Thermo-mechanical Treatment of 0.4C-0.6Mn-2Si Steel with Various Soaking and Annealing Hold Temperatures

This paper deals with the comparison of two tool steels M390 and M398 produced by powder metallurgy of the MICROCLEAN type. The primary use of steel is in the plastics industry to produce screws for injection molding machines. The main purpose of the paper is to analyze the hardness after different stages of heat treatment. The first part of the article evaluates the hardness of steels after hardening, which was performed using a hardening dilatometer DIL805A. A total of 8 different controlled cooling measurements were performed, for both types of powdered tool steels, from a maximum rate of 100 °C/s to a minimum of 0.01 ° C/s. Based on the results of the first set of samples from the hardening dilatometer, the optimal cooling time is evaluated to achieve the highest hardness of both materials. This rate was used to heat treat a second set of samples that had undergone a quenching process from which a selected group was quenched to -78 °C. Freezing was performed to reduce the amount of residual austenite. Before measuring the hardness, the samples were tempered at temperatures of 200, 400, 600 °C for 2x2h. The measured hardness values were then compared with data from the manufacturer BÖHLER.

“…Another possibility to reduce the amount of residual austenite is by tempering. [14] The theoretical decrease in the amount of residual austenite after tempering can be seen in Fig. 8.…”

Section: Fig 6 Graphical Representation Of the Cooling Process Of Steel M390 And M398mentioning

confidence: 93%

Analysis of heat treatment parameters on the properties of selected tool steels M390 and M398 produced with powder metallurgy

Cíger¹,

Barényi²,

Krbaťa³

2022

Influence of Heating Rate on the Transformation Temperature Change in Selected Steel Types

Moravec¹,

Nováková²,

Vondráček³

2020

The paper is focused on the polymorphic transformations of selected steel types. Generally, when creating CCT diagrams, the transformation temperature values Ac1 and Ac3 are determined under at very low heating rates (max. 0.1 °C•s -1 ). The only exceptions are so-called in-situ CCT diagrams, which are determined based upon the real temperature cycles. However, in the case of dynamic processes such as welding technology or heat treatment with magnetic induction heating, cannot be used information from conventional CCT diagrams. Incorrectly selected temperatures lead either to incomplete austenitizing during heat treatment or to a different development of phase transformations in HAZ of welds. Especially, when these processes are carried out without soaking temperature. That is why as the main aim of this paper was to determine the heating rate influence for steels S460MC, S690QL and X23CrMoV12-1 on the shift of their transformation temperatures Ac1 and Ac3. The intensity of the heating rate effect on the transformation temperature depends on the steel structure and amount of alloying elements. Consequently, steels with different structures, different type of processing and mechanical properties were deliberately selected to make the assessment as complex as possible.

Evolution of Mechanical Properties and Microstructure in Q&P Processed Unconventional Medium-Carbon Silicon Steel and Comparison between Q&P Processing, Quenching and Tempering, and Austemperingfor

Jeníček¹,

Opatová²,

Vorel³

2022

This paper investigates the evolution of microstructure and its related mechanical properties of Q-P processed medium-carbon AHSS steel. The investigated informations were compared to the structures and mechanical properties of quenched and tempered, austempered specimens made of the same steel grade. According to the correlations between observed microstructures after Q-P, quenching and tempering, austempering the presence of bainite in Q-P processed specimens was found. The hypothesis of bainite growth durinq Q-P processing was devoleped. The experimental results show that during Q-P heat treatment the bainite transformation can occur even when the partitioning temperatures are below the temperature Ms of experimental steel.