铸态机床工作台球铁铸件内在质量控制

通过对机床工作台的Y型25mm基尔试块、Y型50mm基尔试块和本体金相组织进行对比,发现基尔试块中球化率、珠光体含量和本体中球化率、珠光体含量有较大的差异。反复剖析及实践验证得知.严格控制化学成份,加入少量合金,能得到本体球化率≥80％,本体的珠光体含量≥50％的球墨铸铁。     

铸态机床工作台球铁铸件内在质量控制

通过对机床工作台的Y型25mm基尔试块、Y型50mm基尔试块和本体金相组织进行对比,发现基尔试块中球化率、珠光体含量和本体中球化率、珠先体含量有较大的差异.反复剖析及实践验证得知,严格控制化学成份,加入少量合金,能得到本体球化率≥80%,本体的珠光体含量≥50%的球墨铸铁.     

大断面低温球墨铸铁的生产

正我公司开发的在风能上使用的座体材料牌号FCD370-20LT,该铸件主要部位尺寸40mm,最厚热节部位达到100mm,属于大断面球墨铸铁范畴。其技术条件要求铸件本体最厚部位力学性能为R m≥370MPa,R p0.2≥230 MPa,伸长率大于20%,最厚心部低温冲击韧度三个单值≥6.5J(-40℃),最厚心部球化率要求在80%以上,样品阶段要求100%检验本体。     

铸态珠光体球墨铸铁组织和力学性能数学模型

测定了铸态珠光体球墨铸铁化学成分含量、珠光体体积分数和球化率及力学性能,通过多元线性逐步回归分析,建立了珠光体含量和化学成分之间的数学模型及力学性能和珠光体含量、球化率之间的数学模型,从42组实验数据中,选取33组作为回归方程计算数值,9组作为验证数值,用建立的数学模型预测未知,结果表明,该方法对球墨铸铁的珠光体含量和力学性能得到的计算结果与试验值吻合得很好,模型预测具有很好的准确性,从而可以优化和控制化学成分含量及预测力学性能指标.     

珠光体球化对20G拉伸力学性能的影响

珠光体球化是低碳钢材质20G材质老化的主要表现形式。它使20G材质的拉伸力学性能发生变化，随着球化程度的加深，抗拉强度和屈服强度都会降低，屈服强度降低得更加明显，其降低幅度以完全球化阶段为最大，但其塑性指标稍有改善。本文分析了珠光体球化导致这些变化的微观机理，指出材质老化过程中珠光体的球化会减小位错运动的阻力，使得材料的屈服强度降低，塑性略有上升。并综合材质的拉伸力学性能的变化与实际焦炭塔在工作循环中温度、应力的变化详细地分析了焦炭塔产生腰鼓变形的原因。     

U71Mn钢轨气压焊接头的损伤行为

采用硬度计、轮廓仪、光学显微镜、扫描电子显微镜等对服役后的U71Mn钢轨气压焊接头的硬度、裂纹形貌及显微组织进行测试与观察,分析接头不同区域的损伤行为。结果表明:焊接接头两侧距接头中心30~50 mm处存在低凹区域,其位置与软化区位置吻合;轮轨接触使接头硬度提高,但是软化区的硬度始终低于母材;根据珠光体形态,接头从中心向两侧热影响区可依次分为层片状珠光体区域、部分珠光体球化区Ⅰ、珠光体球化区、部分珠光体球化区Ⅱ;软化区位于珠光体球化区;珠光体球化区与部分珠光体球化区的裂纹深度和裂纹尖端扩展角都较大,这是由于粒状珠光体对裂纹扩展的阻力较小导致的。     

球墨铸铁下汽缸产品生产技术

目前球墨铸铁已广泛应用,但用电弧炉熔化铁液,特别是作为高强度、高塑性的球铁用于耐压、耐震、耐冲击的较大型零件(如打椿机下汽缸),是一种新的尝试。要求零件本体力学性能符合QT500—7的标准,金相组织中珠光体20％～45％,球化率3级以上,球径大小5～6级,碳化物和磷共晶均小于1％,确保使用半年内不发生质量问题。经过努力,产品合格率为100％。     

