NXF UNS A36 S235JR/St37-2/SS400/SM400A/A283C Class 450-800HV Length 16-152mm Black Phosphated Bugle Head Drywall Screw

The complete manufacturing procedure for black‑phosphated bugle‑head drywall screws follows strict standardized working steps, with A36 carbon‑steel selected as the raw‑material base.

1.Raw Wire Rod PreparationHigh‑quality A36 carbon‑steel wire rod is chosen. Raw steel wires are drawn to the required wire diameter through cold‑drawing treatment, which improves steel density, tensile strength and dimensional stability for subsequent stamping.

2.Cold Heading for Bugle Head FormingThe processed steel wire is cut into fixed‑length blanks. Cold‑heading machines stamp the bugle‑shaped countersunk head and form cross recesses. The special horn‑shaped head is designed to sink smoothly into gypsum board and prevent wall‑board cracking.

3.Thread RollingBlank screws go through thread‑rolling equipment. Extruded sharp self‑tapping threads are formed, ensuring sharp thread edges and smooth penetration speed when screwing into wood keels and plaster‑boards.

4.Deburring and CleaningFinished semi‑finished screws remove surface burrs, metal debris and oil stains via chemical cleaning and tumbler polishing. Clean surfaces are essential for firm phosphate adhesion.

5.Black Phosphating Surface TreatmentWorkpieces are soaked inside black‑phosphate solution. A dense black conversion coating covers the screw surface. This treatment boosts lubrication during installation, offers basic rust‑resistance and avoids shiny exposed fastener heads.

6.Heat‑Treatment HardeningQuenching‑and‑tempering heat‑treatment raises screw hardness. It effectively stops thread slipping, head breakage and tip bending under high‑speed installation.

7.Final Inspection and PackingEach batch undergoes checks on dimension, hardness, recess quality and phosphating appearance. Qualified drywall screws are sorted and packed for overseas‑trade shipment.