What is the difference between Q345R (R-HIC) and Q345R (HIC)?

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Q345R (R-HIC) is the steel grade Q345R; the corrosion tests include hydrogen-induced cracking (HIC) testing and sulfide stress corrosion cracking (SSCC) testing. The compositional requirements are P≤0.015 and S≤0.003 as determined by melting analysis； For the finished product analysis, P≤0.015 and S≤0.004. For Q345R (HIC), only corrosion testing is performed, along with hydrogen-induced cracking testing (HIC). Q345R (R-HIC) dual-resistant steel is available in stock; the dimensions are 152*0375*0895. I. Chemical composition of Q345R (R-HIC): The chemical composition of the steel must comply with the specifications given in Tables 1 and 2. Steel grade: CSiMnALCa*O*CE** Q345R (R-HIC). Melting analysis values: ≤0.20, 0.20–0.55, 1.20–1.36; ≥0.020, 0.0015–0.0030, ≤0.004, ≤0.45. Finished product analysis values: 0.20–0.60. Table 1: Resistance to hydrogen and sulfide-induced stress corrosion – Q345R (R-HIC) in stock. Note: (1) The Ca value is for reference only and is not used as a acceptance criterion; the Ca and O contents can be replaced by the values obtained from finished product analysis instead of those from melting analysis ； (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 improve the properties of steel plates, certain microalloying elements can be added. II. The manufacturing method for Q345R (R-HIC) involves electric arc furnacing combined with secondary refining; calcium treatment is applied during the manufacturing process, and it should be an inherently fine-grained steel, with an actual grain size of grade 5 or higher. III. Scope of Application: Q345RHIC | Q245R(HIC) steel plates for normalizing to resist hydrogen sulfide corrosion. These technical specifications apply to Q245R(HIC) steel plates with a thickness of 8 mm–150 mm, which are used in acidic environments; the requirements regarding sulfur and phosphorus content in these steel grades are divided into three categories: I, II, and III. 3.1 Chemical composition: Steel grade CSiMnALCa*O*CE** Q245R(HIC). Melting analysis values: ≤ 0.20, ≤ 0.35, 0.50–1.00; ≥0.020, 0.0015–0.0030, ≤0.004, ≤0.36. Finished product analysis values: ≤0.40, 0.45–1.05. Table 1. Note: (1) The Ca value is for reference only and is not used as a acceptance criterion; the values for Ca and O can be replaced by those from the finished product analysis instead of those from the melting analysis ； (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 improve the properties of steel plates, certain micro-alloying elements can be added. Table 2 Grade Components PS I: Melting value ≤0.015 ≤0.003; Finished product value ≤0.015 ≤0.004. II: Melting value ≤0.010 ≤0.002; Finished product value ≤0.010 ≤0.003. III: Melting value ≤0.008 ≤0.002; Finished product value ≤0.008 ≤0.002