Stud Bolts for Flanges: Sizes Chart

Quick Reference

A stud bolt consists of a fully threaded rod + 2 heavy hex nuts. Common materials: ASTM A193 B7 (high-temp), A320 L7 (low-temp), A453 Gr.660 (high-temp alloy). Nuts: ASTM A194 2H. Sizes per ASME flange bolt chart.

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Need printable charts? Download the Stud Bolt Weight Chart or ASME B16.5 Bolt Dimensions as print-ready PDFs.

Stud Bolt for Flanges

What Is a Stud Bolt?

A stud bolt is a long rod threaded on both ends; the thread may extend along the complete length of the rod. Stud bolts carry tensile loads and serve as a key component in flanged connections throughout piping systems, where they join the flanges and maintain the seal.

Two hexagonal nuts thread onto opposite ends of the stud, applying compressive force to the flange faces. This compression holds the gasket in place and prevents leakage. Stud bolts are standard hardware in oil and gas, petrochemical, and construction applications wherever a secure bolted joint is required.

The threads on a stud bolt are compatible with standard nuts and follow established thread standards such as UNC (Unified Coarse), UNF (Unified Fine), or metric.

Stud bolts come in multiple diameter-and-length combinations, in both metric and imperial sizes. They are manufactured from carbon steel, stainless steel, alloy steel, and specialty alloys to match the service environment and mechanical loading. Common grades include ASTM A193 B7, L7, B8, B8M, B16, Alloy 20, Monel, Hastelloy, Inconel, 17-4PH, and titanium. All of these grades are discussed further in this article.

Selecting the right stud bolt for a given application depends on the required bolt strength, the flange and piping materials, environmental exposure, and the operating pressures and temperatures.

Stud Bolt: A Threaded Rod + 2 Hex Nuts

Key Takeaway: A stud bolt consists of one threaded steel rod (the stud) and two matching hexagonal heavy steel nuts which are tightened on the stud to execute the sealing of the main & companion flanges (the hex nuts). Stud bolts and nuts are standard components of flanged joints for piping systems and shall be purchased together.

Nuts for stud bolts thread onto the ends of the rod to clamp two flanges together. Working in tandem with the stud, they compress the gasket between the flange faces to create a pressure-tight seal.

The ASME B16.5 specification covers stud bolts and nuts for ASME flanges. The flange bolt chart and bolt size chart provides the number, diameter, and length of required stud bolts by flange diameter, pressure class, and face finish (RF, FF, RTJ). This bolt dimensions chart is required for proper flange bolting.

The Threaded Rod

A stud is a threaded rod that is inserted into the holes of the mating flanges and then tightened, at both ends, by applying a specific torque to the steel nuts.

Stud bolt length (OAL/FTF)

In the context of stud bolts, “OAL” stands for “Overall Length,” which is the total length of the stud bolt from end to end. On the other hand, “FTF” stands for “First-to-First,” referring to the length measured from the first full thread on one end to the first full thread on the opposite end, excluding the points.

Measurement	Description	Use
OAL (Overall Length)	Total length from end to end, including unthreaded portions and threads	Specifying manufacturing length; ensuring bolt fits entire assembly (flanges, gaskets, washers, nuts)
FTF (First-to-First)	Length from first full thread on one end to first full thread on the other, excluding points	Ensuring proper thread engagement with nuts; standard stud length measurement for piping (FTF = OAL minus 1/4 inch)

When specifying stud bolts for flange connections, both OAL and FTF matter. The OAL confirms the bolt is long enough to span all components, while the FTF measurement verifies proper thread engagement for a secure assembly.

In piping system assembly, accurate stud bolt length measurement is critical to structural integrity and leak-tightness, especially in pressurized systems. Always refer to engineering standards or specifications to determine the appropriate lengths for specific flange sizes and pressure ratings.

Flanges of different diameters and ratings require studs of different lengths and diameters.

Stud bolt “thread pitch” and “thread series”

Studs are threaded according to the specifications set forth by the ASME B1.1 specification.

Thread Pitch:

Thread pitch is the distance between consecutive thread peaks, measured in millimeters or threads per inch (TPI) in the imperial system. A pitch of 1.5 mm means each thread is 1.5 mm apart from the next. In imperial terms, 13 TPI means each thread peak is 1/13th of an inch apart.

