Regarding the issue of forging grades

I think it still depends on the standards you use when designing. But the medium you mentioned is three. Grade 4 forgings should be reasonable.

Reply 1# The final Fantasy Pig HG20581-1998 is the industry standard. If the container being designed is for use in the chemical industry, HG20581-1998 should be followed. If there are no design standards for pressure vessels in other industries, GB150-1998 can be followed.

There is nothing wrong with what he said in principle, but I think grade III or grade IV forgings should be used. Because: 1. HG20580~585, as detailed rules and supplements to GB150 (an objective fact), need to be implemented, especially under harsh operating conditions. 2. The main difference between grade III and grade II forgings is whether ultrasonic testing is performed ； In situations involving highly hazardous or highly toxic substances, higher requirements should be placed on the materials. 3. For small forgings, the cost difference between grade III and grade II forgings is minimal; considering safety aspects (with only a slight increase in cost but improved safety), grade III can be used ； Large and medium-sized forgings have a lower forging ratio, and there is a higher likelihood of internal defects; therefore, ultrasonic testing is required, using grade III.

It is not a mandatory standard; it is not necessary to comply with it； But when something goes wrong, it’s hard to say

I think grade III or IV forgings should be used; isn’t it better to be more stringent from a safety perspective?

I think the situation described by the original poster is valid; HG20581-1998 actually sets higher requirements, as GB150-1998 does not include such a requirement. However, when I encounter such situations, I usually choose grade III or grade IV forgings

Grade III or Grade IV forgings should be used. Because standards such as GB150 represent relatively low control requirements – they are merely the minimum standards. In situations where the level of hazard is high, it is appropriate to use forgings of a higher grade; otherwise, forgings of grade III or IV would be useless. 1. HG20580~585 can be referred to as detailed rules and supplements to GB150 (an objective fact), and should be applied especially under harsh operating conditions. 2. The main difference between grade III and grade II forgings is whether ultrasonic testing is performed ； In situations involving highly hazardous or highly toxic substances, higher requirements should be placed on the materials. 3. For small forgings, the cost difference between grade III and grade II forgings is minimal; considering safety aspects (with only a slight increase in cost but improved safety), grade III can be used ； Large and medium-sized forgings have a lower forging ratio, and there is a higher likelihood of internal defects; therefore, ultrasonic testing should be performed. 4. Compared to the safety of the equipment, improving it to the level of forgings is reasonable and not a waste.

Safety comes first; the higher the standards for components, the better. Don’t focus only on short-term gains, as it will lead to losses that outweigh any benefits!

The inspection requirements for Grade III/IV forgings are more stringent. For harsh medium conditions, grade III/IV forgings are the best choice. Just as the friend upstairs said, it’s hard to say what will happen if something goes wrong~~~

For such media, high-grade forgings should be chosen; otherwise, regret will be of no use if something goes wrong