本文選題：石油套管鋼 + 夾雜物控制��； 參考：《北京科技大學》2016年博士論文

【摘要】：油套管鋼是高技術含量、高附加值、高風險的冶金產品,對鋼材的強度、韌性、焊接性能、抗氫致裂紋(HIC)、抗硫化物應力腐蝕斷裂(SSCC)等性能有較高要求。這就對鋼中的硫、氧、磷、氮、氫等雜質元素和夾非金屬雜物的控制提出了嚴格的要求。目前攀鋼集團攀枝花鋼釩有限公司(以下簡稱攀鋼)生產油套管鋼過程中存在鈣處理效果不穩(wěn)定、鋼水澆鑄性能差和成品抗硫化物應力腐蝕性能不達標的問題。上述問題均與石油套管鋼中的非金屬夾雜物密切相關,因此,本文以BOF→LF→RH→CC流程生產的27CrMoV石油套管鋼為對象,對不同鈣處理工藝路線鋼、精煉渣和夾雜物變化進行對比,并對鋼中夾雜物的生成和控制機理、鈣處理中間產物及夾雜物演變機理進行研究,在此基礎上,提出改進措施,并在工業(yè)驗證試驗和批量生產中取得了理想效果。本文的主要創(chuàng)新點和工作如下：對三種鈣處理工藝路線的鋼、精煉渣和夾雜物進行分析,其中夾雜物的研究借助FactSage平衡模塊和CaO-Al2O3-MgO-CaS四元相圖,結果表明：三種路線鋼中總氧、氮、鈣、硫等成分含量控制較為理想,但保護澆鑄仍存在問題,易發(fā)生二次氧化現象。精煉渣各成分變化相似,精煉渣堿度為8-27,曼內斯曼指數為0.38～0.96,熔化溫度為1300～1375℃,主要物相為12CaO·7Al2O3。路線A中間包鋼樣中多為高CaS含量的Al2O3-CaO-CaS系、Al2O3-CaS系和CaO-CaS系固態(tài)夾雜物,易引起水口堵塞；路線B中包鋼樣中多為Al2O3-CaO-CaS和Al2O3-CaO-MgO-CaS系夾雜物,多數位于50%-100%液相區(qū)域之內；路線C中包鋼樣中除Al2O3-CaO-MgO-CaS系和Al2O3-CaO-CaS系夾雜物,還存在大量二次氧化生成的A1203和Al2O3-MgO系夾雜物。針對現存評價方法的局限性,提出一種以夾雜物改性指數評估鈣處理改性夾雜物效果的方法,并據此確定最優(yōu)鈣處理工藝路線。針對攀鋼生產27CrMoV石油套管鋼的工藝特點和鋼水成分,同時考慮活度二次相互作用系數和平衡元素的濃度變化對鋼中氧化物夾雜的生成和控制機理進行熱力學研究,并利用格繆爾吸附方程對氧硫復合夾雜物的生成機理進行研究,結果表明：[A1]s=0.05%,若要將夾雜物成分控制在12CaO·7Al2O3附近,則[Ca]=27×10-6, [Ca]/[Al]s=0.054。當MgOAl2O3活度為1,鋼液中[A1]s=0.05%-0.07%時,溶解鎂只要達到0.34×10-6和0.38×10-6,鋼中便可生成MgOAl2O3尖晶石。當[A1]s=0.05%,[Mg]=4×10"6-8×10-6時,鋼中[Ca]含量只要分別達到2.2×10-6和8.0×10-6,鋼液中的MgOAl2O3便開始向CaOAl2O3轉變。夾雜物觀測結果同上述熱力學計算結果較吻合。鈣處理后鋼液中的溶解鈣對后續(xù)工序中二次氧化產物具有一定的改性作用,為了將二次氧化產物改性為液態(tài),應降低二次氧化過程中的增氧量,并提高鋼液中的溶解鈣含量。硫含量為0.003%時,硫在12CaO·7Al2O3夾雜物表面的覆蓋度達到90%以上,易生成CaS外殼,鋼樣中觀測到的氧硫復合夾雜物多基于此機理生成。建立鈣處理中間產物生成動力學模型,對鈣處理中間產物CaS、CaO的生成機理進行研究,并詳細闡述了鈣處理中間產物對氧化物的改性機理。對精煉前期MgO-Al2O3系或高熔點的CaO-Al2O3系夾雜物的生成次序,尚未見文獻報道的CaO-Al2O3-MgO(環(huán)狀)系夾雜物的生成機理進行了研究。結果表明：在鈣處理后的短時間內,根據不同的氧、硫含量會生成不同的中間產物,當鋼中溶解氧為4×10-6時,臨界硫含量為11×10-6。鈣處理中間產物CaO、 CaS均可將氧化鋁夾雜改性為液態(tài)鈣鋁酸鹽夾雜物,不同的鈣處理中間產物對氧化鋁夾雜有著不同的改性機理。鈣處理中間產物CaO對氧化物的改性速率快于CaS,且CaS、CaO對MgO·Al2O3夾雜物進行改性的難度低于對A1203的進行改性。精煉渣CaO/Al2O3=1.4為A1203生成MgO-Al2O3系或高熔點CaO-Al2O3系夾雜物的臨界值。當鋼液中的[Mg]含量較高時,[Mg]將夾雜物外圍的CaO或A1203成分還原出來,形成CaO-Al2O3-MgO(環(huán)狀)系夾雜物。精煉過程鋼液中夾雜物的演變路徑為：Al2O3→Al2O3-MgO系和高熔點Al2O3-CaO系夾雜物→Al2O2-CaO-MgO系或Al2O3-CaO系液態(tài)夾雜物→點塊狀或環(huán)狀MgO、CaS為外殼,低熔點鈣鋁酸鹽或鈣鎂鋁酸鹽為核心的復合夾雜物。改進和優(yōu)化脫氧制度、造渣制度、鈣處理工藝和連鑄保護澆鑄制度后,進行工業(yè)驗證試驗和批量生產,結果表明：試驗爐次精煉過程脫硫脫氧效果較好,中間包中主要為Al2O3-MgO-CaO系、Al2O3-CaO-CaS系復合夾雜物,大多數位于50%-100%液相區(qū)域內,夾雜物改性指數大幅提高至0.77。工業(yè)生產中因水口堵塞造成的流次斷澆率降至2.0%以下,單中間包連澆爐數由小于5爐提高到7-10爐。氧含量、氮含量、硫含量、非金屬夾雜評級和耐硫化物應力腐蝕破裂等性能完全滿足產品標準的要求。
[Abstract]:Oil and casing steel is a high technical, high value-added, high risk metallurgical product. It has high requirements for steel strength, toughness, welding performance, hydrogen induced crack (HIC), resistance to sulfide stress corrosion cracking (SSCC) and so on. This is a strict requirement for the control of sulfur, oxygen, phosphorus, nitrogen, hydrogen and other impurity elements in steel and the control of non metallic inclusion in steel. At present, the production of oil and casing steel in Panzhihua steel vanadium Co., Ltd. of Panzhihua Iron and Steel Group (hereinafter referred to as "Panzhihua Steel") has a problem of unstable calcium treatment, poor casting properties of steel and the resistance to sulphide stress corrosion resistance of finished products. All these problems are closely related to non gold inclusions in the oil casing steel. Therefore, this paper is BOF to LF. The 