BHW35钢的焊接及接头组织性能

分别采用埋弧焊和焊条电弧焊方法进行对接接头性能试验,接头经消应力退火后,进行了冷弯、拉伸、冲击韧性试验,并进行了金相组织及断口分析,力图从宏观、微观机理上解读不同工艺方法下焊接接头的性能变化规律,指出2种工艺方法均能满足焊接性能要求,焊条电弧焊力学性能及冲击韧性优于埋弧焊,热影响区的韧性优于焊缝。冲击断口分析表明,埋弧焊接头存在准解理+韧窝混合断裂特征。而焊条电弧焊焊接接头全部为韧窝断裂特征,其抗起裂及抗裂纹扩展性能优于埋弧焊。     

TP347H与T91焊接管接头工艺试验

对TP347H、T91异种管接头在平焊位置的焊接接头进行了工艺试验.确定了焊接工艺参数,对接头进行拉伸、弯曲、冲击等性能试验和应力腐蚀实验,并分析了接头组织.结果表明:采用钨极氩弧焊(TIG)的接头性能优于TIG焊打底焊条电弧焊盖面的接头性能.该试验结果对于火电厂异种管接头的连接具有较大的实用意义.     

S460M钢板焊接力学性能试验分析

对S460M钢板进行了焊条电弧焊与埋弧焊试验,从试验结果看,S460M钢板在热输入为15～18 kJ/cm的焊条电弧焊与热输入为13～40 kJ/cm的埋弧焊条件下焊接,焊接接头的拉伸性能、弯曲性能和冲击性能良好。试验结果表明,该材料的焊接接头性能优良。     

BHW35钢焊接接头高温冲击试验分析

BHW 35钢采用埋弧自动焊和焊条电弧焊,焊材为H10Mn2N iMoA及E7015-D2焊制的厚壁焊接接头,经正火、回火、消应力退火热处理后,对接头及母材实施了室温、100,200,350℃下缺口冲击试验,并进行了冲击断口、金相组织、硬度及化学成分分析.结果表明,接头硬度Hm ax埋弧焊为270.5 HV,电弧焊条焊为235.2 HV.探明随着温度升高,接头韧度较室温大幅度提高,冲击吸收功均出现峰值温度,埋弧焊接头为100℃,而焊条电弧焊接头为200℃,与母材变化规律相近.热影响区的韧度优于焊缝.焊条电弧焊的韧度优于埋弧焊.接头冲击吸收功室温在96.33 J以上,350℃下在120 J以上.结果表明,接头断口均为延性韧窝特征.冲击吸收功越高,断口韧窝撕裂特征越明显,韧窝越大,分布越不均匀.     

利用脉冲技术改善焊条电弧焊单面焊双面成形质量

针对焊条电弧焊实现单面焊双面成形存在的问题,研究了一种新型的采用脉冲电流的焊条电弧焊工艺——脉冲焊条电弧焊。以Q345E钢板为试验材料,研究了脉冲焊条电弧焊工艺对单面焊双面成形的影响。试验结果表明,脉冲电弧力可对焊接熔池形成有效的振荡和冲击,减少焊接缺陷,很容易实现对接焊缝单面焊双面成形。该研究为脉冲焊条电弧焊开拓了广阔的应用前景,具有重要的工程应用价值。     

抗硫高压分离器UNS N06625堆焊工艺与腐蚀试验

分析了高含H_2S,CO_2的产出物的特性,确定了井口分离器采用低合金钢堆焊625合金的结构形式,并选择合适的焊接工艺方法,对625合金的焊接性进行分析。经过工艺试验,摸索出合适的焊接工艺参数,进行了单层电渣堆焊、焊条电弧焊堆焊和小管内孔自动氩弧焊堆焊3种焊接方法评定,并进行了晶间腐蚀、氯化镁应力腐蚀和模拟分离器工况条件的抗硫化氢应力腐蚀和动态腐蚀评价试验。试验结果合格,满足技术要求,并据此完成了设备制造。     

中俄东线分离器用15MnNiNbDR钢板焊接接头性能分析

介绍了在-50℃低温环境下15MnNiNbDR钢板的焊接工艺,采用了焊条电弧焊和埋弧焊2种焊接方法,并对热处理状态的试件进行了力学性能试验(拉伸、弯曲、-50℃冲击试验),试验结果完全满足项目的要求,可以用于公司的实际生产,为类似项目提供参考借鉴。     

