共查询到20条相似文献,搜索用时 31 毫秒
1.
本文主要研究了2.25C r-1M o钢正火处理后显微组织和回火过程中碳化物相对钢的强韧性的影响,奥氏体化处理后进行冷却(加速冷却和空冷),得到的显微组织为粒状贝氏体和先共析铁素体。对于2.25C r-1M o厚钢板,显微组织和碳化物相的变化是造成2.25C r-1M o钢强韧性能变化的主要原因。 相似文献
2.
R. L. Klueh P. J. Maziasz D. J. Alexander 《Metallurgical and Materials Transactions A》1997,28(2):335-345
Previous work on 3Cr-1.5MoV (nominally Fe-3Cr-2.5Mo-0.25V-0.1C), 2.25Cr-2W (Fe-2.25Cr-2W-0.1C), and 2.25Cr-2WV (Fe-2.25Cr-2W-0.25V-0.1C)
steels indicated that the impact toughness of these steels depended on the microstructure of the bainite formed during continuous
cooling from the austenitization temperature. Microstructures formed during continuous cooling can differ from classical upper
and lower bainite formed during isothermal transformation. Two types of nonclassical microstructures were observed depending
on the cooling rate: carbide-free acicular bainite at rapid cooling rates and granular bainite at slower cooling rates. The
Charpy impact toughness of the acicular ferrite was considerably better than for the granular bainite. It was postulated that
alloying to improve the hardenability of the steel would promote the formation of acicular bainite, just as increasing the
cooling rate does. To test this, chromium and tungsten were added to the 2.25Cr-2W and 2.25Cr-2WV steel compositions to increase
their hardenability. Charpy testing indicated that the new 3Cr-W and 3Cr-WV steels had improved impact toughness, as demonstrated
by lower ductile-brittle transition temperatures and higher upper-shelf energies. This improvement occurred with less tempering
than was necessary to achieve similar toughness for the 2.25Cr steels and for high-chromium (9 to 12 pct Cr) Cr-W and Cr-Mo
steels. 相似文献
3.
采用Formastor-FⅡ全自动相变仪实现不同冷却速度,利用金相显微镜、扫描电子显微镜和透射电子显微镜,研究了45CrMoV钢在不同冷却速度下的组织转变规律以及回火温度对组织的影响。结果表明,随着冷却速度的变慢,45CrMoV钢的组织由马氏体变为马氏体、先共析铁素体、下贝氏体和粒状贝氏体的混合物。冷却速度进一步变慢,先共析铁素体数量增多,下贝氏体和粒状贝氏体总量减少,材料硬度不断下降;45CrMoV钢中的粒状贝氏体为岛状、颗粒状,也有不规则形状,下贝氏体铁素体板条比低碳钢和超低碳钢中的板条更宽,分布更分散,板条形态不规则;随着回火温度的升高,45CrMoV钢中的渗碳体由细针状变为细条状,最后长大为椭球状,材料强度下降,韧性上升。 相似文献
4.
5.
Ming-Wei Wu Guo-Jiun Shu Shih-Ying Chang Bing-Hao Lin 《Metallurgical and Materials Transactions A》2014,45(9):3866-3875
The impact toughness of powder metallurgy (PM) steel is typically inferior, and it is further impaired when the microstructure is strengthened. To formulate a versatile PM steel with superior impact, fatigue, and tensile properties, the influences of various microstructures, including ferrite, pearlite, bainite, and Ni-rich areas, were identified. The correlations between impact toughness with other mechanical properties were also studied. The results demonstrated that ferrite provides more resistance to impact loading than Ni-rich martensite, followed by bainite and pearlite. However, Ni-rich martensite presents the highest transverse rupture strength (TRS), fatigue strength, tensile strength, and hardness, followed by bainite, pearlite, and ferrite. With 74 pct Ni-rich martensite and 14 pct bainite, Fe-3Cr-0.5Mo-4Ni-0.5C steel achieves the optimal combination of impact energy (39 J), TRS (2170 MPa), bending fatigue strength at 2 × 106 cycles (770 MPa), tensile strength (1323 MPa), and apparent hardness (38 HRC). The impact energy of Fe-3Cr-0.5Mo-4Ni-0.5C steel is twice as high as those of the ordinary high-strength PM steels. These findings demonstrate that a high-strength PM steel with high-toughness can be produced by optimized alloy design and microstructure. 相似文献
6.
7.
