Advances in Materials 2015; 4(2-1): 1-8 Published online January 16, 2015 (http://www.sciencepublishinggroup.com/j/am) doi: 10.11648/j.am.s.2015040201.11 ISSN: 2327-2503 (Print); ISSN: 2327-252X (Online) AISI S1 tool steel after deep cryogenic treatment: Tensile properties and microstructure Keyvan Seyedi Niaki 1 , Seyed Ebrahim Vahdat 2, * 1 Department of Mechanical Engineering, Iranian Research Organization for Science and Technology (IROST), Tehran, Iran 2 Department of Engineering, Ayatollah Amoli Branch, Islamic Azad University, Amol, Iran Email address: ksniaki@yahoo.com (K. S. Niaki), e.vahdat@iauamol.ac.ir (S. E. Vahdat) To cite this article: Keyvan Seyedi Niaki, Seyed Ebrahim Vahdat. AISI S1 Tool Steel after Deep Cryogenic Treatment: Tensile Properties and Microstructure. Advances in Materials. Special Issue: Advanced Tool Steels. Vol. 4, No. 2-1, 2015, pp. 1-8. doi: 10.11648/j.am.s.2015040201.11 Abstract: Successful employment of advanced tool steel in engineering applications is related to its ability in terms of meeting service life requirements and fabrication with proper dimensions. Deep cryogenic treatment may be used to produce advanced tool steel by simultaneously increasing toughness, strength, and hardness. Twelve sets of specimens were tested, 9 of which were deep cryogenic treated and then tempered. Tensile properties, hardness, X-ray diffraction, and scanning transmission electron microscopy were applied for macroscopic and microscopic investigations. The best results of simultaneous improvement in tensile toughness, hardness, and strength were obtained for 36 h soaking and 1 h tempering times. Keywords: Hardness, STEM, Strength, Tensile Toughness, XRD 1. Introduction Sustainable development is an important challenge in human life. It refers to changing the process of proper application of resources, conducting investments, and orienting technology development in a way that could be consistent with present and future needs. Proper use of raw materials facilitates sustainable development [1-3]. Advanced tool steel properties include high strength, wear resistance and hardness in addition to suitable toughness for enduring mechanical impact loadings. Researchers [4-9] demonstrated that sub zero treatments improved mechanical properties of several steels. For example, for AISI M2 high speed tool steel hardness and wear resistance improved by using DCT compared with the conventional treatment [6]. Therefore, DCT used in this study for producing advanced AISI S1 tool steel. 2. Experimental methods Table 1 demonstrates the chemical analysis of AISI S1 used in this study. The AISI S1 is mostly used for manufacturing cutting blades for thick sheets and also for punching tools. Table 1. Chemical analysis of the AISI S1 tool steel (W%) Element (W%) Element (W%) Element (W%) Element (W%) Element (W%) Element Rest Fe 0.0281 Mo 1.5700 W 0.0250 S 0.1280 Ni 0.4800 C 0.0567 P 0.3360 Mn 1.1200 Cr 0.0148 V 0.9950 Si Many studies have been published on advanced tool steels; however, each one has focused on one or few sets of specimens rather than collecting data from many specimens. Consequently, it is helpful to collect the published results in order to have thorough representations of the measured effects. Thus, 12 sets of AISI S1 specimens were tested. One set consisted of the specimens which underwent the conventional hardening procedure [10]. The remaining sets of specimens underwent full treatment cycles. The temperature-time history for the specimens is given in Fig. 1(a) and flowchart of the experimental procedure is depicted in Fig. 1(b). The DCT work followed a procedure shown in Fig. 1(b) and used a programmable cryogenic processor which was designed and developed [11]. Considering the