Q235 Overview

• **Q:** Represents the yield strength of the steel (the initial letter of the Chinese word "Qu" for Yield [屈服, Qu Fu]).

• **235:** Indicates the lower limit of the yield strength is $235\text{ MPa}$.

• Based on chemical composition, it is further divided into four grades: Q235A, Q235B, Q235C, and Q235D.

Q235 possesses good plasticity, toughness, weldability, cold stamping performance, a certain degree of strength, and good cold bending performance. It is widely used for manufacturing thin plates, steel bars, various structural steel shapes for steel structures, building structures, bridges, machine bases, mechanical parts, parts for carburizing or carbonitriding, welded parts, supports, tension rods, connecting rods, pins, shafts, screws, nuts, bushings that are not heavily stressed, and more.

Q235 is widely applied. However, do you know the key differences that exist between its different quality grades? These differences also determine their different "missions" in practical applications.

So, do you know where the differences between these four grades lie?

I. Differences in Chemical Composition

II. Differences in Impact Performance and Test Temperature

III. Production Process and Deoxidation Method

Selection Principles

The quality grades of Q235, from A to D, show a sequential increase in low-temperature toughness, a sequential decrease in impurity content, and a gradual increase in price. Selection should consider three main factors:

• **Operating Temperature:** Select Grade A/B for ambient temperatures, Grade C for temperatures around $0^\circ\text{C}$, and Grade D for temperatures around $-20^\circ\text{C}$.

• **Load Type:** Select Grade A/B for static, low-stress loads, and Grade C/D for dynamic or impact loads.

• **Welding Requirements:** Prioritize Grade C/D for critical welded structures (due to lower impurities, resulting in superior weldability).

Typical Application Scenarios for Each Quality Grade

1. Q235-A

Applicable Scenarios: Non-critical structures that only bear static loads, require no toughness, or are used in ambient temperature, low-stress environments.

Specific Applications:

• Embedded parts in construction engineering, steel plates for concrete reinforcement, and non-critical support angle steel.

• Non-stressed parts in mechanical manufacturing (such as protective covers, equipment bases, handles).

• Simple frames and implement accessories in agricultural machinery.

• Components with low welding requirements (Since no impact test is performed, it is prohibited for critical parts of low-temperature, dynamic load, or welded structures).

2. Q235-B

Applicable Scenarios: Structures that bear moderate loads at ambient temperature (above $0^\circ\text{C}$) and require a certain level of toughness and weldability; can be used for simple welded components.

Specific Applications:

• Secondary beams, purlins, and stair railings in building steel structures.

• Auxiliary structures for bridges (such as railings, pedestrian sidewalk supports).

• Chassis accessories, pipe supports, and ordinary carriages in construction machinery.

• Low-pressure vessels (operating temperature above $0^\circ\text{C}$, without severe impact), water storage tanks.

• Welded components (such as electric distribution box casings, machine tool worktables).

3. Q235-C

Applicable Scenarios: Structures required to operate in environments around $0^\circ\text{C}$, subject to a certain dynamic load or impact, and requiring higher weldability.

Specific Applications:

• Main load-bearing components of buildings in cold regions (where winter temperature is around $0^\circ\text{C}$) (such as steel beams, steel columns).

• Load-bearing structures of small and medium-sized bridges (non-extreme low-temperature areas).

• Auxiliary components of low-pressure boilers, oil pipelines (operating temperature $0^\circ\text{C}$ to $-10^\circ\text{C}$).

• Crane arms, excavator chassis in construction machinery (moderate impact loads).

4. Q235-D

Applicable Scenarios: Low-temperature environments ($-20^\circ\text{C}$ and above), bearing impact loads or important structures, with strict requirements for toughness and weldability.

Specific Applications:

• Outdoor load-bearing steel structures in severe cold regions (such as winter in Northeast and Northwest China) (such as elevated bridges, main beams of large factory buildings).

• Low-temperature vessels (such as refrigeration equipment, chemical storage tanks in $-20^\circ\text{C}$ working conditions).

• Crusher frames in mining machinery, heavy truck chassis (high impact loads).

• Critical components in welded structures (due to low sulfur and phosphorus content, the reduction in toughness after welding is small, and cracks are less likely to occur).

Approximate Comparison Table of Q235 Grades

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