Normalizing parameters
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Dear teachers, may I ask how fast the heating rate of normalizing should be controlled? Is there any calculation formula related to the thickness of the workpiece? I checked the warranty on the cover and found that the normalizing heating speeds were written in terms of rapid heating, power, etc. For Q345R, the normalizing and insulation temperature range is 880-940℃, and the lower limit is also specified to be ≥900℃. Can the actual heat treatment temperature of Q345R be lower than 900℃? For example, at 890℃.
Check the iron-carbon alloy status diagram； Understand the purpose of normalizing fire again ； Normalizing is opposite to annealing and requires a more detailed structure than annealing. To make the grain structure more detailed, it needs to be above the phase transformation line. According to the carbon content, check the temperature corresponding to the phase change line, which is close to 910 degrees.
This post was last edited by wanlirn on 2023-2-16 10:05 The normalizing temperature refers to a temperature greater than the upper transition temperature and rapid cooling. The upper transition temperature of steel is around 900, which may vary depending on the amount of alloying elements. Therefore, the normalizing temperature of Q345R, chromium-molybdenum steel, and manganese-niobium steel in our container industry is about 920, leaving a little margin. That is, it is best to write actual values in the heating rate in the report. The heating rate is only based on the shape of the product. The heating rate of a thin-walled part with a uniform wall thickness does not need to be considered.
If it cools quickly, it will not be normalized and the material will be wasted.
This post was last edited by wanlirn on 2023-2-17 10:26 Normalizing means that all low carbon steel or low alloy steel used in the rapid cooling container is no problem, and air cooling and water cooling are both acceptable. Cooling with the furnace or cooling outside the holding furnace are both annealing processes. Please understand them first before drawing any conclusions.
Rapid cooling does not mean rapid cooling. In order to obtain better grain size, normalizing requires rapid cooling, not extreme cooling.