Changes in the structure and properties of the steel S700MC by heat treatment

In order to determine the effect on the properties of precipitation processes conducted S700MC steel heat treatment consisting of annealed steel test temperatures: 100, 200, 300, 400, 500, 600, 700, 800, 900, 1000, 1100, 1200 and 1300 °C. Sample obtained after the heat treatment process has been tested by Charpy V toughness, metallographic testing and measurement of Vickers hardness. In order to determine the strength and plastic properties of simulated heat affected zone S700MC steel material tensile test was carried out according to PN- EN 10002-1 for round samples. The study showed that the stability of bainitic structure is maintained to a temperature of 600 °C. In the temperature range 700 to 1000 °C, the test steel with ferritic-pearlitic structure with a small grain growth. The heat treatment above 1000 °C increases the amount of ferrite in the structure, and a strong growth of grain size. Tested steel retains its strength and hardness properties of the heat treatment does not exceed 600 °C. When this temperature is exceeded the tensile strength and hardness are significantly lower in comparison to the base material. Temperatures warm temperatures corresponding to the normalization cause loss of property obtained in the initial thermomechanical rolling process. It is impossible to return to the property upon cooling to ambient temperature, thus constantly this group should not be hot forming.