The most widely used thread pitch is the symmetrical V-profile type (60-degree angle), because it is easier for the manufacturer to inspect than non-symmetrical profiles.

Thread Series:

Thread series relate to the diameter and pitch combinations, measured by the number of threads per inch (“TPI”) applied to a single diameter:

Thread Series	Designation	Description
Coarse	UNC/UNRC	Most common for screws, bolts, and nuts. Used for low-strength materials (iron, mild steel, copper, aluminum). Tolerant of adverse conditions; quick assembly
Fine	UNF/UNRF	Precision duties; higher tensile strength than coarse thread series
8-Thread	8UN	Elective threading for ASTM A193 B7, A193 B8/B8M, and A320. Used for diameters 1” and above (8 TPI for all sizes)

Stud bolts covered by the ASTM A193 or A320 Specifications use 8UN for all diameters 1” and above, which means that there are 8 threads per inch for these sizes. For any other material grade, the buyer shall specify the thread pitch unless it is given by the applicable ASTM norm.

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Selection of thread pitch/series:

When selecting a stud bolt, choose the thread pitch and series that best match the mechanical and environmental requirements of the application, as well as the nuts that will be used with the bolt. Specifications will often refer to both the diameter and the TPI for imperial measurements (like 1/2”-13 for a 1/2 inch diameter bolt with 13 TPI UNC threads), or the diameter and pitch in millimeters for metric measurements (like M12 x 1.75 for a 12 mm diameter bolt with a 1.75 mm pitch).

Pro Tip

Always order 10-15% extra stud bolts per flange. On-site, threads get damaged during handling, nuts cross-thread, or bolts get lost. Running short during mechanical completion delays the whole project.

The key factors in thread pitch and series selection are:

Factor	UNC (Coarse)	UNF (Fine)
Tensile strength	Lower (smaller stress area)	Higher (larger stress area)
Vibration resistance	Lower; may loosen under vibration	Higher; finer pitch resists loosening
Ease of assembly	Easier; less likely to cross-thread, more durable in dirty or rough conditions	Harder; requires cleaner threads and more care
Thin-wall threading	May strip thin materials	Better thread engagement in thinner sections
Typical use	General industrial bolting, flanges, structural connections	Aerospace, military, precision machinery

Hex Nuts for Stud Bolts

To fasten a stud bolt, two heavy hex steel nuts are threaded onto opposite ends of the rod. The stud and the steel nuts join through friction between their respective threads, by a slight stretching of the bolt, and the compression of the two joined parts.

Function of hex nuts in a flanged joint:

When tightened, the nuts apply compressive force to the flanges, clamping them together and compressing the gasket to prevent leaks. They simultaneously create tension in the stud bolt, which reinforces the structural integrity of the sealed joint.

Features of hex nuts:

Feature	Description
Shape	Hexagonal (six-sided), providing multiple wrench engagement angles for tightening or loosening
Material	Typically the same alloy as the stud bolt (carbon steel, stainless steel, or alloy steel) for uniform thermal expansion and to prevent galvanic corrosion
Threading	Internal threads must match the thread type and size of the stud bolt for a proper fit

Nut types used in bolted flange joints:

Type	Application
Heavy hex nuts	Thicker and wider than standard hex nuts, with a larger contact surface. This is the standard type used with studs in flange connections
Lock nuts	Used in high-vibration environments to prevent loosening
Jam nuts	Used in tandem with standard nuts to lock the bolt’s position

In the past, steel nuts for stud bolts had a squared head. Today, the hexagonal head shape (six sides instead of four) has fully replaced the older design because it allows quicker and more effective tightening.

Standards:

Nuts conform to standards that govern their size, thread pitch, and material properties:

Standard	Scope
ISO	International dimensions and tolerances
ASME	American standards, common in industrial applications
DIN	German standards, widely used in Europe

The material of the hex steel nuts shall match the material of the threaded rod (generally, stud materials ASTM A193 match with nuts materials ASTM A194).

Nuts for petrochemical applications are tightened to a specific torque using special torque wrenches. The mechanical strength of the steel nut material shall be compatible with the strength of the mated bolt.

Field Note

Never mix imperial and metric stud bolts on the same flange - even if they “seem to fit.” Thread engagement will be partial, and under pressure, the joint will leak or fail. Check the thread marking before installation.

The dimensions and weights of heavy steel nuts for stud bolts are covered by the ASME B18.2.2 specification.

