Carbon Steel Grade 4.8 8.8 10.9 12.9 HDG Geomet Dacromet Heavy Duty Hex Bolt

This is a heavy-duty hexagonal bolt designed specifically for high-pressure fastening in industrial and construction scenarios. It is made of four strength grades of carbon steel: 4.8 and 8.8 grades are used for general heavy-duty applications such as mechanical assembly, while 10.9 and 12.9 grades provide higher tensile strength for demanding applications such as structural steel connections. It is also equipped with three corrosion-resistant coatings: HDG (hot-dip galvanized) for outdoor or mild humid environments, Geomet for enhancing durability in industrial environments, and Dacromet for excellent protection against harsh conditions such as chemical exposure. Its hexagonal head design allows for easy tightening using standard tools, making it suitable for heavy machinery installation, building structure fastening, and equipment maintenance that requires reliable load-bearing and long-term corrosion resistance.

1. Fastening machinery components in workshops using Grade 4.8/8.8 bolts with Geomet coating
2. Securing structural steel connections in construction with Grade 10.9 bolts and HDG coating
3. Installing high-demand industrial equipment via Grade 12.9 bolts with Dacromet coating
4. Fixing outdoor structural parts (e.g., steel frames) using HDG-coated Grade 8.8 bolts
5. Assembling chemical plant equipment with Dacromet-coated Grade 10.9 bolts for corrosion resistance

1. Q: What do the numbers (4.8, 8.8, etc.) mean in the bolt’s strength grade?
   A: The first number is the tensile strength (in 100MPa), and the second is the yield ratio (yield strength/tensile strength ×10). For example, Grade 8.8 means tensile strength ≥800MPa and yield strength ≥640MPa (800×0.8).

2. Q: How to choose between HDG, Geomet, and Dacromet coatings?
   A: Pick HDG for outdoor/mild humidity (thick zinc protection). Choose Geomet for indoor industrial use (environmentally friendly, thin coating). Opt for Dacromet if exposed to chemicals or harsh weather (superior corrosion resistance).

3. Q: Can Grade 4.8 bolts be used for structural steel connections?
   A: No. Grade 4.8 has lower tensile/yield strength (≥400MPa/≥320MPa) and is only for general heavy-duty tasks. Structural steel needs Grade 10.9/12.9, which have higher strength to bear heavy loads.

4. Q: Are these bolts compatible with all standard hex nuts?
   A: They are compatible with standard metric hex nuts of the same size and thread type. Ensure the nut’s strength grade matches or exceeds the bolt’s (e.g., use Grade 8 nuts with Grade 8.8 bolts) to avoid weak points.

5. Q: Do Dacromet-coated bolts need extra maintenance compared to HDG ones?
   A: No. Dacromet has better resistance to chemicals and weathering, so it requires less maintenance. HDG may need checks for zinc layer peeling in harsh conditions, but Dacromet holds up longer with only occasional cleaning.