新型2205型双相不锈钢埋弧焊用烧结焊剂

开发了焊接2205型双相钢的埋弧焊用烧结焊剂,渣系为CaF2-SiO2-MgO-Al2O3,属于中性焊剂。该焊剂有良好的工艺性能和冶金性能,配合焊丝ER2209焊接所得熔敷金属为铁素体+奥氏体双相结构。熔敷金属有较高的强度和良好的塑性,其中铁素体含量为22%～35%。研究发现室温时效时间和焊道最终温度对熔敷金属中的铁素体含量有影响,随着室温时效的延长和焊缝最终温度的降低,熔敷金属中的铁素体含量增加。     

操作因素对E308-16焊条熔敷金属抗裂性的影响

从操作因素出发,通过调整电弧长度和焊接电流,对不锈钢E308-16焊奈的抗裂桂进行了研究,对熔敷金属的化学成分、铁素体含量以及微观金相进行了检测和分析,发现随着电弧长度的增加,熔敷金属中的铁素体形成元素Cr含量减少,而奥氏体形成元素Ni和N增加,导致熔敷金属的铁素体含量明显降低,铁素体形态发生明显变化,同时晶界也发生较大的改变,最终其抗裂性变差.随着焊接电流的增加,熔敷金属中的Cr氧化烧损增加,铁素体含量有下降的趋势,熔敷金属的抗裂性能下降.通过分析,从操作因素方面,提出了在实际生产中提高E308-16焊条抗裂性的有效措施.     

低温用碱性不锈钢焊条E308L-15的研制

文中介绍一种用于-196 ℃低温环境下的碱性奥氏体不锈钢焊条E308L-15。测试了熔敷金属的化学成分、铁素体数、金相组织、耐晶间腐蚀性能、室温强度和-196 ℃低温冲击韧性。结果表明,所开发的E308L-15焊条熔敷金属的金相组织由奥氏体和少量铁素体组成,并且随着熔敷金属氧含量的降低,-196 ℃夏比V形缺口冲击吸收能量增加,讨论了影响熔敷金属低温冲击韧性的因素,提出了提高熔敷金属低温冲击韧性的方法。     

核级E309L-16奥氏体不锈钢焊条的研制

核岛主设备核心部件使用的E309L-16奥氏体不锈钢焊条长期依赖进口,严重制约中国核电事业的发展.研究了焊态铁素体含量对熔敷金属经608℃×40 h热处理后断后伸长率的影响,对焊态铁素体含量大于12％的热处理态熔敷金属微观组织进行分析,并研究了热输入和热处理保温时间对熔敷金属拉伸性能的影响,试验结果表明:当铁素体含量大...     

热处理对耐磨熔敷金属组织与性能影响

采用钛钙型药皮堆焊焊条D172,以手工电弧焊工艺在基体材料上堆焊一定厚度的耐磨金属.为了消除焊态过程中残留的残余应力,提高堆焊层熔敷金属的耐磨性能,本试验对基体材料进行了焊前预热,控制层间温度,焊后回火等工艺,分析了焊态、回火工艺下获得的耐磨熔敷金属的显微组织和显微硬度.结果表明,回火温度在400℃时,堆焊层熔敷金属显微组织和硬度与焊态基本一致,其显微组织主要为马氏体和网状残奥氏体;550℃时,残余奥氏体转变为马氏体,且碳化物析出量增多,硬度升高;700℃时,马氏体分解,产生大量碳化物和α-Fe铁素体,硬度显著降低;保温时间延长,堆焊层熔敷金属显微组织和硬度变化不大.     

气保护药芯焊丝熔敷金属组织的选择与控制

介绍了气保护药芯焊丝熔敷金属中组织及形态,分析了熔敷金属组织的影响因素及对焊缝韧性的影响,提出了焊丝熔敷金属组织控制机理。结果表明:该焊丝熔敷金属的组织为大量针状铁素体+少量晶界铁素体+极少量侧板条铁素体。焊缝组织的影响因素中,起决定作用的是熔敷金属化学成分和焊缝的冷却速度。夹杂物尺寸和Ti、B加入量的控制是形成针状铁素体的必要条件,而焊接热输入的控制则是充分条件,二者缺一不可。期待研发一种特殊添加剂,能有效获得所需针状铁素体,并使焊缝韧性对焊接热输入不再敏感。     

