Simulation of the Soaking and Gas Jet Cooling in a Continuous Annealing Line using Dilatometry

Abstract

The present study concerns the simulation of a continuous annealing line (CAL), using dilatometry. Simulations of CAL have been performed on four commercial steel grades with different chemical compositions in order to investigate how the alloying elements C, Mn, Si and B affect the microstructure and hardness of dual phase (DP) and martensitic steels. Three annealing cycles corresponding to those used in a CAL have been applied. When annealing intercritically, as is the case in DP‐steel production, the materials do not reach equilibrium during soaking. Mn and C increase the austenite content and consequently the hardness of the materials. Higher levels of Si (0.4 wt %) are required to retard the formation of new ferrite during cooling in the gas jet section, prior to quenching. B increases hardenability effectively when annealing in the austenite region but is not as efficient during intercritical annealing, which implies that boron restrains ferrite nucleation rather than impeding ferrite growth. Results from DICTRA calculations show that it is possible to simulate the phase transformations during soaking, gasjet cooling and quenching.

Intercritical annealing of cold-rolled ferrite-pearlite steel: Microstructure evolutions and phase transformation kinetics

“…This proportion is deduced from the volume fraction of the pearlite islands (16%), which is lower than a value of 25%, expected from a thermodynamic analysis of pearlite transformation detailed in [49]. It will be seen in the following that these isolated carbides will play a major role during the austenite transformation even if presence of intergranular carbides has rarely been reported [33,40,[69][70][71][72]. According to [69][70][71], these are formed during slow cooling before the pearlite transformation.…”

“…During the proeutectoid ferrite transformation, some carbon-rich regions of austenite would be trapped between growing ferrite grains and would then decompose to one or several cementite carbides and ferrite. Another mechanism assuming the super-saturation in carbon of the ferrite was proposed more recently in [72]. microstructures.…”

“…The role played by these carbides may seem unexpected at first sight, because of their low volume fraction in the initial microstructure (see Figure 1). This is why these carbides are frequently not considered in literature [33,40,[69][70][71][72]. Despite their low volume fraction, the isolated carbides contain (in the studied steel) about one third of the carbon.…”

Numerical Simulation of Single‐Jet Impingement Cooling of a Seamless Steel Tube

“…Jet cooling has a high cooling efficiency, which can achieve rapid cooling of the high-temperature surface by adjusting process parameters, and is widely used in many engineering fields. [1][2][3][4] After extensive research and industrial tests, experts have developed ultrafast cooling technology for steel plate production based on jet cooling. [5][6][7][8] However, this technology has not been popularized in the field of seamless steel tube production.…”

Effect of Prior Microstructure and Heating Rate on the Austenitization Kinetics of 39NiCrMo3 Steel

“…Dilatometry could be used to study austenite formation under continuous heating. Indeed, during the transformation phases of steel, there are some volume variations because of changes in the crystalline structure . To this aim, the present paper is focused on the quantitative assessment of the influence of the prior microstructure and heating rate on the austenite formation kinetics in the case of the 39NiCrMo3 steel, a steel, which is widely used in the industry, especially for induction heating treatments, due to its resistance to thermal cracking.…”