焊后热处理对316LN焊接残余应力的影响

为了研究焊后热处理对316LN焊接残余应力的影响,设计了拘束应力试验件并制定了热处理工艺方案,通过盲孔法测定热处理前后焊接残余应力值,并进行了对比分析。结果表明:(920±10)℃×1h和(400±10)℃×(2~3)h均可以很好地减少316LN焊接残余应力,尤以(920±10)℃×1h去应力效果最为显著。     

焊后热处理对AF1410钢电子束焊接接头组织及性能的影响

研究了三种不同焊后热处理状态下AF1410钢电子束焊接接头的组织及力学性能。结果表明:AF1410钢经电子束焊接后采用预备热处理(900±10)℃×1 h,空冷;(680±10)℃×6 h,空冷+最终热处理(860±10)℃×1 h,油淬;-73℃×1 h,空冷;510℃×5 h,空冷)的焊后热处理工艺能够获得优良的综合力学性能。其中,接头室温抗拉强度不低于母材,伸长率达到母材的88%;焊缝及热影响区室温冲击韧性分别达到母材的64%和89%。     

一种Al-Mg—Si铝合金板材固溶处理及人工时效工艺研究

研究固溶处理温度、保温时间、淬火转移时间、时效前停放时间、时效温度、时效保温时间等工艺参数对一种Al-Mg-Si合金板材的组织及性能的影响.确定:该种Al-Mg-Si板材淬火加热温度为525℃±2℃;淬火加热保温时间为30 min～70 min;淬火转移时间t1≤30 s;淬火后停放时间t2≤4 h;时效温度为180℃±5℃;时效时间为10 h.     

HDM钢热处理工艺研究

通过选择不同固溶、时效温度组合 ,对新型镁合金压铸用模具钢 (HDM钢 )的组织及性能和热处理工艺之间的关系进行了详细地探讨 ,确定出HDM钢最佳固溶时效热处理工艺为 (110 0± 10 )℃× 1h (70 0 10 )℃× 2h。     

工矿机车车轴高温回火脆性的防止

工矿机车车轴所用材料为40Cr钢,其最大直径为210 mm.制造工艺流程为:锻造→正火→粗加工→调质→精加工.正火工艺为:(870±10)℃×4h,空冷.调质工艺为:淬火(850±10)℃×3.5h,油冷;回火(580±10)℃×4h,水冷.技术要求为:表面硬度(241～285)HB,σb≥685 MPa,δ5≥14%, AKU≥31 J.     

热处理制度对不锈钢复合板耐蚀性影响分析

爆炸复合法制备的奥氏体不锈钢因在制备过程中易产生加工硬化,复合后必须进行消应力热处理。而奥氏体钢在消应力热处理时易出现腐蚀倾向,因此本文以奥氏体不锈钢复合板为研究对象,对比分析6种热处理工艺条件下材料的晶间腐蚀性能变化,从而制定合理的热处理工艺。研究结果表明:在((540~680)±10)℃/4 h温度范围内,如果采用炉冷的方式冷却,奥氏体钢均出现晶间腐蚀倾向;而当热处理工艺为(540±10)℃/4 h,空冷时,不足以改善材料的加工硬化现象;当热处理温度升高,工艺为(680±10)℃/4 h空冷时,不锈钢仍出现晶间腐蚀倾向;只有当温度定位(620±10)℃/4 h空冷时,奥氏体钢恢复了良好的塑形,并表现出优良的耐蚀性,且金相检验结果表明,弯曲试样表面仅存在大量的塑形变形,而无裂纹。因此爆炸复合后,不锈钢复合板的最佳热处理制度为:(620±10)℃/4 h空冷。     

延长高速钢模具使用寿命的热处理工艺研究

采用不同的工艺对M2高速钢模具进行热处理,并测试和分析试样的表面硬度、耐磨损性能和抗冷热疲劳性能。结果表明,分级退火和预热后再淬火的热处理工艺有利于细化M2高速钢模具组织中的碳化物、提高表面硬度、耐磨损性能和抗冷热疲劳性能;延长M2高速钢模具使用寿命的热处理工艺优选为:采用(875±5)℃×3 h+(750±5)℃×5h分级退火,空冷;采用(500±5)℃×1 h预热+(1 200±5)℃×3 h淬火,油冷至200℃后空冷;采用(540±5)℃×6 h回火,空冷。     

不同热处理工艺下Ti-Al-Sn-Zr-W-Si高温钛合金的蠕变性能

研究不同热处理工艺下Ti-Al-Sn-Zr-W-Si高温钛合金的蠕变性能。结果表明,Ti-Al-Sn-Zr-W-Si高温钛合金最佳的热处理工艺为1 010℃保温1 h淬火,550℃保温4 h回火。在550℃、300 MPa条件下,Ti-Al-Sn-Zr-WSi高温钛合金试件的持久时间超过了1 000 h,其蠕变性能超过其他钛合金。     

Cr26型高铬铸铁组织性能及其热处理工艺

研究了Cr26高铬铸铁化学成分的控制范围和热处理工艺对其硬度和冲击性能的影响,分析了该成分高铬铸铁经过不同热处理后的组织.结果表明,采用文中所述生产工艺和1 040℃±10℃×6h特殊淬火液淬火+275℃×6h或440℃×6 h回火的热处理工艺,高铬铸铁硬度达60 HRC以上,冲击韧度达10 J/cm2,其耐磨性是高铬铸铁Cr15的1.32倍,高锰钢ZGMn13的1.95倍.     

