Wear of Laying Head Pipes in a Wire Rod Mill

The failure analysis on the premature wear of a “Laying Head Pipe” in a Wire Rod Mill has been presented. The hot-rolled wire rods subsequent to finish rolling pass through the “Laying Head Pipe” which rotates and lays the wire rods in the form of coils for air cooling to achieve the final properties. A worn-out pipe and a thermo-mechanically treated (TMT) re-bar have been analyzed. The material of the pipe is ASTM A335-P5 grade of seamless alloy steel pipe used for high temperature service. The microstructures of the wear groove of the alloy steel pipe show predominantly ferrite and globular cementite/carbide particles along with scales, while that away from the wear groove shows coarse tempered martensite matrix. EDS analysis confirms the presence of alloy carbides near the wear groove. Microhardness profile shows reduction in hardness toward the inner surface of pipe; hardness at the inner surface of the pipe becomes lower than the surface hardness of the TMT re-bar, exhibiting tempered martensite matrix. Softening at the inner surface of the pipe wall occurs due to a rise in temperature/ over-tempering in contact with the passing hot wire rods (900 °C) which causes transformation of martensite into ferrite and coarse globular cementite.     

Stress Intensity Factors of partly circumferential surface cracks at the outer wall of a pipe

By means of the finite element method stress intensity factors were calculated for partly circumferential surface cracks at the outer wall of a pipe. The crack shape considered can be described as curved rectangular shape. The cracks considered have crack depths between 20 and 80 percent of the wall thickness of the pipe and crack lengths (defined by the angle of circumference φ) between φ = 10° and φ = 60°. The pipe is loaded by a constant axial tensile stress σ₀ (equal to 136 Nmm^?2 in the numerial calculations), and the wall thickness to inner radius ratio of the pipe was chosen to 0.1. A wall thickness of 20 mm was used for the numerical calculations.     

传热管道设备的内壁状态监测方法

在特定边界条件下对热传导方程进行求解,优化所得温度分布方程的系数,并利用分段积分法对系数进行化简,建立了传热管道设备表面温度、材料特性与内壁状态3者间的关联模型,并将其应用在传热管道设备的内壁状态监测上。结合导热反问题,利用所建立的关联模型分析传热管道设备外表面的温度数据,得到内壁几何形状。通过仿真实验验证了该方法的可行性,从而为传热管道设备内壁状态的实时监测提供依据。     

Noncontact Laser Inspection Based on a PSD for the Inner Surface of Minidiameter Pipes

A new noncontact laser-inspection technique based on a position-sensitive detector (PSD) to inspect the inner surface of minidiameter pipes is proposed, and the corresponding sensor is developed. A light spot is projected onto the pipe inner wall after the laser beam is reflected by two mirrors. At the same time, four current signals are produced when the light spot is read by the 2-D PSD. According to the magnitude of the current signals and the structure parameters of the sensor, the spot position on the inner wall can be calculated in a local 3-D coordinate system. With a micromotor, the surface of the whole inner wall can be scanned by the laser beam. This way, the coordinates of all the sample points in the section are obtained. After that, several reasonable data-processing methods are used, such as data segmentation and least squares fitting. Finally, the section curve can be reconstructed. The radius and defects of the section can also be obtained. Driven by a micropipe robot, the sensor can inspect a long curved pipe. The inspection system based on this technique can detect the inner surface of minidiameter pipes, which has an inner diameter of 9.5–10.5 mm and a curvature radius of more than 100 mm. The measurement accuracy of this inspection system for the inner diameter and surface defect reaches $pm$0.1 mm.      

基于环形激光的深孔内膛形貌检测系统研究

提出了一种基于环形激光的深孔内膛检测系统,该系统主要由环形激光发生器、反射锥镜、CCD相机以及驱动装置等组成。通过对环形激光器投射在被测身管内膛上的环形光斑进行成像和分析计算,可对身管内膛的一个截面形廓进行检测,并在驱动装置的驱动下,实现对深孔内膛形貌的三维检测。     

An entry-flow problem for a non-isothermal catalytic-wall reactor

A reacting gas flows into a metal, thin-walled, tube which has a catalytic coating on its inner surface. A strong, temperature-dependent, exothermic reaction occurs giving a local hos spot. It is assumed that the surface temperature is controlled by heat conduction through the metal wall, heat transfer into the gas being negligible. A standard approximate technique is used to derive an integral equation which relates the mass transfer at the wall in the Blasius boundary layer to the wall temperature. A second integral equation is derived from the heat-conduction problem for the metal wall, and the coupled equations are solved numerically. The maximum temperature rise at the wall is found to be significantly higher than that obtained when a fully developed flow passes over a catalytic coating.     

空心薄壁细长轴旋转锻造过程材料流动规律研究

目的 为了准确地设计带内台阶的薄壁细长轴类零件的旋转锻造用管坯,研究缩径过程中金属材料的流动规律.方法 针对薄壁细长轴内台阶孔,采用有限元模拟与实验验证相结合的方法,研究管坯旋转锻造过程中,毛坯外径/内径之比、模具入角和摩擦条件对缩径过程金属流动的影响规律.结果 管料外径和内径之比越大,金属的厚向应变越小;摩擦因数越大...     

