Numerical Simulation and Experimental Research on Microstructural Evolution During Compact Hot Extrusion of Heavy Caliber Thick-Wall Pipe

Compact hot extrusion(CHE) process of heavy caliber thick-wall pipe is a new material-saving production process. In order to reveal the optimum hot extrusion parameters in CHE process, the e ects of the extrusion parameters on the microstructural evolution are investigated systematically. The metadynamic recrystallization(MDRX) kinetic models and grain size models of as-cast P91 steel are established for the first time according to the hot compression tests performed on the Gleeble-3500 thermal-simulation machine. Then a thermal-mechanical and micro-macro coupled hot extrusion finite element(FE) model is established and further developed in DEFORM software. The results indicated that the grain size of the extruded pipe increases with the increasing of initial temperature and extrusion speed, decreases when extrusion ratio increases. Moreover, the grain size is more sensitive to the initial temperature and the extrusion ratio. The optimum hot extrusion parameters are including that, the initial extrusion temperature of 1250 °C, the extrusion ratio of 9 and the extrusion speed of 50 mm/s. Furthermore, in order to verify the simulation precisions, hot extrusion experiment verification on the heavy caliber thick-wall pipe is carried out on the 500 MN vertical hot extrusion equipment. The load–displacement curve of the extrusion process and the grain sizes of the middle part extruded pipe are in good accuracy with the simulation results, which confirms that the hot extrusion FE models of as-cast P91 steel could estimate the hot extrusion behaviors. The proposed hot extrusion FE model can be used to guide the industrial production research of CHE process.

CFD-Based Optimization of Hot Primary-Air Pipe Networks in Power Plant Milling Systems

A hot primary-air pipe system is the bridge connecting an air-preheater with a coal mill in power generation stations.The effective geometrical configuration of the pipe network greatly affects the air flow distribution and consequently influences the safe and economic operation of milling systems in power stations.In order to improve the properties of the air flow,in the present work the SIMPLEC method is used to simulate numerically the flow field for the original layout of the system.As a result,the internal mechanisms influencing the uneven pressure drop in each branch are explored and three optimization schemes are proposed accordingly.The numerical results indicate that,for the original layout,the local pressure drop of the tee section accounts for approximately 74%of the total drop of the system,with other pressure drops depending on the specific branch considered.It is shown that after optimization,a roughly balanced flow resistance and flow rate can be obtained.Compared with the original layout,the pressure drop relating to different branches is significantly reduced.

Influencing Factors of Properties of Castables for Hot Blast Stove Pipes

In order to prolong the service life of castables for hot blast stove pipes,effects of SiO2 micropowder addition and aggregate kind on properties of castables for hot blast stove pipes,and properties of silica sol bonded castables were researched using homogenized bauxite,andalusite particles,andalusite fines,white fused corundum fines,α-Al2O3 micropowder,pure calcium aluminate cement,SiO2 micropowder,and silica sol as starting materials. The results show that：（1） as SiO2 micropowder addition increases,the shrinkage rate of fired specimens increases; BD increases firstly,reaches the highest at 4 mass%,and then decreases; CMOR and CCS of all specimens increase gradually; so the appropriate SiO2 micropowder addition is 4 mass%;（2） the specimens with bauxite aggregate have better CCS and volume stability,but specimens with andalusite aggregate have better thermal shock resistance;（ 3） for castables for hot blast stoves using silica sol as binder,the addition of pure calcium aluminate cement can decrease the linear change rate after treatment at 1 400℃ and can slightly enhance CCS and CMOR,but has very little influence on AP and BD; and the introduction of citric acid worsens the thermal shock resistance of specimens.

Hot-rolled strips of up to 19 mm in thickness and their processing to helically welded large diameter pipes of grade X80

Hot-rolled wide strip for production of large diameter,heavy gauged(up to 19 mm) helical line pipe grade X80 was a priority development over the last three years.Microstructure,texture and mechanical properties of strips have been characterised.Also the welding conditions have been simulated.The favourable microstructure is achieved by the proper selection of an appropriate chemical composition of low carbon content and increased niobium micro alloying in combination with suitable strictly controlled hot-rolling parameters.The addition of niobium in combination with the adjustment of other alloying elements increases the recrystallisation stop temperature and thus makes it possible to apply a high temperature processing(HTP) concept.The homogeneous bainitic microstructure across the strip gauge is then formed during accelerated cooling on the run-out table of the hot-rolling mill.All results indicated excellent properties of these hot strips which make it suitable for spiral pipes of grade X80 for example 18.9mm×Φ1 220 mm at dimension.

