Cold Heading Forming Process For Steel Structure Bolts

Steel structure bolts are metal plastic-forming fasteners. Their manufacturing process consists of multiple precise and interrelated procedures, each of which directly determines the dimensional accuracy, mechanical properties and finished quality of the bolts. Cold heading forming serves as the core procedure of bolt manufacturing and plays a decisive role in the overall strength and structural stability of steel structure bolts.

The complete manufacturing process of steel structure bolts is as follows: cold drawing → spheroidizing annealing → mechanical dephosphorization → pickling and fine cleaning → secondary precision drawing → cold heading forming → thread processing → heat treatment → finished product inspection. The entire process is indispensable and must be implemented in strict accordance with standard specifications to guarantee the quality of high-strength steel structure bolts.

In the bolt forming procedure, bolt heads are mainly manufactured by cold heading plastic forming, while only a small number of special bolts adopt cutting processing. Compared with traditional cutting methods, cold heading does not sever the metal fiber structure. It enables continuous and complete metal streamlines distributed along the bolt profile without fracture or truncation defects. This forming process greatly improves the overall strength, toughness and fatigue resistance of bolts, making the comprehensive mechanical properties of cold-headed steel structure bolts far superior to those of cut bolts.

The cold heading forming process mainly includes material cutting, pre-forming and final forming. It can be categorized into three equipment modes: single-stroke single-station cold heading, double-stroke single-station cold heading, and multi-station automatic cold heading. Multi-station automatic cold heading machines can continuously complete stamping, upsetting, extrusion, diameter reduction and other forming procedures in multiple molds. Featuring high processing accuracy and excellent product consistency, they are the mainstream production equipment for high-strength steel structure bolts.

Single-station or multi-station cold heading equipment can be selected according to product specifications. The processing mode and blank forming method depend on the raw material form, including straight bar materials with a length of 5 to 6 meters and large coil wire rods with a weight of 1900 to 2000 kilograms.

The core feature of the cold heading process for steel structure bolts is that prefabricated single-piece blanks are not required. The equipment can directly perform fixed-length cutting, automatic upsetting and step-by-step forming on bar materials and wire rods to complete bolt blank processing in one cycle, delivering high production efficiency and stable blank accuracy.

As an indispensable core procedure in bolt production, cold heading determines the mechanical performance, structural accuracy and service life of steel structure bolts. Therefore, strict control shall be implemented over cold heading process parameters, equipment status and forming quality during production. Every processing detail must be precisely controlled to ensure that finished bolts meet the high-strength and high-stability requirements of steel structure engineering applications.