Stresses in a nonlinearly hardening pipe after expansion to large deformations,inelastic unloading,and removal of its inner layers

The problem of the numerical determination of residual stresses in an elastoplastic nonlinearly hardening pipe of V95ochT2 material in plane strain is examined.It is shown that due to secondary plastic deformations that develop during unloading, the greatest residual circumferential stresses reside at a certain distance from the inner surface of a thick-wall pipe.Removal of the internal layer of the pipe gives rise to a small change in the circumferential compressive stresses on its inner surface. In this case, the zone where the maximum residual circumferential compressive stresses reside is shifted deeper into the pipe with a simultaneous decrease in the distance from this zone to the new inner surface of the piper, which is formed after removal of a layer of metal.Translated from Problemy Prochnosti, No. 11, pp. 111–114, November, 1989.     

基于环形光切图像法的管内壁激光测量系统

研制了基于环形光切图像法的管内壁测量系统。测量系统主要由半导体激光器、环形光发生器以及CCD摄像机组成。来自光环发生器的环形光带投射于被测管内壁上并成像于CCD摄像机。根据光散射和反射的理论,测量系统参数被选择以优化系统。实验结果显示原理正确、技术可行。     

Hydraulic transport of solids in pipes: a simple method for the prediction of pressure drop

Suspensions such as grouting slurries, concrete and dredge muds exhibit a complex flow behaviour in pipes which is not fully understood. This flow in cement systems is often complicated by the time-dependent behaviour of the material and the apparent slippage at the wall of the pipe. Most of the methods which have been developed to predict the flow behaviour of thick suspensions are very complex and are frequently inaccurate. In this paper a simple method is discussed which can be used to predict the pressure drop in pipes for time-dependent or time-independent materials with a yield stress. The method is based on the assumption that the sheared layer in the pipe can be simulated by a similar layer in the coasial cylinder viscometer, and the properties of the layer are only dependent on plug speed in both systems. The implication of this assumption is that the shear stresses at the surface of the pipe and at the surface of the inner cylinder of the coaxial viscometer are independent of the pipe diameter and the diameter of the cylinders. The method was tested against the authors’ own data and by other data from the literature.     

Fast scanning method for one-dimensional surface profile measurement by detecting angular deflection of a laser beam

A fast scanning method for one-dimensional surface profile measurement is proposed. The profile is measured by integration of a slope distribution of the surface obtained from angular deflection of a scanning laser beam. A scanning optical system that consists principally of a spherical concave mirror and a rotating scanner mirror has reasonably low cost and is insensitive to mechanical vibration because of its high-speed scanning, of the order of milliseconds. A surface profile of a polygonal mirror along a 5-mm width was measured with the scanning method and with an interferometer. The root-mean-square difference between the two measured results is 0.98 nm.     

Degradation of C-1/2Mo Steel Pipe by Metal Dusting in a Steam Reforming Process

A C-1/2Mo steel pipe of a heat recovery economizer in a steam reforming process used in the production of high-purity hydrogen has developed large pits at the inner surface. Light optical microscopy, x-ray diffraction, scanning electron microscopy combined with energy dispersive x-ray spectroscopy and transmission electron microscopy have been used to characterize the microstructure of the pitted pipe. Degradation of the pipe has been correlated with higher than normal temperature enhancing metal dusting as well as a material not intended to function in such an environment. Microstructural characterization shows that the sequence of events leading to the observed pitting follow a model proposed to explain metal dusting of carbon and low-alloy steels.     

Stress intensity factors for long axial surface cracks at the outer wall of a pipe loaded by stress gradients

By means of the finite element method crack opening displacements were calculated for long axial surface cracks at the outer wall of a pipe. The wall thickness to inner radius ratio of the pipe was 1 to 10. Following a procedure introduced be Mattheck et al. weight functions were evaluated by means of the finite element results. Using these weight functions it is possible to calculate stress intensity factors for arbitrary radially varying stress distributions. In this paper stress intensity factors were evaluated for a constant hoop stress loading as well as for stress distributions with a linear and a quadratic dependence on the radius.     

Characterization of corrosion products formed on mild steel in deoxygenated water by Raman spectroscopy and energy dispersive X-ray spectrometry

The corrosion of steel parts of heating systems is nowadays not commonly observed failure because of the lack of oxygen in circulated media. In rare cases corrosion rapidly initiates and propagates due to various, mostly unexplained mechanisms. A voluminous corrosion product that was found in the vicinity of a perforation to a pipe wall was investigated in order to understand the reasons for the observed rapid corrosion processes. Raman spectroscopy and energy dispersive X-ray microanalysis were used to examine this corrosion product across the whole cross-section of the pipe. It was observed that the inner part of the corrosion product at the contact with the pipe's inner surface mostly consisted of magnetite. The outer part of the corrosion product, which was in contact with the water in the pipe, was mostly goethite. These findings confirmed the hypothesis that the magnetite sediments on the surface of the new pipe caused oxygen concentration cell formation, which triggered corrosion dissolution of the pipe wall and led to a rapid perforation.     

