冷旋压高压气瓶瓶底结构强度分析

以冷旋压高压气瓶瓶底结构为研究对象,气瓶材料为34CrMo4H高强度合金,采用有限元法,对各载荷工况条件下瓶底的应力分布进行分析,结合相关的强度设计标准对瓶底结构进行强度分析,并对高压气瓶瓶底结构进行了优化。结果表明:瓶底结构满足强度要求,所产生冷旋压气瓶的爆破压力远小于设计极限压力,且还有相当的安全裕量;在满足气瓶强度要求的条件下,提出了一种更为合理的冷旋压高压气瓶的瓶底结构,从而为冷旋压高压气瓶的优化改进提供了技术支撑。     

高压气瓶用34CrMo4钢的抗氢脆性能及影响因素

为保证具有氢脆风险的高压气瓶的安全使用,对国内两个钢厂生产的高压气瓶用34CrMo4钢进行了化学成分分析、力学性能测试和抗氢脆性能试验,对比研究了不同厂家34CrMo4钢的抗氢脆性能及影响因素。结果表明:不同钢厂生产的34CrMo4钢中的主要化学成分基本一致,但由于钢中气体元素氧、氮、氢,有害元素磷、硫和微量元素(钒+铌+钛+硼+锆)的含量,非金属夹杂物级别,以及钢的冲击性能相差较大,导致其通过氢脆试验的抗拉强度不同,分别为901,968 MPa,对应的最大氢脆化指数分别为1.93,1.92;对具有氢脆风险的高压气瓶,除应限定材料最大抗拉强度与屈强比外,还应限定有害元素磷、硫和微量元素(钒+铌+钛+硼+锆)的含量。     

压缩天然气用34CrMo4高压气瓶开裂分析

针对韩国某公司所使用的太钢34CrMo4热轧中板,热冲压成压缩天然气用车载贮气瓶后,在设定压力反复试验过程中发生气瓶泄露的问题进行了研究。检测了该钢板的力学性能,对气瓶开裂部位进行了金相观察及夹杂物分析。结果表明,气瓶开裂的原因是用户在热冲压成形过程中多次热处理造成钢瓶内表面脱碳及内表面划伤所致。用户采取防范措施后,钢瓶未再发生此类事故。     

气瓶坯料错距反旋成形的工艺研究

简述了气瓶坯料筒形件流动成形的工艺路线的制定、试验方法,旋压过程中采用反旋错距方法,探索了反旋错距流动旋压的工艺参数对尺寸精度的影响,为气瓶坯料旋压成形提供工艺支持。     

高压气瓶用34CrMo4-H高强度钢的研究

为设计开发工作压力30 MPa的高压气瓶,研究了ISO 9809-2:2010对气瓶钢化学成分与力学性能的要求。结合国外工作压力30 MPa高压气瓶用高强度钢的使用经验,在34Cr Mo4中添加0.050%~0.080%钒,并分析和试验研究合金元素Mo和Ni在不同的热处理工艺条件下对34Cr Mo4-H钢力学性能的影响,设计出工作压力30 MPa高压气瓶用34Cr Mo4-H高强度钢化学成分。试验结果表明,设计开发的工作压力30 MPa的高压气瓶用34Cr Mo4-H高强度钢力学性能指标均超过ISO 9809-2:2010标准要求,特别是延伸率、冲击值富裕较大。     

抗拉强度1100MPa以上高强度气瓶的研究

通过研究抗拉强度1100 MPa以上高强度气瓶钢,采用ISO 9809-2:2010壁厚计算公式和有限元技术,对ф229 mm,50 L高强度气瓶进行了设计与分析;并通过"未爆先漏(LBB)"试验对设计进行了验证。结果表明,34CrMo4H高强度气瓶钢在870℃加热、水介质冷却淬火、570~600℃回火空冷热处理条件下,能够满足1100 MPa以上高强度气瓶的设计要求;高强度气瓶的壁厚设计按照ISO 9809-2:2010公式是合理的,但凹底厚度应结合有限元技术进行分析确定,不能直接取值为2倍最小设计壁厚;与GB 5099—1994标准设计相比,高强度气瓶的空瓶质量降低20%以上,实现了气瓶的轻量化,并大大提高了气体充装量;预制裂纹疲劳试验次数在11000次左右,疲劳寿命接近完好气瓶规定值12000次的水平。预制裂纹爆破试验表明,当采用爆破试验方法时预制裂纹深度为实际壁厚的75%左右,当采用疲劳试验方法时预制裂纹深度为实际壁厚的60%~70%,试验结果均能够满足设计要求。     

