钢筋横肋末端间隙超出标准的原因分析及优化改进

分析了带肋钢筋横肋末端间隙超出标准的原因,包括加工成品孔型的刀具磨损量太大、轧钢时的轧槽磨损严重等。通过定期更换成品孔型加工刀具、改变轧槽横肋末端的加工方法和及时更换轧槽,使成品带肋钢筋横肋末端间隙尺寸满足热轧带肋钢筋标准GB/T1499.2-2018的要求。     

带肋钢筋尺寸超差原因及其消除

分析带肋钢筋肋间距超偏差、内径尺寸超负偏差、横肋高度尺寸超负偏差、横肋高度尺寸超正偏差、无纵肋、纵肋尺寸超正偏差、单线轧制时纵肋局部超正偏差、切分轧制时中两条纵肋大小不均、飞边等尺寸超差的原因,总结消除办法,提出持续改进措施。     

热轧带肋钢筋负公差控制与成品孔槽设计的关系

利用3D软件,对热轧带肋钢筋底圆、横肋、纵肋进行了重量计算,各部分对负公差的影响大小依次为内径—横肋—纵肋,内径尺寸的设计是控制负公差的重点,对孔型设计、加工提出了原则性建议：设计较小的内径,适当加深横肋,减小螺旋角。     

修订GB1499理解及其工作导向(下)

7　保持标准严密性,解决其自相矛盾之处标准提出带肋钢筋横肋设计原则之一就是横肋间距l不得大于公称直径d的0.7倍,而原标准中又根据不同公称直径列出横肋间距的公称尺寸和允许偏差。见表1。表1公称直径d,mm8101214161820222528323640横肋间距乴坢m设计原则基数(0.7d)5.67.08.49.811.212.614.015.417.519.622.425.228.0公称尺寸5.57.08.09.010.010.010.010.512.512.514.015.015.0允许偏差±0.5±0.8±1.0　　从上表可以看出,若公称直径12mm以上规格,设计原则基数(0.7d)与横肋间距允许值(l),即公称尺寸土允许偏差的关系服从l≤0.7d。若公称直…     

横肋分布特征对带肋钢筋轴向变形分布的影响

实验研究了延伸变形在带肋钢筋中的分布.发现横肋对称的钢筋,延伸变形呈明显正弦规律分布;而横肋非对称的,变形相对均匀,无明显规律.随着变形量增加,变形分布的不均匀程度加重.分析表明:横肋对称的带肋钢筋,其不均匀程度较横肋非对称的严重,当钢筋整体变形达到2.8%时,前者为后者的2.5倍.从抗震的角度出发,建议提倡使用横肋非对称的带肋钢筋,且两侧横肋最好以肋间距的1/2交替分布.     

切分轧制热轧带肋钢筋横肋顶端平面缺陷的控制实践

文章介绍了棒线材生产线采用切分轧制工艺,热轧带肋钢筋横肋顶端出现平面缺陷问题,该缺陷导致成品热轧带肋钢筋横肋高度不达国标.通过从切分轧制工艺孔型系统、轧制参数、工艺备件、调整方法等多方面入手,解决了切分轧制热轧带肋钢筋横肋顶端出现平面现象,从而提升了切分轧制热轧带肋钢筋成品质量,确保了热轧带肋钢筋产品符合国家标准.     

微合金化和余热处理热轧带肋钢筋高低周疲劳性能对比研究

通过试验研究,对比分析了微合金化和余热处理带肋钢筋的高周疲劳和低周疲劳性能。研究表明,微合金化钢筋比余热处理钢筋具有更好的疲劳性能。在微合金化和余热处理带肋钢筋的高低周疲劳试验中,观察到在横肋根部裂纹萌生并沿该区域扩展。有限元模拟结果显示在横肋根部出现应力集中,应力三轴度变大。模拟过程中也发现在横肋根部拉应变累积。有限元模拟结果有助于解释试验观察结果,即疲劳裂纹沿热轧带肋钢筋的横肋根部萌生及扩展。     

