1. Marking Methods for Steel Pipe Fittings: Steel pipe fittings should be permanently marked. If stamping is used, care should be taken to ensure the stamp is not too deep or too sharp, which could cause cracks or reduce the pipe wall thickness to below the minimum allowable thickness.

2. Marking Locations for Steel Pipe Fittings: Marking should be done directly on the steel pipe fitting whenever the dimensions permit. Regardless of the marking method, the marking should be placed in a suitable and easily observable location on the pipe fitting. When using stamped markings, avoid high-stress areas.

3. The markings on steel pipe fittings shall include the following:
a) The manufacturer's name or trademark;
b) The material grade of the steel pipe fitting;
c) The nominal size of the steel pipe fitting (marking may be omitted for Series I outer diameters; marking shall be made for Series II outer diameters) or the specified outer diameter;
d) The nominal wall thickness of the steel pipe fitting or the specified wall thickness value;
e) The serial number of the steel pipe fitting or the raw material smelting furnace number;
f) The code of the steel pipe fitting;
g) The standard number of the steel pipe fitting (excluding the year);
h) Other markings required by the contract.

4. Exceptions to Steel Pipe Fittings
When the dimensions of the steel pipe fitting cannot be fully marked, the markings may be omitted in reverse order as described in section 3, or a label may be used.

5. Examples of Marking Steel Pipe Fittings
Example 1: The marking for a 90° short-radius seamless elbow with material grade AF12, nominal size DN100, outer diameter of series I, and wall thickness grade Sch40 is: Manufacturer's name or trademark AF12-DN100-Sch40 Product number or raw material smelting furnace number 90ESGB/T12459
Example 2: The marking for a welded tee with material grade CF415K, main pipe outer diameter ϕ820, thickness 14mm; branch pipe outer diameter ϕ630, thickness 12mm, and design calculations conforming to the minimum wall thickness requirements of Appendix B is: Manufacturer's name or trademark CF415K-ϕ820×14-ϕ630×12 Product number or raw material smelting furnace number WTRGB/T12459-B
Example 3: The marking for a CF485K material grade, nominal size DN150×100, outer diameter of series II, and wall thickness grade... The markings for seamless concentric reducers of Sch80 are: Manufacturer's name or trademark CF485K-DN150×100-Ⅱ-Sch80 Product number or raw material melting furnace number REGB/T12459. Example 4: A 90° long radius seamless elbow made of SF304/SF304L material grade, nominal size DN300, outer diameter of series I, wall thickness grade Sch120, and subjected to GB/T13401 A.1.2 (stabilization treatment) and A.6.1 (intergranular corrosion test) tests is marked as follows: Manufacturer's name or trademark SF304/SF304L-DN300-Sch120 Product number or raw material melting furnace number 90ELGB/T12459GB/T13401 A.1.2-A.6.1.