Some people often confused tool steels with mold steels because their definitions seem similar. Generalized tool steels include mold steels, which have some common characteristics, such as the need to bear great local pressure and strong wear, how to achieve the balance of toughness and wear resistance is their biggest contradiction. In a narrow sense, tool steel refers to cutting tool steel, low alloy tool steel and high-speed steel. Generally, according to different working situations, different chemical elements and heat treatment methods are added to achieve the required performance. It can be seen that the content of alloying elements varies greatly even within the scope of tool steels. Therefore, tool steels are more of a definition of use than a strict definition of composition. For example, low alloy tool steels and carbon steels may also be used in mold steels with low requirements. Today we will introduce the difference between these steel in detail.
Tool steels are steels used to make cutting tools, gauges, dies, and wear tools. Tool steels have high hardness and high wear resistance and appropriate toughness, which can maintain high hardness and red hardness at high temperature, According to their use, tool steels can be divided into measuring tool steel, cutting tool steel and die steel. According to alloying element tool steels, they are generally divided into carbon tool steels, alloy tool steels and high-speed tool steels. Plain carbon steel or structural steel is divided into low carbon, medium carbon and high carbon steel. The hardness, wear-resistance and strength of ordinary steel basically increase with the increase of carbon content, but the plasticity and toughness will decrease.
The tool steel can maintain high hardness and good red hardness under high cutting speed and high-temperature heating conditions generated by machining. Carbon tool steels and alloy tool steels generally maintain high hardness at the operating temperature of 180℃~250℃ and high speed tool steels at about 600℃. Red hardness is an important property of steel used in hot deformation dies and high speed cutting tools. Carbon tool steels are basically high quality or advanced high quality carbon steels, which have good cold and hot working properties, the highest quenching hardness can reach HRC66 ~ 67, but usually, the tempering hardness is HRC60 ~ 64, good wear resistance, low price, wide use, accounting for about half of the consumption of the whole tool steel. The main disadvantages are:
① Low hardenability. Water quenching can only for small tools whose section thickness is not greater than 8mm;
② Poor heat resistance. At 250℃, the hardness drops sharply, so it is generally limited to use below 200℃.
Carbon tool steels, with carbon content ranging from 0.65 to 1.35%, belong to hypoeutectoid and eutectoid steels, has been used for making tools with simple shapes and woodworking tools. With the largest amount of supereutectoid steel, it is suitable for the manufacture of tools requiring high wear resistance, cold stamping dies, wire drawing dies, edge cutting dies, taps and low-precision measuring tools with simple shapes. Higher carbon materials although offer high wear resistance, but low toughness, impact resistance, only suitable for the manufacture of file, tap, cutting knife, scissors and other hand tools.
Mold steel is used to make molds such as cold stamping mold, hot forging mold, die casting mold, etc. According to the service conditions and applications of molds, the United States divided it into 12 types of cold work mold steels, 9 kinds of hot work mold steels, 2 kinds of plastic mold steels, 5 kinds of plastic mold steels, etc. Therefore, we conclude that tool steels differ from mold steels but more because of their use than their composition.