QT700-2型球墨铸铁的铸造工艺分析

球墨铸铁具有强度高、韧性好、耐磨、减震和对缺口不敏感等优点,因此被广泛应用于工业领域。大量的减速机壳体材料都采用球墨铸铁,球墨铸铁的铸造工艺对减速机壳体强度和稳定性至关重。本文详细介绍了减速机壳体材料QT700-2的熔炼及球化和孕育处理过程。     

35钢螺钉断裂分析

采用化学成分分析、断口分析、硬度测试及金相检验等方法,对螺钉断裂的原因进行了分析。结果表明:回火处理的温度偏低,使螺钉的塑性和韧性下降,在外力作用下引发了螺钉的早期脆性断裂。     

铸态高韧性球墨铸铁生产工艺过程分析

对影响铁素体球墨铸铁性能的化学成份、球化、孕育处理等因素进行分析。阐述了在使用中频感应电炉熔炼铸态铁素体球铁时,通过对化学成分的控制、合理的球化孕育处理,可以实现铸态铁素体球墨铸铁的稳定生产。     

铸态球墨铸铁阀体铸件的生产试验

在分析化学成分对铸态球墨铸铁影响的基础上，通过采用低稀土球化剂、使用盖包法球化处理以及复合孕育工艺等一系列措施，成功实现了完全铸态条件下球墨铸铁件的生产。该方法无需对铸件进行热处理，提高了生产效率，降低了铸件生产成本，改善了生产环境。     

Ni合金化球墨铸铁组织和性能研究

为获得兼具较高强度和良好低温冲击韧性的球墨铸铁铸件,向球墨铸铁中加入质量分数约0.5%的Ni进行合金化,并对其进行中温奥氏体化(880℃+3 h)和低温退火(720℃+4 h)处理.采用光学显微镜(OM)、扫描电子显微镜(SEM)对铸态和热处理态试样的显微组织和冲击断口形貌进行分析;利用万能试验机、布氏硬度计和摆锤式冲击试验机等对铸态和热处理态试样进行了室温拉伸、硬度检测、低温冲击等力学性能测试.结果表明:铸态球墨铸铁的微观组织由珠光体、铁素体和球状石墨及少量的渗碳体组成,其强度、硬度偏高,塑性、韧性较差;热处理态试样中的珠光体向铁素体转变后为铁素体和球状石墨,试样强度、硬度有所降低,塑性、韧性得到明显的改善;铸态试样呈现典型的脆性断裂特征,热处理态试样冲击断口处存在少量韧窝,断裂模式以解理断裂为主,伴有少量塑性变形的韧脆混合断裂,且在-40℃冲击功达到12.4 J;比较铸态与热处理态的冲击断口形貌可知,试样断裂方式由脆性断裂转变为韧脆混合断裂.     

改性纳米SiC粉体强化球墨铸铁的组织和力学性能研究

在生产条件下用改性纳米SiC粉体对球墨铸铁进行了强韧化处理,研究了不同的纳米SiC粉体加入量对球墨铸铁组织和力学性能的影响.结果表明,经改性纳米SiC粉体强韧化后,球墨铸铁中的石墨球尺寸减小,圆整度提高,铁素体含量增多,球墨铸铁的韧性提高.断口分析结果表明,经过强韧化处理后,球墨铸铁的断裂方式为脆性韧性混合断裂.     

铸造Al-Cu合金在固液态的力学性能

本文采用自行改装设计的固液态力学性能测试装置对铸造Al—Cu合金在固液态时的强度和塑性进行了研究。考察了温度、钢含量、铸态晶粒形状、钛的孕育作用及低熔点杂质对合金在固液态时的强度和塑性的影响。研究结果表明,合金在固液态时由于液体在晶间的分布,呈现出一个明显热脆弱区,强度和塑性值都很低,是铸件形成热裂的主要原因。单向凝固获得的柱状晶,在固液态时的横向力学性能比普通柱状晶横向性能可以高出十倍。对合金进行孕育处理,减少晶界的低熔点杂质对提高固液态的力学性能,防止热裂纹产生具有重要的作用。     

QT400—18L铸件的缩松缺陷对其力学性能的影响

通过静拉伸试验、低温冲击试验、布氏硬度试验和组织形貌分析,研究了QT400—18L球墨铸铁的缩松缺陷对其力学性能的影响。结果表明：缩松使材料的强度和塑性大幅度降低,断裂形式主要为韧性断裂;冲击断裂形式为大量解理和少量韧窝构成的混合断裂;布氏硬度值比标准硬度值至少降低9％;缩松对石墨形态、分布和材料的显微组织无明显影响。     

组织与成分对510L钢力学性能的影响

采用化学成分分析、力学性能测试和微观检验等方法对影响510L钢力学性能的组织与成分因素进行了分析。结果表明,化学成分中的铌能提高钢的强度,使510L满足性能要求;夹杂物和带状组织致使冷弯开裂;粒状贝氏体在回火处理后能优化钢的强韧性。并针对以上对性能影响情况提出了一些相应措施。     

超高强度结构钢的组织细化及韧性改善

通过合理设计化学成分以及有效地优化热处理工艺,新研制的系列贝氏体结构钢在保证超高强度(σb>1400MPa)条件下,塑性与韧性配合良好,且V型缺口冲击能(AKV>140J)与同强度级别的马氏体钢相比提高一倍多.结合显微分析结果,深入地讨论了韧性改善的物理机制.     

