248–327 BHN

Brinell Hardness (BHN)

175 ksi

Proof Load Stress (Heavy Hex)

¼"–4"

Imperial Size Range

M6–M180

Metric Size Range

455°C

Min. Tempering Temperature

What Are ASTM A194 Grade 2H Nuts?

ASTM A194 Grade 2H is a standard specification covering high-strength nuts and other internally threaded fasteners produced from heat-treated medium carbon steel. The designation “2H” indicates that these nuts are quenched and tempered, a thermal process that develops the mechanical properties needed for demanding bolted joint applications, particularly in high-pressure piping, flanged connections and structural assemblies.

Grade 2H nuts are most commonly paired with ASTM A193 Grade B7 stud bolts and heavy hex bolts used in pressure vessels, heat exchangers, pipelines and refineries. Their high proof load of 175,000 psi for heavy hex nuts makes them the industry-standard choice wherever joint integrity under elevated stress is non-negotiable.

Jade Alloys manufactures ASTM A194 Grade 2H nuts as standard hex nuts and heavy hex nuts, in both imperial (¼” to 4″) and metric (M6 to M180) sizes. Raw material used is AISI 1045, EN8 or EN8D medium carbon steel. Nuts may be produced by hot forging, cold forging or machining from heat-treated bar stock, then quenched and tempered at a minimum temperature of 455°C (850°F).

Mating Fastener: ASTM A194 Grade 2H heavy hex nuts are the standard mating hardware for ASTM A193 B7 stud bolts. For sour gas / NACE service, Grade 2HM nuts with 100% hardness testing are required.

High Proof Load

175 ksi proof load stress for heavy hex nuts ensures reliable clamping force under high bolt preloads without yielding the nut thread.

Controlled Hardness

Brinell hardness is tightly controlled between 248–327 BHN to prevent thread stripping or hydrogen-induced cracking in critical service.

Heat Treatment

Quenched and tempered at a minimum tempering temperature of 455°C (850°F), fully documented on material test reports (MTRs).

Wide Size Range

Available from ¼" to 4" in imperial and M6 to M180 in metric, covering virtually all standard flange and pressure-vessel bolt sizes.

ASTM A194 Grade 2H Specification

Full specification parameters including standards, dimensions, thread configuration, and certifications.

Parameter	Details
Specification	ASTM A194 / ASME SA194 Grade 2H
Material Description	Medium Carbon Steel, Quenched and Tempered
Raw Material Grades	AISI 1045, EN8, EN8D
Manufacturing Method	Hot Forging, Cold Forging, or Machining from Heat-Treated Bar Stock
Dimensional Standards	ASME B18.2.1, ASME B18.2.2, ASME B18.3, DIN 934, DIN 6915, ISO 4032, ISO 4775
Metric Standards	ASME B18.2.4.1M (Hex Nut), ASME B18.2.4.2M (Heavy Hex Nut), ASME B18.2.4.6M (Heavy Hex Nut — metric)
Imperial Standards	ASME B18.2.2 Table 4 (Hex Nut), ASME B18.2.2 Table 10 (Heavy Hex Nut)
Thread Configuration	ASME B1.1 2B/3B Unified Inch Threads; ASME B1.13M 6H Metric Coarse Threads
Imperial Size Range	¼” to 4″
Metric Size Range	M6 to M180
Heat Treatment	Quenched & Tempered — min. tempering temperature 455°C (850°F)
Dual Certification	Dual certified per ASTM & ASME codes
Additional Certifications	PED 97/23/EC; Merkblatt AD 2000 W2
NACE Compliance	NACE MR0103 / MR0175 / ISO 15156
Grade Marking	“2H” stamped on nut face per ASTM A194 marking requirements
Mandatory Requirements	Free from Mercury & Radioactive Contamination

Chemical Composition of ASTM A194 Grade 2H Nuts

Chemical requirements for ASTM A194 Grade 2H nuts per the standard specification.

Element	Carbon (C)	Manganese (Mn)	Phosphorus (P)	Sulfur (S)	Silicon (Si)
Limit	0.40% max	1.00% max	0.040% max	0.050% max	0.40% max

Note: Chromium, Nickel, and Molybdenum are not specified for Grade 2H. The grade relies on carbon and manganese for strength, achieved through the quench-and-temper heat treatment cycle.