Automatic girth welding and performance evaluation of the joints of hot-induction-bend and line pipes with different wall thickness

During the process of laying long-distance oil and gas transmission pipelines, the hot-induction-bend method is extensively used when the direction has to be changed. By considering the pipeline＇ s ongoing processing and loading states during service, the pipeline that is generally used exhibits thicker walls than those that are observed in the line pipe. As such, during pipeline construction, hot-induction-bend and line pipes with different wall thickness are girth-welded. The chemical composition of hot-induction-bend and line pipes differs, with the carbon content being particularly higher in the hot-induction-bend pipe;it also depicts a higher carbon equivalent, which makes it possible to modify the girth of the pipe. In this study, using Baosteel＇ s standard X70M UOE hot- induction-bend and line pipes, solid-wire automatic gas-metal-arc girth welding was performed and the performance of the girth-welded joint was evaluated. Furthermore,the weldability of the pipeline girth and the microstructure of the girth-welded joint were analyzed. The results reveal that Baosteel＇ s standard UOE hot-induction-bend and line pipes exhibit good girth weldability, and their technical quality can be guaranteed in case of consumer field- construction applications.

Hot Blast Flow Measurement in Blast Furnace in Straight Pipe

This article shows an innovative method to model and validate the hot air flow through the blast furnacés tuyeres. This study will be the basis for flow measurements implementation and safety interlocks for the pulverized coal injection. The flow measurements were taken in the blast furnace down leg pipes by installing refractory Venturi tubes. The system for the calculation of differential pressure takes into consideration the dimension of the Venturi, the air density and compressibility. The objective is to specify the flow transmitters required to automate a control system and implement safety interlocks for the coal injection plant.

Numerical study on forming complex fitting body on end of integrated stainless steel pipe without welds

It is necessary to use the integrated stainless steel pipe having two fitting bodies without welds while train travelling at high speed. In order to form this type of integrated stainless steel pipe, the method of preforming combined finish forming process is developed. The preforming process is characterized by flaring combined upsetting for left fitting body which is like a flange, and is characterized by tube axial compressive process under die constraint for right fitting body which is like a double-wall pipe. The finite element simulations of the processes are carried out by software package DEFORM, and the results indicate that: 1) left or right fitting body can be formed by a two-step forming process without folding and under-filling defects; 2) by using two-step forming, strain and stress in left fitting body are larger than those in right fitting body, and deformation in right fitting body is more homogenous than the deformation in left fitting body; 3) two or more preforming steps may be needed for left fitting body considering the distributions of strain and stress.

异形分流管热流道家族注塑模具设计

介绍了某款异形分流管零件热流道注塑模具的设计过程。模具设计中,首先,分析了注塑件的零件特征和生产要求,确定了模具的基本结构方案;再利用Moldflow软件分析模具注塑成型过程,预测零件的成型时间、翘曲变形量、熔接痕位置等,最终完成整套模具的设计。模具采用两板式热流道冷浇口注塑成型,浇口选择潜伏式点浇口形式,开模时自动拉断与注塑件分离;模具定模型腔设计了1个弹性脱模镶件,保证了开模时塑件紧贴型芯侧;模具分型面上共分布了5个侧抽芯滑块结构,由弯销导向并延时开模。对常用型弯销滑块机构进行了改进,将两段式弯销改进为三段式弯销,有效地避免了常用弯销滑块机构容易出现卡死和锁闭不紧的问题。模具经过实际生产验证可知,结构合理可靠,制备得到的零件尺寸精度满足设计要求。

L360QS+UNS N08825双金属复合管热丝TIG自动焊接工艺

双金属复合管作为一种油气输送管道材料,具有较强的耐蚀性能,特别适用于输送强腐蚀性介质。我国川渝地区的油气资源含有较高的硫化氢(H2S)和其他硫化物,管道内部形成了复杂的腐蚀环境,易导致管道内壁腐蚀、应力腐蚀开裂等多种失效形式。川渝地区油气管道常采用镍基合金、不锈钢等高性能的耐腐蚀材料,其中铁山坡项目中选用了L360QS+UNS N08825双金属复合管作为输送管道材质。针对825镍基复合管传统手工焊接方式效率不高,质量受人为因素影响大的问题,通过焊材匹配、自动焊接设备选型、焊接工艺参数优化等手段,开展焊接试验,研发了L360QS+UNS N08825双金属复合管热丝TIG自动焊接工艺,并在铁山坡项目中进行了实施应用,取得了显著的效果,一次焊接合格率可达99.2%,同时针对焊接缺陷返修和易出现的质量问题进行了分析,提出了相应的工艺措施。该工艺对于同类材质管道焊接具有重要的指导意义和参考价值。

