Q235B is ordinary carbon steel with a yield strength of 235MPa. It has good toughness, is easy to weld, and is easy to process. It is inexpensive and readily available.
Q355B is low-alloy high-strength steel with a yield strength of 355MPa. Its load-bearing and deformation resistance are increased by nearly 50%. It has excellent low-temperature impact toughness and stable weldability, making it suitable for heavy-duty applications.

Some vendors are selling Q235B as Q355B. They appear identical, and only the material certificate and spectral testing can distinguish them. While mixing Q235B with Q355B has a relatively small impact on small-span lightweight supports, it is problematic for large-span main load-bearing structures. Insufficient steel strength can lead to continuous bending and deformation under long-term stress, posing a collapse safety hazard. If the material fails to meet the standards, the supervisor will demand complete removal and Replacement.
To differentiate between the two specifications of steel, a material certificate from the steel mill should be required to be provided with the shipment to verify the material grade; large-scale on-site spectral testing should be conducted to confirm that the manganese and alloy element content meets the standards; the material grade should be specified in the contract; stipulating unconditional returns and exchanges for non-compliant materials; and compensation for lost work time.

Time：08/07/2026 15:29:05

It involves using low-strength Q235 steel to impersonate high-strength, high-value Q355 steel.

The core properties differ: Q235 is carbon structural steel with a yield strength of approximately 235 MPa; while Q355 is low-alloy high-strength steel with a yield strength of at least 355 MPa and significantly higher tensile strength. Q355 has superior overall performance due to the addition of more alloying elements (such as manganese).

Because of its superior performance, Q355 is more expensive. Unscrupulous merchants use Q235 to impersonate Q355 for illegal profit.

Using Q235 instead of Q355 would significantly reduce the load-bearing capacity of the building's main structure, seriously jeopardizing the inherent safety of the project.

Because they look almost identical, and are even more difficult to distinguish after painting, professional methods are needed to prevent counterfeiting.
First, check the material certificate, verifying each item's grade, performance indicators, official seal, and batch number, and checking for any alterations.
Seek third-party testing. Testing personnel will use a handheld spectrometer to test the content of key elements such as carbon and manganese on-site to ensure they meet standards.
Entrust a qualified institution to conduct comprehensive testing on the steel's chemical composition and mechanical properties (yield strength, tensile strength), etc.

Time：06/07/2026 17:29:48

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