利用Gleeble-3500热模拟试验机、扫描电镜、透射电镜、电子背散射衍射技术等手段研究V对700 MPa级高强度汽车大梁钢组织细化的影响.在冷却速度2~7℃·s-1时,显微组织为针状铁素体+粒状贝氏体组织.V添加提高粒状贝氏体体积分数,细化粒状贝氏体组织,并明显降低粒状贝氏体中M/A岛的尺寸.与无V钢相比,含V钢中大角度晶界比例提高18.2%,对提高钢的韧性有利.由于C含量过低,在实验钢中未观察到单独的VC析出,由此推测V主要固溶在基体中,以合金化方式促进钢的贝氏体相变,使组织得到有效细化. 相似文献
8.
对一种新型70Si3MnCrMo钢进行了等温和连续冷却贝氏体相变热处理。利用拉伸和冲击试验研究试验钢的力学行为,利用XRD、SEM和TEM等方法对试验钢进行了相组成分析和微观组织形貌观察。研究结果表明,试验钢经等温贝氏体相变,其最佳综合力学性能出现在200 ℃回火,强塑积为26.4 GPa·%。经连续冷却贝氏体相变,其最佳综合力学性能出现在300 ℃回火,强塑积达到28.6 GPa·%。回火温度较低的情况下,热处理后的组织为由贝氏体铁素体和残余奥氏体组成的无碳化物贝氏体组织,这种无碳化物贝氏体由超细贝氏体铁素体板条而获得超高强度,由一定量的高碳残余奥氏体来保证较高的塑性和韧性。试验钢经连续冷却贝氏体相变,其贝氏体铁素体板条中出现了超细亚单元,并且残余奥氏体呈薄膜状和小块状两种形态分布于贝氏体铁素体板条之间,这两种形态残余奥氏体的稳定性不同。拉伸试样在变形过程中残余奥氏体持续发生TRIP效应,直至全部残余奥氏体都发生转变生成应变诱发马氏体,从而使钢得到更好的强、塑性配合,表现出十分优异的综合性能。 相似文献
9.
10.
Zheng Chen Zhi-Wei Shan Scott X. Mao Ming-Jian Hua N. Q. Wu V. K. Sikka 《Metallurgical and Materials Transactions A》2004,35(4):1281-1288
Both the 3Cr-3WV and the 3Cr-2WVTa steels exhibit an acicular bainite microstructure under the normalized and the normalized-and-tempered
condition. The addition of Ta to the 3Cr-3WV steel substantially decreases the prior austenite grain size, but it has little
effect on the bainite packet size. Fine TaC precipitates are formed in the normalized 3Cr-3WVTa specimen. After further tempering
of 3Cr-3WVTa steel, fine TaC particles are further precipitated and dispersed within grains. The carbides at the prior austenite
grain boundaries in the Ta-containing steel are much smaller than those in the steel without Ta. Tensile tests and fracture
toughness (K
IC
) tests have been performed on both the 3Cr-3WV and 3Cr-3WVTa steels at room temperature. The 0.2 pct yield strength of the
Ta-containing steel is higher than that of the steel without Ta, especially under the normalized-and-tempered condition. The
3Cr-3WVTa steel is primarily strengthened by a secondary-phase precipitation mechanism represented by the formation of fine
carbides after tempering. The 3Cr-3WVTa steel exhibits higher fracture toughness than the 3Cr-3WV steel. The toughening mechanism
is also discussed based on the dependence of the calculated fracture stress upon the carbide size and the bainite packet size. 相似文献
11.
12.
For the purpose of getting the best properties, the thermal expansion experiment and the orthogonal experiments were investigated in an ultra- high strength martensitic steel for crusher liner composed of medium content of C and medium content of Cr. And the 4 influencing factors of quenching temperature, quenching holding time, tempering temperature and tempering time were considered in designing orthogonal experiment. Based on the orthogonal experiment, the mechanical properties of the test steel under different heat treatment conditions were analyzed by means of the extreme method. The optimal heat treatment process was as follows: (950?? holding 1. 5h) oil quenching + (250?? holding 3h) tempering + air cooling to room temperature. After the heat treatment, the martensite + retained austenite multi- phase microstructure was obtained after the heat treatment, the tensile strength reached 1774. 6MPa, the yield strength was 1369. 4MPa, the hardness was 55. 3HRC, and the impact energy(none notch) was 22J. 相似文献
13.