2024年ASME PVP会议简介

美国机械工程师协会(ASME)压力容器与管道(PVP)会议是全球压力容器与管道领域的顶级国际会议,由美国机械工程师协会主办。报道了2024年在美国西雅图举行的ASME PVP2024会议的主要内容,包括主题和分议题;同时,还对比了2021~2024年美国、中国、日本等主要国家在ASME PVP会议上的论文收录和研究领域情况;分析了压力容器和管道领域的发展趋势和热点问题;最后,介绍了中国在本次会议上的获奖情况及近年来中国学生论文竞赛的情况。

湿热老化下车用尼龙管的力学性能

为了提高车用尼龙(PA)管的耐老化性能,本文对湿热老化下具有不同宏观层间结构及微观聚合物结构的PA管的力学性能和老化机理进行了研究。在工业生产平台上制备了PA11、PA12、PA12-聚氟乙烯(ETFE)和PA12-PA黏结剂(TIE)-乙烯-乙烯醇共聚物(EVOH)-TIE-PA612共4种试样,对PA试样进行6种温湿度工况下的老化处理,结合扫描电镜(SEM)图给出了试样的拉伸性能和冲击性能的变化规律和机理。结果表明,PA12管拉伸性能良好但冲击性能较差,断裂形式为韧性断裂;PA11管拉伸性能差但冲击性能好,断裂形式为脆性断裂;PA管力学性能随老化温度、湿度和老化时间增加而降低,且拉伸性能对湿度变化更敏感;随着温度湿度的升高和老化处理时间的延长,PA管的冲击功整体呈下降趋势;PA12-TIE-EVOH-TIE-PA612管在相同湿热老化下抗冲击性退化最不明显;PA12经240 h湿热老化后的断裂面光滑度明显下降;在4种PA管中,PA12和PA12-TIE-EVOH-TIE-PA612具有优良的力学性能和耐老化性能。本文可为车用PA管的材料和结构设计提供一定指导。

钻杆接头用含铌钒37CrMnMo钢的热变形行为及热加工图

采用Gleeble-3500热模拟试验机对含铌钒37CrMnMo钢进行等温单道次热压缩试验,研究了在不同变形温度和应变速率下钢的热变形行为及组织演变规律,并根据真应力-真应变曲线建立了该钢的热变形方程和热加工图。结果表明:在相同变形条件下,流变应力随变形温度的升高或应变速率的降低而降低;在高温、低应变速率条件下,试验钢的动态再结晶行为较显著;试验钢的热变形激活能为339.448 kJ/mol,基于动态材料模型和Prasad失稳准则确定了应变量为0.7时该钢的最佳热加工参数为1055~1250℃、0.05~0.12 s^(-1)和1130~1250℃、0.12~2.79 s^(-1)。

L360N无缝管线钢管的控轧控冷生产工艺开发

某PQF连轧管机组生产Ф273 mm×8 mm规格L360N无缝管线钢管时,采用常规热轧、控制轧制、控制轧制+控制冷却三种方式组织生产,分析了这三种工艺生产的无缝钢管的性能与组织差别。工业试验表明,控制轧制+控制冷却可以明显细化晶粒,在提高钢管拉伸性能的同时,可大幅提高钢管的冲击韧性,合理的控轧控冷工艺可使钢管稳定满足-30℃冲击值的要求。