27CrMoV oil casing steel produced by RH to CC is the object. The changes of the steel, refining slag and inclusions in different calcium treatment process are compared. The formation and control mechanism of inclusions in the steel and the mechanism of the intermediate product and inclusion evolution mechanism of the calcium treatment are studied. On the basis of this, the improvement measures are put forward, and the test and batch of industrial verification and batch are also put forward. The main innovation and work of this paper are as follows: the analysis of steel, refining slag and inclusions in three kinds of calcium treatment process, including the use of FactSage balance module and CaO-Al2O3-MgO-CaS four element phase diagram, shows that the content of total oxygen, nitrogen, calcium and sulfur in the three kinds of route steel is controlled. The system is ideal, but there are still problems in the protection casting. Two oxidation phenomena are easy to occur. The composition of the refining slag is similar, the alkalinity of the refining slag is 8-27, the MannesMann index is 0.38 ~ 0.96, the melting temperature is 1300~1375, and the main phase is the Al2O3-CaO-CaS system with high CaS content in the 12CaO. 7Al2O3. route of A. The Al2O3-CaS system and the Al2O3-CaS system are the main components. CaO-CaS is a solid inclusion, which is easy to cause the blockage of the nozzle; in the route B, most of the steel samples are Al2O3-CaO-CaS and Al2O3-CaO-MgO-CaS inclusions, most of which are located in the 50%-100% liquid phase. In the route C, there are a large number of A1203 and Al2O3-MgO clips formed by two oxidation in addition to the Al2O3-CaO-MgO-CaS and Al2O3-CaO-CaS system inclusions in the Baotou steel samples. In view of the limitations of the existing evaluation methods, a method is proposed to evaluate the effect of calcium treatment modified inclusions by inclusion modification index, and the optimal calcium treatment process is determined accordingly. In view of the technological characteristics and steel composition of the 27CrMoV oil cased steel produced in Panzhihua steel, the two times interaction coefficient and balance element of the activity are considered. The formation and control mechanism of oxide inclusions in steel are studied thermodynamically, and the formation mechanism of oxygen and sulfur compound inclusions is studied by using the method of the [A1]s=0.05%. The results show that if the inclusion composition is controlled near 12CaO 7Al2O3, [Ca]=27 x 10-6 and [Ca]/[Al]s=0.054. are the activity of MgOAl2O3. For 1, when the molten steel is [A1]s=0.05%-0.07%, as long as the dissolved magnesium reaches 0.34 * 10-6 and 0.38 x 10-6, the MgOAl2O3 spinel can be generated in the steel. When [A1]s=0.05%, [Mg]=4 x 10 "6-8 * 10-6, the [Ca] content of the steel is 2.2 * 10-6 and 8 x 10-6, and the MgOAl2O3 in the molten steel begins to change to the CaOAl2O3. The inclusion observation results with the above thermodynamics. The calculation results are more consistent. The calcium dissolved in the molten steel after calcium treatment has a certain modification effect on the two oxidation products in the subsequent process. In order to change the two