Typical Raw Material: AISI 1045 carbon steel (C: 0.43–0.50%, Mn: 0.60–0.90%) and EN8/EN8D are the most commonly used starting materials. Both satisfy the A194 Grade 2H chemical requirements and respond predictably to Q&T heat treatment.

ASTM A194 Grade 2H Nuts Mechanical Properties & Hardness

Proof load, hardness, and tempering requirements for ASTM A194 Grade 2H nuts — both completed nuts and sample nuts after heat treatment.

Hardness Requirements — Completed Nuts

Grade & Size	Brinell Hardness (BHN)	Rockwell HRC	Rockwell HRB	Min BHN (Sample after HT)	Min HRB (Sample after HT)
2H — Up to 1½” incl. (M36)	248–327	24–35	—	179	89
2H — Over 1½” (over M36)	212–327	35 max	95 min	147	79

Heat Treatment: Grade 2H nuts shall be quenched and tempered at a minimum tempering temperature of 455°C (850°F).

Mechanical Properties Summary

Property	Heavy Hex Nuts	Standard Hex Nuts	Nominal Size Range	Tempering Temp.
Proof Load Stress	175,000 psi (175 ksi)	150,000 psi (150 ksi)	¼” – 4″	Min. 455°C (850°F)
Hardness — Min	248 BHN / HRC 24 (up to 1½”)		212 BHN / HRB 95 (over 1½”)
Hardness — Max	327 BHN / HRC 35

Proof Load by Size — Imperial (Heavy Hex & Hex Nuts)

Nominal Size (in.)	Threads Per Inch	Stress Area (in²)	Heavy Hex Proof Load (lbf)	Hex Nut Proof Load (lbf)
1/4	20	0.0316	5,570	4,770
5/16	18	0.0524	9,170	7,860
3/8	16	0.0774	13,560	11,620
7/16	14	0.1063	18,600	15,940
1/2	13	0.1419	24,830	21,280
9/16	12	0.1820	31,850	27,300
5/8	11	0.2260	39,550	33,900
3/4	10	0.3340	58,450	50,100
7/8	9	0.4620	80,850	69,300
1	8	0.6060	106,000	90,900
1-1/8	8	0.7900	138,200	118,500
1-1/4	8	1.0000	175,000	150,000
1-3/8	8	1.2330	215,800	185,000
1-1/2	8	1.4920	261,100	223,800

Heavy hex: proof stress of 175,000 psi. Standard hex: proof stress of 150,000 psi.

Proof Load by Size — Metric (Heavy Hex & Hex Nuts)

Nominal Size (mm)	Thread Pitch	Stress Area (mm²)	Heavy Hex Proof Load (kN)	Hex Nut Proof Load (kN)
M6	1.0	20.1	29.2	20.8
M8	1.25	36.6	44.1	37.9
M10	1.5	58.0	69.9	60.0
M12	1.75	84.3	101.6	87.3
M14	2.0	115.0	138.6	119.0
M16	2.0	157.0	189.2	162.5
M20	2.5	245.0	295.2	253.6
M22	2.5	303.0	365.1	313.6
M24	3.0	353.0	425.4	365.4
M27	3.0	459.0	553.4	475.1
M30	3.5	561.0	676.0	580.6
M36	4.0	817.0	984.5	845.6

Types of ASTM A194 Grade 2H Nuts

Jade Alloys stocks and manufactures the following Grade 2H nut types to suit various flanged, structural, and mechanical applications.

🔩 Heavy Hex Nuts

Most common for B7 bolting

⬡ Hex Nuts

Standard profile

🔧 Heavy Hex Jam Nuts

Low-profile locking

🔗 Coupling Nuts

Rod extension / coupling

🟥 Square Nuts

Anti-rotation applications

🔒 Lock Nuts

Vibration resistance

🏠 Acorn / Cap Nuts

Exposed thread protection

🎰 Castle Nuts

Slotted with cotter pin

Dimensions of ASTM A194 GR. 2H Nuts

Dimensional data for ASTM A194 Grade 2H hex nuts and heavy hex nuts per ASME B18.2.2. All measurements in inches unless noted.