Tensile and impact properties were determined for a steel (3 wt pct Cr-1.5 wt pct Mo-0.1 wt pct V-0.1 wt pct C) considered
a candidate for elevated-temperature pressure-vessel applications. The steel was tested in two heat-treated conditions: normalized
and tempered and quenched and tempered for various tempering conditions. Similar tempering treatments for the quenched and
the normalized steels led to similar strengths. However, for the lowest tempering parameter used, the impact properties for
the quenched-and-tempered steel exceeded those for the normalized-and-tempered steel, resulting in an excellent ductile-brittle
transition temperature (-70 °C) and upper-shelf energy (225 J) for the quenched-and-tempered steel at a high strength (770
MPa ultimate tensile strength). Further tempering reduced the strength for the steel in both heat-treated conditions. The
impact properties of the quenched steel were only slightly changed by further tempering, but those for the normalized steel
improved, eventually equaling those for the quenched-and-tempered steel. The difference in impact properties after the two
heat treatments was attributed to a difference in bainite microstructures. 相似文献
14.
为了提高建筑用钢的屈服强度,优化轧制工艺和降低生产成本,通过实验室轧钢并结合室温、高温拉伸试验以及扫描和透射电镜观察,研究了4种不同轧制工艺下的高强抗震耐火钢板的组织和力学性能。研究结果表明,试验用耐火钢板的组织主要由铁素体+粒状贝氏体组成。粗轧开轧温度较高时,试验用钢板的室温屈服强度和高温屈服强度都较高,粒状贝氏体的体积分数也较多。开轧和开冷温度较高时,试验钢板的高温屈服强度可以满足建筑用耐火钢板的力学性能要求。随着开冷温度的提高,试验钢板的屈服强度会进一步提高,但是组织中铁素体晶粒尺寸较大,而且塑性较差。根据冲击试验结果可以发现,随着冲击温度的降低,试验钢板的断裂吸收功下降较多。析出相分析结果表明,析出相主要是(Nb,Ti)C和(Ti,Nb,Mo)C,析出相颗粒尺寸较大。 相似文献
15.
16.
抗大变形管线钢加热并保温一段时间后,钢管力学性能将发生变化,通常会有屈服强度、屈强比升高,均匀延伸率降低,应力—应变曲线形状改变等,这些性能变化将降低钢管抵抗变形的能力。利用扫描镜等设备研究了冷却工艺对21mmX70HD抗大变形管线钢组织、性能和应变时效硬化的影响。结果表明,随着开始冷却温度的降低,先共析铁素体含量逐渐增加,贝氏体组织含量逐渐降低,贝氏体的组织相态由粒状贝氏体逐渐向板条贝氏体转变。当开始冷却温度在700℃时,试验钢板具有最佳的综合力学性能。试验钢板制成1016mm钢管后,钢管在200℃时效保温5min下,纵向屈服强度Rt0.5为497MPa,抗拉强度Rm为695MPa,伸长率为41%,屈强比Rt0.5/Rm为0.72,Rt1.5/Rt0.5为1.24、Rt2.0/Rt1.0为1.09,均匀变形伸长率达到9.0%。 相似文献
17.
18.
New Duplex Microstructure of Grain Boundary Allotriomorphic Ferrite/Granular Bainite 总被引:5,自引:0,他引:5
XU Ping guang FANG Hong sheng BAI Bing zhe WANG Zhen jia YANG Zhi gang HUANG Jin feng 《钢铁研究学报(英文版)》2002,9(2):33-38
hemostpopularmicrostructureincurrentstructuralsteelsisstillamixtureofferriteandpearlite .Microalloying (andtheassociatedthermo mechanicalprocess)andsecond phasestrengtheningareusuallyappliedtoobtainhighstrengthandtoughness.Sincethestructurestrengthofgran… 相似文献
19.
20.
为了稳定亚温淬火工艺与工业化生产,通过力学性能分析及显微组织观察,对比了正火+亚温淬火+回火、在线淬火+亚温淬火+回火、离线淬火+亚温淬火+回火3种热处理工艺对690 MPa级海洋工程用钢板组织性能的影响。结果表明,采用离线淬火+亚温淬火+回火工艺结果最理想,能够大幅度提高钢板的低温冲击性能和伸长率。同时,还能够获得较低的屈强比,断口形貌全部为韧窝,呈明显的韧性断裂,而且随着亚温保温时间的增加,强度逐渐提高,当保温时间达到30 min以后,强度及条片状铁素体基本不发生变化;采用直接淬火态+亚温淬火+回火虽然可以保证高强度低屈强比,但是冲击功表现较为离散,稳定性欠佳,断口形貌为混合型,以韧性断裂为主;采用正火态+亚温淬火+回火工艺效果最差,尤其是不能保证钢板低温韧性,断口形貌全部为解理,呈明显的脆性断裂,其中片条状铁素体形貌是决定优良低温冲击性能的关键因素。 相似文献