共查询到19条相似文献,搜索用时 187 毫秒
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锰对高铬铸铁奥氏体化过程的影响 总被引:4,自引:1,他引:3
研究锰对高铬铸铁奥氏体化过程的影响结果表明,锰能增加奥氏体化温度下奥氏体的平衡含碳量和合金元素量,显著影响奥氏体的稳定性;随着含锰量的增加,高铬铸铁的最佳奥氏体化温度下降,保温时间延长,所能得到的最高淬火硬度稍有下降。 相似文献
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Mo、Cu对高铬铸铁凝固组织和亚临界热处理硬化行为的影响 总被引:5,自引:1,他引:5
研究了Mo和Cu对高铬铸铁凝固组织和亚临界热处理硬化行为的影响。研究表明,添加Mo和Cu可以使高铬铸铁的凝固组织获得更多的残留奥氏体。含有Mo和Cu的高铬铸铁在亚临界热处理过程中有明显的二次硬化现象。由于Mo是强碳化物形成元素与碳原子之间有强的相互吸引作用,阻碍碳原子在凝固冷却时碳从奥氏体向液相扩散,使共晶奥氏体的碳含量较高,导致奥氏体的Ms点降低,使得铸态组织获得更多的残留奥氏体。固溶于奥氏体中的Cu对奥氏体中碳在亚临界热处理过程中的析出具有很强的阻碍作用,所以与没有添加Mo和Cu的高铬铸铁比较,添加Mo和Cu的高铬铸铁二次硬化峰的出现需要更高的温度或者更长的保温时间。 相似文献
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3C-15Cr-0.75Si系高铬铸铁锰合金化规律的热力学分析 总被引:3,自引:0,他引:3
基于Thermo-Calc软件的热力学平衡相计算,研究了高铬铸铁中锰的合金化规律及其对组织的影响.结果表明,锰虽然对高铬铸铁中的各相数量影响不大,但一定数量的锰存在促使合金元素在奥氏体和碳化物两相中的重新分配,并降低平衡相的转变温度;在平衡条件下3C-15Cr-4Mn-0.75Si系高铬铸铁中莱氏体数量约占87%,而非平衡条件下M7C3型碳化物数量在23%~32%之间,且奥氏体中锰铬互替现象保证了奥氏体的稳定性和加锰高铬铸铁的淬透性.Thermo-Calc软件计算预测结果与现有试验数据基本相符. 相似文献
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锰硼抗磨白口铸铁组织及性能的试验研究 总被引:1,自引:0,他引:1
通过试验研究了锰硼抗磨白口铸铁的碳化物结构类型(M3C型)和锰含量及奥氏体化温度对其组织中残余奥氏体量的影响,试验结果表明:锰含量和奥氏体化温度提高,残余奥氏体量增加,材料硬度降低,冲击韧度提高。 相似文献
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热处理对高铬铸铁组织和硬度的影响 总被引:1,自引:0,他引:1
利用X-射线衍射、金像显微镜和洛氏硬度计,对不同淬火温度、保温时间以及回火后组织进行了分析,研究了不同的热处理工艺对高铬铸铁组织和性能的影响。结果表明:在970℃淬火,保温4h,200℃回火,使硬度值达到62.8HRC。随着淬火温度升高和保温时间的延长,能使奥氏体中的碳含量增加,转变成的马氏体中的含碳量也增加,提高基体硬度;当淬火温度过高或保温时间过长,奥氏体中的碳含量过高,降低MS点,增加残余奥氏体,降低基体硬度。随着回火温度的升高,加速了马氏体的分解和碳化物的析出,马氏体硬度下降,使高铬铸铁的硬度下降。 相似文献
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研究了锰、铬元素对白口铸铁力学性能的影响以及等温淬火温度对力学性能和抗磨性能的影响,并与铸态合金白口铸铁、高铬铸铁及高锰钢的抗磨性进行比较。结果表明,选取适量的碳、硅元素,并加入适量的锰和少量铬以及微量的铋有利于铸态全白口,等温淬火后得到无碳化物贝氏体加奥氏体复相基体组织。于325℃等温淬火2h可获得硬度和韧性均较高的奥氏体和贝氏体组织,且耐磨性能良好,是一种有希望的廉价耐磨新材料。 相似文献
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锰对高铬铸铁凝固组织和亚临界硬化行为的影响 总被引:3,自引:0,他引:3
采用电子探针、X射线衍射、磁性法和硬度测量等方法研究了两种不同含锰量高铬铸铁的凝固组织和在亚临界处理过程中的硬化行为。结果表明,含锰量分别为2.68%和1.98%的两种高铬铸铁的凝固组织都由奥氏体、马氏体和M7C3型碳化物组成。二者的共晶碳化物数量相当,前者和后者的奥氏体和马氏体含量分别为66.2%、13%和11.8%、68.2%。在亚临界处理中,高铬铸铁出现二次硬化,且前者的二次硬化更明显。这一现象归因于高铬铸铁在亚临界处理过程中所发生的马氏体相变。 相似文献
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利用光学显微镜、洛氏硬度计等研究了不同淬火工艺对Cr26高铬耐磨铸铁组织与硬度的影响。结果表明:铸态Cr26高铬铸铁组织主要由初生奥氏体和碳化物组成。经980~1060 ℃不同温度淬火、空冷后,高铬铸铁组织中有大量二次碳化物析出。随着淬火温度的升高,析出的二次碳化物先增加后减少,试样硬度先升高后降低。1020 ℃淬火试样硬度达到峰值,为65.7 HRC。1020 ℃淬火高铬铸铁,经空淬、油淬和水淬不同方式冷却,随着冷却速度的增大,高铬铸铁组织中碳化物颗粒、碳化物比例逐渐增大,硬度逐渐增大,其中水淬高铬铸铁试样硬度最大,达到68.2 HRC。 相似文献
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Effects of RE,V, Ti and B composite modification on the microstructure and properties of high chromium cast iron containing 3% molybdenum 总被引:1,自引:0,他引:1
The effects of RE, V, Ti and B on the microstructure and properties of high chromium cast iron containing 3% molybdenum under
as-cast and heat treatment conditions were investigated with the method of comparing experiments. The results show that with
the increase of RE content, the primary austenite of high chromium cast iron is obviously refined. The morphology of carbide
is changed from netlike and lath to small multiangular isolated blocks or massive blocks, the isolated degree of carbide is
improved obviously, and the size is significantly refined. The addition of V and B into high chromium cast iron can refine
the microstructure, reduce coarse columnar crystals and make the carbide smaller and uniform. Through composite modification
with RE, V, Ti and B, the hardness, wear resistance and impact toughness of high chromium cast iron are increased conspicuously.
After heat treatment, the hardness of high chromium iron is increased significantly, but the toughness and wear resistance
