Can 35CrMo be used for pipes?

35CrMo is likely to be in the form of bars; this grade is not specified in the standards for pipes, and grades that are not listed cannot be used

This post was last edited by Liu Jiajia on 2017-2-20 at 10:09. Can 35CrMo be used to make pipes and pipe fittings? What are the corresponding standards for American and Chinese standards? I would appreciate some guidance. 1. Chromium-molybdenum steels commonly used in the petrochemical industry serve as materials resistant to hydrogen corrosion, high-temperature sulfur or hydrogen sulfide corrosion, as well as heat resistance (at moderate high temperatures). For example, 12CrMo and 15CrMo are commonly used in high-temperature applications below 550°C, or in hydrogen-containing environments below 320°C ； 12Cr1MoV is commonly used in high-temperature and high-pressure steam conditions below 575°C. 2. Even when made into pipes and pipe fittings, 35CrMo has poor weldability due to its high carbon content and large carbon equivalent. As stated in the first point, when high temperatures or hydrogen exposure are present, there are other chromium-molybdenum steels available for use; so why choose 35CrMo? 3. 35CrMo is a medium-carbon chromium-molybdenum steel with high strength; it is usually used for bolts after being quenched and tempered. 4. Regarding the weldability issue, TSG D0001-2009 \"Regulations on Safety Supervision of Pressure Piping – Industrial Piping\" contains clear provisions on this matter; Article 5 of Section 2 specifies that the carbon content in carbon steel and low-alloy steel used for welding shall be less than or equal to 0.30% ； In GB/T3077-2015, the carbon content of 35CrMo is 0.32–0.40%, which clearly exceeds the allowable value specified in the pipeline standards. It definitely can’t be used anymore.

Thank you for your reply. The pipes we use are intended for high-pressure conditions with sand present, and they are used in natural gas wellhead equipment to prevent pipe wear. I checked today and found a corresponding standard in API 6A. The issue you mentioned does indeed exist – it’s difficult to weld such pipes. Additionally, we use American standards; I’m not sure if there is a similar issue regarding carbon content under those standards

I’m not familiar with mining operations; first, you need to determine what type of pipe you are using, and then look up the relevant regulations and standards. Regardless of the material, a high carbon equivalent (mainly a high carbon content) will result in poorer weldability, and this is a common issue.

Takami really cannot be used as a pipe material.

In oil field extraction, in practice, 35CrMo pipes are used for high-pressure sand-containing pipelines, as they can be welded perfectly. Using other materials doesn’t work. 35Mpa pipelines, 70Mpa pipelines, 105Mpa pipelines, and so on. The standard applied is API 16C «Throttling and Well Control Equipment»

I’m actually using it right now; it’s been many years and there have been no problems.

I’m actually using it right now; it’s been many years and there have been no problems.

This is the upstream side; if the pipeline belongs to GC and TSG pipeline regulations must be followed, then it’s not allowed. Additionally, 35CrMo is indeed difficult to weld. Do you have any welding technical documents for 35CrMo? Could you please share them?