Ce合金化下FAB法埋弧焊縫組織與性能研究
發(fā)布時間：2018-08-04 18:10
【摘要】：FAB(flux aided backing)法埋弧焊是一種利用背面陶質(zhì)襯墊獲得雙面成形的單面焊接方法,具有生產(chǎn)效率高、裝配簡單、焊縫成形質(zhì)量好等優(yōu)點,廣泛應用于船舶建造、海洋平臺、大型儲罐等領域鋼結(jié)構的焊接制造中。在焊接過程中,FAB法埋弧焊的焊接熱輸入通常在50 kJ/cm以上,使得焊接熔池高溫停留時間較長,焊縫中生成大量先共析鐵素體和側(cè)板條鐵素體,從而降低焊縫金屬強韌性,導致焊縫金屬性能無法滿足使用要求。由此,如何降低大熱輸入下FAB法埋弧焊縫中先共析鐵素體和側(cè)板條鐵素體生成量,提高焊縫金屬的強韌性成為亟需解決的問題。針對這一問題本文研究了Ce合金化下FAB焊縫金屬的組織及性能,取得的研究成果如下:使用田口法設計正交試驗,分析討論了DH36低合金高強鋼FAB法埋弧焊中焊接電流、焊接電壓、焊接速度及焊絲干伸長四個工藝參數(shù)對焊縫成形質(zhì)量的影響,建立了FAB法埋弧焊接工藝參數(shù)與焊縫成形質(zhì)量的數(shù)學模型,優(yōu)化得出了最優(yōu)工藝參數(shù)組合。通過信噪比(S/N)分析和方差分析(ANOVA)得出,各因素對FAB焊縫成形質(zhì)量影響程度排序為:焊接電流I干伸長L焊接速度v焊接電壓U。FAB法焊接20mm厚DH36低合金高強鋼時,最佳工藝參數(shù)組合為:焊接電流I=1010A,焊接電壓U=32V,焊接速度v=23cm/min,干伸長L=35mm。對不同厚度DH36鋼板進行FAB焊接工藝試驗,分析了純Fe粉條件下不同焊接熱輸入量對FAB法埋弧焊接接頭微觀組織及力學性能的影響。8mm、12mm、15mm和20mm厚的FAB焊接接頭焊縫組織都主要由先共析鐵素體(GBF)、側(cè)板條鐵素體(FSP)和針狀鐵素體(AF)構成。隨著焊接熱輸入量增加,晶粒尺寸變大,焊縫中AF含量減少,GBF和FSP含量增加。粗晶熱影響區(qū)組織是粗大的奧氏體晶粒,晶內(nèi)有大量細小板條狀的貝氏體鐵素體,細晶熱影響區(qū)組織為鐵素體+珠光體,并有少量細小貝氏體鐵素體。FAB法埋弧焊接20mm厚DH36鋼板時,熱輸入量最大,焊接接頭的室溫拉伸性能、-20°C沖擊功、彎曲性能均無法滿足使用要求。試驗測定的焊接熱影響區(qū)不同區(qū)域的熱循環(huán)曲線表明,隨著熱輸入增大,高溫停留時間和冷卻速率均有較大幅度增加。研究了稀土Ce元素對FAB法埋弧焊縫金屬的組織與性能的影響。在FAB埋弧焊劑中加入不同含量CeO2粉,稀土Ce能夠過渡到焊縫金屬中對夾雜物進行改性,使夾雜物由Al2O3、Si O2、Ti2O3和MnS的復合物轉(zhuǎn)變?yōu)锳l2O3、SiO2、Ti2O3、MnS、Ce2O2S及CeS的復合物。稀土Ce的加入使焊縫金屬中直徑小于1.0μm的夾雜物比例明顯增加,細小的夾雜物增加了焊縫中誘導AF的形核質(zhì)點。含Ce夾雜物表層的Ce2O2S和CeS與α-Fe的錯配度小是誘導AF形核的主要機理。Ce元素提高了焊縫中AF比例,降低了GBF和FSP比例,顯著提高了FAB焊縫金屬的抗拉強度、延伸率和低溫沖擊性能。當焊劑中CeO2含量為3.0 wt.%時,夾雜物密度最大,AF比例高達76%,FAB焊縫金屬的抗拉強度高達582 MPa,延伸率為24%,-20°C的V型缺口沖擊功高達142J。對FAB焊接熔池中含Ce夾雜物的析出條件及存在形式進行熱力學計算。在焊接熔池中,O、S元素同時存在時,Ce總是先進行脫氧反應,Ce的脫氧產(chǎn)物僅有Ce2O3。Ce與S元素生成CeS還是Ce2S3取決于S元素的活度大小。當a[O]0.13,a[S]/a2[O]97.72時,生成夾雜物是CeO2。a[O]0.13,a[S]/a[O]12.59時,生成夾雜物是Ce2O3;當a[O]0.13,12.59a[S]/a[O]263,或a[S]0.51,97.72a[S]/a2[O]134896時,夾雜物是Ce2O2S。當a[S]0.51,a[S]/a[O]263時,夾雜物是Ce2S3。而當a[S]0.51,a[S]/a2[O]134896時,夾雜物是CeS。根據(jù)熱力學計算結(jié)果,對FAB法埋弧焊縫金屬中含Ce夾雜物類型進行判定,判定結(jié)果與試驗測定結(jié)果一致。
[Abstract]:FAB (flux aided backing) submerged arc welding is a single side welding method using the backside pottery liner to obtain double side forming. It has the advantages of high production efficiency, simple assembly and good weld forming quality. It is widely used in the welding of steel structures in shipbuilding, offshore platform, large storage tank and so on. In the welding process, the FAB method of submerged arc welding The welding heat input is usually more than 50 kJ/cm, which makes the welding pool stay at high temperature for a long time, producing a large number of pre eutectoid ferrite and side strip ferrite in the weld, thus reducing the strength and toughness of the weld metal, which leads to the failure of the weld metal properties to meet the requirements. Thus, how to reduce the first eutectoid ferrite in the FAB submerged arc weld under the high heat input is reduced. The formation of ferrite and side plate ferrite has become an urgent problem to improve the strength and toughness of weld metal. In this paper, the microstructure and properties of FAB weld metal under Ce alloying are studied. The results obtained are as follows: Using Taguchi method to design orthogonal experiments and analyze and discuss the welding electricity in FAB submerged arc welding of DH36 low alloy high strength steel. The influence of four technological parameters of flow, welding voltage, welding speed and welding wire elongation to weld forming quality, a mathematical model of FAB method for welding arc welding process parameters and weld forming quality was established, and the optimal process parameters