高温回火热处理对核级E316L不锈钢焊条熔敷金属性能的影响

对经历610℃恒温16 h高温热处理的E316L不锈钢焊条熔敷金属进行力学性能、抗晶间腐蚀性能和微观结构检验分析,结果表明:E316L不锈钢焊条熔敷金属室温抗拉强度升高,非比例延伸强度下降,断后伸长率下降,室温冲击吸收功下降10 J左右,微观组织中的岛状铁素体发生部分分解,析出相少量增加,但强度、断后伸长率、冲击吸收功、抗晶间腐蚀性能仍符合技术条件的要求,铁素体相基本特征未改变,少量M23C6析出相分布在奥氏体晶粒内部,未发生在晶界的聚集。研究表明,研发的E316L焊条熔敷金属经历610℃恒温16 h高温热处理后,其力学性能和抗腐蚀性能满足技术要求。     

电磁搅拌对管线钢埋弧焊熔敷金属低温韧性的影响

研究了电磁搅拌对管线钢埋弧焊熔敷金属低温韧性的影响。结果表明：电磁搅拌使０．２－０．６μｍ的夹杂物数量增加,促进了奥氏体晶粒内针状铁素体的生成和细化。使晶内铁素体含量由８５．１％提高到９１．７％,抑制了晶界铁素体和侧板条铁素体的形成,使熔敷金属的低温冲击性明显提高。     

保护气体中氧气含量对低合金高强钢熔敷金属组织和力学性能的影响

使用不同氧气含量的保护气体对低合金高强钢HSLA-65进行了实心焊丝和药芯焊丝的熔化极气体保护焊。通过拉伸试验、冲击试验等力学性能检测,结合光学显微镜、扫描电镜、透射电镜和能谱分析等,研究了保护气体中氧气含量的变化对熔敷金属组织和力学性能的影响。结果表明:实心焊丝和药芯焊丝的熔敷金属显微组织均由针状铁素体和晶界铁素体组成。在相同保护气体成分下,药芯焊丝熔敷金属中针状铁素体比例大于实心焊丝熔敷金属,药芯焊丝熔敷金属的综合力学性能优于实心焊丝熔敷金属。随着保护气体中氧气比例的增加,实心焊丝熔敷金属中针状铁素体的含量先增加后减少;而药芯焊丝熔敷金属中针状铁素体含量一直在减少。两者熔敷金属的综合力学性能随针状铁素体比例的变化呈现出相同的变化规律。     

Al对金红石型药芯焊丝熔敷金属组织性能的影响

通过在金红石型药芯焊丝中加入不同含量的铝铁,研究了Al对熔敷金属组织及力学性能的影响,并对夹杂物的数量和成分进行了分析。随着焊丝中铝铁含量的增加,Al对促进其他脱氧元素过渡的作用不明显,熔敷金属强度基本保持不变,韧性变化显著。微观组织及夹杂物分析发现,当Al以合金元素的形式固溶于基体中时,促进晶界块状铁素体的析出,使韧性恶化;当Al以脱氧剂的作用与Ti、Mn等元素联合脱氧时,可以优化夹杂物尺寸,增大原奥氏体晶粒尺寸,促进针状铁素体的形核,使熔敷金属获得良好的韧性。     

元素V对奥氏体焊缝金属晶间腐蚀敏感性的影响

采用透射电镜(TEM)分析技术研究了1Cr19Ni23N焊条熔敷金属中钒含量对组织及对熔敷金属抗晶间腐蚀性能的影响.结果表明,低钒含量焊条熔敷金属组织中沿奥氏体晶界析出M23C6型富铬碳化物,在晶界附近形成贫铬层,导致晶间腐蚀的发生;高钒含量焊条熔敷金属组织中,V优先于Cr与C形成细小弥散的碳化钒分布在晶粒内部,使得该焊条在保持原较高碳含量的基础上,通过改变碳化物形态和分布达到了保持高强度和改善晶间腐蚀敏感性的目的.     

