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

Stelco Canada是北美最大的钢铁生产商之一，经营着北美大陆最现代化的绿地综合钢铁制造设施。Stelco最近重新成立为一家独立的德国公司，拥有2,200多名员工，为汽车、能源和建筑行业生产各种钢材。最近，Stelco为一家客户生产了一种高强度低合金（HSLA）钢热轧卷，该客户打算使用该材料建造车辆防撞栏（护栏）。该材料需要满足低温下的落锤撕裂试验（DWTT）规范。使用550 ℃的冷却温度生产线圈，但不符合DWTT规范，导致Stelco损失。第二个线圈是使用卷取温度为500摄氏度，这符合DWTT规格，但与混合的结果。卷取温度对该等级HSLA钢的（i）显微组织（ii）低温DWTT性能和（iii）零星DWTT结果的影响尚未得到很好的理解，并形成了拟议研究的基础。高分辨率光学和场发射扫描电子显微镜将被用来量化的影响，卷绕温度对微观结构和损伤演变的DWTT测试的HSLA材料。这些结果将使Stelco深入了解卷取温度对HSLA（和类似）钢种低温DWTT性能的影响，并通过减少客户线圈拒收而使公司受益。Stelco面临的另一个问题与DWTT测试本身以及测试参数（试样厚度、缺口类型、测试能量和剪切测量）如何影响结果有关。将在Stelco的研发机构进行参数DWTT研究，以更好地了解测试并使其测试程序标准化。

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.