合金元素对SPA-H耐候钢显微组织和低温冲击韧性的影响

通过L9(34)正交实验设计,在实验室轧制了9种铜、硅、镍含量不同的SPA-H耐候钢,研究了合金元素对试验钢显微组织、夹杂物和低温冲击韧性的影响以及对低温冲击韧性的影响机理。结果表明:试验钢中的夹杂物均为Al2O3脆性夹杂物;合金元素对试验钢晶粒度和珠光体含量的影响不大,但对低温冲击韧性有明显影响,三种合金元素对低温冲击韧性的影响从大到小的顺序为硅、镍、铜;试验钢冲击韧性的变化是显微组织和夹杂物综合作用的结果。     

提高无缝气瓶用34Mn2V钢强韧性的两种淬火工艺的研究

本文根据无缝气瓶用34Mn2V钢特点，对提高该钢强韧性的亚温淬火和低温淬火工艺进行试验研究，分析了工艺及组织变化对34Mn2V钢强韧性的影响，推荐了亚温淬火和低温淬火两种热处理工艺。     

气瓶旋压成形技术

与冲压、焊接结构的气瓶相比,旋压气瓶从根本上消除了与焊缝有关的不连续、强度降低、脆裂和拉应力集中等缺陷,故此,旋压气瓶的气密性和耐压性能有了大幅提高。本文重点阐述了钢质气瓶、铝合金气瓶的旋压成形工艺特点及其成形工艺规范。     

表面质量和加载方式对洁净42CrMo高强钢的高周及超高周疲劳行为的影响

本文运用超声疲劳试验技术研究了洁净42CrMo高强钢在高周和超高周循环加载下的疲劳性能,并考虑了不同表面质量和加载方式对其疲劳性能的影响。主要关注了表面质量和加载方式对其S-N曲线特征的影响,使用Miner准则预测变幅疲劳寿命的准确性,通过断口观察分析了不同表面质量和加载方式下的微观失效机理,并分析了变幅加载中低载荷的影响。综合考虑了表面质量和加载方式对洁净42CrMo高强钢疲劳性能的影响,能指导该材料的加工制造和明确该材料的使用场合。     

如何提高液压缸筒用无缝钢管材料利用率

液压缸筒用高精度无缝钢管只有内径几何尺寸精度达到H9～H10,内表面粗糙度Ra≤0.8μm,才能满足在制作液压缸筒时高精度无缝钢管经过珩磨后内孔尺寸精度达到H7～H8,内表面粗糙度Ra≤0.2μm,否则,需要预留大量的珩磨及车削加工余量。即便如此,高精度无缝钢管的材料利用率依然比较低下,不仅需要对高精度无缝钢管内孔进行1～5mm的珩磨,而且需要对外圆进行0.5～1mm的车加工。改变传统的高精度无缝钢管冷拔生产工艺,在生产液压缸筒用高精度无缝钢管初期,对钢管的内表面进行微量珩磨和外表面抛光,再进行制头、润滑处理、冷拔、矫直、剪切和检验,那么,得到的高精度无缝钢管几何尺寸精度高、内外表面好。这样一来,制作液压缸筒时,可减小内孔珩磨量至0.5～2mm,并且高精度无缝钢管外表面直接作为液压缸筒的外表面使用,有效的提高液压缸筒用高精度无缝钢管的材料利用率、生产效率,尤其是产品质量能够得到进一步提高。     

Rotary ultrasonic drilling of needle-punched carbon/carbon composites: comparisons with conventional twist drilling and high-speed drilling

Refillable seamless steel gas cylinders are widely used to store and transport clean energy, such as compressed natural gas (CNG) and hydrogen. Conventional manufacturing processes have some disadvantages which bring potential hazard for the safety and reliability of cylinders. After reviewing the conventional manufacturing processes, a hot deep drawing process is recommended with solid steel billet stock. Based on this, an integral manufacturing process with cold flow forming process is proposed for large-diameter seamless steel gas cylinders to improve the performance of gas cylinders. Several cylinder properties including size error and fatigue lives are compared. The uniformity of wall thickness is further improved for gas cylinders by the integral process. The gas cylinders obtain fine surface finish, high tolerance of size, and commensurately enhanced fatigue lives. Meanwhile, the failure mode and effect analysis (FMEA) method is adopted to study the reliability of steel gas cylinders. The reliability of steel gas cylinder with cold flow forming process is compared with the conventional processes. The probabilities of most causes are ameliorated, except for the lamination that is usually resulted from wrong flow forming process parameters, e.g., high reduction rate and feed rate. As a whole, there is a marked drop in the risk priority number of the integral process. It is worth to further spread this in gas cylinder industry.     