热熔焊接工艺参数对聚乙烯燃气管道焊接残余应力的影响

高密度聚乙烯(PE-HD)管道具有韧性高、抗腐蚀等优点,广泛应用于输水输气、核工业和氢能等领域。受加工工艺和焊接技术的限制,PE-HD管道系统存在生产残余应力和焊接残余应力。残余应力的存在,会加速管道内部裂纹的萌生和扩展,显著降低了管道的使用寿命。因此,研究残余应力对准确评价PE-HD管道可靠性具有重要意义。分别采用开口圆环法和盲孔法测得了PE-HD管基材和热熔接头的环向残余应力,并基于弹塑性本构建立了温度-位移耦合的热熔焊接有限元模型,探究了热熔焊接接头残余应力的分布及焊接工艺参数对温度场和残余应力的影响。结果表明:盲孔法和开口圆环法测量结果近似相等;与传统的黏弹性模型相比,建立的弹塑性热熔焊接有限元模型计算结果更接近实验测量值;熔融层厚度随焊接温度和加热时间的增加而增大,延长加热时间可导致热熔接头长度增加;焊缝和熔合区的残余应力为拉应力,且内壁的拉应力大于外壁的拉应力,距离焊缝5 mm处残余应力由拉应力转变为压应力,焊接温度升高和加热时间延长会使残余应力数值增大。

聚乙烯管焊缝超声检测工艺探讨

通过对聚乙烯管不同焊接工艺所形成的焊缝结构分析,了解相应的焊接缺陷产生的机理,针对各自形成的焊缝形状,选择不同的超声检测工艺。对电熔焊接接头检测,采用相控阵超声检测工艺,优化其灵敏度、扫查孔径和聚焦深度的工艺参数来提高检测效率;对热熔焊接接头采用TOFD检测方法,选择合适TOFD楔块材质和规格来提高检测分辨力。

城市集中供热水处理专家帮助系统的开发

随着智能城市的不断发展,专家帮助系统在人们的生活中发挥着至关重要的作用。针对热电联产机组和热水管网水处理经常出现的一些故障进行分析,将热源厂水处理中常出现的设备故障问题及其解决方案制作成数据库和专家知识库,在windows环境下,将数据库与Visual Basic6.0软件对接,开发出供水管网故障诊断专家帮助系统软件。主要功能有查询数据库中的供热管网故障类型、解决方案、即时更新数据库内容。

热丝TIG在接管Ni基合金内壁堆焊工艺要点

针对公司正在生产的蒲城德士古式气化炉,因其堆焊要求特殊,上下筒体全部堆焊Ni基材料,难度大并且质量不易保证,尤其在筒体大直径接管内壁堆焊过程中,如何获得高质量的接管内壁堆焊,对整体堆焊质量和生产效率有着非常大的影响。文中针对上述气化炉堆焊技术要求,以公司采用热丝TIG设备堆焊蒲城大直径接管内壁为实例,综述了热丝TIG在接管内壁堆焊Ni基合金的应用情况。结果表明,焊缝裂纹率减少了16%,焊后无损检测一次性合格率提升了40%,焊接效率提高了近30%。

热水翻转原位固化法在城市排水管道修复中的应用

近年来,南京市大量污水整治项目采用热水翻转原位固化法进行修复。热水翻转原位固化法具有材料强度高、铺设方便、施工周期短、交通影响小、造价经济等优点。文章结合实际工程案例,详细介绍热水翻转原位固化法的基本原理、特点、适用范围,叙述了该方法设计要点和施工及验收工艺流程,并对其具体应用中的注意事项和要点进行了总结和归纳,希望能给类似工程提供参考与借鉴。

镀锌钢管环氧粉末涂层附着力的研究

简述了钢管热浸镀锌-环氧粉末复合防护涂层体系的特点,详细分析了钢管热镀锌后水冷及钝化、镀锌层表面处理对粉末涂层附着力的影响情况。分析认为,应根据镀锌层风化状态制定热镀锌水冷、钝化及表面处理流程及操作规程,建议采取清扫级喷砂清理清洁锌层表面,以获取合适的表面粗糙轮廓,改善粉末涂层附着力。

马氏体不锈钢油井管短流程生产关键技术创新和应用

马氏体不锈钢管的传统生产工艺是铸锭经过锻造,然后通过穿孔热轧工艺成型,容易产生折叠缺陷,并且合格率低、流程长、成本高。介绍了一种通过连铸坯+热挤压生产马氏体不锈钢油井管的短流程新工艺,并进行了系列马氏体不锈钢管的试制和检测。实践证明:采用连铸坯+热挤压工艺生产的马氏体不锈钢管表面质量好,铸态组织充分破碎;调质处理后,显微组织均匀致密,晶粒细小,强度、伸长率、硬度和冲击性能均满足API Spec 5CT-2018和ISO 13680:2020标准要求,说明新工艺是合理可行的。