ASTM A194 Grade 2H Hex Nut Dimensions (ASME B18.2.2 Table 4)

Basic Thread Dia.

Nominal Size (in.)	Width Across Flats F (Basic)	Width Across Flats F (Max)	Width Across Flats F (Min)	Width Across Corners G (Max)	Width Across Corners G (Min)	Thickness H (Basic)	Thickness H (Max)	Thickness H (Min)
1/4	.2500	7/16	.438	.428	.505	.488	7/32	.226	.212
5/16	.3125	1/2	.500	.489	.577	.557	17/64	.273	.258
3/8	.3750	9/16	.562	.551	.650	.628	21/64	.337	.321
7/16	.4375	11/16	.688	.675	.794	.768	3/8	.385	.365
1/2	.5000	3/4	.750	.736	.866	.840	7/16	.448	.427
9/16	.5625	7/8	.875	.861	1.010	.982	31/64	.496	.473
5/8	.6250	15/16	.938	.922	1.083	1.051	35/64	.559	.535
3/4	.7500	1-1/8	1.125	1.088	1.299	1.240	41/64	.665	.617
7/8	.8750	1-5/16	1.312	1.269	1.516	1.447	3/4	.776	.724
1	1.0000	1-1/2	1.500	1.450	1.732	1.653	55/64	.887	.831
1-1/8	1.1250	1-11/16	1.688	1.631	1.949	1.859	31/32	.999	.939
1-3/8	1.3750	2-1/16	2.062	1.994	2.382	2.273	1-11/64	1.206	1.138
1-1/2	1.5000	2-1/4	2.250	2.175	2.598	2.480	1-9/32	1.317	1.245
1-3/4	1.7500	2-5/8	2.625	2.538	3.031	2.893	1-1/2	1.540	1.460
2	2.0000	3	3.000	2.900	3.464	3.306	1-23/32	1.763	1.675
2-1/4	2.2500	3-3/8	3.375	3.263	3.897	3.719	1-15/16	1.986	1.890
2-1/2	2.5000	3-3/4	3.750	3.625	4.330	4.133	2-5/32	2.209	2.105
2-3/4	2.7500	4-1/8	4.125	3.988	4.763	4.546	2-3/8	2.431	2.319

ASTM A194 Grade 2H Heavy Hex Nut Dimensions (ASME B18.2.2 Table 10)

Nominal Size (in.)	Basic Thread Dia.	Width Across Flats F (Basic)	Width Across Flats F (Max)	Width Across Flats F (Min)	Width Across Corners G (Max)	Width Across Corners G (Min)	Thickness H (Basic)	Thickness H (Max)	Thickness H (Min)
1/4	.2500	1/2	.500	.488	.577	.556	15/64	.250	.218
5/16	.3125	9/16	.562	.546	.650	.622	19/64	.314	.280
3/8	.3750	11/16	.688	.669	.794	.763	23/64	.377	.341
7/16	.4375	3/4	.750	.728	.866	.830	27/64	.441	.403
1/2	.5000	7/8	.875	.850	1.010	.969	31/64	.504	.464
9/16	.5625	15/16	.938	.909	1.083	1.037	35/64	.568	.526
5/8	.6250	1-1/16	1.062	1.031	1.227	1.175	39/64	.631	.587
3/4	.7500	1-1/4	1.250	1.212	1.443	1.382	47/64	.758	.710
7/8	.8750	1-7/16	1.438	1.394	1.660	1.589	55/64	.885	.833
1	1.0000	1-5/8	1.625	1.575	1.876	1.796	63/64	1.012	.956
1-1/8	1.1250	1-13/16	1.812	1.756	2.093	2.002	1-7/64	1.139	1.079
1-1/4	1.2500	2	2.000	1.938	2.309	2.209	1-7/32	1.251	1.187
1-3/8	1.3750	2-3/16	2.188	2.119	2.526	2.416	1-11/32	1.378	1.310
1-1/2	1.5000	2-3/8	2.375	2.300	2.742	2.622	1-15/32	1.505	1.433
1-5/8	1.6250	2-9/16	2.562	2.481	2.959	2.828	1-19/32	1.632	1.556
1-3/4	1.7500	2-3/4	2.750	2.662	3.175	3.035	1-23/32	1.759	1.679
2	2.0000	3-1/8	3.125	3.025	3.608	3.449	1-31/32	2.013	1.925
2-1/4	2.2500	3-1/2	3.500	3.388	4.041	3.862	2-13/64	2.251	2.155
2-1/2	2.5000	3-7/8	3.875	3.750	4.474	4.275	2-29/64	2.505	2.401
2-3/4	2.7500	4-1/4	4.250	4.112	4.907	4.688	2-45/64	2.759	2.647
3	3.0000	4-5/8	4.625	4.475	5.340	5.102	2-61/64	3.013	2.893
3-1/4	3.2500	5	5.000	4.838	5.774	5.515	3-3/16	3.252	3.124
3-1/2	3.5000	5-3/8	5.375	5.200	6.207	5.928	3-7/16	3.506	3.370
3-3/4	3.7500	5-3/4	5.750	5.562	6.640	6.341	3-11/16	3.760	3.616
4	4.0000	6-1/8	6.125	5.925	7.073	6.755	3-15/16	4.014	3.862