外场处理细化管线钢埋弧焊缝的显微组织

研究了电磁搅拌和氩弧表层快速加热等外场对管线钢埋弧焊缝显微组织的影响。结果表明,电磁搅拌改变了焊缝中非金属杂夹物的大小和尺寸分布,使尺寸位于0.2～0.6μm之间的夹杂物数量增加,促进了奥氏体晶粒内针状铁素体的生成和细化,针状铁素体的含量由85.1%提高到了91.7%,提高了熔敷金属的韧性。而氩弧加热处理使焊缝表层的柱状晶消失,针状铁素体晶粒明显细化,并消除了对性能有害的组织-晶界铁素体和侧板条铁素体。     

氧对00Cr13Ni5Mo熔敷金属组织和韧性的影响

文中研究了MAG焊保护气体氧含量变化对00Cr13Ni5Mo熔敷金属中氧化物夹杂类型、尺寸、数量、分布和残余奥氏体、逆变奥氏体含量以及冲击韧性的影响.结果表明,Si-Mn-O,Si-Mn-Al-O复合氧化物夹杂是导致00Cr13Ni5Mo熔敷金属冲击韧性下降的主要原因.氧化物夹杂对00Cr13Ni5Mo熔敷金属回火过程中产生的逆变奥氏体具有抑制作用,随着氧化物夹杂的增加,逆变奥氏体含量呈减少趋势.     

碳和氮元素对高强度奥氏体焊缝组织和性能的影响

采用扫描电镜(SEM)和透射电镜(TEM)等分析研究了碳、氮元素对奥氏体焊条熔敷金属组织和性能的影响.结果表明,随着碳含量的增加,熔敷金属晶界上M23C6碳化物析出物逐渐增多,析出颗粒增大,虽然熔敷金属的抗拉强度有所提高,但韧性明显降低,碳含量增加到一定程度后,对强度的影响趋于平缓,但对晶界碳化物的数量和尺寸仍然有强烈的促进作用,韧性持续降低,耐晶间腐蚀性能大大降低.随着氮含量的增加,抗拉强度呈持续上升趋势,同时韧性仍能保持在较高水平,晶界上析出碳化物少,抗晶间腐蚀性能良好.     

超级双相不锈钢多层多道焊接接头组织及腐蚀性能

选用2507超级双相不锈钢作为研究对象,研究钨极氩弧焊多层多道焊接接头的组织和腐蚀性能.采用两种不同保护气进行钨极氩弧焊,主要讨论焊接道次和氮气添加对组织和腐蚀性能的影响.结果表明,焊缝中心均有较高的奥氏体含量,其腐蚀速率是焊根部位的0.68倍;盖面和焊根奥氏体含量相近,但盖面由于其弥散且尺寸相对较大的晶内奥氏体表现出更好的耐腐蚀性,焊根是焊缝金属的薄弱区域.混合区由于热影响区的存在腐蚀速率最快.保护气中氮气的添加促进了奥氏体的生成,降低了腐蚀电流密度一个数量级,提高了整体的腐蚀性能.     

THE EFFECT OF BORON AS A FUNCTION OF AUSTENITISING TEMPERATURE

奥氏体化温度对硼钢淬透性的影响,从实验结果得到,在各种热处理条件下均随温度的提高逐渐降低。氧化及氮化的因素对硼钢淬透性的下降是有一定的影响,但硼原子本身在奥氏体中的分布情况对淬透性的影响是更重要的一个因素。 在渗硼试样中观察硼化合物的形成,指出,从高奥氏体化温度直接淬火后,硼的沉淀物是在奥氏体晶界上及晶粒内均匀分布的,但在等温处理、正火处理或慢冷试样中,硼化合物大部份沉淀在奥氏体晶界上。因此,硼钢在高温奥氏体化后失去良好淬透性的原因,可能是由于硼原子从奥氏体晶界上的回扩散作用,使晶界上得不到足够的硼原子降低晶界能,引起硼的效能暂时的消失。     

Effect of nitrogen on corrosion behavior of 28Cr-7Ni duplex and microduplex stainless steels in air-saturated 3.5 wt% NaCl solution

