# Principles and Characteristics of Different EDM Processes in Machining Tool and Die Steels
## 3 Various Grades of Tool Steels  
Steels can be categorized into four groups, namely, stainless steel, tool steel, carbon steel, and alloy steel. Each of these groups has its own characteristics which make it suitable for specific applications. This paper focuses on tool steels. As the name implies, tool steels are mainly employed for making cutting and metal-working tools [12]. In order to meet the required conditions these tools encounter under service conditions, tool steels must have many properties such as the ability to withstand high load, the ability to operate in rapidly changing temperatures, high abrasive resistance, etc. Normally, the tool steels are used in hardened conditions by heat treatment, and they are subsequently tempered to meet the required properties for specific application [12]. Tool steels are high-hardness and abrasion-resistant alloy steels. In addition to iron and carbon, tool steels include many other elements to increase hardness and wear resistance and hot strength and hot hardness. Furthermore, they also possess adequate toughness which can be achieved by tempering, which is performed subsequent to hardening. Applications of tool steels include stamping and extrusion dies, cutting tools, hammers, and machine parts [10]. Properties of widely and recently used different grades of tool steels, as well as the EDM processes considered for each grade, are summarized in Table 1.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Different Grades and** & **Composition (Weight \%)** & **Properties** \\ \hline
**AISI D2** & & High-carbon and high-chromium tool steel. It has high resistance to wear and abrasion. D2 grade is heat-treatable steel with hardness in the range 55–62 HRC. Its corrosion resistance depends on the percentage of chromium [117]. High-carbon, high-chromium tool steel. It has excellent resistance to wear and abrasion and has good dimensional stability and high compressive strength. Its hardness is in the range of 58–64 HRC [120]. \\
**AISI D5** & & High-carbon, high-chromium tool steel. It has excellent resistance to wear and abrasion and has good dimensional stability and high compressive strength. Its hardness is in the range of 58–64 HRC [120]. \\
**Wire EDM [121; 122].** & & Similar to other grades in group D, D5 has high carbon and high chromium content; it is the most commonly used steel among the group D steels [123]. \\
**AISI D6** & & Cr 12.5, C 2.05, W 1.3, Mn & D6 steel has high compressive strength, high wear resistance, high surface hardness, and good hardening stability [125]. \\ Die sinking EDM [124]. & & & \\ \hline \hline \end{tabular}
\end{table}
Table 1: Details of various EDM processes used by researchers for different grades of tool steels.  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Different Grades and** & **Composition (Weight** & **Properties** \\
**Operations** & **\%)** & **H11 grade is one of the most commonly used chromium hot-work steels. It has low carbon content and has good toughness and deep hardness due to air quenching from heat treatment [133]. \\
**AISI O1** & C 0.85-1.00, Mn 1.00-1.40, Die sinking EDM [76]. & Si 0.50, Cr 0.40-0.60, Ni \\
**Wire EDM [134]. & 0.30, W 0.40-0.60, V 0.30, Powder-mixed EDM [135,136]. & Cu 0.25, P 0.0, S 0.03 \\
**AISI O2** & OHNS: C 0.82, Si 0.18, & On 0.52, Cr 0.49, V 0.19, \\ Powder-mixed EDM [116]. & Mo 0.13, Ni 0.05; & Mo 0.13, Ni 0.05; \\
**AISI M2** & C 0.78-1.05, Cr 3.75-4.50, Die sinking EDM [139,141,130]. & W 5.50-6.75, Mo \\
**Wire EDM [142]. & 4.50-5.50, V 1.75-2.20. & \\
**SKD11** & C 1.40-1.60, Si Max 0.40, & Mn Max 0.60, P Max \\
**Wire EDM [148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,