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Q345R (R-HIC) hydrogen-resistant steel. I. Application range of Q345R (HIC): These technical specifications apply to Q345R(HIC) steel plates with a thickness of 8 mm to 150 mm, which are used in acidic environments. To meet the various requirements of users and to facilitate production management, the P requirement is divided into three levels: I, II, and III. This steel grade is a specialty of Wugang, with mature production technology. II. Description of the Q345R (HIC) grade: 1. Q345R (HIC)-I refers to the steel grade Q345R; the corrosion testing involves only the assessment for hydrogen-induced cracking (HIC). The compositional requirements are P≤0.015 and S≤0.003 as determined by melting analysis ； P≤0.015, S≤0.004. 2 Dimensions, shape, weight and allowable tolerances: 2.1 The dimensions, shape, weight and allowable tolerances of Q345R (HIC) steel plates shall comply with the provisions of GB/T709. 2.2 The thickness deviation shall comply with Class B or Class C of GB/T709, as specified in the contract. 2.3 The steel plates are delivered based on their theoretical weight, with the thickness used for this theoretical calculation being the arithmetic average of the maximum and minimum allowable thicknesses of the steel plates. The density of steel is 7.85 g/cm3. III. Technical requirements for Q345R (HIC): 3.1 Chemical composition of Q345R (HIC): The chemical composition of the steel shall comply with the specifications in Tables 1 and 2. Steel grade Designation C Si Mn Al Ca O CE Q345R(HIC) Melting analysis ≤0.20 0.20–0.55 1.20–1.36 ≥0.020 0.0015–0.0030 ≤0.004 ≤0.45 Finished product analysis 0.20–0.60 Note: (1) The Ca value is for reference only and is not considered a acceptance criterion; the values for Ca and O can be based on the finished product analysis rather than the melting analysis results ； (2) The formula for calculating the carbon equivalent (CE) is as follows: CE = C + Mn/6 + (Cu + Ni)/15 + (Cr + Mo + V)/5. (3) To further enhance the properties of the steel plate, certain micro-alloying elements can be added. Grade Composition P S I Melted product ≤0.015 ≤0.003 Finished product ≤0.015 ≤0.004 II Melted product ≤0.010 ≤0.002 Finished product ≤0.010 ≤0.003 III Melted product ≤0.008 ≤0.002 Finished product ≤0.008 ≤0.002 3.2 Q345R (HIC) Smelting method: Smelting is carried out using an electric furnace combined with secondary refining; Ca treatment is applied during the smelting process. It should be a steel with essentially fine grain structure, with an actual grain size of grade 5 or higher. 3.3 Q345R (HIC) delivery condition: normalized. 3.4 Condition of Q345R (HIC) test specimens: All steel plates shall undergo simulated post-weld heat treatment on their test specimens. The recommended temperature for this simulated post-weld heat treatment is 620±10°C; the holding time is 8 hours. The rate of temperature change, whether rising or falling, should be ≤150°C/h. If the conditions differ from those recommended, the specific parameters for the simulated post-weld heat treatment shall be specified in the contract. 3.5 Mechanical properties of Q345R (HIC): 3.5.1 The mechanical properties of the steel plate specimens in a state simulating post-weld heat treatment shall meet the requirements specified in the table below. Steel grade Thickness (mm) ReL MPa Rm MPa A % Impact Temperature °C Impact value J 180° bending test b=2a Properties in the thickness direction ψZ (%) Average Single value Q345R(HIC) 8–16 ≥345 510–640 ≥21 –30 Average ≥34 Single value ≥24 d=2a ≥35 ≥25 >16–36 ≥325 500–630 d=3a >36–60 ≥315 490–620 >60–100 ≥305 490–620 >100– ≥20 150 ≥285 480–610 Note: (1) For steel plates with a thickness of ≥15 mm, properties in the thickness direction are evaluated ； 3.5.2 Brinell hardness: The steel plates shall be tested for Brinell hardness at each rolling pass, with the Brinell hardness value being ≤ 200 HB. 3.6 Ultrasonic testing: Steel plates shall be subjected to ultrasonic flaw detection one by one, and the standard level for such detection shall be specified in the contract. IV. Inspection rules for Q345R (HIC): 4.1 The surface quality of the steel plates shall comply with the provisions of GB713-2008. 4.2 The packaging, marking, and quality certificates of the 4.2 steel plates shall be as follows: V. Other HIC steels: Q245R (R-HIC), Q345R (R-HIC), 15CrMoR (HIC), 16MnDR (HIC), SA516Gr70 (HIC), 12Cr2Mo1R (H), 14Cr1MoR (H), 12Cr1MoR (H), SA387Gr11 (H). This steel grade is a special steel plate from Wuhan Iron and Steel, with mature technical specifications. The steel plate has excellent quality and strong flaw detection capabilities