【摘要】：為應對能源短缺與環(huán)境危機,我國電力行業(yè)面臨著提高煤電使用的經(jīng)濟性以及環(huán)保性的嚴峻考驗,而通過提高火電機組的蒸汽參數(shù)(溫度、壓力),可以有效提高火力發(fā)電廠效率,因此這就對超(超)臨界火電機組鍋爐用鋼的性能提出了更高的要求。P92鋼是在P91鋼基礎上通過改善合金成分,采用復合多元強化手段而研發(fā)出的一種新型9%Cr鐵素體耐熱鋼,P92鋼以其優(yōu)異的綜合性能應用于超(超)臨界火電機組的鍋爐本體過熱器、再熱器之中,有效的提升了電廠效率和火電機組長期安全運行的穩(wěn)定性,目前已逐漸應用于我國的超超臨界機組建設中。而目前國內(nèi)對P92鋼焊接實際應用研究方面還比較少,所以通過研究合適可行的焊接工藝和焊后熱處理工藝,分析接頭中組織與性能之間的關系,為P92鋼焊接的應用提供理論與數(shù)據(jù)支持。本文選取由寶鋼生產(chǎn)的6 mm板厚的P92鐵素體耐熱鋼作為研究對象,采用鎢極氬弧焊(TIG)技術,選用合適的焊接工藝參數(shù)對P92鋼進行表面自熔焊,隨后制定不同焊后熱處理工藝。對經(jīng)不同焊后熱處理工藝的接頭進行金相組織、力學性能和電化學腐蝕的測試,其中力學性能測試評估包括顯微硬度分布、沖擊性能以及摩擦磨損性能,金相分析著重對接頭中δ-鐵素體的大小以及形態(tài)進行對比,并對接頭的沖擊斷口形貌和磨損形貌進行微觀觀察和機理的分析,對P92鐵素體耐熱鋼接頭中組織與性能之間的關系進行了研究。研究結(jié)果表明:P92鋼經(jīng)TIG自熔焊后在接頭中會出現(xiàn)δ-鐵素體,δ-鐵素體多分布于熱影響區(qū),在焊縫中心呈條狀且出現(xiàn)幾率小,δ-鐵素體的硬度要明顯低于臨近板條馬氏體的硬度。P92鋼接頭中焊縫的平均硬度值要高于母材的平均硬度值,焊態(tài)下焊縫硬度最高,沖擊韌性最低,這主要因為焊態(tài)下焊縫所生成的淬火馬氏體組織硬度和脆性很高。經(jīng)760℃回火熱處理,焊縫區(qū)顯微硬度顯著降低,沖擊韌性提高,接頭中δ-鐵素體含量顯著減少。隨著回火時間的延長,對接頭的硬度影響不大,但焊縫沖擊韌性提升,斷口形貌從韌/脆混合斷裂向韌性斷裂過渡。同時,經(jīng)焊后熱處理工藝,接頭的抗電化學腐蝕能力逐漸減弱,耐磨性能逐漸降低,磨損形貌從磨粒磨損向粘著磨損和表面疲勞磨損轉(zhuǎn)變。本文還對P92鋼進行活性氬弧焊(A-TIG)探索性實驗,研究結(jié)果發(fā)現(xiàn)其焊縫的硬度和沖擊韌性較傳統(tǒng)TIG焊縫差異不大,但是熔深有明顯的增加。此種焊接方法焊接P92鋼在活性化焊劑的選擇上還有待進一步研究。
[Abstract]:In order to cope with the shortage of energy and the environmental crisis, the electric power industry of our country is faced with the severe test of improving the economy and environmental protection of coal power use. Pressure), can effectively improve the efficiency of thermal power plants, so this puts forward higher requirements for the performance of supercritical thermal power unit boiler steel. P92 steel is based on P91 steel by improving the alloy composition. A new type of 9%Cr ferrite heat-resistant steel, P92 steel, developed by means of composite multicomponent strengthening, has been applied to superheater and reheater of supercritical thermal power unit with its excellent comprehensive properties. It has effectively improved the efficiency of power plant and the stability of long-term safe operation of thermal power units, and has been gradually used in the construction of ultra-supercritical units in China. However, there are few researches on the practical application of P92 steel welding in China, so the relationship between microstructure and properties in the joint is analyzed by studying suitable and feasible welding process and post-welding heat treatment process. To provide theoretical and data support for the application of P92 steel welding. In this paper, the P92 ferrite heat-resistant steel with thickness of 6 mm produced by Baosteel is selected as the research object. The surface self-fusion welding of P92 steel is carried out by using TIG welding (TIG) technology and suitable welding process parameters, and then different post-welding heat treatment processes are established. The microstructure, mechanical properties and electrochemical corrosion of joints with different post-weld heat treatment processes were tested. The mechanical properties of the joints were evaluated including microhardness distribution, impact properties and friction and wear properties. Metallographic analysis focuses on the comparison of the size and morphology of 未-ferrite in the joint, and the microcosmic observation and mechanism analysis of the impact fracture and wear morphology of the joint. The relationship between microstructure and properties of P 92 ferrite heat resistant steel joint was studied. The results show that 未 -ferrite will appear in the joint after TIG self-welding, and 未 -ferrite is distributed in the heat-affected zone. The hardness of 未-ferrite is obviously lower than that of adjacent lath martensite. The average hardness of weld is higher than that of base metal. The impact toughness is the lowest, which is mainly due to the high hardness and brittleness of the quenched martensite. After tempering at 760 鈩，

本文編號：2217440