Use of Q235A

This post was last edited by kk52i on 2020-8-28 at 11:43. GB150－1998 specifies that carbon structural steel of grade Q235A.R should be used for such containers. The applicable conditions are as follows: the design pressure of the container shall be ≤1.0 MPa; the operating temperature of the steel plates shall be between 0 and 350°C; the thickness of the plates when used to form the container shell shall be ≤16 mm. The medium used in such containers must not be liquefied petroleum gas, nor must they be used for pressure vessels handling media with a high or extremely high degree of toxicity.

The last edit to this post was made by kk52i on 2020-8-28 at 10:09; Appendix D of GB150-2001.2 specifies the requirements for the Q235 series

These two steel grade designations, Q235AF and Q235A, were already removed as early as in Amendment No. 1 of 2002 to the original GB150-1998 \"Steel Pressure Vessels\". With the recent updates to the standards, this grade is no longer mentioned in GB/T150-2011 \"Pressure Vessels\"; as a result, no one has used Q235A for components that are subject to pressure in vessels. The current standards stipulate that the steel used for pressure-bearing components in pressure vessels should be killed steel produced through oxygen converters or electric furnaces. ”(Part of Clause 2.2.1.1 of TSG 21-2016) Q235AF does not meet this requirement. “For carbon steel and low-alloy steel, the contents of carbon (C), phosphorus (P), and sulfur (S) must be such that C ≤ 0.25%, P ≤ 0.035%, and S ≤ 0.035% (TSG 21-2016, Article 2.2.1.2.1). The sulfur and phosphorus levels in Q235A do not meet these requirements, so it cannot be used. Therefore, the new version of GB/T150.2-2011 specifies in Appendix D that, under certain restricted conditions, the use of Q235-B and Q235-C steel plates is permitted.

It’s been 9 years already – why do some people still ask such questions? Some people even make jokes about standards from over 20 years ago, claiming that Q235A should not be used in the manufacture of components that are subject to significant compressive forces, and that those manufactured using this material should be phased out. Why isn’t it allowed to be used? The minimum standard for steel materials in GB150-2011 is Q235B, and usage requirements are specified. GB150 is also a referenced standard in TSG 21-2016, and GB150-2011 is the currently valid version. Can the owner understand this way? If not, they can continue to ask questions or check out the explanatory posts at the legal level. Of course, Q235A steel plates are also not available on the market at present; any that exist are remnants from the past. Therefore, those in charge should stop worrying about such issues that will never arise.

This was just found – it is Amendment No. 1 of 2002 to GB150-1998 \"Steel Pressure Vessels\". Starting in 2002, the use of Q235A steel plates in pressure-bearing components was prohibited; therefore, the effective version from 2011 specifies requirements only for Q235B and C.

Dude, Q235A is still available on the market. ★In GB150, the Q235 series has been moved to the appendix, indicating that it is no longer a steel plate designated for use in pressure vessels. Secondly, for B and C in the Q235 series, which are temporarily retained, restrictions on temperature, thickness, etc., have also been added [see Standard Clarifications p101]. ★★The most bizarre thing is the horizontal container: JBT 4731-2005 for steel horizontal containers, with the saddle material being Q235B [but in examples 1, 2, and 3, the saddle material is Q235A] ； JB/T 4712.1~4712.4-2007 Container supports: Q235A with low saddle stress and at temperatures ≥ -20°C ； NBT 47042-2014: Horizontal containers – Saddle material Q235B; Q235A added ； NBT 47065.1-5-2018 Container Supports – Saddle Material Q235B ； ★★★The Steel Structure Standards 2018 no longer include Q235A either. The source of the controversy is that for Category A materials, the contents of C, Mn, and Si need not be specified as delivery conditions; Q235A cannot be used in cold regions with temperatures of ≤-20 degrees 【For oil tanks, Q235B with a thickness of ≯12 mm】 ； For any material with a thickness of ≯6 mm, it can be used at a minimum temperature of -20 degrees without undergoing impact testing, and this is related to its good toughness and the fact that three-axis tensile stress is less likely to occur in the presence of defects. Based on various sources, it is estimated that the thickness is no more than 6–12 mm; it cannot be used in primary load-bearing structures due to issues related to fatigue and cracking, and can only be applied in secondary structures. Various standards are established by large companies and design institutes; in order to reduce disputes related to material procurement and engineering accidents, Q235A is no longer found in these different standards.

Components that are not used as the main load-bearing elements do exist, but only in very small numbers.

After reviewing TSG 21-2016 clauses 1.9 and 2.1.3.1, there should be no further doubts.