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| Customization: | Available |
|---|---|
| Material: | ASTM A194 Grade 2h,A563 Grade 10s Qt |
| Type: | Hexagon Head |
| Shipping Cost: | Contact the supplier about freight and estimated delivery time. |
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Core Specification Table
| Item | Specification |
|---|---|
| Product Name | ASTM A194 Grade 2H Heavy Hex Nut |
| Dimension Standard | ASME B18.2.2 |
| Material Grade | ASTM A194 2H (Carbon Steel, Quenched and Tempered) |
| Hardness | HRC 24-38 (Core Hardness) |
| Surface Finish | Black Oxide |
| Service Environment | H2S Sour Gas Service, NACE MR0175 / ISO 15156 Compliant |
| Certificate | EN 10204 3.1 MTC (Chemical Composition, Hardness, Proof Load Test) |
| Size Range | 2-3/8" to 3-3/4" |
| Matching Bolt | ASTM A193 B7 / B7M (For NACE service, B7M with hardness max 22 HRC is required) |
What is ASTM A194 Grade 2H
A194 2H is a carbon steel nut grade, quenched and tempered, designed for high pressure and high temperature flange connections. Typical chemical composition for Grade 2H: Carbon min 0.40%, Manganese max 1.0%, Phosphorus max 0.04%, Sulfur max 0.05%, Silicon max 0.40%.
Hardness Control
Finished nuts require core hardness HRC 24-38. Our products are tested batch by batch after heat treatment to ensure compliance with A194.
Why NACE MR0175 Matters
NACE MR0175 / ISO 15156 is the international standard for metallic materials in H2S-containing oil and gas environments. H2S causes sulfide stress cracking (SSC). Higher hardness increases cracking risk. NACE compliant nuts require hardness control, chemical composition limits, and heat treatment to reduce cracking risk.
Note: NACE Service Typically Requires B7M, Not B7
Standard A193 B7 bolts have a maximum hardness of 35 HRC. NACE service requires bolt hardness max 22 HRC, corresponding to grade B7M. The matching nut grade is 2HM (hardness max 22 HRC). If your customer uses these in NACE service, confirm the bolt grade is also compliant.
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Your size range 2-3/8" to 3-3/4" corresponds to ASME B18.2.2 heavy hex nut dimensions. The detail page should list width across flats and thickness tolerances for each size, so engineers can verify flange connection space.
Reference ASME B18.2.2 dimensions (excerpt for your size range):
| Nominal Size | Width Across Flats (Max/Min) | Thickness (Max/Min) |
|---|---|---|
| 2-1/4" | 3.500 / 3.388 | 2.251 / 2.155 |
| 2-1/2" | 3.875 / 3.750 | 2.505 / 2.401 |
| 2-3/4" | 4.250 / 4.112 | 2.759 / 2.647 |
| 3" | 4.625 / 4.475 | 3.013 / 2.893 |
| 3-1/4" | 5.000 / 4.838 | 3.252 / 3.124 |
| 3-1/2" | 5.375 / 5.200 | 3.505 / 3.364 |
| 3-3/4" | - | - |
Note: Dimensions above are in inches. A complete dimension table should be provided as a PDF attachment or referenced directly from ASME B18.2.2.
Certificate Content
EN 10204 3.1 is a certificate issued by the manufacturer, based on actual shipped products. It must include:
Chemical composition: Heat number level chemical analysis
Hardness test: Actual hardness values of finished nuts
Proof load test: Load bearing verification of nuts
Material traceability: Complete traceability from heat number to finished product
Purpose of Certificate
Large buyers need the 3.1 certificate for incoming inspection and project audits. Without a 3.1 certificate, the buyer cannot prove material compliance to the end user or EPC.
Other Documents Available on Request
Third party inspection report (SGS / BV / TUV)based on client 's cost
Dimensional inspection report
Surface finish inspection report (black oxide film thickness)
Oil and Gas / Refinery
A194 2H nuts are recommended for high pressure and high temperature service. In oil and gas and refinery units, flange connections must withstand high temperature, high pressure, and H2S corrosion. The NACE MR0175 compliant version is specifically for sour oil and gas fields, gas processing plants, and sour gas pipelines.
Matching Recommendations
Standard high temp high pressure flange: A193 B7 bolt + A194 2H nut
NACE sour gas service: A193 B7M bolt + A194 2HM nut (both hardness max 22 HRC)
Low temperature sour service: A320 L7M bolt + A194 7M nut
NACE Compliance: NACE MR0175 compliance declaration available, hardness controlled for sour gas service
EN 10204 3.1 Certificate: Supplied with shipment, including chemical composition, hardness, and proof load data
Size Coverage: 2-3/8" to 3-3/4" heavy hex nuts, semi-finished stock available for common sizes
Surface Finish: Black oxide standard, phosphate, Xylan, and zinc plating available on request
Lead Time: XX days for standard sizes, XX days for custom sizes
NACE Matching: In NACE MR0175 service, 2H nuts must be matched with B7M bolts for full sour gas compliance. Using 2H nuts with standard B7 bolts does not meet NACE requirements.
Hardness Verification: NACE compliant nuts typically require hardness max 22 HRC (corresponding to 2HM grade). If you supply standard 2H (HRC 24-38), clearly state the applicable service to avoid misuse in NACE environments.
Certificate Type: EN 10204 3.1 certificate must be based on the actual shipped batch. Do not use test data from other batches.
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