oxidation product into liquid, the amount of oxygen increasing in the two oxidation process should be reduced and the content of calcium dissolved in the molten steel is increased. When the sulfur content is 0.003%, the sulfur is on the surface of the 12CaO. 7Al2O3 inclusion. The coverage of CaS is more than 90%, and the formation of oxygen and sulfur composite inclusions in steel samples is mostly generated based on this mechanism. A kinetic model for the formation of intermediate products of calcium treatment is established. The formation mechanism of CaS and CaO, the intermediate product of calcium treatment, is studied, and the modification mechanism of the intermediate products of calcium treatment to the oxide is described in detail. The formation of the inclusions in the CaO-Al2O3 system of the early MgO-Al2O3 or high melting point has not yet been studied. The results show that in the short time after calcium treatment, the sulfur content will produce different intermediate products according to the different oxygen, when the dissolved oxygen in the steel is 4 * 10-6. The boundary sulfur content is 11 x 10-6. calcium treatment intermediate product CaO, CaS can change alumina inclusion into liquid calcium aluminate inclusions. Different intermediate products of calcium treatment have different modification mechanism to alumina inclusion. The modification rate of calcium treatment intermediate product CaO to oxide is faster than CaS, and CaS and CaO modify the MgO. Al2O3 inclusion. The difficulty is lower than the modification of A1203. The refining slag CaO/Al2O3=1.4 is a critical value for the formation of MgO-Al2O3 or high melting point CaO-Al2O3 inclusions in A1203. When the [Mg] content in the molten steel is high, [Mg] reduces the CaO or A1203 components outside the inclusions to form a CaO-Al2O3-MgO (ring) inclusion. The evolution of inclusions in the molten steel in the refining process. The path is: Al2O3, Al2O3-MgO and high melting point Al2O3-CaO inclusions, Al2O2-CaO-MgO or Al2O3-CaO liquid inclusions, dot or ring MgO, CaS as a shell, low melting point calcium aluminate or calcium magnesium aluminate as the core composite inclusions. Improvement and optimization of deoxidization system, slag making system, calcium treatment process and casting protection casting system After the industrial test and batch production, the results show that the desulfurization deoxidization effect of the secondary refining process is better, the main package in the middle bag is Al2O3-MgO-CaO, Al2O3-CaO-CaS is a compound inclusion, most of them are located in the 50%-100% liquid phase region, the inclusion modification index is greatly improved to the 0.77. industrial production due to the plugging of the nozzle. The rate of flow breaking was reduced to less than 2%, and the number of single tundish continuous pouring furnace increased from less than 5 to 7-10. The oxygen content, nitrogen content, sulfur content, non-metallic inclusion rating and sulfide stress corrosion cracking were fully satisfied with the requirements of the product standard.

【學位授予單位】：北京科技大學
【學位級別】：博士
【學位授予年份】：2016
【分類號】：TF76;TG142

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本文編號：1825671