The corrosion behavior of 28Cr-7Ni-O-0.34N duplex stainless steels in air-saturated 3.5-wt% NaCl solution at pH 2, 7, 10 and 27 °C was studied by the potentiodynamic method. Two types of microstructures were investigated: the as-forged duplex and microduplex (average austenite grain size 5-16 μm) structures. The austenite volume fractions of the tested steels were between 0.35 and 0.64. The nitrogen effect on corrosion behaviors of both duplex and microduplex stainless steels were the same. At pH 2, the corrosion potential increased when the nitrogen content increased, however, corrosion current density as well as corrosion rate decreased. At pH 7 and 10, the effect of nitrogen on corrosion potential and corrosion rate could not be observed. Corrosion potential at pH 10 was lower than at pH 7. Pitting potential increased when the nitrogen content in the tested steels increased at all tested pH. For the nitrogen effect on the passive current density, it seemed that only at pH 2, the average passive current densities reduced when the nitrogen content increased. Nitrogen may have participated in the passive film or has been involved in the reaction to build up passive film. The ammonium formation and nitrogen enrichment at the interface metal/passive film with adsorption mechanism were discussed. The dissolute nitrogen might have combined with the hydrogen ions in solution to form ammonium ions, resulting in increasing solution pH. The steel could then easily repassivate, hence the corrosion potential and pitting potential would increase. However, the ammonium formation mechanism could not explain the decrease of corrosion potential in basic solution. Nitrogen enrichment at the metal/passive film interface with adsorption mechanism seemed to be an applicable consideration in increasing pitting potential. However, this mechanism did not involve the ammonium ion formation. In general, for the duplex and microduplex stainless steels tested, nitrogen increased the general corrosion resistances in acid solution and pitting corrosion resistance at all solution pH. Metallographic observation in both tested duplex and microduplex steels after pitting corrosion at all tested pH revealed that, the corroded structure in the tested steels without nitrogen alloying was austenite, but those with nitrogen alloying was ferrite. Even though ferrite had a higher chromium content than austenite but higher dissolved nitrogen in austenite than in ferrite may have increased the pitting resistance equivalent number (PRE) of austenite to be higher than that of ferrite.     

Effect of normalising heat treatment on microstructure and properties of nickel alloyed C-Mn weld metals

Abstract

Five different basic manual metal arc welding electrodes, containing varying amounts of nickel (from 0 to 3.5%) were deposited in an all weld metal joint. Mechanical testing and microstructure examination was performed in the as deposited and heat treated conditions. The heat treatment was carried out at three different temperatures (930, 980, and 1030° C) for 20 min. The tensile strength was decreased by the heat treatment, but the magnitude of the decrease varied between the weld metals. The impact properties were also affected by the heat treatment. For impact properties, however, a decrease was found at low testing temperatures, whereas an increase was observed at higher testing temperatures. The decrease in tensile strength after normalisation, compared with the as deposited condition, is due to an increasing grain size and a decreasing dislocation content. The strength achieved by the different weld metals in the normalised condition can be explained by the variation in solid solution hardening resulting from differences in the alloying content.Two factors seemed to be especially important in determining the variations in impact properties between weld metals in the as deposited condition. The nitrogen content of the weld metals decreased the impact toughness, whereas increasing nickel content was associated with improved impact toughness. In the normalised condition, reduced at lower testing temperatures, because cleavage fracture started readily in the resulting coarser grains. Furthermore, traces of segregated bands of microphases probably acted as initiation sites for cleavage cracks. At higher testing temperatures, higher impact toughness was obtained, owing to the lower strength of the weld metals. One of the electrodes showed superior impact toughness values to the other electrodes, in both the as deposited and heat treated conditions. The main reason for the high toughness in the as deposited condition was the ability of this electrode to refine previously deposited beads to a high degree. The reason for the high toughness after normalising is still not certain, but it was noted that this weld metal had a very low oxygen content and also a comparatively low volume fraction of segregated microphases. These factors might be important in achieving the very high impact toughness observed.     

Comparison of two types of low-transformation-temperature weld metals based on solidification mode

Two types of low-transformation-temperature weld metals were devised, one associated with primary austenite solidification, the other primary ferrite solidification. The martensite start temperature of both low-transformation-temperature weld metals was about 125°C. Experimental results showed that low-transformation-temperature weld microstructure associated with primary austenite solidification was martensite with 8.0% retained austenite, whereas that one related to primary ferrite solidification primarily consisted of martensite and δ-ferrite. Accordingly, both welded joints had little distinction between distortion and residual stress, indicating that weld metal associated with primary ferrite solidification played the same function as primary austenite solidification on residual stress reduction. Moreover, the low-transformation-temperature weld metal associated with primary ferrite solidification had higher tensile strength and hardness than that based on primary austenite solidification.