Q345B seamless steel pipe is the old national standard GB / T6479-1988 high-strength low-alloy structural steel grades, the new national standard GB / T6479-2000 seamless steel grades for the Q345 (Q345 have five quality grades, Q345A ~ Q345E) , Q345A seamless corresponding U.S. ASTM seamless steel grades are Gr.50

Several other level with the American standard ASTM grades controls as follows:

ANSI American National Standards

AISI American Iron and Steel Institute Standard

ASTM American Society for Testing and Materials Standards

ASME American Society of Mechanical Engineers standards

Aerospace Material Specification AMS(US aviation industry the most commonly used material specification, developed by the SAE)

API American Petroleum Institute standards

AWS American Welding Society Standards

SAE American Association of Motor Vehicle Engineers Standards

MIL US military standard

QQ US Federal Standard

API American Petroleum Institute standards

ANSI American National Standards

ASME American Society of Mechanical Engineers standards

ASTM American Society for Testing and Materials Standards

Are American standards, these standards complement each other, learn from each other in terms of standards such as ASME materials used are from ASTM, standard in terms of multi-valve reference API, and aspects of the standard pipe fittings from ANSI. The difference is that the industry in which the focus is different, so different from the standard adopted. API, ASTM, ASME are constituent members of ANSI. American National Standards Institute, the vast majority from various professional standards. On the other hand, professional societies, associations may also develop certain product standards based on existing national standards. Of course, it may not be in accordance with national standards to develop their own Association standards. ANSI standards are voluntary adopted.