低合金耐热钢的高温球化过程研究

以10CrMo910、13CrMo44为研究对象，进行了在不同温度与不同保温时间的高温球化模拟试验，分析了试验后试样的显微组织演变和珠光体球化的原因。结果表明：温度和保温时间对球化的影响非常显著。10CrMo910比13CrMo44球化速度快，但随着温度的升高，10CrMo910球化速度呈明显的下降趋势，说明10CrMo910在高温下更稳定。球化是个扩散过程，在一定温度下的球化过程进行是需要时间的。该结果可为选材和球化后的设备能否继续服役提供一定的参考依据。     

高温蒸汽管道材质检验初探

珠光体球化是高温环境下,珠光体中渗碳体的形态以层片状逐渐转变为球状的过程,管道材料发生珠光体球化会影响管道的安全使用.以高温蒸汽管道母材为研究对象,按照国家标准及行业标准,进行各项性能试验,对实验数据进行分析,得到虽然目前高温蒸汽管道母材球化等级为3.5级,但各项性能满足国家标准及行业标准要求,为高温蒸汽管道的安全使用...     

20钢珠光体球化对材质损伤程度的试验研究

通过不同球化程度的20钢的常温力学性能及高温短时拉伸性能的试验与分析，研究珠光体球化程度与材料力学性能之间的对应关系。     

低压铸造在铝硅壳体类铸件中的应用

针对采用重力浇注试制生产铝硅合金箱体类铸件中存在的缺陷,介绍了工程车中铝硅壳体铸件的砂型低压铸造技术.采用开放式浇注系统和底注法充型;华铸CAE凝固模拟分析;铝液的浇注温度为680℃～710℃;充型压力为0.12 MPa～0.16 MPa;实践结果表明,生产出的铝硅壳体类铸件组织致密、气密性好,力学性能达到或超过产品技术要求,已大批量投入生产.     

Plaster casting process for prototyping of die casting based on rapid tooling

Rapid prototyping (RP) combined with a gravity casting process can provide a suitable substitute with steel tool die casting for prototyping metal casting. Due to differences between die casting and gravity casting, there are several drawbacks in RP simulated die casting. This paper is concerned with the development of a new plaster die casting process that combines pressurization and vibration for prototyping of die castings, and with a plaster die casting machine that has a structure similar to that of a die casting machine. The machine utilizes an oil cylinder for pressurization and a magnetic actuator for vibration. A rapid prototyped pattern is made by the laminated object manufacturing (LOM) process to prepare a plaster mold. In the process, a plunger in the developed machine simultaneously pressurizes and vibrates the molten metal to fill the plaster mold completely and to facilitate the creation of nuclei in the molten metal, respectively. The developed machine has produced a prototype of an end clutch cover with remarkable improvement in mechanical properties.     

Plaster casting process for prototyping of die casting based on rapid tooling

Rapid prototyping (RP) combined with a gravity casting process can provide a suitable substitute with steel tool die casting for prototyping metal casting. Due to differences between die casting and gravity casting, there are several drawbacks in RP simulated die casting. This paper is concerned with the development of a new plaster die casting process that combines pressurization and vibration for prototyping of die castings, and with a plaster die casting machine that has a structure similar to that of a die casting machine. The machine utilizes an oil cylinder for pressurization and a magnetic actuator for vibration. A rapid prototyped pattern is made by the laminated object manufacturing (LOM) process to prepare a plaster mold. In the process, a plunger in the developed machine simultaneously pressurizes and vibrates the molten metal to fill the plaster mold completely and to facilitate the creation of nuclei in the molten metal, respectively. The developed machine has produced a prototype of an end clutch cover with remarkable improvement in mechanical properties.     