do not show great improvement. 相似文献
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LIUYan-xia MAYong-qing WANGYue-hua ZHANGZhan-ping ZHANGYang 《材料热处理学报》2004,25(5):631-634
The changes of tempering microstructure and properties of Fe-Cr-V-Ni-Mn-C cast alloys with martensite matrix and much retained austenite are studied. The results showed that when tempering at 200℃ the amount of retained austenite in the alloys is so much that is nearly to as-cast, and a lot of retained austenite decomposes when tempering at 350℃ and the retained austenite decomposes almost until tempering at 560℃. When tempering at 600℃, the retained austenite in the alloys all decomposes. At 560℃ the hardness is highest due to secondary hardening. The effect of nickel and manganese on the microstructure and properties of Fe-Cr-V-C cast alloy were also studied. The results show that the Fe-Cr-V-C cast alloy added nickel and manganese can obtain martensite matrix and much retained austenite microstructure, and nickel can also prevent pearlite transformation. With the increasing content of nickel and manganese, the hardness of as-cast alloy will decreases gradually, so one can improve the hardness of alloy by tempering process. When the content of nickel and manganese is 1.3~1.7%, the hardness of secondary hardening is the highest (HRC64). But when the content of nickel and manganese increase continually, the hardness of secondary hardening is low slightly, and the tempering temperature of secondary hardening rises. 相似文献
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Effect of austempering time on mechanical properties of a low manganese austempered ductile iron 总被引:1,自引:0,他引:1
Susil K. Putatunda Pavan K. Gadicherla 《Journal of Materials Engineering and Performance》2000,9(2):193-203
An investigation was carried out to examine the influence of austempering time on the resultant microstructure and the room-temperature
mechanical properties of an unalloyed and low manganese ductile cast iron with initially ferritic as-cast structure. The effect
of austempering time on the plane strain fracture toughness of this material was also studied. Compact tension and round cylindrical
tensile specimens were prepared from unalloyed ductile cast iron with low manganese content and with a ferritic as-cast (solidified)
structure. These specimens were then austempered in the upper (371 °C) and lower (260 °C) bainitic temperature ranges for
different time periods, ranging from 30 min. to 4 h. Microstructural features such as type of bainite and the volume fraction
of ferrite and austenite and its carbon content were evaluated by X-ray diffraction to examine the influence of microstructure
on the mechanical properties and fracture toughness of this material.
The results of the present investigation indicate that for this low manganese austempered ductile iron (ADI), upper ausferritic
microstructures exhibit higher fracture toughness than lower ausferritic microstructures. Yield and tensile strength of the
material was found to increase with an increase in austempering time in a lower bainitic temperature range, whereas in the
upper bainitic temperature range, time has no significant effect on the mechanical properties. A retained austenite content
between 30 to 35% was found to provide optimum fracture toughness. Fracture toughness was found to increase with the parameter
(XγCγ/d)1/2, where Xγ is the volume fraction of austenite, Cγ is the carbon content of the austenite, and d is the mean free path of dislocation motion in ferrite. 相似文献