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Please use this identifier to cite or link to this item: http://nchuir.lib.nchu.edu.tw/handle/309270000/102507

標題: 309系列手銲條 應用於超高強度鋼板對接之研究
The study of AISI 309 series SMAW electrode apply to butt joining with ultra high strength steel
作者: 翁新凱
Weng, Shin-Kai
Contributors: 吳威德
Weite Wu
中興大學
關鍵字: 309 serial stainless steel electrode;ultra high strength steel;butt join
309系列不�袗�銲條;超高強度鋼板;對接
日期: 2008
Issue Date: 2012-09-04 11:46:25 (UTC+8)
Publisher: 材料科學與工程學系
摘要: 本實驗主要是將超高強度鋼板利用309系列不�袗�銲條進行銲接後,觀察與量測其銲接後之顯微結構以及機械性質對銲接性質之影響。本次實驗所選用之銲條為309、309L、309MoL,並以手工電弧銲(Shielded Metal Arc Welding, SMAW)的方式進行超高強度鋼板之對接;並且不�袗�銲條成份中碳含量以及鉬含量的變化,進而探討銲接顯微結構與機械性質之影響。藉由X-ray繞射分析與金相顯微結構觀察來鑑定銲道內部之顯微結構;並利用拉伸試驗與衝擊試驗,來量測銲接工件之抗拉強度與破裂韌性;再利用掃描式電子顯微鏡(SEM)觀察拉伸以及衝擊後之破斷表面,藉此了解破裂模式。
利用銲道成份與Schaeffler-Delong Diagram所推導出的鉻當量比與鎳當量比之公式得知,超高強度鋼板經309系列不�袗�銲條銲接後,其顯微組織皆為基地沃斯田鐵與殘留δ-肥粒鐵,與經過X-ray繞射分析後有相同之結果;其中以低碳且添加合金元素鉬之309MoL銲道內部殘留δ-肥粒鐵含量為最高(34.64%);309銲道內所殘留δ-肥粒鐵含量次之(18.52%);309L銲道內所殘留δ-肥粒鐵含量為最低(11.31%)。經由經驗式所計算出的殘留δ-肥粒鐵含量多寡,在金相顯微結構中可獲得證實。
在本實驗中發現,銲道沃斯田鐵基地相之晶粒大小深受殘留δ-肥粒鐵含量的影響,殘留δ-肥粒鐵含量愈多基地沃斯田鐵相之晶粒愈小,故於抗拉強度可藉由沃斯田鐵晶粒細化而提升;不過,在衝擊試驗結果顯示,沃斯田鐵晶粒細化卻無法提升破壞韌性,導致破壞韌性劣化主要原因為,殘留δ-肥粒鐵為連續蠕蟲狀結構,以致於提供了裂紋較容易傳播路徑,亦即銲道中沃斯田鐵晶粒細化效果不及裂縫沿著殘留δ-肥粒鐵相與沃斯田鐵相界面傳播的影響。
This study was focused on the microstructure and mechanical properties of ultra high strength steel butt join with 309 serial stainless steel electrode. 309, 309L, and 309MoL stainless steel was employed for electrode, and carrying on the butt joint of the ultra high strength steel by Shielded Metal Arc Welding (SMAW). From the chemical composition of the carbon content and molybdenum content in welding metal compositions of 309 serial stainless steel electrode, it found different carbons and molybdenum content had the significant effect on microstructure and mechanical properties of weldments. Therefore, the crystalline structure was determined by X-ray diffraction (XRD) and metallographic method was used for investigating the microstructure of weld. As to the mechanical properties of weld, tensile test and impact test were carried on the gauge of tensile strength and fracture toughness. In addition, the draw and breaking fractured surface after tensile test and impact test were observed with scanning electron microscope (SEM), analyzed the fracture mode.
By using the formula of Crequ./Niequ. ratio from Schaeffler-Delong Diagram, austenitic and ferritic phases were co-existed among the weld of ultra high strength steel butt join, welded with 309 serial stainless steel electrode. The predictive results were proved from metallographic structure and XRD analysis. Besides, 309MoL weld possessed the highest amount of residual δ-ferrite (34.64%)and 309L weld had the lowest content of residual δ-ferrite(11.31%). It can be calculated accurately according to metallography.
In this study, it found that the austenitic grain size of matrix in weld was affected by the variation of residual δ-ferrite content obviously. The austenitic grain size was decreased with the residual δ-ferrite content increasing. From the mechanical test results, tensile strength of weldment was enhanced devoted to the austenitic grain size refining and higher residual δ-ferrite content. And after impact test, the result appeared the existence of continuous vermicular residual δ-ferrite offered the route for the cracks to propagate spite of austeniteic grain refinement.
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