Base material selection determines the safety margin, low‑temperature toughness and service life of air receivers. Q235B, Q355B and Q345R are three widely‑used carbon‑alloy steel grades in the industry. Many purchasers confuse general structural steel with dedicated pressure‑vessel steel. Different steel grades carry distinct limits in allowable pressure, operating temperature, impact resistance and inspection requirements. YCZX strictly differentiates material characteristics and selects suitable plate according to actual site working‑conditions to guarantee compliance with GB150 and global export pressure‑vessel standards.
Q235B (General carbon structural steel)
Q235B is common construction‑grade carbon steel, permitted for pressure‑vessel use with strict constraints. Its yield strength reaches 235 MPa. It is limited to design pressure below 1.6 MPa, shell thickness ≤16 mm and operating temperature from 20 ℃ to 300 ℃. Only 20 ℃ room‑temperature impact test is required. Cost‑effective for simple indoor low‑pressure compressed‑air systems. Not allowed for low‑temperature outdoor, cyclic pressure‑fluctuation or high‑risk working‑conditions, due to limited toughness reserve.
Q355B (General low‑alloy high‑strength structural steel)
Q355B delivers higher yield strength of 355 MPa. As structural steel (GB/T 1591), it is not special‑purpose pressure‑vessel plate. It only requires impact testing at 20 ℃ without mandatory zero‑degree low‑temperature verification, nor compulsory ultrasonic inspection for every steel sheet. Though mechanical strength data looks attractive, its internal purity, impurity control and toughness reserve cannot match pressure‑vessel‑specific steel. It is mainly for building structures and mechanical frames, not recommended as primary shell material for pressure‑bearing air receivers under GB150 specification.
Q345R (Pressure‑vessel‑special low‑alloy steel, GB/T 713)
Q345R (“R” stands for pressure vessel) is the dedicated steel plate for Chinese pressure‑vessel manufacturing. It implements stricter control over sulfur and phosphorus impurities for higher material purity. Mandatory 0 ℃ low‑temperature impact test and sheet‑by‑sheet ultrasonic inspection eliminate internal material defects. It features balanced strength, plasticity, weldability and anti‑fatigue performance under cyclic pressure loading. It supports wider temperature and thickness ranges, adapts to indoor‑outdoor, northern cold‑climate and medium‑high‑pressure operating scenarios. For industrial air receivers, Q345R is the preferred compliant material for most heavy‑duty and export‑oriented projects.
| Item | Q235B | Q355B | Q345R |
|---|---|---|---|
| Steel type | General carbon structural steel | General low‑alloy structural steel | Special‑purpose pressure‑vessel steel |
| Yield strength | 235 MPa | 355 MPa | 345 MPa |
| Impact requirement | 20 ℃ | 20 ℃ | Mandatory 0 ℃ impact |
| Ultrasonic test | Not mandatory | Not mandatory | Sheet‑by‑sheet required |
| Application scope | Simple indoor low‑pressure only | Structural frames, not preferred for vessel shells | Standard material for industrial air receivers, wide working‑condition coverage |
Material performance gaps cannot be judged merely by yield‑strength figures. General structural steel Q235B and Q355B have clear regulatory restrictions when applied to pressure vessels. YCZX prioritizes Q345R pressure‑vessel‑grade steel for most of our air‑receiver production. We strictly verify mill test certificates for every incoming steel plate, perform full process inspection covering welding, grinding and air‑pressure tightness testing. According to customer‑site pressure, temperature and environment parameters, we offer rational material‑selection advice, avoiding unsafe material substitution and delivering reliable, code‑compliant pressure vessels for worldwide industrial users.