基于密度聚类和圆外切线斜率拟合的埋地排水管道声呐点云去噪技术

针对环扫声呐扫描结果受到排水管道内混合水声的影响问题,提出一种声呐扫描点云数据去噪的方法:在环扫声呐扫描得到的三维点云数据基础上,通过密度聚类优化算法,去除点云数据中的噪声,然后采用类圆外切线斜率拟合的方式,识别出管道内壁界限和淤泥淤积线,最终得出包含排水管道内壁界限和淤积线特征的模型。为验证有效性,以武汉市某排水管道为例进行分析,基于现场采集的98万个点云坐标进行数据去噪和特征提取,结果表明:采用密度聚类优化算法进行点云数据初筛后,通过圆外切线斜率拟合算法能有效识别出排水管道内壁界限和淤积线,拟合半径均方误差0.0071m,相较于单一密度聚类算法拟合精度更高,去噪效果更好。     

Experimental and numerical studies on corrosion failure of a three-limb pipe in natural gas field

A bursting incident occurred in a three-limb pipe, having 16Mn steel for the main pipe and 316L + L416 composite metal for the branch pipe, in a natural gas field. The failure analysis was performed by means of inspection, experiments and computational fluid dynamics (CFD) simulation. The CFD results indicated the radical change in the flow characteristics inside the three-limb pipe due to its upright structure and the formation of a low vortex in the downstream near the junction, which indicated the condensation of water vapor containing high salinity. The condensed brine saturated with CO₂ adhered to the inner wall surface of the main pipe. In such a corrosive medium, 16Mn steel acts as an anode and is preferentially corroded due to galvanic corrosion. In addition, the downstream area, covered by low vortex, exhibited high shear stress and droplet impingement stress, resulting in an increase in flow erosion. Thus, the failure of the three-limb pipe can be attributed to the synergistic effect of galvanic corrosion and flow erosion.     

Failure analysis and prediction of pipes due to the interaction between multiphase flow and structure

Frequently found in piping, erosion failures may lead to the leakage of pipes and even damage the whole system. Erosion is a form of material degradation that involves electrochemical corrosion and mechanical wear processes encountered on the surface of metal pipes. Research on the erosion–corrosion mechanism indicates that the erosion mainly results from the interactions between the pipe surface and the fluid traveling along the surface. This paper studied multiphase flow induced erosion–corrosion in pipes, mainly focusing on the interactions between the multiphase flow and the structure. In order to evaluate the erosion effects caused by the flow and the coupled dynamics, the multiphase flow regimes, flow dynamics parameters and the distribution of phases on different positions of the boundary layer in REAC pipe inner surface were analyzed. The CFD simulation results proved that the location, rate and the extent of erosion failures on the pipe surfaces can be well predicted, as compared with actual instances. Practically, this method can be used in optimizing the design of the inner sleeves of pipes.     

Laser beam intensity profile transformation with a fabricated mirror

A nonaxisymmetric mirror is designed by the same method as a computer-generated hologram for laser beam intensity profile transformation and is fabricated by plasma chemical vaporization machining. We successfully transformed a circular Gaussian beam of a He-Ne laser into a rectangular uniform beam maintaining spatial coherence and using a nonaxisymmetric surface profile mirror. There are ripples in the intensity profile of the transformed rectangular beam. These ripples in the intensity profile result from small ripples on the mirror surface. These results show that we can perform coordinate transformation using these fabricated mirrors, which has so far been possible only by using computer-generated holograms.     

Distributed brillouin scattering sensor for discrimination of wall-thinning defects in steel pipe under internal pressure

A distributed Brillouin scattering sensor has been employed to identify several inner wall cutouts in an end-capped steel pipe by measuring the axial and hoop strain distributions along the outer surface of the pipe. The locations of structural indentations that constitute 50-60% of the inner pipe wall are found and distinguished by use of their corresponding strain-pressure data. These results are quantified in terms of the fiber orientation, defect size and depth, and behavior relative to those of unperturbed pipe sections.     

Adaptive control of a micromachined continuous-membrane deformable mirror for aberration compensation

The nonlinear response and strong coupling of control channels in micromachined membrane deformable mirror (MMDM) devices make it difficult for one to control the MMDM to obtain the desired mirror surface shapes. A closed-loop adaptive control algorithm is developed for a continuous-surface MMDM used for aberration compensation. The algorithm iteratively adjusts the control voltages of all electrodes to reduce the variance of the optical wave front measured with a Hartmann-Shack wave-front sensor. Zernike polynomials are used to represent the mirror surface shape as well as the optical wave front. An adaptive experimental system to compensate for the wave-front aberrations of a model eye has been built in which the developed adaptive mirror-control algorithm is used to control a deformable mirror with 19 active channels. The experimental results show that the algorithm can adaptively update control voltages to generate an optimum continuous mirror surface profile, compensating for the aberrations within the operating range of the deformable mirror.