Steel Q345 and Q345R difference

1. Different content of trace elements. The phosphorus and sulfur content of Q345R is slightly lower than that of low-alloy high-strength steel Q345. P≤0.025, S≤0.015 of Q345R; For Q345, P≤0.045, S≤0.045.

2. the application range is different. Q345 has good comprehensive mechanical properties, good low temperature performance, good plasticity and weldability, and can be used as medium and low pressure vessels, oil tanks, vehicles, cranes, mining machinery, power stations, Bridges and other structures, mechanical parts, building structures, general metal structural parts, etc.; The Q345R is the most widely used and the largest pressure vessel special steel plate.

Q345R Note the problem

First, it is necessary to consider the operating conditions of the equipment (such as design pressure, design temperature, characteristics of the medium), the welding performance of the material, cold and hot processing performance, heat treatment and the structure of the container.

consider economic rationality:

1. when the required steel plate thickness is less than 8mm, between carbon steel and low-alloy high-strength steel, carbon steel plate should be used as far as possible (except multi-layer containers).

2. in the case of stiffness or structural design, ordinary carbon steel should be used as far as possible. In the case of strength design, Q235B, 20R(20g), Q345R(16MnR) and other steel plates should be selected according to the use of pressure, temperature, media and other restrictions.

3. the required stainless steel thickness is greater than 12mm, should be used in lining, composite, surfacing and other structural forms.

4. stainless steel should be as far as possible not used as a design temperature of less than or equal to 500 degrees Celsius heat resistant steel.

5. pearlitic heat-resistant steel should be as far as possible not used as a heat-resistant steel with a design temperature less than or equal to 350 degrees Celsius. When pearlitic heat-resistant steel must be used for heat-resistant steel or hydrogen resistant purposes, the variety and specifications of steel should be reduced and combined as far as possible.

Third, the thickness of Q345R steel plate greater than 60mm, the upper limit of carbon content can be increased to 0.22%.

Q345R steel plate can be added niobium, vanadium, titanium elements, its content should be filled in the quality certificate, the sum of the above three elements should be no more than 0.050%, 0.10%, 0.12%.