Why such a fondness for 16Mn

It is inevitable that some designers do not give enough consideration to manufacturing costs or are not well aware of the market availability of materials; it is possible to discuss with the design team whether alternative materials can be used

That is, using 20 forgings will suffice. Talk to the designers and make the changes.

It may be that the nominal pressure required for pipe flanges is high; the nominal pressure of pipe flanges is indeed determined by the pipeline system. The loading conditions associated with them are more complex than those in equipment, as there are factors such as pipeline thrust in addition to static loads. Moreover, to ensure sealing, the nominal pressure required for pipe flanges also needs to be slightly higher. Sometimes, 16Mn material needs to be selected. Of course, if the maximum allowable operating pressure at the design temperature as per the table is much higher than the design pressure, it is necessary to consult with the design team to determine whether a design change is required.

Most designs do not take manufacturing costs into account, which is a bit of a waste. However, the price difference between 16Mn forgings and 20 forgings is not significant now.

If the cylinder is made of Q235-B, it’s sufficient to use 20 for the nozzles and flange forgings. If 16Mn is used, one reason might be that the pressure-temperature requirements dictate the use of 16Mn; another reason could be that many designers do not take costs into consideration

I guess what the original poster is trying to say is that since the cylinder body is made of Q235-B, why isn’t the flange also made of Q235-B or some other type of steel? Of course, this reduces costs. I also come from a manufacturing factory, so I understand what costs mean for them. But I think manufacturers should consider various factors; they can’t focus solely on cost. There might be reasons behind the choices made by the design team. If a flange is subject to high stress, then it makes sense for the design team to use 16Mn. Another example: if a flange is designed with specific dimensions, using 16Mn will result in smaller dimensions. Besides, the prices of 20 and 16Mn are pretty much the same these days. I think if the poster has doubts, it would be best to contact the design team promptly to discuss whether using 20-grade forgings or 20R, or materials such as Q235, would be an appropriate option. Last edited by zhjun on 2009-3-6 13:24.]

Taking everything into account, the price difference between 16Mn forgings and 20 forgings is not significant, and it’s also easier to purchase 16Mn! !

The original poster definitely isn’t in the design field – without conducting any research, one doesn’t have the right to comment. There must be a reason why the design firm made such a decision; it’s possible to consult with the design firm. It’s a bit irresponsible to make statements without first understanding the situation, haha

In fact, the prices of 16Mn and 20 forged products are roughly the same

Generally, the impact-free operating pressure of 16Mn flanges at room temperature is equivalent to their nominal pressure, whereas the impact-free operating pressure of 20# steel flanges at room temperature usually does not reach the nominal pressure; therefore, design institutes often use 16Mn as the material for flanges.

I think this issue might sometimes be due to the designers not having a clear concept of the materials, or it might be because they took into account the stresses associated with connections to external pipes.