were optimized. By means of S/N analysis and variance analysis (ANOVA), each factor was formed on the shape quality of the FAB weld. The influence degree of quantity is: welding current I dry elongation L welding speed V welding voltage U.FAB method to weld 20mm thick DH36 low alloy high strength steel, the optimum process parameters are as follows: welding current I=1010A, welding voltage U=32V, welding speed v=23cm/min, dry elongation L=35mm. to FAB welding process test of different thickness DH36 steel. The influence of different welding heat input on the microstructure and mechanical properties of FAB submerged arc welding joints.8mm, 12mm, 15mm and 20mm thick FAB welded joints are mainly composed of the eutectoid ferrite (GBF), the side plate ferrite (FSP) and the needle ferrite (AF). With the increase of the welding heat input, the grain size becomes larger and the AF content in the weld seam is contained. The content of GBF and FSP increases. The microstructure of the coarse grain heat affected zone is a coarse austenite grain, and there are a large number of fine bainite ferrite in the crystal. The microstructure of the fine crystal heat affected zone is ferrite and pearlite, and a small amount of fine bainite ferrite.FAB method is used to weld 20mm thick DH36 steel, and the heat input is the largest and the welding joint room temperature is the most. The tensile properties, -20 C impact power and bending performance can not meet the requirements of the use. The thermal cycle curves of different regions of the heat affected zone measured by the test show that the high temperature residence time and cooling rate are greatly increased with the increase of heat input. The effect of rare earth Ce elements on the microstructure and properties of the submerged arc weld metal by FAB method is studied. Adding different content of CeO2 powder to the FAB submerged arc welding flux, the rare earth Ce can be transferred to the weld metal to modify the inclusions, so that the inclusions from Al2O3, Si O2, Ti2O3 and MnS are converted to Al2O3, SiO2, Ti2O3, MnS, and the composite. Small inclusions increase the nucleation point of AF in the weld. The mismatch between Ce2O2S and CeS containing the surface of Ce inclusions is the main mechanism to induce AF nucleation, the main mechanism for inducing AF nucleation is.Ce element, which improves the proportion of AF in the weld, reduces the proportion of GBF and FSP, and significantly improves the tensile strength, elongation and low temperature impact properties of the FAB weld metal. When the content of CeO2 is 3 wt.%, the density of inclusions is the largest and the proportion of AF is up to 76%. The tensile strength of the FAB weld metal is 582 MPa, the elongation is 24%, the V type notch impact power of -20 degree C is as high as 142J. to the thermodynamic calculation of the precipitation conditions and the existence form of Ce inclusions in the weld pool of FAB. E always first deoxidize, Ce deoxidize product only Ce2O3.Ce and S element to produce CeS or Ce2S3 depends on the activity of S element. When a[O]0.13, a[S]/a2[O]97.72, the inclusion is CeO2.a[O]0.13, a[S]/a[O]12.59, the inclusion is Ce2O3. The inclusion is Ce2O2S. when a[S]0.51 and a[S]/a[O]263, the inclusion is Ce2S3. and when a[S]0.51, a[S]/a2[O]134896, the inclusion is CeS. according to the thermodynamic calculation result, it determines the type of Ce inclusions in the embedded arc weld metal of FAB method, and the result is in agreement with the test result.