带肋钢筋反弯特性中的尺寸效应与方向效应

按ＧＢ１４９９－９１标准附录Ａ的技术要求,采用ＧＢ５０２９－８５规定的试验方法,研究了直径１２－４０ｍｍ１０种规格的２０ＭｎＳｉ热轧月牙肋钢盘的反弯性能。试验研究结果表明：钢筋的反弯性能合格率高低与钢筋的“尺寸效应”、“方向（位置）效应”密切相关。本文从力学观点出发,论述了钢筋的“尺寸效应”与“方向效应”对反弯性能影响的本质问题,并提出增大变上径或弯曲力臂、增大横肋根部曲率半径ｒ与降低横肋高度ｈ、     

一种计算热轧钢筋成品辊轧制时前滑值的经验公式

通常热轧带肋钢筋轧制时,因成品需充填横肋和纵肋,使之金属流动过程复杂,造成影响前滑值因素增多,故计算其前滑值困难。充分利用钢筋成品轧制时,前滑值便于实测的有利条件,在对大量数据进行统计分析的基础上,归纳总结出一种经验公式,以便计算出棒材机组钢筋成品轧辊轧槽的横肋个数,从而准确确定出钢筋横肋间距,使得钢筋横断面金属量得到合理分配,促进了钢筋生产质量的稳定。     

防止热轧带肋钢筋横肋高度出格的探讨

本文阐明了对热轧带肋钢筋(简称带肋钢筋)横肋高度符合GB/1499—1998标准要求的看法,对在工艺条件不变的情况下生产较大规格带肋钢筋横肋高度出格的原因进行了分析,指出加强过程控制是保证产品质量的重要环节。     

超高强度抽油杆用热轧带肋圆钢25CrMoA研制

山东寿光巨能特钢有限公司采用电炉、LF炉、连铸、控制轧制工艺及特殊的产品外观结构设计开发了超高强度抽油杆用热轧带肋圆钢25CrMoA。钢中碳含量控制精度在0.05%以内;横肋肋槽的月牙形设计,防止了横肋表面纵向裂纹的产生;通过控制终轧温度、导卫和辊道上的夹钢等,横肋的过度磨损有所控制;通过控制冷却,使钢材弯曲度≤3mm/m;成品钢材采用弧形剪刃剪切,使钢材的端部质量得以控制。通过对断后伸长率的分析,认为固定标距未考虑规格的变化对测试结果的影响,由此将回火温度波动范围控制在15℃以内对热处理操作是一个考验。     

Measurement of Truck Axle Weights by Instrumenting Longitudinal Ribs of Orthotropic Bridge

The longitudinal ribs of an orthotropic box-girder bridge were instrumented to measure axle weights of trucks. The bending stress in the longitudinal rib is composed of a girder component, i.e., the flexural stress due to the rib’s function as part of the box-girder’s upper flange in carrying vehicles, and a rib component, i.e., the part of stress produced in the rib when it is viewed as a continuous beam supporting wheel loads. The instrumentation locations were set close to the middle support of the two-span continuous bridge to reduce girder component and impact effect. All possible wheel-supporting ribs inside the box girder were instrumented to cover most transverse locations of truck wheels. Deviating passes as well as central passes were carried out for each traffic lane in calibration tests to catch maximum stress response. The results of the calibration tests were used to solve the influence lines of the girder component and rib component at each strain gauge. With these influence lines, the rib component was separated from girder one in the stress waves of the 3-day live traffic measurements, and axle weights of the truck traffic were subsequently calculated.     

