A194 Heavy Hex Nuts
ASTM A194 Heavy Hex Nuts are manufactured according to ASTM A194 specifications, which define the material requirements, mechanical properties, and performance grades for nuts used in high-pressure and high-temperature applications. Unlike dimensional standards, ASTM A194 mainly specifies the chemical composition, heat treatment, hardness, and mechanical performance requirements of heavy hex nuts. The dimensions of ASTM A194 heavy hex nuts are generally produced according to ASME B18.2.2 requirements, including nut width across flats, thickness, and thread dimensions.
ASTM A194 covers various performance grades, including 2H, 2HM, Grade 7, Grade 7M, Grade 8, and Grade 8M, allowing customers to select suitable materials according to different service conditions. Depending on the required strength, temperature resistance, and corrosion resistance, these nuts can be manufactured from medium carbon steel such as C45, alloy steel such as AISI 4140, as well as stainless steel materials including 304 and 316. Our production processes include cold heading, tapping, chamfering, heat treatment, and surface finishing such as zinc plating, black oxide, passivation, and hot-dip galvanizing to meet various industrial fastening requirements.
Chemical Composition and Material A194 Nut:
ASTM A194 specifies the chemical requirements for different nut grades to ensure the required mechanical properties and service performance. The chemical composition varies depending on the grade, material type, and intended application. Carbon steel, alloy steel, and stainless steel grades are selected according to strength requirements, operating temperature, and corrosion resistance conditions.
| Grade | Material | C | Mn | S | Si | Cr | Ni | Mo |
|---|---|---|---|---|---|---|---|---|
| A194 2H/2HM | C45 Carbon Steel | 0.4min | 1max | 0.04max | 0.05max | 0.4max | ||
| A194 GR.7/7M | AISI4140 | 0.38-0.48 | 0.75-1 | 0.035max | 0.15-0.35 | 0.8-1.1 | 0.15-0.25 | |
| A194 GR.8 | 304 Stainless Steel | 0.08max | 2max | 0.045max | 1 | 18-20 | 8-11 | |
| A194 GR.8M | 316 Stainless Steel | 0.08max | 2max | 0.045max | 1 | 16-18 | 10-14 |
Hardness of A194 Nut:
ASTM A194 Heavy Hex Nuts are subject to hardness requirements specified for each individual grade to ensure proper mechanical performance and service reliability. Hardness testing is commonly used to verify the material condition, heat treatment effectiveness, and consistency of finished nuts. The acceptable hardness range varies depending on the grade, such as ASTM A194 2H, 2HM, Grade 7, Grade 7M, Grade 8, and Grade 8M, as each grade is designed for different operating conditions.
During production, hardness inspection is performed after the required manufacturing and heat treatment processes. Testing methods may include Rockwell hardness testing according to the applicable ASTM requirements. By controlling hardness values within the specified range, ASTM A194 heavy hex nuts can provide reliable strength, load-bearing capacity, and compatibility with matching high-strength bolts or studs in high-pressure and high-temperature applications.
| Grade | HB | HRC | HRB |
|---|---|---|---|
| 2H ≤ 1-1/2“ | 248-327 | 24-35 | |
| 2H ＞1-1/2” | 212-327 | 35max | 95min |
| 2HM/7M | 15-235 | 84-99 | |
| GR.7 | 248-327 | 24-35 | |
| A194 GR.8/GR.8M | 126-300 | 60min |
Dimension Chart of A194 Heavy Hex Nuts:
| Mon | 3/8 | 1/2 | 9/16 | 5/8 | 3/4 | 7/8 | 1 | 1-1/8 | 1-1/4 | 1-3/8 | 1-1/2 | 1-5/8 | 1-3/4 | 1-7/8 | 2 | 2-1/4 | 2-1/2 | 2-3/4 | 3 | 3-1/4 | 3-1/2 | 3-3/4 | 4 |
| P | 16|24|32 | 13|20|28 | 12|18|24 | 11|18|24 | 10|16|20 | 9|14|20 | 8|12|20 | 7|12|18 | 7|12|18 | 6|12|18 | 6|12|18 | 6|12|18 | 5|8|12 | 6 | 4.5 | 4.5 | 4 | 4 | 4 | 4 | 4 | 4 | 4 |
| s min | 0.669 | 0.85 | 0.909 | 1.031 | 1.212 | 1.394 | 1.575 | 1.756 | 1.938 | 2.119 | 2.3 | 2.481 | 2.662 | 2.844 | 3.025 | 3.388 | 3.75 | 4.112 | 4.475 | 4.838 | 5.2 | 5.562 | 5.925 |