【學位授予單位】：江蘇科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG445
本文編號：2164688
[Abstract]:FAB (flux aided backing) submerged arc welding is a single side welding method using the backside pottery liner to obtain double side forming. It has the advantages of high production efficiency, simple assembly and good weld forming quality. It is widely used in the welding of steel structures in shipbuilding, offshore platform, large storage tank and so on. In the welding process, the FAB method of submerged arc welding The welding heat input is usually more than 50 kJ/cm, which makes the welding pool stay at high temperature for a long time, producing a large number of pre eutectoid ferrite and side strip ferrite in the weld, thus reducing the strength and toughness of the weld metal, which leads to the failure of the weld metal properties to meet the requirements. Thus, how to reduce the first eutectoid ferrite in the FAB submerged arc weld under the high heat input is reduced. The formation of ferrite and side plate ferrite has become an urgent problem to improve the strength and toughness of weld metal. In this paper, the microstructure and properties of FAB weld metal under Ce alloying are studied. The results obtained are as follows: Using Taguchi method to design orthogonal experiments and analyze and discuss the welding electricity in FAB submerged arc welding of DH36 low alloy high strength steel. The influence of four technological parameters of flow, welding voltage, welding speed and welding wire elongation to weld forming quality, a mathematical model of FAB method for welding arc welding process parameters and weld forming quality was established, and the optimal process parameters were optimized. By means of S/N analysis and variance analysis (ANOVA), each factor was formed on the shape quality of the FAB weld. The influence degree of quantity is: welding current I dry elongation L welding speed V welding voltage U.FAB method to weld 20mm thick DH36 low alloy high strength steel, the optimum process parameters are as follows: welding current I=1010A, welding voltage U=32V, welding speed v=23cm/min, dry elongation L=35mm. to FAB welding process test of different thickness DH36 steel. The influence of different welding heat input on the microstructure and mechanical properties of FAB submerged arc welding joints.8mm, 12mm, 15mm and 20mm thick FAB welded joints are mainly composed of the eutectoid ferrite (GBF), the side plate ferrite (FSP) and the needle ferrite (AF). With the increase of the welding heat input, the grain size becomes larger and the AF content in the weld seam is contained. The content of GBF and FSP increases. The microstructure of the coarse grain heat affected zone is a coarse austenite grain, and there are a large number of fine bainite ferrite in the crystal. The microstructure of the fine crystal heat affected zone is ferrite and pearlite, and a small amount of fine bainite ferrite.FAB method is used to weld 20mm thick DH36 steel, and the heat input is the largest and the welding joint room temperature is the most. The tensile properties, -20 C impact power and bending performance can not meet the requirements of the use. The thermal cycle curves of different regions of the heat affected zone measured by the test show that the high temperature residence time and cooling rate are greatly increased with the increase of heat input. The effect of rare earth Ce elements on the microstructure and properties of the submerged arc weld metal by FAB method is studied. Adding different content of CeO2 powder to the FAB submerged arc welding flux, the rare earth Ce can be transferred to the weld metal to modify the inclusions, so that the inclusions from Al2O3, Si O2, Ti2O3 and MnS are converted to Al2O3, SiO2, Ti2O3, MnS, and the composite. Small inclusions increase the nucleation point of AF in the weld. The mismatch between Ce2O2S and CeS containing the surface of Ce inclusions is the main mechanism to induce AF nucleation, the main mechanism for inducing AF nucleation is.Ce element, which improves the proportion of AF in the weld, reduces the proportion of GBF and FSP, and significantly improves the tensile strength, elongation and low temperature impact properties of the FAB weld metal. When the content of CeO2 is 3 wt.%, the density of inclusions is the largest and the proportion of AF is up to 76%. The tensile strength of the FAB weld metal is 582 MPa, the elongation is 24%, the V type notch impact power of -20 degree C is as high as 142J. to the thermodynamic calculation of the precipitation conditions and the existence form of Ce inclusions in the weld pool of FAB. E always first deoxidize, Ce deoxidize product only Ce2O3.Ce and S element to produce CeS or Ce2S3 depends on the activity of S element. When a[O]0.13, a[S]/a2[O]97.72, the inclusion is CeO2.a[O]0.13, a[S]/a[O]12.59, the inclusion is Ce2O3. The inclusion is Ce2O2S. when a[S]0.51 and a[S]/a[O]263, the inclusion is Ce2S3. and when a[S]0.51, a[S]/a2[O]134896, the inclusion is CeS. according to the thermodynamic calculation result, it determines the type of Ce inclusions in the embedded arc weld metal of FAB method, and the result is in agreement with the test result.
【學位授予單位】：江蘇科技大學
【學位級別】：碩士
【學位授予年份】：2017
【分類號】：TG445
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