ASTM A325 Bolts

zhao77jie — Thu, 20 Mar 2025 02:14:00 +0000

ASTM A325 bolts are high-strength structural bolts used in steel-to-steel connections, particularly in buildings, bridges, and other heavy construction projects. These bolts are designed for structural applications where high load capacity and durability are required.

Unlike other ASTM grades, A325 is specific not only in the chemical and mechanical requirements, but also in the allowed configuration. These bolts range in diameter from 1/2″ through 1-1/2″ and are manufactured from a medium-carbon or medium-carbon alloy steel that is quenched and tempered to develop the desired mechanical properties.

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What does A325 mean on a bolt?

The designation A325 on a bolt refers to the ASTM A325 specification, which defines a type of high-strength structural bolt commonly used in steel-to-steel connections for buildings, bridges, and other infrastructure projects.

Key Characteristics of ASTM A325 Bolts

High Strength:

Made from medium carbon steel, carbon boron steel, or medium carbon alloy steel

Minimum tensile strength: 120,000 psi (for diameters ≤ 1 inch)

Minimum yield strength: 92,000 psi

Heat Treatment:

Bolts are quenched and tempered to enhance strength and toughness.

Threading:

Standard threading is Unified National Coarse (UNC), unless specified otherwise.

Identification Markings:

A325 is stamped on the bolt head along with the manufacturer’s mark.

Type 1 or Type 3 variations may have additional markings to differentiate them.

Types

TYPE 1	Medium carbon, carbon boron, or medium carbon alloy steel.
TYPE 2	Withdrawn November 1991.
TYPE 3	Weathering steel.
T	Fully threaded A325. (Restricted to 4 times the diameter in length)
M	Metric A325.

What is the difference between ASTM A325 type 1 and type 3?

Feature	ASTM A325 Type 1	ASTM A325 Type 3
Material	Medium carbon steel, carbon boron steel, or medium carbon alloy steel	Weathering steel (corrosion-resistant steel)
Corrosion Resistance	Standard corrosion resistance; often requires galvanizing for protection	High corrosion resistance due to the formation of a protective oxide layer (similar to Corten steel)
Appearance	Silver/gray when galvanized or plain black	Reddish-brown patina due to weathering steel properties
Coating Options	Can be galvanized (hot-dip, mechanical, or electroplated)	Not recommended for galvanizing (it affects weathering properties)
Common Applications	General structural connections, bridges, buildings	Outdoor structures, bridges, exposed steel applications
Equivalent Material	Similar to ASTM A490 (high-strength bolts)	Similar to ASTM A588 (weathering steel)

ASTM A325 bolts are high-strength structural bolts commonly used in steel-to-steel connections in construction and infrastructure. The main difference between Type 1 and Type 3 lies in their material composition and corrosion resistance.

Which One Should You Use?

Use Type 1 if the bolts will be galvanized or painted for corrosion protection.

Use Type 3 if the bolts are in an outdoor environment where natural weathering is preferred over coating.

Connection type of ASTM A325 Bolts

SC	Slip critical connection.
X	Bearing-type connection with threads excluded from the shear plane.
N	Bearing type connection with threads included in the shear plane.

ASTM A325 Bolt Chemical Composition

Type 1 Bolts
Element	Carbon Steel	Carbon Boron Steel	Alloy Steel	Alloy Boron Steel
Carbon	0.30 – 0.52%	0.30 – 0.52%	0.30 – 0.52%	0.30 – 0.52%
Manganese, min	0.60%	0.60%	0.60%	0.60%
Phosphorus, max	0.04%	0.04%	0.04%	0.04%
Sulfur, max	0.05%	0.05%	0.04%	0.04%
Silicon	0.15-0.30%	0.10 – 0.30%	0.15 – 0.35%	0.15 – 0.35%
Boron		0.0005 – 0.003%		0.0005 – 0.003%
Alloying Elements			*	*

ASTM A325 Bolt Mechanical Properties

Size	Tensile, ksi	Yield, ksi	Elong. %, min	RA %, min
1⁄2 – 1	120 min	92 min	14	35
11⁄8 – 11⁄2	105 min	81 min	14	35

Recommended Nuts and Washers

Nuts			Washers
Type 1		Type 3	Type 1	Type 3
Plain	Galvanized	Plain
A563C, C3, D, DH, DH3	A563DH	A563C3, DH3	F436-1	F436-3

Note: Nuts conforming to A194 Grade 2H are a suitable substitute for use with A325 heavy hex structural bolts. The ASTM A563 Nut Compatibility Chart has a complete list of specifications.

ASTM A325 Bolt Dimensions

Bolt Diameter	D	F			C		H			T
	Body Diameter	Width Across Flats			Width Across Corners		Height			Thread Length
	Max	Basic	Max	Min	Max	Min	Basic	Max	Min	Basic
1⁄2	0.515	7⁄8	0.875	0.85	1.01	0.969	5⁄16	0.323	0.302	1
5⁄8	0.642	11⁄16	1.062	1.031	1.227	1.175	25⁄64	0.403	0.378	1.25
3⁄4	0.768	11⁄4	1.25	1.212	1.443	1.383	15⁄32	0.483	0.455	1.38
7⁄8	0.895	17⁄16	1.438	1.394	1.66	1.589	35⁄64	0.563	0.531	1.5
1	1.022	15⁄8	1.625	1.575	1.876	1.796	39⁄64	0.627	0.591	1.75
11⁄8	1.149	113⁄16	1.812	1.756	2.093	2.002	11⁄16	0.718	0.658	2
11⁄4	1.277	2	2	1.938	2.309	2.209	25⁄32	0.813	0.749	2
13⁄8	1.404	23⁄16	2.188	2.119	2.526	2.416	27⁄32	0.878	0.81	2.25
11⁄2	1.531	23⁄8	2.375	2.3	2.742	2.622	15⁄16	0.974	0.902	2.25