A 2.5-dimensional Analytical Model of Cold Leveling for Plates with Transverse Wave Defects

Waves occurring in cold-rolled plates or sheets can be divided into longitudinal and transverse waves. Classical leveling theories merely solve the problem of longitudinal waves, while no well accepted method can be employed for transverse waves. In order to investigate the essential deformation law of leveling for plates with transverse waves, a 2.5-dimensional(2.5-D) analytical approach was proposed. In this model, the plate was transversely divided into some strips with equal width; the strips are considered to be in the state of plane strain and each group of adjacent strips are assumed to be deformation compatible under stress. After calculation, the bending deformation of each strip and the leveling effect of overall plate were obtained by comprehensive consideration of various strips along with the width. Bending of roller is a main approach to eliminate the transverse waves, which is widely accepted by the industry, but the essential effect of bending of roller on the deformation of plates and the calculation of bending of roller are unknown. According to the 2.5-D analytical model, it can be found that, for plates, it is neutral plane offsetting and middle plane elongation or contraction under inner stress that can effectively improve plate shape. Taking double side waves as an example, the appropriate values of bending of roller were obtained by the 2.5-D analytical model related to different initial unevenness, which was applicable to the current on-line adjusting of bending of roller in rolling industry.     

A 3-D Differential Method for Solving Rolling Force of PC Hot Strip Mill

 According to the character of the deformation zone on pair cross rolls, which is different from the regular 4-high mill, there are longitudinal and transverse two-way shear deformation in the deformation zone, the character of metal particles flowing velocity is more complicated than normal rolling. Comprehensive influences of normal stress and shear stress in rolling direction, width direction and thickness direction are considered. Establish the rolling force calculation model of PC hot strip mills. After the longitudinal and transverse discretization of deformation zone, the longitudinal and transverse distribution of rolling force is worked out by the differential method, then calculate total rolling force. Calculated results are verified by experimental data.     

Flexural Performance of Carbon Fiber-Reinforced Polymer Prestressed Concrete Side-by-Side Box Beam Bridge

The effect of varying transverse posttensioning levels and arrangements on the load response of a one-half scale 30° skewed seven box beam bridge model was investigated. The effective span of the bridge model was 9.45?m (31?ft) with a width of 3.35?m (11?ft) and depth of 355.6?mm (14?in.). The bridge model was prestressed and reinforced with carbon fiber composite cables (CFCCs). CFCCs were also used as shear reinforcement. The bridge model was provided with five transverse diaphragms equally spaced along the length of the bridge. The experimental investigation included load and strain distribution tests and a flexural ultimate load test. The load and strain distribution tests were conducted on the bridge model with and without full-depth longitudinal cracks at the shear-key locations. The investigation showed that the application of an adequate transverse posttensioning force was successful in restoring the load distribution of the bridge model with full-depth longitudinal deck cracks to that of the case without deck cracks. The ultimate load and the associated compression-controlled failure mode of the bridge model agreed well with that predicted according to ACI 440.4R-04 and numerical analysis. The behavior of the bonded pretensioned and reinforced CFCC strands was linear elastic and remained intact throughout the collapse of the bridge model. The unbonded transverse posttensioned CFCC strand also remained intact.     

1720 mm冷轧平整机辊形优化技术的研究

某1720 mm平整机组在生产中普遍存在板形缺陷,尤其是电工钢的生产,板形封闭量达到5%以上。为提高该机组的板形控制质量,针对机组的工艺特点,以前张力和辊间接触压力分布均匀为目标优化设计出工作辊和支撑辊新辊形。现场应用表明,优化后新辊形使工作辊和支撑辊间接触压力更加均匀,弯辊控制效果得到增强,板形质量显著提高,取得了良好的经济效益。     

Two-dimensional echocardiography with a wide angle (60 degrees) sector scanner

A wide angle (60 degrees) sector scanner producing a real-time two-dimensional echocardiogram has been used to examine healthy infants, children, and adults. Its method of use is described and findings from longitudinal and transverse scans are presented. The points of difference between the various types of electronic and mechanical two-dimensional scanning systems are discussed. This equipment minimises problems of chest contact and rib and lung interference and, by providing echocardiograms of high line density from a wide angle, is a suitable real-time two-dimensional scanning system for examining patients of all ages.