热处理设备(十五)

正4.2技术参数一般包括:型号RT×;额定功率×;额定功率几十至几百k W;额定电压380 V;频率50 Hz;相数3相;最高温度一般1200℃;工作温度一般1100℃;炉膛尺寸长×宽×高分别在几百至几千mm;加热元件接法Y型;空炉升温时间3~3.5 h;控温精度±1℃;炉温均匀性±3~5℃或±5~8℃;最大装载量1至10 t多;自     

PM René 95合金涡轮盘等温锻造工艺的模拟式设计

利用热力耦合有限元程序FORMT,对PM　Rene95合金中等尺寸（外径尺寸约为630mm）涡轮盘的等温锻造工艺进行了模拟式设计.结果表明,采用TZM钼基合金模具。在1050℃以接近10-3s-1的应变速率进行闭式模锻和开式模锻,模具材料均能满足使用要求,且开式模锻设备最大载荷不超过31×103kN;采用K21合金模具,在1000℃以相同条件等温成形。模具材料因变形热效应及边界摩擦引起温升而失效且所需设备吨位相对较大.     

Oxidation behaviour of Fe‐Cr‐Al alloys during resistance and furnace heating

The behaviour of thin Fe‐Cr‐Al heating element strips was investigated with respect to the oxidation limited life times and geometrical changes during resistance and furnace heating. For this purpose, isothermal and cyclic oxidation tests varying in their total exposure time and cycle duration were performed in the temperature range 1050–1200 °C. Specimens subjected to rapid cyclic, resistance heating revealed shorter life times than calculated for specimens subjected to isothermal exposure. The life times were found to increase with increasing cycle duration and hence decreasing number of cycles for a given time at temperature. This life time decrease is related to an “hour glass” waviness of the specimens, which develops during prolonged thermal cycling. The development of this plastic deformation also occurred during furnace heated, thermal cycling tests. A two‐step mechanism is introduced combining an oxidation kinetics related time to the onset of significant waviness with an enhancement of this waviness as a result of a ratcheting effect. The latter seems to strongly depend on the number of cycles and on the plastic deformation generated during each cycle rather than on the total time at temperature. The development of an “hour glass” waviness leads to an enhanced aluminium depletion due to an increase of the specimen surface area. Additional deformation phenomena like “hot tube” or “corkscrew” behaviour occur during the resistance heating tests. These are related to a temperature gradient that develops over the specimen width due to the poor aspect ratio of the specimens.     

Effects of Semi-solid Isothermal Heat Treatment on Microstructures and Damping Capacities of Fly Ash Cenosphere/AZ91D Composites

The fly ash cenosphere/AZ91D composites were successfully prepared and isothermally heat-treated at different temperatures for different time.The effects of semi-solid isothermal heat treatment on the microstructures and damping capacities of fly ash cenosphere/AZ91D composites were investigated.With the increase in isothermal temperature or holding time,the small liquid droplets within grains increased in size but decreased in quantity.The average size and shape factor of Mg_2Si particles increased with the rise of isothermal temperature.The damping capacities of the composites were improved by isothermal heat treatment.At room temperature,the composites after heat treatment at 520 and 550°C had a higher damping capacity due to interface damping when the strain amplitude was lower than about 8.8 9 10~(-5),and the composite after heat treatment at 580°C had a better damping capacity because of the dislocation damping under the condition of high strain amplitude.The damping capacities of the composites increased with the rise of the test temperature,and the damping mechanisms varied depending on different test temperatures.The interface damping played an important role when the test temperature was below about 100°C,and the dislocation damping and grain boundary damping took effect with the rise of test temperature.     

Heat treatment of superbainitic steels

Abstract

Two experimental high silicon high carbon steels (with 5 and 24 ppm of boron separately) have been investigated for the development of superbainite structure. After austenitisation, the specimens were held respectively at three different isothermal transformation temperatures (150, 200, and 300°C) for a variety of time intervals. The microstructures were examined via optical metallography (with microhardness measurement) and transmission electron microscopy. It was found that after isothermal transformation at 200°C for 10 days, both steels produced a high volume fraction of sheaf structures with nanometre scaled bainitic ferrite subunits, which contributed to an ultrahigh microhardness, up to 675 HV. It was also found that adding 24 ppm of boron accelerated the bainitic transformation in the early stage of isothermal transformation at 200°C, but did not have a significant effect on reducing the finish transformation time. Both isothermal temperature of 150 and 300°C could not lead to the development of high amount of bainite.     

