Microstructure engineering for high productivity welding of pipeline steels

目前有许多关于扩建北美石油和天然气管道系统的重要提案，包括麦肯齐山谷、阿拉斯加北坡和Keystone XL管道。这些项目将涉及使用新的高强度钢（X80和X100）和新的焊接技术（串联和双焊炬气体金属电弧或激光混合），以降低施工成本。对于这些管道系统的完整性来说，焊缝具有良好的机械性能至关重要。北方管道由于低温和可能融化的大量永久冻土区而面临进一步的挑战。这些考虑导致了新的基于应变的设计性能标准。 该项目的目标是模拟邻近熔合区的关键区域，即热影响区（HAZ）的显微组织和力学性能。该区域的材料经历了复杂的热历史，通常被发现是系统中最薄弱的环节。该项目的目标是：i）测量一些焊接工艺（气体保护金属极电弧焊，激光混合焊和埋弧焊）的温度-时间历史，ii）开发热影响区的微观结构演变模型，解释其空间变化，iii）检查焊缝的机械性能，将热影响区视为梯度结构。这将通过实验和建模活动相结合来实现， 与我们的合作伙伴Evraz NA Inc. TransCanada PipeLines Ltd. 该项目的结果将是：i）增加先进钢材和高生产率焊接工艺热影响区微观结构/机械性能的知识基础，ii）将这些知识转移给我们的行业合作伙伴，iii）培养6名高素质人员（2名博士，2 M.A.Sc和2 PDF）。

There are currently a number of significant proposals for expansion of the North American oil and natural gas pipeline system including the Mackenzie Valley, the Alaska North Slope and Keystone XL pipelines. These projects will involve the use of new higher strength steels (X80 and X100) and new welding techniques (tandem and dual torch gas metal arc or laser hybrid) to lower construction costs. It is critical for the integrity of these pipeline systems that the welds have well understood mechanical behaviour. There are further challenges for northern pipelines due to the low temperatures and the probable melting of significant regions of permafrost. These considerations have led to new strain based design performance criteria. This project has the objective to model the microstructure and mechanical properties of the critical region adjacent to the fusion zone, the heat affected zone (HAZ). The material in this region undergoes a complex thermal history and is usually found to be the weakest link in the system. The objectives of this project are i) to measure the temperature-time history for a number of welding procedures (gas metal arc, laser hybrid and submerged arc welding), ii) to develop microstructure evolution models for the HAZ which account for its spatial variation and iii) to examine the mechanical properties of the weld considered the HAZ as a graded structure. This will be done through a combination of experimental and modelling activities with a strong collaboration with our partners, Evraz NA Inc. and TransCanada PipeLines Ltd. The results from this project will be i) an increased knowledge base for the microstructure/mechanical properties in the heat affected zone for advanced steels and high productivity welding procedures, ii) transfer of this knowledge to our industry partners and iii) the education of 6 high qualified personal (2 Ph.D., 2 M.A.Sc and 2 PDFs).