FCVI工艺制备SiCf/SiC复合材料结构与性能研究

采用热梯度强制流动化学气相渗积（FCVI）工艺制备SiCf/SiC复合材料，测试了复合材料的性能。制备的复合材料密度达到2.3g/cm3，强度为291 MPa，断裂韧性为11.4 MPa*m1/2。运用SEM，TEM，X射线衍射等分析手段对复合材料的微观结构进行了表征。结果表明：渗积的基体材料为β-SiC，晶粒尺寸为亚微米级，结晶度良好。通过对断口形貌的观察，分析了增韧机制。，SiCf/SiC composite was fabricated by forced flow thermal-gradient chemical vapor infiltration (FCVI). The density of composite is 2.3g/cm3.The flexural strength and fracture toughness of SiCf/SiC compsites were tested: the flexural strength is 291 MPa, the fracture toughness is 11.4 MPa*m1/2. The microscopy structure was characterized by SEM, TEM and X-ray diffraction. The results show that SiC matrix fabricated by FCVI is β-SiC, which has sub-micron grain size and good crystallinity.And the toughening mechanism was also investigated by morphology of the fractrue surface.     

Fracture toughness of the nano-particle reinforced epoxy composite

Although thermoset polymers have been widely used for engineering components, adhesives and matrix for fiber-reinforced composites due to their good mechanical properties compared to those of thermoplastic polymers, they are usually brittle and vulnerable to crack. Therefore, ductile materials such as micro-sized rubber or nylon particles are added to thermoset polymers are used to increase their fracture toughness, which might decrease their strength if micro-sized particles act like defects.In this work, in order to improve the fracture toughness of epoxy adhesive, nano-particle additives such as carbon black and nanoclay were mixed with epoxy resin. The fracture toughness was measured using the single edge notched bend specimen at the room (25 °C) and cryogenic temperature (−150 °C). From the experimental results, it was found that reinforcement with nano-particles improved the fracture toughness at the room temperature, but decreased the fracture toughness at the cryogenic temperature in spite of their toughening effect.     

高等级海上风力发电机用钢的研发及力学性能

基于超快冷热机械控制工艺(TMCP),成分设计上遵循低碳含量、低碳当量、微合金化,焊接时采用大热输入的原则,成功研发出了屈服强度为460 MPa的高等级海上风力发电机用钢。阐述了开发的两种钢的化学成分设计及试制工艺流程,并对其综合力学性能进行分析。结果表明:开发的两种钢具有生产周期短、强度高、韧性好、抗层状撕裂性能好、耐疲劳性能好、止裂性能优异及可采用大热输入焊接等特点,符合海上风力发电机用钢的发展方向。     

Effects of weld strength undermatch on fracture toughness of HAZ notched weldments in a HSLA steel

In the present work the effects of weld strength undermatch on fracture toughness of heat affected zone (HAZ) have been studied. In the investigation a high strength low alloyed steel (HSLA) with 800 MPa strength class was used, and the undermatched welded joints were made with two weld strength mismatch levels. Three-point bending test specimens with crack depth to specimen width ratio a/W ranging from 0.05 to 0.5 were extracted from the welded joints. The test results show that strength mismatching gives an obvious influence on the fracture toughness of coarse grained HAZ for the undermatched joints. The lower the weld strength mismatching, the higher the fracture toughness of the HAZ. In addition the tendency of fracture toughness change with crack depths is much the same as in previous studies on base metals or weld metals, that is, fracture toughness of the HAZ is increased with reduction of crack depths. From the measured results it shows that the macroscopically mechanical heterogeneity of the welds may have more important influence on the fracture toughness of the HAZ than the meso-heterogeneity in the reheated coarse grained HAZ. Furthermore, numerical verification indicates that the stress triaxiality at crack tip may be the essential reason for the change of fracture toughness of HAZ. It is also shown that the yield strength of HAZ determined by the limit load in the three-point bend test represents the combinative effects of HAZ and its surrounding materials. This revised version was published online in August 2006 with corrections to the Cover Date.     

