Engineering Guide · 3 min read
Chinese GB/T 700 Carbon Steel Grades: What Are Q195, Q235 and Q275?
Learn what Q195, Q235 and Q275 mean under GB/T 700, how their chemistry and strength compare, and how Q235A, Q235B, Q235C and Q235D differ.
The short answer: Q195, Q235 and Q275 are GB/T 700 carbon structural steel grades with different strength levels; Q235A–D identify quality categories within Q235. [1]
A Q235B callout identifies both a strength family and a quality category. Product thickness or diameter then determines the applicable yield-strength requirement in GB/T 700-2006. [1]
This article is part of the Chinese GB/T steel grades series.
The Q195, Q215, Q235 and Q275 family
The letter Q comes from the Chinese term for yield strength. The complete designation may add a quality letter and a deoxidation symbol. The grade is usually supplied as structural steel used in its delivery condition, rather than as a steel defined primarily for subsequent quenching and tempering.
GB/T 700 covers hot-rolled plate, strip, sections and bars. Its chemistry provisions also apply to the relevant ingots, continuous-cast stock, billets and products. Common applications include frames, brackets and general steel structures.
Q195 and Q235B chemical composition
The representative grades below show how the composition limits change across the series. Each row uses a complete grade where a quality suffix is needed.
| Grade | C max. (%) | Si max. (%) | Mn max. (%) | P max. (%) | S max. (%) |
|---|---|---|---|---|---|
| Q195 | 0.12 | 0.30 | 0.50 | 0.035 | 0.040 |
| Q215A | 0.15 | 0.35 | 1.20 | 0.045 | 0.050 |
| Q235B | 0.20 | 0.35 | 1.40 | 0.045 | 0.045 |
| Q275A | 0.24 | 0.35 | 1.50 | 0.045 | 0.050 |
Composition values are mass percentages. Selected heat-analysis maxima, Table 1. Q235B carbon may reach 0.22% with purchaser agreement. [1]
These rows set carbon maxima. GB/T 699 quality carbon steel instead defines narrower carbon intervals for many grades, giving a manufacturer more control over the chemistry selected for forging or heat treatment.
Material strength: Q195 versus Q235 and Q275
| Grade family | Minimum yield strength (MPa), thickness / diameter ≤16 mm | Tensile strength (MPa) |
|---|---|---|
| Q195 | 195 (reference only) | 315–430 |
| Q215 | 215 | 335–450 |
| Q235 | 235 | 370–500 |
| Q275 | 275 | 410–540 |
Selected material values from Table 2. Q195 yield is reference only. For thickness >100 mm, the tensile lower limit may decrease by 20 MPa; the tensile upper limit is not a delivery condition for wide strip and plate cut from it. These are steel-product values, not finished-bolt classes. [1]
The main gain from Q195 toward Q235 and Q275 is the higher specified structural strength level. This can support a structural design that needs higher stress capacity in the steel section. The published tensile ranges also overlap, so the family name identifies a specification rather than one exact tensile value.
GB/T 700 makes an important distinction for Q195: its tabulated yield value is for reference and is not a delivery condition. For Q215, Q235 and Q275, use the relevant product-size column when applying the yield requirement. The steel's dimensions belong with these numbers.
What Q235A, Q235B, Q235C and Q235D add
Q235A has no specified impact value. Q235B, Q235C and Q235D have impact-test temperatures of +20°C, 0°C and −20°C respectively. The standard’s full-size Charpy V-notch specimen requirement is 27 J; its subsize-specimen rules apply where a full-size specimen cannot be taken. For Q235B steel less than 25 mm thick, the impact test may be omitted by purchaser agreement if the supplier guarantees that the impact absorbed-energy requirement is met. The suffix also affects the composition provisions. [1]
The grade number and quality category therefore serve different purposes: Q235 identifies the structural strength family; B, C or D identifies the accompanying quality provisions. The complete designation is the material being ordered.
What the next material family adds
For a forged or machined part, 35# steel, 45# or 35Mn under GB/T 699 provides a defined carbon range and, in the Mn series, a higher manganese interval. Those choices are useful when heat treatment establishes the final condition.
A welded bracket used in its delivered condition may be adequately described by structural-steel requirements. A separate pin or stud hardened after shaping calls for closer attention to carbon content and the heat-treatment route.
Browse the HexFastener homepage or submit a drawing with the required material callout.
References
- GB/T 700-2006 — Carbon structural steels. Tables 1–2; composition and size-dependent material properties.