A Microstructural and Damage Investigation into the Low Temperature Drop Weight Tear Test (DWTT) Behavior of an HSLA Steel

加拿大Stelco公司是北美最大的钢铁生产商之一，拥有北美大陆最现代化的绿地综合炼钢设施。最近作为一家独立的加拿大公司重新成立，Stelco拥有2200多名员工，为汽车，能源和建筑行业生产各种钢材。最近，Stelco为客户生产了一种高强度低合金（HSLA）钢的热轧卷，该客户打算使用该材料建造车辆防撞护栏（护栏）。该材料需要在低温下满足苛刻的落锤撕裂试验（DWTT）规范。该线圈是在550摄氏度的缠绕温度下生产的，但不符合DWTT规格，导致Stelco损失。第二个线圈在500℃的卷绕温度下生产，符合DWTT规格，但结果好坏参半。卷取温度对(i)微观结构（ii）低温DWTT性能和（iii）零星DWTT结果的影响尚不清楚，这是拟议研究的基础。高分辨率光学和场发射扫描电子显微镜将用于量化卷曲温度对dwtt测试的HSLA材料的微观结构和损伤演变的影响。研究结果将使Stelco深入了解卷取温度对HSLA（及类似）钢种低温DWTT性能的影响，并通过减少客户的卷取废品率使公司受益。Stelco面临的另一个问题与DWTT测试本身有关，以及测试参数（couponthickness，缺口类型，测试能量和剪切测量）如何影响结果。参数DWTT研究将在Stelco的研发设施进行，以更好地了解测试并标准化他们的测试程序。

Stelco Canada is one of the top steel producers in North America, which operates the most modern greenfieldintegrated steel making facility on the continent. Recently re-established as an independent Canadiancompany, Stelco employs more than 2,200 personnel and produces a variety of steels for the automotive,energy and construction sectors.Recently, Stelco produced a hot rolled coil of a High Strength Low Alloy (HSLA) steel for a customer thatintended to use the material to construct vehicle impact barriers (guard rails). The material needed to meet ademanding Drop Weight Tear Test (DWTT) specification at low temperatures. The coil was produced using acoiling temperature of 550 degC, but did not meet the DWTT specification and resulted in a loss for Stelco. Asecond coil was produced using a coiling temperature to 500 degC, which met the DWTT specification, butwith mixed results. The effect of the coiling temperature on the (i) microstructure (ii) low temperature DWTTperformance and (iii) sporadic DWTT results for this grade of HSLA steel is not well understood, and formsthe basis of the proposed research. High resolution optical and field emission scanning electron microscopywill be used to quantify the effect of coiling temperature on the microstructure and damage evolution for theDWTT tested HSLA materials. The results will provide Stelco insight into the effect of coiling temperature onlow temperature DWTT performance of HSLA (and similar) steel grades and benefit the company by reducingcustomer coil rejections.Another problem faced by Stelco is associated with the DWTT test itself and how testing parameters (couponthickness, notch type, test energy and shear measurement) affect the results. A parametric DWTT study will beconducted at Stelco's R&D facility to better understand the test and standardize their testing procedure.