TP316L与Q345B异种钢焊接接头力学性能的研究

针对公司在建FLNG项目中不锈钢板(TP316L)与低合金钢板(Q345B)的焊接问题,结合此项目的技术要求及结构设计特点,选择焊条电弧焊(SMAW)进行单面焊双面成形的焊接工艺试验,焊条选用GES-309L (?3.2 mm),坡口形式为单面V形坡口,并对焊接接头进行拉伸、弯曲、冲击、硬度和宏观腐蚀试验研究,结果表明:该试验可获得满足要求的综合性能良好的焊接接头。     

超低碳贝氏体高强度钢焊接接头强韧性表征

采用焊条电弧焊、埋弧自动焊和焊接热模拟试验对控轧控冷工艺生产的超低碳贝氏体高强度厚钢板进行了焊接性能研究.结果表明,焊接热影响区具有较小的硬度差异.焊条电弧焊、埋弧自动焊实际焊接接头中热影响区硬度的最大差值小于60HV10,与相同级别低合金高强度钢相比,焊接热影响区强度的均匀性显著提高.焊接热影响区具有高的低温冲击韧性.当焊接热输入为56kJ/cm时,模拟过热区-40℃冲击吸收功可达到60J以上.在焊条电弧焊、埋弧自动焊实际焊接工艺条件下,焊接热影响区的-40℃冲击吸收功可达到100J以上.     

工程机械钢板Q960D焊接工艺参数的研究

对Q960D板材进行CO2焊和焊条电弧焊焊接工艺试验,CO2焊的热输入分别为83及13.2 kJ/cm,焊条电弧焊的热输入分别为11.3及12.0 kJ/cm.焊接工艺试验结果显示:在不同的焊接热输入下,此钢种的焊接性能符合工程中焊接的要求,该材料的焊接接头性能优良.     

液压支架主要承载构件焊接残余应力对比分析

针对综合机械化采煤工程中的安全性问题,以高强钢液压支架的掩护梁和底座为研究对象,应用X射线法对焊后及热处理后的残余应力水平进行评价.对液压支架掩护梁和底座在焊接后热处理后进行两次残余应力现场实测,分别选择各构件特殊部位6～ 10个区域(40多个测点)进行研究,定量给出了残余应力的总体水平及应力分布规律.结果表明,焊接后底座应力水平普遍高于掩护梁,最高应力为429.4 MPa(0.62ReL),掩护梁最高应力为348 MPa(0.50ReL).经过整体热处理,残余应力明显下降,底座及掩护梁残余应力最大值降幅为37％及71％;平均值降幅为46％及76％,新型热处理工艺对降低焊接残余应力有显著效果.     

Stress corrosion cracking of a recent rare-earth containing magnesium alloy,EV31A,and a common Al-containing alloy,AZ91E

Stress corrosion cracking of the magnesium alloy Elektron 21 (ASTM–EV31A) and AZ91E was studied using constant load test in 0.1 M NaCl solution (saturated with Mg(OH)₂), and slow strain rate test using glycerol, distilled water and Mg(OH)₂ saturated, 0.01 M and 0.1 M NaCl solutions. Slow strain rate test indicated that EV31A was less susceptible to stress corrosion cracking than AZ91E. Under less intense loading of constant load, EV31A was found to be resistant to stress corrosion cracking. Fractography of EV31A specimens showed little evidence of hydrogen embrittlement. The superior resistance of EV31A is attributed to a more robust oxide/hydroxide layer.     

Effect of Gd on microstructure and stress corrosion cracking of the AZ91-extruded magnesium alloy

AZ91 and AZ91–xGd (x = 0.5, 1.0, 1.5 wt%) magnesium alloys are extruded into plates. The addition of Gd promotes the formation of Al₂Gd, effectively reducing the volume fraction of the β-Mg₁₇Al₁₂ phase and making the banded structures of the extruded magnesium alloys thinner. The corrosion weight loss tests and electrochemistry analyses demonstrate that Gd significantly improves the pitting resistance of the AZ91 in 3.5-wt% NaCl solution saturated with Mg(OH)₂. Slow strain rate tensile tests show that in a corrosive environment, compared with AZ91, the elongation to failure of the AZ91–1.0Gd alloy is increased by 47%, and the alloy exhibits excellent stress corrosion resistance in this study. The fracture mode of AZ91 is changed from typical intergranular fracture to a mixture of transgranular and intergranular fracture in the corrosion solution by adding Gd. The mechanism of Gd to improve the stress corrosion resistance of the AZ91 magnesium alloy is that Gd increases the corrosion resistance, especially the pitting of AZ91.     

