Varestraint testing is commonly used to evaluate hot cracking susceptibility of materials. In this paper, the dependence of operators and evaluation technique on test results is studied for a high-temperature austenitic stainless steel (UNS S31035). Samples were tested at six different strain levels ranging from 0.7 to 3.8%. Four different operators evaluated the same samples following the same instructions on how to measure the cracks manually in an optical microscope at × 25 magnification. The largest variation among operators evaluation was found for low strain levels where small and few cracks were found. In addition, one of the four operators used image analysis to evaluate the samples at × 50 magnification. The average total crack length and total number of cracks in fusion zone and heat-affected zone were approximately 1.5 times higher when using image analysis compared with manual evaluation. Image analysis at × 50 made it possible to detect smaller cracks compared with manual evaluation at × 25 magnification, contributing to an increased number of cracks detected.The maximum crack length using image analysis at × 50 was similar to manual evaluation made at × 25 magnification and was the criterion that showed the least variation in this study. However, further comparisons using other magnifications are needed to verify the agreement between manual evaluation and image analysis found in this study. An advantage with evaluation using image analysis is that it provides traceable results. A harmonized standard for Varestraint testing, and especially for evaluation, would decrease the variation among operators and laboratories.

中文翻译：

---

奥氏体高温合金Varestraint测试的测试结果和排名标准的评估

Varestraint测试通常用于评估材料的热裂敏感性。本文研究了高温奥氏体不锈钢（UNS S31035）的操作人员和评估技术对测试结果的依赖性。在六种不同的应变水平（0.7至3.8％）下测试了样品。四个不同的操作人员按照相同的说明对相同的样品进行了评估，有关如何在光学显微镜下以×25的放大率手动测量裂纹。在低应变水平下，发现裂纹很少且很少的情况下，在操作人员评估中发现的变化最大。此外，四名操作员之一使用图像分析来评估×50放大倍率下的样品。熔合区和热影响区的平均总裂纹长度和裂纹总数约为1。与手动评估相比，使用图像分析时高5倍。×50的图像分析与放大25倍的手动评估相比，可以检测到较小的裂纹，从而增加了检测到的裂纹的数量。×50的图像分析的最大裂缝长度类似于×25的放大倍数下的手动评估。这是在这项研究中显示出最小差异的标准。但是，需要使用其他放大倍数进行进一步比较，以验证本研究中发现的手动评估和图像分析之间的一致性。使用图像分析进行评估的一个优势在于，它可以提供可追溯的结果。对Varestraint测试（尤其是评估）的统一标准将减少操作人员和实验室之间的差异。