What are the differences in chemical composition and tissue morphology between 16MnR and 16MnⅡ?
Thread Content
As title: What are the differences in chemical composition and tissue morphology between 16MnR and 16MnⅡ?
The main components are the same, namely C and Mn. Other elements are slightly different.
Does the second Ⅱ just refer to forging? Is there any more detailed information?
May I ask what is the difference between Q345B and Q345R?
16MnR is now changed to Q345R. 16MII is a forged piece with the same main composition as Q345R and a finer structure. Q345R is mainly used for cylinders and large pipes, etc., and 16MII is mainly used for flanges and tube sheets.
The big difference is that the former is a low-alloy structural steel that undergoes normal temperature impact testing and the latter is a pressure vessel steel that undergoes a 0-degree impact test and requires at least level 3 flaw detection when the finished product is delivered. The chemical composition of C and Mn is basically the same, but the P and S content may be lower in the latter. During smelting, the purity and gas content of the molten steel are more stringent. Wugang Hengsheng Company Panglong QQ57244114
The comprehensive mechanical properties of forgings are better than those of carbon steel. Its structure is dense and uniform, and its ductility and plasticity are better than steel plates. The comprehensive mechanical properties of forgings are better than those of plates. Forgings can replace plates (economically uneconomical, forgings are expensive), but plates cannot replace forgings casually. For example, when manufacturing flanges, flanges that require forgings should not be replaced with plates. The allowable stress specified in GB150 is related to the thickness. At 20°, it is 150MPa when it is greater than 100~120mm, and it can reach 170MPa when it is the thinnest. The main consideration for forgings is that their working conditions do not change with thickness. At 20°, it is uniformly stipulated as 150MPa when it is less than 300mm. The two are basically the same. The allowable stress is just a reference value, which is obtained by dividing various stress limits by a safety factor. Different safety factors are selected according to different working conditions. Due to manufacturing technology reasons, the internal quality of thick plates has different cooling rates and is prone to delamination. Although forgings are slightly lower in tensile strength and yield strength, they are more uniform in structure.