超低温对超高韧性水泥基复合材料抗压韧性影响试验

超高韧性水泥基复合材料(UHTCC)是一种具有超高韧性及良好耐久性能的新型复合材料,其抗压韧性是评价其工作性能的重要指标。通过对5组不同纤维掺量的UHTCC在超低温作用后的单轴受压试验,研究超低温作用下UHTCC的抗压韧性评价指标,并对其变形能力进行等效分析,为UHTCC在超低温环境下的工程应用提供理论支持。研究结果表明:在一定范围内,随着纤维体积掺量的增加,UHTCC的抗压强度、抗压韧性均有明显提升,而超出最优掺量后性能反而略有下降;超低温对于UHTCC的抗压强度具有一定的提升作用,当温度降低至?196℃,其轴向抗压强度最大可提升约74.42%,但其脆性性能更明显。      

Effect of austenitising temperature on microstructure and mechanical properties of 30Si2CrNi4MoNb ultrahigh strength steel

Abstract

The microstructure and mechanical properties of 30Si2CrNi4MoNb ultrahigh strength steel were investigated after austenitising over a range of temperature between 1133 and 1483 K. The experimental results show that the isotropy of impact toughness and mechanical properties were greatly improved due to the disappearance of undissolved aligned second phase when the austenitising temperature was over 1233 K. When the austenitising temperature was over 1383 K, martensite lath and packet abnormally grew up due to dissolution of spheroidal Nb rich carbonitrides; both the platelet size and morphology of martensite were changed, which has an effect on the mechanical properties of the samples. It was noticed that the finer self-tempered carbides, which strengthened martensitic matrix, appeared after austenitising temperature over 1283 K. The strength profiles show a marked plateau for the samples austenitised from 1283 to 1433 K; however, the strength was deteriorated due to coarsening of these self-tempered carbides at 1483 K. It was confirmed that calcium treatment can help improve the isotropy of mechanical properties by modifying sulphide inclusion morphology.     

应用炉卷轧机开发700MPa级高强韧性钢板

700MPa级高强韧性钢板具有强度高、低温韧性好以及焊接性能优良的特点.然而,传统的铁素体/珠光体钢的屈服强度一般低于500MPa,不能满足强度要求.本研究采用现代炉卷轧机并结合控轧控冷工艺在安阳钢铁公司研制开发出700MPa级高强韧性钢板,其屈服强度大于560MPa、抗拉强度大于670MPa、延伸率大于16%、-40℃冲击功大于47J.     

Self-propagating High-temperature Synthesis, Microstructureand Mechanical Properties of TiC-TiB2-Cu Composites

TiC-TiB2-Cu composites were produced by self-propagating high-temperature synthesis combined with pseudo hot isostatic pressing using Ti, B4C and Cu powders. The microstructure and mechanical properties of the composites were investigated. The X-ray diffraction （XRD） and scanning electron microscopy （SEM） results showed that the final products were only TiC, TiB2 and Cu phases. The clubbed TiB2 grains and spheroidal or irregular TiC grains were found in the microstructure of synthesized products. The reaction temperature and grain size of TiB2 and TiC particles decreased with increasing Cu content. The introduction of Cu into the composites resulted in a drastic increase in the relative density and flexual strength, and the maximum values were obtained with the addition of 20 wt pct, while the fracture toughness was the best when Cu content was 40 wt pct.     

C、Cu和Cr对10CrNiCu埋弧焊丝配烧结焊剂焊缝力学性能的影响

针对船用10CrNiCu钢设计了4种不同化学成分的埋弧焊丝,研究了焊丝与烧结焊剂配套使用时C、Cu、Cr元素对焊缝力学性能的影响。结果表明C、Cu可以增加焊缝中针状铁素体的含量,细化晶粒尺寸,从而提高焊缝的低温冲击韧性和拉伸强度,Cr含量增加可以提高焊缝强度,但会降低焊缝的冲击韧性。     

Effect of Aging on Microstructure and Mechanical Property of 1900 MPa Grade Maraging Stainless Steel

The 18%Ni alloy steels provide high strength and toughness, while age-hardenable or PH stainless steels also have good corrosion resistance. This paper focuses on an investigation of the heat treatment, mechanical properties and microstructural development of a new maraging stainless steel. It is reported that the heat treatment process should consist of solution treatment and cryogenic cooling to attain a fully martensitic structure, followed by aging at 813 K. This heat treatment resulted in an ultimate tensile strength of over 1900 MPa combined with good impact toughness. Transmission electron microscopy is used to show that, for the peak-aged condition （813 K/4 h）, nano-sized precipitates, e.g. Ni3Mo and/or R-phase, and a high density of dislocations were uniformly dispersed in the lath martensite matrix. The calculated yield strength, based on a revised Orowan mechanism, is in good agreement with the test data. The steel studied has an ultimate tensile strength over 1900 MPa, excellent fracture toughness, and good resistance against over-aging and relatively good corrosion resistance as well.