High temperature performance of arc-sprayed aluminum bronze coatings for steel

1 Introduction The aluminum bronze coatings on steel substrate which are sprayed by electric arc process have been developed as possible new candidates for the use to high temperature applications, while their corrosion properties at high temperature in …     

Microstructure and Element Distribution during Partial Remelting of an Al-4Cu-Mg alloy

The effects of the isothermal temperature and holding time on the microstructure and element distribution have been investigated during partial remelting of the semisolid Al-4Cu-Mg alloy. The experimental results show that the optimal process parameter should be chosen at isothermal temperature of 540-580 °C with the holding time of less than 10 min. Coalescence and coarsening of α grains occur at low liquid fraction. At high liquid fraction, coarsening of α grains and melting of small grains were promoted by an increase of the isothermal temperature and the holding time. The coalescence of grains and Ostwald ripening are two main mechanisms of the microstructural evolution during partial remelting. Meanwhile, the higher the isothermal temperature and the longer the holding time, the more segregation of Cu at the grain boundary would be, which conform to the theory of element distribution affected by heating condition.     

In-situ observation on the isothermal decomposition process of γ-Fe[N] by X-ray diffraction

The isothermal decomposition process of γ-Fe[N] (9.32 at.% N) prepared by a two-step gas nitriding method was investigated in-situ by X-ray diffraction (XRD). The XRD spectra showed that the α-Fe phase precipitated first from the parent austenite when the sample was aged at 225 °C, while the γ′-Fe₄N phase appeared half an hour later as extra fine particles. The quantity of these two phases increased quickly with the ageing time until the original austenite of γ-Fe[N] was completely consumed. Further investigation by scanning electronic microscopy (SEM) revealed that the α-Fe nucleated first at the primary grain boundaries and grew towards the grain interior with a lamellar bainitic-like structure, which was different to the homogeneous precipitates of γ′-Fe₄N and α-Fe inside the grains. A new transformation mechanism has thus been proposed for the isothermal decomposition of high nitrogen austenite on the grain boundaries (GBs).     

High-Temperature Oxidation Behavior of Chromium: Effect of Different Batches

The isothermal and cyclic-oxidation behavior of three different batches of commercial chromium (purity >99.9%) at 900 and 1000°C has been investigated by means of conventional thermogravimetry and thin-layer activation. Two batches with a similar microstructure and one, with a five times larger average grain size, were used. Isothermal-oxidation experiments were performed in synthetic air for 150 hr. Cyclic-oxidation experiments were executed in static laboratory air with each cycle corresponding to a period of 1 hr at test temperature and 12 min at ambient temperature up to a maximum of 3000 cycles. Results showed significant differences between the oxidation behavior of chromium derived from the three different batches. This was found under isothermal as well as under cyclic-oxidation conditions, especially at 1000°C. The mass-loss rates during cyclic oxidation for the different batches differed up to more than 30 times at 1000°C. In addition, the complementary nature of the different specimen-evaluation techniques, i.e., conventional thermogravimetry and thin-layer activation in cyclic oxidation is shown.     

Co-Ti-Ta三元系富Co区的相平衡

研究Co-Ti-Ta三元系富Co区的相平衡。显微组织和XRD分析以及EDS检测结果表明,在1000～1200℃温度范围内,L12结构Co3Ti相和Laves_36_Co3Ta相与α-Co构成相平衡。Co3Ti相中Ta的固溶度超过10%,Ta的加入使Co3Ti相更稳定。根据实验结果构建Co-Ti-Ta三元系富Co区在1000、1100和1200℃等温截面图。     

6351铝合金的淬火敏感性

采用分级淬火的实验方法,结合合金时效态硬度和淬火态电导率的测试拟合得到6351合金的TTP和TTT曲线,并采用透射电镜对6351合金的淬火敏感性进行研究.结果表明,当6351合金在相同温度下等温时,随着保温时间延长,淬火态电导率呈上升趋势,时效态硬度呈下降趋势.透射电镜分析发现,在等温初期,过饱和固溶体分解形成针状的β”相;随着保温时间延长,逐渐形成棒状β'相和片状β相.TTT和TTP曲线的鼻温为360℃,淬火敏感温度区间为230～430℃.在鼻温附近等温相转变最快,低温区相转变次之,高温区最慢.淬火因子分析结果表明,要获得最佳的力学性能,淬火敏感温度区间的冷却速率需大于15℃/s.