Heavy hex nuts have a larger across-flat dimension than standard hex nuts at the same nominal size, providing greater bearing area and resistance to pull-through in flange applications.

Weight Chart of ASTM A194 Grade 2H Nuts

Approximate weight of ASTM A194 Grade 2H nuts in pounds (lbs) per 100 pieces.

Size (in.)	Finished Hex	Heavy Hex	Finished Jam	Heavy Hex Jam	Square	Heavy Square
1/2	3.750	6.540	2.620	4.000	5.780	7.870
5/8	7.330	11.900	4.930	6.960	10.800	14.300
3/4	11.900	19.300	7.700	11.000	15.400	23.500
7/8	19.000	29.700	12.000	16.700	24.500	36.200
1	28.300	42.500	17.600	23.500	36.300	51.500
1-1/4	54.300	78.600	36.100	45.800	70.600	95.500
1-1/2	94.300	131.000	60.900	74.800	122.000	161.000
1-3/4	151.000	204.000	100.000	114.000	—	—
2	224.000	299.000	140.000	165.000	—	—
2-1/2	—	564.000	—	332.000	—	—
3	—	950.000	—	545.000	—	—
3-1/2	—	1,526.000	—	851.000	—	—
4	—	2,180.000	—	1,200.000	—	—

Weights are approximate and may vary slightly based on exact dimensions and manufacturing method. Use for estimating shipping and handling costs only.

Dimensional Standards by Nut Type

ASTM A194 Grade 2H nuts are produced to the following international dimensional standards.

Nut Type	DIN	ISO	ASME (Imperial)	ASME (Metric)	IS (India)
Hex Nut	DIN 934	ISO 4032	ASME B18.2.2 Table 4	ASME B18.2.4.1M / B18.2.4.2M	IS 1363-3 / IS 1364-3
Heavy Hex Nut	DIN 6915	ISO 4775	ASME B18.2.2 Table 10	ASME B18.2.4.6M	—
Hex Jam Nut	DIN 439	ISO 4035	ASME B18.2.2	ASME B18.2.4.5M	—

Surface Finishes & Coatings

ASTM A194 Grade 2H nuts can be furnished in the following surface finishes to suit corrosion protection requirements and application environments.

⬛ Plain Black (As-Manufactured)

🟫 Black Phosphate

🔘 Zinc Plated (Electrogalvanized)

🟡 Cadmium Plated

🟢 Hot-Dip Galvanized (HDG)

🟣 Xylan / PTFE Coated

Hot-Dip Galvanized Note: For HDG nuts, the internal thread is overtapped to the Class 2B tolerance to accommodate the zinc coating thickness. This is required by ASTM A563 and ensures proper fit with galvanized bolts.

Coating Selection Guide

Finish	Corrosion Protection	Typical Application	Temperature Limit
Plain Black	Minimal	Indoor / oil-coated storage; painted assemblies	No limit from coating
Black Phosphate	Low–Moderate	Temporary corrosion protection; oil & gas indoor	~200°C
Zinc Plated	Moderate	General industrial; mild outdoor exposure	~120°C
Cadmium Plated	High	Marine, aerospace, sour environments	~230°C
Hot-Dip Galvanized	Very High	Outdoor / offshore structures; water treatment	~200°C
Xylan / PTFE	High + Low Friction	Flange bolting requiring controlled torque / anti-seize	~260°C

ASTM A194 Grade Comparison

How Grade 2H compares to other commonly specified ASTM A194 nut grades — helping you select the right grade for your application.

