And the production efficiency is higher under the large line energy. Therefore, it is recommended that the energy range of electrode arc welding line is between 25~35KJ/cm, that of argon rich gas shielded welding line is between 25~35KJ/cm and that of submerged arc welding wire is between 28~35KJ/cm. According to the analysis of two adjacent passes in multilayer and multi-pass welding, the properties of coarse grain zone and sub-critical coarse grain region in unreheated and subcritical reheat have little change and are similar to those in primary coarse crystal region, and the grain size is refined and the strength and ductility are improved in the supercritical reheat coarse grain area. In the critical reheat coarse-grained region, the grain size and composition are not uniform, and the ductility is decreased, but the properties are still better than those in the primary phase transition zone. Therefore, the interaction between welding passes makes the performance of welding temperature field coincidence region better, and the weak zone of the joint is still the primary coarse crystal zone and the first partial phase transition zone.
【學(xué)位授予單位】：西南交通大學(xué)
【學(xué)位級(jí)別】：碩士
【學(xué)位授予年份】：2017
【分類(lèi)號(hào)】：TG457.11;TM622

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本文編號(hào)：1950349