Abstract:The friction and wear behaviors of a new hot-work die steel, SDCM-SS, were studied at high temperature under dry air conditions. The wear mechanism and microstructural characteristics of the SDCM-SS steel were also investigated. The results showed that the SDCM-SS steel had greater wear resistance compared with H13 steel; this was owed to its high oxidizability and temper stability. These features facilitate the generation, growth, and maintenance of a tribo-oxide layer at high temperature under relatively sta… Show more
“…Additionally, V is not contained in the alloy, but it has a significant effect on the precipitation of carbides' type, size and chemical composition. Although W is less able to form carbides, it will provide a good solid solution strengthening effect [4,16,17]. The calculation results in Figure 1 show that there are mainly three kinds of carbides, namely, MC, M 6 C, and M 23 C 6 carbides in the steel.…”
Section: Introductionmentioning
confidence: 99%
“…Hot working dies have been widely used in the field of machining techniques. With the development of modern industry toward higher efficiency and better precision, the hot work die steel with excellent performance has received extensive attention [1][2][3][4]. In addition to mechanical stress during the die filling process, such as die casting, hot extrusion, hot forging and hot stamping, hot-work die steel also endures rapid heating and cooling impact when interacting with hot metals due to the extremely harsh and complex working environment [5,6].…”
In this paper, a new type of hot-work die steel with excellent high-temperature mechanical properties at 700 °C was designed based on the traditional 25Cr3Mo3NiNb steel with the help of Thermo-calc software. The effects of C, Cr, Mo, W and V on the types and mass fractions of carbides were studied. Phase diagram calculation revealed that with the increase of V and W contents and the decrease of Cr content, the precipitation temperature and the mass fraction of M23C6 carbides decreased. Meanwhile, the mass fraction of MC carbides increased as the Mo content decreased. Based on the thermodynamic calculation, new material 25Cr3Mo2NiWVNb steel was designed. Compared to the 25Cr3Mo3NiNb steel, more finely dispersed MC and M2C carbides with high thermal stability, as well as fewer M23C6 carbides with low thermal stability, were precipitated in the new steel. The high-temperature tensile showed that the new steel showed high thermal stability and strength even at 700 °C. The high-temperature strengthening effect might be ascribed to the fine and stable nano-scale MC and M2C carbides which precipitated during tempering.
“…Additionally, V is not contained in the alloy, but it has a significant effect on the precipitation of carbides' type, size and chemical composition. Although W is less able to form carbides, it will provide a good solid solution strengthening effect [4,16,17]. The calculation results in Figure 1 show that there are mainly three kinds of carbides, namely, MC, M 6 C, and M 23 C 6 carbides in the steel.…”
Section: Introductionmentioning
confidence: 99%
“…Hot working dies have been widely used in the field of machining techniques. With the development of modern industry toward higher efficiency and better precision, the hot work die steel with excellent performance has received extensive attention [1][2][3][4]. In addition to mechanical stress during the die filling process, such as die casting, hot extrusion, hot forging and hot stamping, hot-work die steel also endures rapid heating and cooling impact when interacting with hot metals due to the extremely harsh and complex working environment [5,6].…”
In this paper, a new type of hot-work die steel with excellent high-temperature mechanical properties at 700 °C was designed based on the traditional 25Cr3Mo3NiNb steel with the help of Thermo-calc software. The effects of C, Cr, Mo, W and V on the types and mass fractions of carbides were studied. Phase diagram calculation revealed that with the increase of V and W contents and the decrease of Cr content, the precipitation temperature and the mass fraction of M23C6 carbides decreased. Meanwhile, the mass fraction of MC carbides increased as the Mo content decreased. Based on the thermodynamic calculation, new material 25Cr3Mo2NiWVNb steel was designed. Compared to the 25Cr3Mo3NiNb steel, more finely dispersed MC and M2C carbides with high thermal stability, as well as fewer M23C6 carbides with low thermal stability, were precipitated in the new steel. The high-temperature tensile showed that the new steel showed high thermal stability and strength even at 700 °C. The high-temperature strengthening effect might be ascribed to the fine and stable nano-scale MC and M2C carbides which precipitated during tempering.
“…The contact of these oxides with the hot stamping dies stimulates wear and, consequently, decreases the tools life. Abrasive wear processes including plowing, adhesion wear, erosion, corrosion wear, thermomechanical fatigue and deformation are the main phenomena which lead to the end of tools lives which may be improved by modifying the tools materials, by die coatings, by thermochemical treatments and by designing the dies, aiming a better access and retention of the lubricant during hot stamping [11][12][13][14][15][16][17][18].…”
The surfaces of molds and dies need to present a good quality because their roughness profiles are transferred to either cast or formed products. Dies and molds are frequently made of complex surfaces, and consequently, an adequate milling strategy is important to result in a proper workpiece surface. To evaluate the adequacy of a surface to be used as forming tool involves the use of roughness parameters like S a , S sk , S ku , S p and S v. These parameters influence some surface properties like wear resistance and lubrication capacity. In this work, different tool paths of milling and turning processes were chosen to machine a typical spherical surface used as die (punch) of hot stamping, in order to analyze the surface parameters S a , S sk , S ku , S p and S v of hardened steel samples. The used milling strategies were circular (upward and downward), radial (upward and downward), parallel contours and spiral (upward). Punches machined by all strategies were submitted to thermochemical treatments, plasma nitriding and nitrocarburizing Tenifer ® process. The cited roughness parameters were measured in both moments, before and after the thermochemical treatments. There was similarity between milled and turned results, and thermochemical treatments presented significant influence on measured surface parameters. Machining marks were smoothed by thermochemical treatments which altered surface parameters. Thermochemical treatments effects were affected by the combination of machining marks and micro-burrs from machining processes. All tests resulted in S ku parameter either close or above 3. At 45° position of the workpiece, plasma nitriding tended to decrease roughness S a , S p and S v values and present positive values of parameter S sk. Nitrocarburizing process tended to increase roughness S a , S p and S v values and present negative values of parameter S sk , while not treated samples presented positive and negative S sk values, depending on the machining strategy.
“…Meanwhile, Extensive research have been conducted to explore the optimization of the chemical composition of H13 steel. H13 steel has high thermal strength, hardenability, wear resistance and hardness, and has good toughness and thermal fatigue at moderate temperatures [12][13][14]. Many TBM companies have produced H13 steel as a cutter material.…”
The material of disc cutters is important to full-face tunnel boring machines (TBM). In recent years, disc cutters were optimized and tested by many scholars all around the world. H13(4Cr5MoSiV1) steel is widely used due to its excellent properties, especially in TBM disc cutters. In this paper, H13 steel with optimized composition was prepared and heat treatment. The high temperature compression of H13 steel was conducted at the temperatures ranging from 100 °C to 700 °C, with strain rate at 0.01 s−1. The stress-strain curves, Rockwell hardness and microstructure of H13 steel after compression were obtained and analyzed. The results showed that the compression strength and hardness decreased as the temperature increased; and the compression strength, hardness and ductility decreased rapidly between 600 °C and 700 °C, HR700 (the hardness of H13 steel at 700 °C) only reached 33.23 HRC. It is not recommended for TBM disc cutters to work in an environment over 600 °C.
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