Assessment of the electrochemical corrosion properties and environmentally induced cracking of an A106 Gr B steel pipe weld in a NaCl solution saturated with H2S gas

In the area of heavy construction, welding processes are vital in the production and maintenance of pipelines and power plants. The fusion welding process generates formidable welding residual stress and metallurgical change, which together increase the crack driving force and reduce the resistance against brittle fracturing and environmental fracturing. This is a serious problem with many alloys, and it also arises in A106 Gr B steel pipes. This type of piping, which is used in petrochemical and heavy chemical plants, either degrades due to the corrosive environment, e.g., those containing chlorides and sulfides, and/or become damaged during service due to various corrosion damage mechanisms. Thus, in this study, after numerical and experimental analyses of the welding residual stress of a multi-pass welded A106 Gr B steel pipe weld, the electrochemical corrosion properties and environmentally induced cracking of an A106 Gr B steel pipe weld were assessed in a 5.0 wt.% NaCl solution that was saturated with H2S gas at room temperature on the basis of NACE TM 0177-90. In terms of sulfide stress corrosion cracking (SSCC) and sulfide corrosion fatigue (SCF), the low SSCC limit of smooth specimens, σ_SSCCsmooth, and the SCF limit, Δσ_SCF, were 46 % and 32 % (160 MPa) of the ultimate tensile strength (502 MPa) of an A106 Gr B steel pipe weld, respectively. Further, (Δσ_res)_SCF was assessed under 75 MPa, which is 15 % of the tensile strength.     

The stress corrosion cracking behavior of austenitic stainless steels in boiling magnesium chloride solutions

The change in the mechanism of stress corrosion cracking with test temperature for Type 304, 310 and 316 austenitic stainless steels was investigated in boiling saturated magnesium chloride solutions using a constant load method. Three parameters (time to failure; t_f, steady-state elongation rate; l_ss and transition time at which a linear increase in elongation starts to deviate; t_ss) obtained from the corrosion elongation curve showed clearly three regions; stress-dominated, stress corrosion cracking-dominated and corrosion-dominated regions. In the stress corrosion cracking-dominated region the fracture mode of type 304 and 316 steels was transgranular at higher temperatures of 416 and 428 K, respectively, but was intergranular at a lower temperature of 408 K. Type 310 steel showed no intergranular fracture but only transgranular fracture. The relationship between log l_ss and log t_f for three steels became good straight lines irrespective of applied stress. The slope depended upon fracture mode; −2 for transgranular mode and −1 for intergranular mode. On the basis of the results obtained, it was estimated that intergranular cracking was resulted from hydrogen embrittlement due to strain-induced formation of martensite along the grain boundaries, while transgranular cracking took place by propagating cracks nucleated at slip steps by dissolution.     

Corrosion of reinforcing steel in neutral and acid solutions simulating the electrolytic environments in the micropores of concrete in the propagation period

Steel embedded in concrete passivates due to the alkaline nature of the concrete pore solution. Reinforcement corrosion develops when the alkalinity is neutralized. Corrosion, in turn, induces acidification of the surrounding pore solution. In the present paper, corrosion rate of corrugated steel bars is studied and measured at different pH values in solutions simulating chloride environments. The media considered consists of saturated calcium hydroxide solutions containing Na and K⁺, neutralized with ferrous chloride. This latter substance is the soluble compound produced during the corrosion of steel after chloride attack. Hydrochloric acid solutions of different pHs were prepared in order to compare the steel corrosion rates in these solutions with those observed in ferrous chloride solutions of the same pH. A comparison of polarization resistance measurements (R_p) with gravimetrically weight loss determined is presented. Tafel slopes results are also included. Additionally, a comparison is made between measurements of AC impedance with those of the R_p method. The results indicate that the corrosion rate in the studied media follows the general trend found in other media of similar pH values: corrosion increases in acidic solutions, remains rather stable for pH range 3-11 and decreases significantly in highly alkaline solutions.     