| s max | 0.688 | 0.875 | 0.938 | 1.062 | 1.25 | 1.438 | 1.625 | 1.812 | 2 | 2.188 | 2.375 | 2.562 | 2.75 | 2.938 | 3.125 | 3.5 | 3.875 | 4.25 | 4.625 | 5 | 5.375 | 5.75 | 6.125 |
| e min | 0.763 | 0.969 | 1.037 | 1.175 | 1.382 | 1.589 | 1.796 | 2.002 | 2.209 | 2.416 | 2.622 | 2.828 | 3.035 | 3.242 | 3.449 | 3.862 | 4.275 | 4.688 | 5.102 | 5.515 | 5.928 | 6.341 | 6.755 |
| e max | 0.794 | 1.01 | 1.083 | 1.227 | 1.443 | 1.66 | 1.876 | 2.093 | 2.309 | 2.526 | 2.742 | 2.959 | 3.175 | 3.392 | 3.608 | 4.041 | 4.474 | 4.907 | 5.34 | 5.774 | 6.207 | 6.64 | 7.073 |
| k min | 0.341 | 0.464 | 0.526 | 0.587 | 0.71 | 0.833 | 0.956 | 1.079 | 1.187 | 1.31 | 1.433 | 1.556 | 1.679 | 1.802 | 1.925 | 2.155 | 2.401 | 2.647 | 2.893 | 3.124 | 3.37 | 3.616 | 3.862 |
| k max | 0.377 | 0.504 | 0.568 | 0.631 | 0.758 | 0.885 | 1.012 | 1.138 | 1.251 | 1.378 | 1.505 | 1.632 | 1.759 | 1.886 | 2.013 | 2.251 | 2.505 | 2.759 | 3.013 | 3.252 | 3.506 | 3.76 | 4.014 |
A194 2H Nuts:
ASTM A194 2H Heavy Hex Nuts are one of the most commonly used grades for high-pressure bolting applications. Manufactured from medium carbon steel, such as C45 or equivalent materials, Grade 2H nuts provide a reliable combination of strength, hardness, and cost efficiency. They are widely selected for general industrial bolted connections where high mechanical performance is required without extreme corrosion or temperature conditions.
For customers looking for a proven and economical fastening solution, ASTM A194 2H nuts are commonly paired with ASTM A193 B7 stud bolts in applications such as oil and gas pipelines, pressure equipment, and industrial machinery. Different surface treatments, including black oxide, zinc plating, and hot-dip galvanizing, can be supplied according to the required corrosion protection.
A194 Grade 7 Nuts:
ASTM A194 Grade 7 Heavy Hex Nuts are designed for applications requiring enhanced strength and improved performance under elevated temperature conditions. Compared with carbon steel grades, Grade 7 nuts are manufactured from alloy steel, commonly based on AISI 4140 material, providing higher strength and better resistance to demanding service environments.
When equipment operates under higher pressure, temperature fluctuations, or heavy loading conditions, ASTM A194 Grade 7 nuts provide a suitable fastening solution for critical bolted joints. They are commonly used in refineries, power generation equipment, pressure vessels, and other industrial systems where reliable mechanical performance is essential.
A194 Gr.8 Nuts:
ASTM A194 Grade 8 Heavy Hex Nuts are stainless steel fasteners selected for applications where corrosion resistance and long-term durability are important requirements. Manufactured from stainless steel materials such as 304, Grade 8 nuts offer excellent resistance against moisture, chemicals, and general corrosive environments while maintaining reliable fastening performance.
These nuts are widely used in chemical processing equipment, food processing machinery, water treatment systems, and outdoor industrial applications. For projects requiring both mechanical reliability and improved corrosion resistance, ASTM A194 Grade 8 provides an effective alternative to carbon steel and alloy steel grades.
A194 Gr.8M Nuts:
ASTM A194 Grade 8M Heavy Hex Nuts are manufactured from molybdenum-containing stainless steel, typically using 316 stainless steel, for applications requiring higher corrosion resistance than standard stainless steel grades. The addition of molybdenum improves resistance to chloride environments and chemical exposure, making Grade 8M suitable for more aggressive operating conditions.
Customers often select ASTM A194 Grade 8M nuts for marine environments, offshore facilities, chemical plants, and other applications where corrosion protection is a critical consideration. By combining stainless steel durability with heavy hex nut design, Grade 8M fasteners provide dependable performance for demanding industrial fastening applications.