Q420B is a type of high-strength low-alloy structural steel defined in the Chinese national standard GB/T 1591-2018 "High Strength Low Alloy Structural Steels," characterized by high yield strength and good welding and processing properties. The "B" in the grade typically indicates the quality level of the material, which relates to the impact test temperature.

Internationally, there is no direct equivalent material for Q420B, but similar foreign standard materials can be identified based on its chemical composition and mechanical properties. The following are some possible international equivalents:

1. **European Standard (EN)**: The chemical composition and performance of Q420B may be similar to S460M or S460NL in the European standard EN 10025-6. These materials also have a yield strength of approximately 460 MPa, with comparable high strength and good toughness.

2. **ASTM Standard**: Q420B may be similar to A572 Grade 65 or A709 Grade 50W, which are high-strength low-alloy steels defined in American standards.

3. **Japanese Industrial Standard (JIS)**: Q420B may be similar to SM490YB or SM490C in JIS G 3106, which are steels for welded structures defined in Japanese standards.

4. **German Industrial Standard (DIN)**: Q420B may be similar to St 52-3 U in DIN 17100 or W St E 460 in DIN 17102, which are structural steels defined in German standards.

5. **British Standard (BS)**: Q420B may be similar to 55D or 50D in BS 4360, which are steels for welded structures defined in British standards.

In practical applications, specific engineering requirements and usage environments must be considered when selecting alternative materials. Steel standards from different countries may vary in terms of chemical composition, mechanical properties, impact test temperatures, etc. Therefore, engineers and procurement personnel should conduct detailed comparisons of the specific requirements of relevant standards and perform material testing when necessary to ensure that the selected material meets engineering needs and safety standards. Additionally, considering the demands of international trade and project collaboration, using internationally recognized material standards can help reduce obstacles in material substitution and certification processes.