Difference Between “Stud” vs. “Bolt”

A common question is: what is the difference between the concepts “stud” vs. “bolt”?

Stud

A stud is a fully threaded metal rod that requires two heavy hexagonal nuts to be tightened. Unlike a bolt, it has no head. One end installs into a tapped hole while the opposite end receives a nut, a configuration common where one of the joined components is permanently fitted with a tapped hole.

Studs are the standard choice for mounting engines, large equipment, and piping systems where space constraints make headed bolts impractical. They also provide more uniform tensioning across the joint because they are less prone to over-torquing than headed bolts. For these reasons, studs are preferred in applications that do not require frequent disassembly.

A bolt:

A bolt is a threaded fastener with a head. It passes through holes in all the assembled parts and is tightened by torquing the head, typically with a nut (and often a washer) on the other end. Bolts are versatile and well-suited for connections that require regular assembly and disassembly. However, they are more susceptible to loosening under vibration unless lock washers or other retention methods are used.

Stud Bolt Materials (Threaded Rod)

The most common materials for the threaded rod of stud bolts are ASTM A193 (grade B7, B8, B8M, B8T), ASTM A453 (grade 660), ASTM A320 (grade L7, L7M), and ASTM A182 (duplex and super duplex bolting). For aggressive fluids and environments, stud bolts can be coated with Xylan, Xylar, and other materials.

Below are the most common grades for the rod of a stud bolt assembly (the materials for the hex nuts are examined in a separate article).

ASTM A193 (High-Temp. Service)

The ASTM A193 specification covers low-alloy steel and stainless steel stud bolt materials for high-temperature or high-pressure service.

ASTM A193 stud bolts are available in national coarse (UNC) thread pitches, generally used in traditional applications, which means that there are 8 threads per inch (“thread per inch”) for rod diameters above 1 inch.

The main grades covered by the ASTM A193 specification are:

• ASTM A193 B7: a chromium-molybdenum alloy steel, the most common choice for high-strength applications such as pressure vessels and flanges in the oil and gas industry.
• ASTM A193 B8/B8M: stainless steel grades. B8 is 304 stainless steel and B8M is 316 stainless steel. Both provide corrosion resistance for environments with chemical or moisture exposure.
• ASTM A193 Grade B6: 410 stainless steel, heat-treated, used where both high strength and moderate corrosion resistance are needed.
• ASTM A193 Grade B7M: similar to B7 but with controlled hardness, specified where resistance to stress corrosion cracking (SCC) is required.
• ASTM A193 Grade B8C/B8T/B8R: stainless steel grades with different compositions: 347 (B8C), 321 (B8T), and Alloy 20 (B8R), all specified for corrosive service.

threaded stud boltThe most common stud bolts materials covered by ASTM A193 are:

• ASTM A193 B5
• ASTM A193 B6
• ASTM A193 B7: Alloy steel, AISI 4140/4142 quenched and tempered
• ASTM A193 B7M
• ASTM A193 B16
• ASTM A193 B8: Class 1 Stainless steel, AISI 304, carbide solution treated.
• ASTM A193 B8A
• ASTM A193 B8M: Class 1 Stainless steel, AISI 316, carbide solution treated.
• ASTM A193 B8MA
• ASTM A193 B8T (SS 321)
• ASTM A193 B8cl2: Class 2 Stainless steel, AISI 304, carbide solution treated, strain hardened
• ASTM A193 B8Tcl2
• ASTM A193 B8Mcl2: Class 2 Stainless steel, AISI 316, carbide solution treated, strain hardened

ASTM A193: Chemical Composition

Physical Element	ASTM A193 grade B7 (AISI 4140)	ASTM A193 grade B8 (AISI 304)	ASTM A193 grade B8M (AISI 316)
Carbon	0.38 - 0.48%	0.08% max	0.08% max
Manganese	0.75 - 1.00%	2.00% max	2.00% max
Phosphorus, max	0.035%	0.045%	0.045%
Sulfur, max	0.040%	0.030%	0.030%
Silicon	0.15 - 0.35%	1.00% max	1.00% max
Chromium	0.80 - 1.10%	18.0 - 20.0%	16.0 - 18.0%
Nickel	absent	8.0 - 11.0%	10.0 - 14.0%
Molybdenum	0.15 - 0.25%	absent	2.00 - 3.00%