衬套铸造工艺改进

阐述了衬套加工过程中影响产品质量的因素，并对铸造工艺进行了改进，从而降低了废品率，保证了产品质量。     

Determining casting defects in near-net shape casting aluminum parts by computed tomography

Three types of near-net shape casting aluminum parts were investigated by computed tomography to determine casting defects and evaluate quality. The first, second, and third parts were produced by low-pressure die casting (Al-12Si-0.8Cu-0.5Fe-0.9Mg-0.7Ni-0.2Zn alloy), die casting (A356, Al-7Si-0.3Mg), and semi-solid casting (A356, Al-7Si-0.3Mg), respectively. Unlike die casting (second part), low-pressure die casting (first part) significantly reduced the formation of casting defects (i.e., porosity) due to its smooth filling and solidification under pressure. No significant casting defect was observed in the third part, and this absence of defects indicates that semi-solid casting could produce high-quality near-net shape casting aluminum parts. Moreover, casting defects were mostly distributed along the eutectic grain boundaries. This finding reveals that refinement of eutectic grains is necessary to optimize the distribution of casting defects and reduce their size. This investigation demonstrated that computed tomography is an efficient method to determine casting defects in near-net shape casting aluminum parts.     

Modeling of thermal processes in making a steel casting in a chill casting machine

Results of modeling the temperature distribution in the uncooled and cooled walls at casting in a steel chill mold of a lead-antimony alloy are presented. The process parameters for casting steel in the chill mold are determined with the use of the Fourier, Biot, and Kossovitch similarity criteria.     

DPVC工艺充模过程数值模拟和实验研究

为探究真空差压注型工艺(Differential Pressure Vacuum Casting,DPVC)中充模阶段充模速度及充模压差对薄壁产品质量的影响。采用一种基于SIMPLEC-VOF法的液-气两相耦合数学模型,对DPVC充模过程的流动形态进行了分析;并进行了相应的充模实验,数值模拟和实验结果表明:充模薄壁类产品(壁厚3mm内),注型材料黏性力占据了主导地位,扰动得到了有效抑制,流动是稳定的,差压充模过程卷气现象较少,但排气穴位置、数量对产品气穴缺陷影响较大,合理设置可基本消除注件内的气泡缺陷。     

Rapid casting of turbine blades with abnormal film cooling holes using integral ceramic casting molds

Film cooling is an important cooling method to decrease the turbine blade surface temperature, and its average cooling efficiency is mainly dependent on the cooling structures of internal passageways and the shapes of film cooling holes. Compared with standard cylindrical film cooling holes, abnormal film cooling holes have higher average cooling efficiency. But it is difficult to manufacture these holes using traditional machining methods. In this paper, a novel process was developed to fabricate turbine blades with abnormal film cooling holes by combining stereolithography (SL) technology with gelcasting technology. To decrease the drying shrinkage, the freeze-drying technique was applied to treat the wet ceramic casting mold green body surrounded by the SL mold, and the proper sintering process parameters were determined for lowering the sintered shrinkage. Finally, the integral ceramic casting mold was obtained, and a turbine blade with converging–diverging film cooling holes was rapidly cast to verify the feasibility of the proposed process.     

挤压铸造工艺知识结构研究

分析挤压铸造的工艺过程与工艺知识的关系,建立了广义和狭义的挤压铸造工艺知识结构.广义挤压铸造工艺知识结构包含基础知识、挤压铸造工艺参数设计知识、模具设计知识和挤压铸造设备相关知识层,具有实体相关性、复杂性、重复交叉性和层次性的特点;狭义挤压铸造知识结构面向工艺参数设计而构建,主要包含铸件属性、工艺参数和铸件质量指标三种知识.并基于面向对象理论,建立了狭义挤压铸造工艺知识的语义模型,为其存储和还原表示提供了桥梁.