1. In the grade designations of Japanese steel (JIS series), ordinary structural steel is primarily composed of three parts:  - The first part indicates the material, such as S (Steel) for steel and F (Ferrum) for iron.  - The second part denotes different shapes, types, and applications, such as P (Plate) for plates, T (Tube) for tubes, and K (Kogu) for tools.  - The third part represents characteristic numbers, typically the minimum tensile strength. For example, SS400—where the first S stands for steel (Steel), the second S signifies "structure" (Structure), and 400 indicates a minimum tensile strength of 400 MPa, collectively representing ordinary structural steel with a tensile strength of 400 MPa.

2. SPHC: The first letter "S" stands for Steel, "P" for Plate, "H" for Heat, and "C" for Commercial. The acronym represents general-purpose hot-rolled steel plates and strips.

3. SPHD — Indicates hot-rolled steel plates and steel strips for stamping.

4. SPHE—Indicates hot-rolled steel plates and strips for deep drawing.

5. SPCC—Indicates general-purpose cold-rolled carbon steel sheets and strips, equivalent to the Chinese Q195-215A grade. The third letter "C" is the abbreviation for "Cold." To ensure tensile testing compliance, add "T" at the end of the grade, resulting in SPCCT.

6. SPCD—Represents cold-rolled carbon steel sheets and strips for stamping, equivalent to China's 08Al (13237) high-quality carbon structural steel.

7. SPCE—denotes cold-rolled carbon steel thin plates and steel strips for deep drawing, equivalent to China's 08Al (5213) deep-drawing steel. To ensure non-ageing properties, an "N" is added to the grade, resulting in SPCEN.

Cold-rolled carbon steel sheets and strips tempering codes: Annealed state as A, standard tempering as S, 1/8 hard as 8, 1/4 hard as 4, 1/2 hard as 2, hard as 1.

Surface finishing codes: D for dull finish (finishing rolling), B for bright finish (bright rolling). For example, SPCC-SD indicates standard tempering, dull finish, general-purpose cold-rolled carbon steel sheet. Another example, SPCCT-SB denotes standard tempering, bright finish, and cold-rolled carbon steel sheet with guaranteed mechanical properties.

8. The designation method for JIS mechanical structural steels is as follows:

S+carbon content+letter code (C, CK), where the carbon content is expressed as the midpoint ×100. The letter C denotes carbon, and K denotes carburizing steel. For example, the carbon structural steel plate S20C has a carbon content of 0.18-0.23%.