ASTM A193: Mechanical Properties

Grade	Size	Tensile (ksi min)	Yield (ksi min)	Elong. (% min)	RA (% min)	Max HBW	Max HRC
A193 B7	Up to 2-1/2	125	105	16	50	321	35
A193 B7	2-5/8 to 4	115	95	16	50	321	35
A193 B7	4-1/8 to 7	100	75	18	50	321	35
A193 B8 Class 1	All	75	30	30	50	223	35
A193 B8M Class 1	All	75	30	30	50	223	96
A193 B8 Class 2	Up to 3/4	125	100	12	35	321	35
A193 B8 Class 2	7/8 to 1	115	80	15	35	321	35
A193 B8 Class 2	1-1/8 to 1-1/4	105	65	20	35	321	35
A193 B8 Class 2	1-3/8 to 1-1/2	100	50	28	45	321	35
A193 B8M Class 2	Up to 3/4	110	95	15	45	321	35
A193 B8M Class 2	7/8 to 1	100	80	20	45	321	35
A193 B8M Class 2	1-1/8 to 1-1/4	95	65	25	45	321	35
A193 B8M Class 2	1-3/8 to 1-1/2	90	50	30	45	321	35

The threaded stud and hex nut materials should be compatible. The following table shows bolting material selection based on process working temperature:

Material	Min Temp °C (°F)	Max Temp °C (°F)
Carbon Steel	-29 (-20)	300 (572)
A193 B7, L7	-73 (-100)	400 (752)
A193 B6	0 (32)	500 (932)
A193 B8	-200 (-325)	575 (1067)
A193 B16	0 (32)	520 (968)
A193 B17B	-29 (-20)	650 (1202)
A913 Inconel 718	0 (32)	750 (1382)
A453 Gr. 660	-29 (-20)	538 (1000)

Stud bolts can be produced also with “dual certification,” i.e. they conform to multiple sets of ASTM standards (A193 B7 stud bolts can meet the requirements of A320 L7; B8 and B8m stud bolts also typically conform to both A193 and A320).

Common Mistake

Using standard A193 B7 bolts in sour service without checking hardness. NACE MR0175 requires B7M with max 22 HRC hardness. Standard B7 (up to 35 HRC) will crack in H₂S environments - this is a safety-critical error.

ASTM A453 (High-Temp.)

The ASTM A453 specification covers standards for Grade 660 (Class A, B, C, and D), Grade 651 (Class A and B), Grade 662 (Class A and B), and Grade 665 (Class A and B) of bolting materials, with ten classes of yield strength ranging from 50 to 120 KSI [345 to 827 MPa], for use in high-temperature service such as fasteners, pressure vessels and flanges.

Bolting materials in ASTM A453 are covered rolled, forged, or hot-extruded bars, and also bolts, nuts, screws, washers, studs, and stud bolts. Materials shall adhere to specified contents of carbon, manganese, phosphorus, sulfur, silicon, nickel, chromium, molybdenum, tungsten, titanium, columbium, aluminum, vanadium, boron, and copper.

According to ASTM A453, materials shall be subjected to tension, stress-rupture, and hardness tests. Materials shall conform to yield strength, tensile strength, elongation, reduction of area, Brinell hardness, and Rockwell hardness requirements.

Hardening and solution treatment requirements for each material class are also given. The most common grades under ASTM A453 are:

• ASTM A453 660A
• ASTM A453 660B
• ASTM A453 660C
• ASTM A453 660D

ASTM A453 Chemical Composition

Element (%)	Grade 660	Grade 651	Grade 662	Grade 665	Grade 668
Carbon	0.08 max	0.28-0.35	0.08 max	0.08 max	0.08 max
Manganese	2.00 max	0.75-1.5	0.40-1.00	1.25-2.00	2.00 max
Phosphorus	0.040 max	0.040 max	0.040 max	0.040 max	0.040 max
Sulfur	0.030 max	0.030 max	0.030 max	0.030 max	0.030 max
Silicon	1.00 max	0.30-0.80	0.40-1.00	0.1-0.80	1.00 max
Nickel	24.0-27.0	8.0-11.0	24.0-28.0	24.0-28.0	17.5-21.5
Chromium	13.5-16.0	18.0-21.0	12.0-15.0	12.0-15.0	13.5-16.0
Molybdenum	1.00-1.50	1.00-1.75	2.0-3.50	1.25-2.25	1.50 max
Tungsten	-	1.00-1.75	-	-	-
Titanium	1.9-2.35	0.1-0.35	1.80-2.10	2.70-3.30	2.20-2.80
Columbium	-	0.25-0.6	-	-	-
Aluminum	0.35 max	-	0.35 max	0.25 max	0.50 max
Vanadium	0.10-0.50	-	-	-	0.50 max
Boron	0.001-0.010	-	0.001-0.010	0.01-0.07	0.001-0.010
Copper	-	0.50 max	0.50 max	0.25 max	-

