Hardware & Fasteners Heat Treatment | Bolts, Nuts & Washers

Solution

Fasteners require uniform hardness and stable carburized layers to prevent assembly defects. Uneven heating leads to inconsistent batch quality. Rexin mesh belt heat treatment lines serve 4.8–14.9 grade bolts and nuts. Integrated processes support continuous mass production and lower rejection rates.

Fastener Heat Treatment Principle & Full Process

We adjust heating temperature, holding time and cooling speed to control internal metal grain, achieving target tensile strength and hardness for different strength grades. Standard Fastener Production Flow:

Feeding

Carburizing Furnace

Oil Quenching Tank

Washing Degreasing

Tempering Furnace

Cooling & Discharge

Fastener Grade Material & Heat Treatment Standard

Strength Grade	Raw Material	Heat Treatment Craft	Hardness HRC	Main Application
4.8 / 5.8	Ordinary Carbon Steel	Quenching + High Temp Tempering	12–22	General machinery, furniture
8.8 / 10.9	Medium Carbon Steel	Quenching + Medium Temp Tempering	22–39	Automotive, construction machinery
12.9 / 14.9	Alloy Structural Steel	Carburizing + Low Temp Tempering	39–44	New energy, high-load equipment
304 / 316 Stainless	Stainless Steel Bar	Solid Solution Annealing	—	Corrosion resistant hardware

Core Mesh Belt Equipment For Fastener Production

Equipment Name	Working Temp	Core Function
Mesh Belt Carburizing Furnace	850–950℃	Automatic carbon potential control for low-carbon bolts
Mesh Belt Quenching Furnace	800–950℃	Uniform rapid heating for consistent quenching hardness
Mesh Belt Tempering Furnace	150–650℃	Multi-zone temp control to eliminate quenching stress
Continuous Degreasing Washer	50–80℃	Remove residual quenching oil to avoid surface discoloration

Hardness Control by Grade

8.8# HRC22–32 / 10.9# HRC32–39 / 12.9# HRC39–44

Case Depth Control by Size

M6 below 0.1–0.3mm / M8–M16 0.3–0.8mm / M20 above 0.8–1.5mm

Distortion Control

Total deformation ≤0.05mm per single fastener

Surface Quality

No oxidation, no decarburization, uniform matte finish

Fastener Industry Pain Points & Our Solutions

Unstable hardness batch to batch → Multi-zone independent PID temperature system
High continuous operation power cost → Nano composite energy-saving furnace lining
Quenching oil fume environmental trouble → Integrated fume purification system
Lack of production traceability → MES data recording intelligent control

Advanced Fastener Heat Treatment Tech

Automatic Carbon Potential Closed-loop Control: Real-time enriching gas adjustment, stable case depth
Waste Heat Recovery System: Recycle quenching waste heat for cleaning water preheating
MES Intelligent Production Line: Automatic parameter storage, real-time abnormal alarm MES

Conclusion

Fastener heat treatment determines the safety and service life of all mechanical connecting parts. As automotive, wind power and new energy industries demand higher 12.9+ grade fasteners, intelligent low-energy continuous mesh belt lines become mainstream.

Rexin China factory provides complete mesh belt quenching, carburizing, and tempering heat treatment lines for the fastener industry, supporting wholesale supply and custom manufacturing. Contact our engineering team for more information or to request a quote.

Our Products: Mesh Belt Furnace, Vacuum Furnace, Box Furnace, Pit Nitriding Furnace, Brazing Line, Sintering Furnace

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