About A193|ASTM A193 covers alloy and stainless steel bolting for high-temperature and high-pressure service. The most common grade is B7 (
4140/
4142 chromoly, quenched and tempered). This isn't a material specification. It's a fastener specification that defines required mechanical properties, heat treatment, and testing for bolts, studs, and threaded rod used in pressure vessels, flanged joints, and power generation equipment. If you're machining A193 material, it's usually pre-hardened 4140 that machines like 4140 pre-hard. Compare to 4140 (same base material) and A320 (the low-temperature version of A193).