GB/T 1591 -2018 Q355B steel is a new Chinese steel grade of Q345B Low Alloy High Strength Structural Steel. The material density is 7.85 g/cm3.  Q355B plates can be delivered in as rolled, normalized or normalizing rolling, thermomechanical processed condition.  According to GB/T 1591 -2018, Q355 steel has 3 quality levels: Q355B, Q355C and Q355D. “Q” is the first letter of Chinese Pinyin: “qu fu dian”, which means Yield Strength, “355” is the minimum value of yield strength 355 MPa for steel thickness ≤16mm, and tensile strength is 470-630 Mpa. Email: bebon.steel@outlook.com Q355 Steel Chemical Composition (Hot rolled) Steel Grade Quality Grade C % (≤) Si % (≤) Mn (≤) P (≤) S (≤) Cr (≤) Ni (≤) Cu (≤) N (≤) Mo (≤) B (≤) Nb (≤) V (≤) Ti (≤) Q355 Q355B 0.24 0.55 1.6 0.035 0.035 0.30 0.30 0.40 0.012 – – – – – Q355C 0.20 0.030 0.030 0.012 Q355D 0.20 0.025 0.025 – Q355 Steel Mechanical Properti

ASTM A36 steel is similar to Q235B steel, but the differences between A36 and Q235B are as follows: 1. The yield point is different (A36=250MPa, Q235B=235MPa) 2. Different tensile strength (A36=400-550MPa, Q235B=375-500MPa); 3. Different requirements for the content of elements: (A36: C≤0.25%, Si≤0.4%, P≤0.04%, S≤0.05%; Q235B: C=0.12- 0.2%, Si≤0.3, P≤0.045%, S≤0.045%). Q235 has requirements for manganese content Mn=0.30-0.70% A36 has no requirements for manganese content. Q235B and ASTM A36 Standard A36 is the material of American standard ASME standard (equivalent to ASTM specification), SS400 is the material of Japanese standard JIS G3101 (rolled steel for general structure), and Q235 is the material of national standard GB700 standard. Although the mechanical properties of Q235 material are worse than that of A36 material, in the actual operation process, as long as the owner does not clearly request, often the three materials can be substituted for each other.

Both 42CrMo4 steel and 42CrMoS4 steel are alloy steel hardened and tempered plates under EN 10083-3 standard. There are little differences between 42CrMo4 steel and 42CrMoS4 steel plate. Below are the technical requirements comparison for your reference. 42CrMo4 steel and 42CrMoS4 steel chemical composition(%) Grades Material no. C Si max. Mn P  max. S Cr Mo 42CrMo4 1.7225 0.38 - 0.45 0.40 0.60 - 0.90 0.025 max. 0.035 0.90 - 1.20 0.15 - 0.30 42CrMoS4 1.7227 0.38 - 0.45 0.40 0.60 - 0.90 0.025 0.020 - 0.040 0.90 - 1.20 0.15 - 0.30 42CrMo4 steel vs 42CrMoS4 steel hardness in quenched condition Steel Grade Range limits HRC Hardness Measured From The Quenched End Of The Test Tube (MM) symbolic 1,5 3 5 7 9 11 13 15 20 25 30 35 40 45 50 42CrMo4 max 61 61 61 60 60 59 59 58 56 53 51 48 47 46 45 42CrMoS4 min 53 53 52 51 49 43 40