Property	A194 Grade 2H	A194 Grade 2HM	A194 Grade 7	A194 Grade 8M
Material	Carbon Steel (Q&T)	Carbon Steel (Q&T)	Cr-Mo Alloy Steel (Q&T)	316 Stainless Steel
Hardness	248–327 BHN	248–327 BHN	248–327 BHN	126–300 BHN
Proof Load (Heavy Hex)	175 ksi	175 ksi	175 ksi	150 ksi
Hardness Testing	Sample Basis	100% Individual	Sample Basis	Sample Basis
NACE MR0175 Sour Service	Grade 2HM required	Yes (2HM)	Yes	Depends on grade variant
Mating Bolt Grade	A193 B7 / B7M	A193 B7M	A193 B7	A193 B8M
Corrosion Resistance	Low (carbon steel)	Low (carbon steel)	Moderate (Cr-Mo)	High (316 SS)
Typical Applications	Flanges, pressure vessels, structural	Sour service / NACE environments	High-temp Cr-Mo bolting	Chemical, marine, cryogenic

Grade 2H vs 2HM — Key Differences

Grade 2H

Hardness Testing: Sample basis only
Proof Load: 175 ksi (heavy hex)
NACE MR0175: Not directly qualified
Mating Bolt: A193 B7 (standard)
Cost: Lower

Grade 2HM

Hardness Testing: 100% individual nuts
Proof Load: 175 ksi (heavy hex)
NACE MR0175: Qualified for sour service
Mating Bolt: A193 B7M (NACE)
Cost: Higher (100% testing)

Mating Hardware & Bolting Combinations

Correct hardware pairing is critical for joint integrity. The following are the standard bolting combinations used with ASTM A194 Grade 2H nuts.

Bolt / Stud Grade	Recommended Nut	Washer	Application
ASTM A193 B7	A194 Grade 2H Heavy Hex	F436 Type 1 / F959	Standard flange, pressure vessel, structural
ASTM A193 B7M (NACE)	A194 Grade 2HM Heavy Hex	F436 Type 1	Sour gas / NACE MR0175 service
ASTM A307 Grade B	A194 Grade 2H Hex Nut	F436 Type 1	Structural, AISC connections
ASTM A325 Structural Bolt	A194 Grade 2H / A563 DH	F436 Type 1	Steel structure, moment frames
ASTM A193 B16	A194 Grade 16	F436 Type 1	High-temperature Cr-Mo-V service

Industries & Applications of ASTM A194 Grade 2H Nuts

ASTM A194 Grade 2H heavy hex nuts are specified across heavy industries wherever high-strength, controlled-hardness nut fasteners are required.

Oil & Gas Pipelines

Petrochemical Refineries

Power Generation Plants

Pressure Vessels & Boilers

Heat Exchangers

Structural Steel & Infrastructure

Water Treatment Plants

Chemical Processing

In flange bolting, Grade 2H heavy hex nuts are used at ASME B16.5 Class 150 through Class 2500 pressure ratings, covering virtually all standard piping flange applications. Their controlled hardness band also ensures compatibility with the maximum hardness limits imposed by NACE MR0175 for environments containing hydrogen sulfide (H₂S).

International Equivalent Grades

ASTM A194 Grade 2H nuts are not always called by the same designation in every market. The following grades are broadly equivalent in material and mechanical requirements.

ASTM A194 / ASME SA194

Grade 2H (USA)

DIN / ISO

Class 10 Hex Nut (similar strength)

BS 1769

Grade T (UK equivalent)

IS 1363 / IS 1364

Property Class 10 (India)

JIS B 1052

Class 10H (Japan)

GB / T 6170

Property Class 10 (China)

Note: International equivalents are approximate. Always specify ASTM A194 Grade 2H by its full designation on engineering drawings and purchase orders to ensure compliance with proof load and hardness testing requirements.

Why Source from Jade Alloys?