Hydrogen damage in 34CrMo4 pressure vessel steel with high tensile strength

Various efforts have been made to improve the safety of high-pressure gas cylinders for hydrogen or natural gas with high strength steel liners. Metal liners with high tensile strength have a safety concern, particularly with hydrogen gas or hydrogen generating environments. The hydrogen can permeate into the liner material, and make the material brittle, causing hydrogen damage. This study investigated resistance to hydrogen damage for two kinds of 34CrMo4 steel with different strength levels. Hydrogen was charged with the electrochemical method, and the material strength was measured by the small punch testing technique. Hydrogen concentration of the specimen was also measured for every testing condition, with various charging periods. The specimens with high tensile strength absorbed more hydrogen than the regular tensile strength specimens. The absorbed hydrogen caused internal damage of intergranular cracking and blistering. Material ductility at failure decreased, as the hydrogen concentration of the specimen increased. But the hydrogen concentration had virtually no effect on the strength of the materials with hydrogen. These results confirm that the susceptibility to hydrogen damage of the high tensile strength materials is much higher than that of the materials with regular strength. If the metal liner of a hoop-wrapped cylinder vessel of type II has high tensile strength, general corrosion at the liner surface can cause a hydrogen rich environment, and the cylinder can suffer hydrogen damage and embrittlement. Therefore, controlling the strength level under an optimal level is critical for the safety of a cylinder made with 34CrMo4 steel.     

Evaluation of Occurrence of Surface Brightness Irregularity in Cold Rolling of Stainless Steel with Emulsion

The manufacturing of stainless steel with higher brightness is improved using emulsion oil. However, in cold rolling of stainless steel with emulsion oil, it is well known that the surface brightness irregularity on the sheet surface after rolling occurs when the rolling speed is higher. It is estimated from the experimental results that the cause of the surface brightness irregularity is due to the degree of starvation in the emulsion rolling. The rolling experiments of the stainless steel with oil-in-water emulsion were carried out at various rolling speeds. The inlet oil film thickness was estimated using the evaluating system. In cold sheet rolling of stainless steel with emulsion oil, the surface brightness irregularity occurred at a rolling speed of 0.6 m/s with emulsion concentrations of 3, 5, and 10%. The experimental results showed that the surface brightness irregularity at cold coil rolling with emulsion of stainless steel occurred under a degree of starvation value of 0.16.     

金属薄板冷轧工艺润滑基础实验研究

以铝合金板和IF钢板为代表,研究金属薄板冷轧工艺润滑的作用与效果。实验对不同润滑条件下冷轧时的轧制工艺参数进行分析,并对金属薄板轧后表面形貌情况进行观察。结果表明:通过冷轧工艺润滑可以明显提高轧机轧制能力、显著降低轧制过程中的力能消耗(轧制力、轧制力矩),有效地改善轧件表面质量。     

Measure dimension of rotating large hot steel shell using pulse laser on PRRR robot

During the industrial forging or rolling of hot steel shells, the raw material utilization ratio is very low because of the absence of precise on-line measurement instrument for the forging dimensions. In order to reduce the waste and increase the productivity, the pulse laser measuring instrument with dual PRRR mechanism has been developed in this study. The adjusting algorithm of rotary table based on the dual PRRR mechanism has been presented, which ensures that the scanning plane is perpendicular to the axis of cylinder shell. So the circle fitting can be adopted and the robust and accurate dimensions can be obtained rapidly by the present data-processing method. The measurement error of cold cylinder shell’s diameter is less than 3 mm. The measuring results of hot steel shells are also very accurate. The present system has been used in the rolling production of large hot steel shells, which enhances the raw material utilization ratio during the rolling.     

Photoelastic study of the influence of oil film on contact stresses

The paper describes some experiments, the object of which was to determine the stress distribution at a contact surface or below of it. Plastic and glass cylinders were rolled on the inner surface of a hardened steel ring under dry and lubricated conditions. The ring and the cylinder were driven by separate motors to enable rolling and sliding contact.     

The coefficient of kinetic friction for aluminum

The translational and rotational motions of a cylinder traveling down a straight incline, which provides a constant linear acceleration, depend on the angle of inclination. For small angles above the horizontal, free rolling takes place, but, above a critical angle, rolling and slipping occur. This critical angle is used to evaluate the coefficient of friction for steel cylinders progressing over aluminum surfaces. The moment of inertia is varied by using solid and annular cylinders and the aluminum surface is smooth, rough or corrugated. The coefficient of friction is shown to be independent of the moment of inertia but to depend on the type of surface and the angle of inclination.     

Fe3O4纳米粒子添加量对润滑油润滑特性的影响

主要研究了润滑油中纳米粒子添加剂的含量对冷挤压过程中润滑特性的影响规律。采用粒径为20～30nm的Fe3O4纳米粒子分散于52#汽缸油中配置成具有不同质量分数的纳米粒子改性润滑油,并将该润滑油应用于钛合金（TA2）棒材的冷挤压实验,论文系统研究了润滑油中Fe3O4纳米粒子的添加量对钛合全冷挤压成形的最大成形力、成形功、表面质量（Ra）及HV的影响规律并对其润滑机理进行了分析,结果表明：当润滑油中Fe3O4纳米粒子质量分数为8％时。纳米改性润滑油的润滑效果最佳,挤压成形力和成形功最小,成形件表面质量最好。纳米粒子的填充与滚动作用及其对52#汽缸油膜的支承作用是改善润滑油润滑性能的主要原因。