Tensile Load Requirements for Bolts Tested Full-Size

Bolt Size, Threads per Inch, and Series Designation		Tensile Load,B min, lbf	Proof Load,B Length Measure- ment Method	Alternative Proof Load,B Yield Strength Method
Column 1	Column 2	Column 3	Column 4	Column 5
1⁄2 –13 UNC	0.142	17050	12050	13050
5⁄8 –11 UNC	0.226	27100	19200	20800
3⁄4 –10 UNC	0.334	40100	28400	30700
7⁄8 –9 UNC	0.462	55450	39250	42500
1–8 UNC	0.606	72700	51500	55750
11⁄8 –7 UNC	0.763	80100	56450	61800
11⁄4 –7 UNC	0.969	101700	71700	78500
13⁄8 –6 UNC	1.155	121300	85450	93550
11⁄2 –6 UNC	1.405	147500	104000	113800

What is the difference between A325 and A490 bolts?

1. Comparison Table: A325 vs. A490

Feature	ASTM A325	ASTM A490
Material	Medium carbon steel, carbon boron steel, or medium carbon alloy steel	Alloy steel, quenched and tempered
Tensile Strength	120 ksi (for bolts ≤ 1” diameter)	150 ksi (higher strength)
Yield Strength	92 ksi	130 ksi
Coating (Galvanizing)	Can be hot-dip galvanized or mechanically galvanized	Cannot be galvanized (Risk of hydrogen embrittlement)
Corrosion Resistance	Requires coating for corrosion resistance	Limited (since galvanizing is not allowed)
Hardness	HRC 19-30	HRC 33-39 (harder steel)
Fully Threaded Options	Available as A325T	Available as A490T
Applications	General structural connections, bridges, steel frames	High-strength applications where extra load capacity is required
Replacement Standard	Now classified under ASTM F3125 Grade A325	Now classified under ASTM F3125 Grade A490

✅ Strength & Material:

A490 bolts are much stronger than A325 bolts due to their alloy steel composition and higher heat treatment levels.

A325 bolts are made of medium carbon steel and are slightly softer.

✅ Coating & Corrosion Resistance:

A325 bolts can be galvanized for corrosion resistance.

A490 bolts cannot be galvanized because the high-strength alloy steel is susceptible to hydrogen embrittlement, which can lead to cracking.

If corrosion resistance is needed for A490, a better alternative is weathering steel (A490 Type 3), which naturally develops a protective rust layer.

✅ Usage & Applications:

A325 bolts are commonly used for standard structural connections in buildings and bridges.

A490 bolts are preferred for high-strength applications where greater load-bearing capacity is required.

Are A325 bolts fully threaded?

No, ASTM A325 bolts are typically not fully threaded. They are partially threaded with a designated grip length (unthreaded portion) to provide maximum strength in structural connections.

However, fully threaded A325 bolts do exist but are classified under a different designation.

Standard Threading for A325 Bolts

Standard A325 Bolts (Partially Threaded)

Designed with a shank (unthreaded portion) to handle shear loads.

Commonly used in structural steel connections, where the unthreaded portion improves load-bearing capacity.

A325T (Fully Threaded)

The “T” suffix indicates a fully threaded version.

Used in applications where a full-thread design is necessary for clamping force rather than shear strength.

A325 Bolts in Shorter Lengths

For bolts ≤ 4 times the diameter, they may be fully threaded simply because of their short length.

You can get an offer for products in below material forms:

-Pipe and Tube (EN 10216-5, ASTM A213, ASTM A249, A312, A790,)

-Forged Fitting and Flange (ASTM A182 , ASTM A105,ASTM B564 )

-Butt Weld Fittings (ASTM A234, ASTM A403,ASTM A815)

-Round bar , Billet (ASTM A276, ASTM A479)

– Plate, Sheet, Strip(ASTM A240, EN 10028-7, A480)

-Bolting, Nuts（ASTM A193, A194, A320）

ASTM A325 Bolts Exported Countries

We Export ASTM A325 Bolts to Saudi Arabia, United Arab Emirates, Qatar, Bahrain, Oman, Kuwait, Turkey, Egypt, Yemen , Syria, Jordan, Cyprus, Singapore, Malaysia, Indonesia, Thailand, Vietnam, South Korea, Japan, Sri Lanka, Maldives, Bangladesh, Cambodia, Argentina, Bolivia, Brazil, Venezuela, Colombia, Ecuador, Guyana, Paraguay, Uruguay, United States Of America, Canada, Mexico, Panama, Jamaica, Bahamas, Denmark, Norway, Germany, France, Italy, United Kingdom, Spain, Belgium, Greece, Czech Republic, Portugal, Hungary, Albania, Austria, Finland, Ireland, Croatia, Malta, Nigeria, Algeria, Angola, South Africa, Libya, Egypt, Sudan, Europe, Africa, Asia, North America, South America, Middle East. etc

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