Jade Alloys is a Mumbai-based manufacturer and exporter with over a decade of experience supplying ASTM-certified fasteners to global industrial projects.

Full Material Traceability

Every batch ships with a material test report (MTR) covering chemical analysis, hardness, and heat treatment records traceable to the raw material heat.

Ready Stock & Fast Dispatch

We maintain ready inventory of Grade 2H heavy hex nuts in common imperial sizes (½" to 2"), enabling same-week dispatch for urgent requirements.

Global Export Network

We export to 40+ countries including USA, UAE, Saudi Arabia, Singapore, Malaysia, UK, Germany, and Australia — with competitive freight terms.

Third-Party Inspection

We support TPI by Bureau Veritas, SGS, TÜV, and other inspection agencies as required by project specifications or end-user requirements.

Competitive Pricing

Direct manufacturer pricing — no middleman markups. Volume discounts are available for project procurement and blanket orders.

Custom Sizes & Specials

Non-standard sizes, special coatings, NACE-compliant Grade 2HM, and dual-certified ASTM/ASME nuts are available on request with short lead times.

Frequently Asked Questions

Q1: What is ASTM A194 Grade 2H?

ASTM A194 Grade 2H is a material specification for heavy hex nuts manufactured from medium carbon steel (typically AISI 1045 / EN8), quenched and tempered to a Brinell hardness of 248–327 BHN and a proof load stress of 175 ksi. It is commonly used with ASTM A193 B7 bolts in pressure vessel and flange bolting applications.

Q2: What is the hardness of ASTM A194 Grade 2H nuts?

For nuts up to 1½", hardness is 248–327 BHN (HRC 24–35). For larger sizes, it is 212–327 BHN. All nuts are quenched and tempered at a minimum tempering temperature of 455°C (850°F), documented in the mill test report.

Q3: What is the difference between Grade 2H and Grade 2HM?

Grade 2H requires sample-based hardness testing, while Grade 2HM requires 100% individual hardness testing of every nut. Grade 2HM is also qualified for NACE MR0175 / ISO 15156 sour service applications.

Q4: Which bolts are used with Grade 2H nuts?

ASTM A194 Grade 2H nuts are commonly used with ASTM A193 Grade B7 bolts. They are also compatible with A325, A490, and A307 bolts in structural and pressure applications.

Q5: Is ASTM A194 Grade 2H the same as ASME SA194 Grade 2H?

Yes. ASME SA194 Grade 2H is the ASME BPVC equivalent of ASTM A194 Grade 2H. Both have identical chemical, mechanical, and testing requirements.

Q6: What surface finishes are available for A194 Grade 2H nuts?

Available finishes include plain black, black phosphate, zinc plated, cadmium plated, hot-dip galvanized (HDG), and PTFE/Xylan coated. HDG nuts are overtapped to accommodate coating thickness.

Q7: Are ASTM A194 Grade 2H nuts suitable for sour service?

Standard Grade 2H is not NACE qualified. For sour service (H₂S environments), Grade 2HM must be used with A193 B7M bolts.

Q8: What raw material is used to manufacture Grade 2H nuts?

Grade 2H nuts are typically manufactured from AISI 1045, EN8, or EN8D medium carbon steel, then quenched and tempered to achieve required strength and hardness.

Export Countries

Jade Alloys exports ASTM A194 Grade 2H nuts to industrial buyers and project contractors across 40+ countries. Key markets include:

🇺🇸 USA

🇦🇪 UAE

🇸🇦 Saudi Arabia

🇬🇧 United Kingdom

🇸🇬 Singapore

🇨🇦 Canada

🇩🇪 Germany

🇦🇺 Australia

🇲🇾 Malaysia

🇶🇦 Qatar

🇳🇱 Netherlands

🇮🇩 Indonesia

We offer FOB Mumbai, CIF, and DDP incoterms. Contact our export team at sales@jadealloys.com for freight estimates.

Related Products

› ASTM A193 B7 Stud Bolts › ASTM A193 B16 Fasteners › ASTM A194 Grade 7 Nuts › ASTM A194 Grade 8 Nuts › ASTM A194 Grade 8M Nuts › ASTM A194 Grade 4 Nuts › ASTM A563 Nuts › ASTM A320 L7 Bolts › Alloy Steel Nuts

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