Properties

Below are the chemical and mechanical requirements per the ASTM A325 specification. In addition, you will find the estimated mechanical property requirements for each diameter of bolt required. One thing to note is that with the implementation of ASTM F3125 Grade A325, the mechanical properties differ slightly as indicated below.

A325 Chemical Properties

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 0.040% 0.040% 0.035% 0.035%
Sulfur, max 0.050% 0.050% 0.040% 0.040%
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 * *
* Steel, as defined by the American Iron and Steel Institute, shall be considered to be alloy when the maximum range given for the content of alloying elements exceeds one of more of the following limits: Manganese, 1.65%, silicon, 0.60%, copper, 0.60%, or in which a definite range or a minimum quantity of any of the following elements is specified or required within the limits of the recognized field of constructional alloy steels: aluminum, chromium up to 3.99%, cobalt, columbium, molybdenum, nickel, titanium, tungsten, vanadium, zirconium or any other alloying elements added to obtain a desired alloying effect.

A325 Mechanical Properties

Size Tensile, ksi Yield, ksi Elong. %, min RA %, min
12 - 1 120 min 92 min 14 35
118 - 112 105 min 81 min 14 35

Mechanical Requirements per Diameter

The minimum strength requirement of a specified grade of bolt is given in pounds per square inch (psi) or thousands of pounds per square inch (ksi). This works when analyzing what grade of material should be used for a given application, but this doesn’t tell us the actual or ultimate strength of that material for a specific diameter.  Below are the approximate minimum mechanical properties specific to a given diameter of A325 fastener.

Diameter Ultimate Yield, lbs. Ultimate Tensile, lbs.
12" 13,054 17,028
58" 20,792 27,120
34" 30,728 40,080
78" 42,504 55,440
1" 55,752 72,720
118" 61,803 80,115
114" 78,489 101,745
138" 93,555 121,275
112" 104,814 147,525

Mechanical Property Requirement Comparison Between A325 & F3125 Grade A325

Below is a chart comparing the mechanical property requirements for A325 versus F3125 Grade A325.  As you can see, the requirements are identical through 1” diameter, but beyond that, F3125 Grade A325 has a higher minimum strength requirement.

A325 Mechanical Properties
Size Tensile, ksi Yield, ksi Elong. %, min RA %, min
12 - 1 120 min 92 min 14 35
118 - 112 105 min 81 min 14 35
F3125 Grade A325 Mechanical Properties
Size Yield, ksi Tensile, ksi Elong. %, min RA %, min
12" - 112" 92 min 120 min 14 35

Ultimate Mechanical Property Comparison

Diameter A325 Ultimate Yield, lbs. F3125 A325 Ultimate Yield, lbs. A325 Ultimate Tensile, lbs. F3125 A325 Ultimate Tensile, lbs.
12" 13,054 13,054 17,028 17,028
58" 20,792 20,792 27,120 27,120
34" 30,728 30,728 40,080 40,080
78" 42,504 42,504 55,440 55,440
1" 55,752 55,752 72,720 72,720
118" 61,803 70,196 80,115 91,560
114" 78,489 89,148 101,745 116,280
138" 93,555 106,260 121,275 138,600
112" 104,814 129,260 147,525 168,600