A36 carbon steel round bar is selected as the base raw material. Incoming inspection covers spectrometer chemical composition detection, tensile strength and yield strength mechanical testing to confirm conformity to A36 carbon steel specifications. Inspect the steel bar surface for rust, cracks, folding, scratches and inclusion defects. According to the 2D engineering drawing of T-type nut, perform precision band saw cutting to separate fixed-length blanks. Remove sharp cutting burrs and metal chips by tumbling preliminary deburring, ensuring blank size tolerance and clean surface for subsequent hot forging operation.
2.Hot Forging & Stress Relief:
Transfer qualified steel blanks to the heating furnace and heat up to the controlled forging temperature range. Use custom closed forging die for hot forging to form the integral T-shaped contour of the nut. Precisely regulate forging temperature, impact force and forging cycle to avoid incomplete filling, shrinkage cavities and surface cracking. After hot forging, the forged parts are placed in a slow cooling zone for natural cooling to release internal forging stress, preventing workpiece deformation in later machining.
3.Finish Machining & Thread Tapping:
Remove black oxide scale generated in hot forging via shot blasting. Carry out CNC finish machining on the outer T profile, trimming edges and controlling all dimensional tolerances of the T-shape to match drawing requirements. Perform internal tapping to create standard threads. Strictly monitor thread pitch, tooth profile, thread concentricity and minor diameter. After tapping, use compressed air to blow away thread chips, and conduct manual deburring to eliminate sharp burrs inside the thread hole without damaging thread profile.
4.Multi-stage Surface Pre-treatment for Galvanizing:
Implement sequential pre-treatment procedures: alkaline degreasing to strip surface grease and lubricants; water rinsing to wash residual degreasing liquid; acid pickling to remove rust and heavy oxide scale; secondary rinsing to wash pickling residue; surface activation to activate steel substrate. Special attention is paid to thoroughly cleaning the inner thread cavity to avoid trapped chemical residues, which guarantees stable bonding between A36 steel substrate and zinc coating.
5.Galvanizing Treatment & Corrosion Performance Testing:
Carry out galvanizing process to form uniform zinc protective coating on the workpiece surface, monitor coating thickness to meet specified requirement. After galvanizing, post-treatment including passivation and sealing is performed to enhance anti-corrosion capacity. Conduct multiple tests: thread mating test with matched screws; zinc coating adhesion test; salt spray test for corrosion resistance. Workpieces with coating peeling, uneven zinc thickness, thread galling or surface defects are picked out and rejected.
6.Final Full Inspection & Moisture-proof Packaging:
Carry out 100% visual and dimensional inspection referencing engineering drawings. Check T-slot contour dimension, thread integrity, zinc coating surface quality and coating uniformity. All non-conforming items are sorted out for rework or scrap. Qualified nuts go through ultrasonic cleaning and hot air drying to remove moisture. Pack finished T-type nuts into anti-rust moisture-proof bags, affix labels marked with product name, material grade, thread specification, batch number and production date, to prevent rusting and mechanical damage during warehouse storage and ocean transportation.