Stress corrosion cracking behaviour of Al‐Li alloy 8090‐T8171 plate exposed to various synthetic environments

The stress corrosion cracking (SCC) behaviour of 8090‐T8171 plate material was investigated in short transverse direction performing constant load tests and constant extension rate tests under permanent immersion conditions. At an applied stress of 100 MPa, smooth round tensile specimens were exposed to synthetic environments containing chlorides and various nonhalide anions. Environment‐induced cracking was not observed in aqueous solutions of 0.6 M NaCl, LiCl, NH₄Cl, or MgCl₂. In 0.6 M NaCl solutions containing 0.06 M Na₂SO₄ or Na₃PO₄, the SCC behaviour of 8090‐T8171 plate was similar to that observed in pure 0.6 M NaCl solution. Sodium chloride solutions with additions of nitrate, hydrogen carbonate, or carbonate promoted stress corrosion cracking. Threshold stresses below 100 MPa were obtained from constant load tests using the latter environments. When sodium sulfite or sodium hydrogen phosphate was added, values being 100 MPa or slightly higher were determined. Lithium and ammonium present as cations in mixed salt electrolytes accelerated SCC failure. Lithium chloride solutions containing nitrate, hydrogen carbonate, carbonate, or sulfite were highly conducive to stress corrosion cracking. Very low SCC resistance was found for alloy 8090‐T8171 exposed to synthetic environments with additions of ammonium salts. Constant extension rate tests were carried out using notched tensile specimens. Displacement rates were in the range 2 × 10^?6 ? 2 × 10^?5 mms^?1. Aqueous 0.6 M NaCl solutions with additions of 0.06 M NH₄HCO₃, (NH₄)₂SO₄, or Li₂CO₃ promoted environment‐induced cracking with 8090‐T8171 plate, as indicated by severe degradation of notch strength. The constant extension rate testing technique did not indicate SCC susceptibility using sodium chloride solutions containing sodium sulfate or lithium sulfate. For specimens exposed to substitute ocean water a slight degradation of notch strength was found at the lowest displacement rate applied.     

Zum Spannungsrißkorrosionsverhalten rekristallisierter Bleche der AlLi-Legierung 8090-T81

On the stress corrosion cracking behaviour of recrystallized 8090-T81 Sheets The stress corrosion cracking behaviour of a recrystallized sheet of the Al-Li-Cu-Mg-Zr alloy 8090-T81 was studied performing accelerated tests under constant deformation, constant load, and slow strain rate conditions. The used electrolytes were an aqueous 3.5% NaCl solution, an aqueous solution of 2% NaCl + 0.5% Na₂CrO₄ at pH = 3, and synthetic seawater according to ASTM D1141. Alternately immersed in 3.5% NaCl solution according to ASTM G44 the investigated alloy was found to be susceptible to stress corrosion cracking was not promoted by continuous immersion in aerated 3.5% NaCl solution, 3.5% NaCl solution saturated with carbon dioxide, and in acid chromate inhibited 2% NaCl solution. Using the slow strain rate technique with continuously immersed flat tensile specimens stress corrosion cracking was only observed in synthetic seawater. Under specific environmental conditions hydrogen embrittlement can occur in the investigated material.     

High-temperature high-pressure SCC testing of corrosion-resistant alloys

Stress corrosion cracking test methods of corrosion-resistant alloys are reviewed. The interest to write a review on this topic was drawn by demands for oil country tubular goods applicable in deep wells with high pressures, high temperatures, and the presence of H₂S, where stress corrosion cracking is one of the most critical failure modes. All conventional methods for determining the stress corrosion cracking resistance of an alloy, mainly slow strain rate testing, constant load testing (tensile, 4-PB), constant strain testing (U-bend, C-ring), and fracture mechanics (double cantilever beam sample) are covered. Considering the variety of testing solutions, the field of search is narrowed to hot (up to 250°C) aqueous chloride solutions with dissolved H₂S and CO₂ gases under high pressure (up to 200 bar total pressure).     

Potentiodynamische und potentiostatische Messungen an gespannten Drahtelektroden in gesättigten Ca(OH)2-Lösungen mit verschiedenen Zusätzen

Potentio-dynamic and potentio-static measurements on tensioned wire electrodes in saturated Ca(OH), solutions with different admixtures The influence of mechanical tensile stresses on the corrosion behaviour of unalloyed steel wires has been examined in saturated calcium hydroxide solutions with and without additions of chloride or chromate ions to simulate the practical conditions encountered with steel reinforcement in concrete. In order to account for the influence of oxygen dissolved in the corrosion medium, the tests were carried out in an air-saturated solution as well as in a solution free from oxygen. The tests revealed a considerable increase in the dissolution rate of iron in the active potential range as well as an increase in the passive current density with increasing tensile stress. Also with increasing tensile stress the stress corrosion cracking potential is shifted towards the negative side. The test results indicate that the thickness of the passive film increases with the tensile stress. All these effects are even more marked in air-saturated solution.