In oil country tubular goods (OCTG), the choice between 30CrMo and 35CrMo hinges primarily on the trade-off between strength and toughness/corrosion resistance. The key distinction is carbon content: 30CrMo contains approximately 0.26–0.34% carbon, while 35CrMo contains 0.32–0.40%. After quenching and tempering, 35CrMo achieves higher tensile and yield strength, making it suitable for high-load components such as drill collars and heavy-duty tool joints where maximum load capacity is essential. However, the lower carbon content of 30CrMo yields superior impact toughness and elongation, which translates into better resistance to brittle fracture under dynamic loads. More importantly, field experience in oilfields has shown that 30CrMoA sucker rods exhibit markedly better resistance to hydrogen embrittlement in H₂S-rich environments, significantly reducing corrosion rates and extending service life compared with 35CrMoA. For OCTG applications in corrosive sour service conditions, this durability advantage often outweighs the strength deficit. Therefore, 30CrMo is generally preferred where toughness and corrosion resistance are prioritized, while 35CrMo remains the choice for high-strength, less corrosive applications.
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