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Automatic Hot Forging Production Line | Bolt Nut Hot Stamping Press | Besco

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Complete Guide to Automatic Hot Forging Production Line for Nuts and Bolts

Ⅰ、Understanding Hot Forging Technology for Fasteners

Hot forging is a metal forming process where metal is heated above its recrystallization temperature—typically between 900°C and 1250°C for steel—and then shaped using a forging press. This process is essential for manufacturing large-sized nuts and bolts, especially those requiring high strength grades like 8.8, 10.9, or 12.9.

For fastener production, the choice between cold forging and hot forging depends primarily on size:

·Cold forging is suitable for M12 and below, offering high efficiency (300+ pieces/minute) with material utilization up to 85-99%.

·Hot forging is recommended for M12 and above, particularly for M20-M100 nuts and bolts that require high mechanical properties. Heat treatment after hot forging can significantly enhance tensile strength and toughness.

Ⅱ、Key Components of an Automatic Hot Forging Production Line

A complete automatic hot forging line for nuts and bolts consists of eight core equipment components:

Hydraulic Billet Cutting Machine	Cuts steel bars into required billet length
Automatic Bar Feeder	Lifts and feeds billets into the induction furnace
Induction Heating Furnace	Heats billets to 1000-1100°C for forging
Cooling Tower	Circulates cooling water for furnace operation
Automatic Spray Lubrication System	Cools and lubricates the forging die
Hot Forging Press + 3-Station Manipulator	Forms bolt heads / nut blanks in multi-step process
Trimming Press	Removes flash after forging
Shot Blasting Machine	Removes scale and cleans forging surface

Downstream Processing Equipment (Optional/Add-on):

·Automatic Tapping Machine – Cuts internal threads for nuts (M12-M48, 600-700 pcs/hour)

·Thread Rolling Machine – Forms external threads for bolts

·Heat Treatment Line – Quenching (830-860℃) + Tempering (500-650℃) for high-strength fasteners

·Surface Finishing – Blackening, phosphating, or coating for rust prevention

How the Automatic Hot Forging Line Works: Step by Step

	Stage 1: Billet Cutting Steel bars are cut to length by a hydraulic billet cutter (e.g., LYQ-50). For hex bolts, length = head weight + 30% allowance.
Stage 2: Induction Heating Billets are heated to 1000–1100°C in a 400kW induction furnace (>90% efficiency). An automatic sorter rejects out-of-temperature billets.
	Stage 3: Manipulator Transfer A 3‑station hot punch manipulator moves heated billets into the press die. Encoder‑synchronized with the press: left to load, hold during forging, right to unload.
Stage 4: Hot Forging 250T pneumatic press (2500kN, 180mm stroke). Three stations: upsetting → forming → piercing (for nuts).
	Stage 5: Trimming & Descaling Flash is removed by a trimming press. High‑pressure water (1.8–2.0 MPa) removes scale; temperature drop ≤30°C.
Stage 6: Post‑Forging Nuts: automatic tapping. Bolts: thread rolling + chamfering / necking as required.

Stage 7: Heat Treatment (for 8.8 grade & above)

Complete line: pre‑clean → quench (830–860°C, oil bath 60–100°C) → hot clean → temper (500–650°C) → blackening → dry → oil coat.

Stage 8: Inspection & Packaging

Sorted and packed for shipment.

Ⅲ、Technical Specifications of Core Equipment

250T Pneumatic Forging Press (JH21-250)

Parameter	Value
Nominal Pressure	2500 kN
Nominal Pressure Stroke	8 mm
Slide Stroke	180 mm
Strokes per Minute	40
Max. Die Height	400 mm
Motor Power	22 kW
Machine Weight	21,500 kg

Key features: Electric die height adjustment, hydraulic overload protection, pneumatic clutch-brake, PLC control with encoder feedback, C-shaped opening for easy manipulator access.

Three-Station Hot Punch Manipulator

Parameter	Value
Die Spacing	170 mm
Number of Stations	3
Max. Clamping Capacity	50 pieces
Max. Workpiece Weight	2 kg
Applicable Nut/Bolt Size	M14-M27
Power	5 kW

Key features: Front-rear jaw clamping design, servo motor-driven lead screw with dual linear guide rails, PLC control synchronized with press crankshaft position. Fault detection automatically stops the entire line.

400kW Induction Heating Furnace

Parameter	Value
Working Voltage	340-420V
Maximum Input Current	400A
Maximum Input Power	400kW
Resonant Frequency	8-15 kHz
Efficiency	≥90%
Cooling Water Requirement	0.1-0.2 MPa

Ⅳ、Forging Press Tonnage Selection Guide

Choosing the right press tonnage is critical for optimal production:

Bolt/Nut Size	Recommended Press Tonnage (Semi-auto)	Recommended Press Tonnage (Fully Auto)
M12-M14	63T	Not recommended
M16-M18	80T	Not recommended
M20-M22	80T	100T
M24-M27	100T	125T
M30-M33	125T	160T
M36-M39	160T	200T
M43-M45	200T	250T
M48-M52	250T	315T
M56-M60	315T	400T
M64-M68	400T	500T
M72-M76	500T	630T
M80-M85	500T	630T
M90-M100	630T	800T