ASTM A453: Mechanical Properties

Grade	Class	Tensile (MPa)	Yield (MPa)	Elong. (% min)	RA (% min)
Grade 660	A, B, & C	895 min	585 min	15	18
Grade 660	D	895 min	725 min	15	18
Grade 651	A	690 min	485 min	18	35
Grade 651	B	655 min	415 min	18	35
Grade 662	A	895 min	585 min	15	18
Grade 662	B	860 min	550 min	15	18
Grade 665	A	1170 min	830 min	12	15
Grade 665	B	1070 min	830 min	12	15
Grade 668	A & B	895 min	585 min	15	18

ASTM A453: Heat Treatment Requirements

Grade	Class	Solution Treatment	Hardening Treatment
660	A	1650 +/- 25 °F [900 +/-14 °C], hold 2h min, liquid quench	1325 +/- 25 °F [720 +/- 14 °C] 16h, air cool
660	B	1800 +/- 25 °F [980 +/-14 °C], hold 1h min, liquid quench	1325 +/- 25 °F [720 +/- 14 °C] 16h, air cool
660	C	1800 +/- 25 °F [980 +/-14 °C], hold 1h min, oil quench	1425 +/- 25 °F [775 +/- 14 °C] 16h, air cool then 1200 +/- 25 °F [650 +/- 14 °C] 16h, air cool
660	D	1650 +/- 25 °F [900 +/-14 °C], hold 2h min, liquid quench or 1800 +/- 25 °F [980 +/-14 °C], hold 1h min, liquid quench	1325 +/- 25 °F [720 +/- 14 °C] 16h, air cool then 1200 +/- 25 °F [650 +/- 14 °C] 16h, air cool
651	A	-	Hot-cold worked at 1200 °F [650 °C] min, 15% min reduction, stress-relief anneal at 1200 °F [650 °C] min, 4h min
651	B	-	Hot-cold worked at 1200 °F [650 °C] min, 15% min reduction, stress-relief anneal at 1350 °F [730 °C] min, 4h min
662	A	1800 +/- 25 °F [980 +/-14 °C], hold 1h min, liquid quench	1350-1400 °F [730-760 °C] 20h, furnace cool to 1200 +/- 25 °F [650 +/- 14 °C] 20h, air cool
662	B	1950 +/- 25 °F [1065 +/-14 °C], hold 2h min, liquid quench	1350-1400 °F [730-760 °C] 20h, furnace cool to 1200 +/- 25 °F [650 +/- 14 °C] 20h, air cool
665	A	1800 +/- 25 °F [980 +/-14 °C], hold 3h min, liquid quench	1350-1400 °F [730-760 °C] 20h, furnace cool to 1200 +/- 25 °F [650 +/- 14 °C] 20h, air cool
665	B	2000 +/- 25 °F [1095 +/-14 °C], hold 3h min, liquid quench	1350-1400 °F [730-760 °C] 20h, furnace cool to 1200 +/- 25 °F [650 +/- 14 °C] 20h, air cool
668	A	1650 +/- 25 °F [900 +/-14 °C], hold 2h min, liquid quench	1325 +/- 25 °F [720 +/- 14 °C] 16h, air cool
668	B	1800 +/- 25 °F [980 +/-14 °C], hold 1h min, liquid quench	1325 +/- 25 °F [720 +/- 14 °C] 16h, air cool

A453: Time to Rupture and Elongation

Grade	Class	Test Temp °F [°C]	Stress (ksi)	Stress (MPa)	Time to Rupture (h min)	Elong. (% min)
660	A, B & C	1200 [650]	56	385	100	5
651	A & B	1200 [650]	40	275	100	5
662	A & B	1200 [650]	55	380	100	5
665	A	1200 [650]	75	515	100	3
665	B	1200 [650]	70	485	100	5

ASTM A320 (Low-Temp.)

The ASTM A320 specification covers alloy steel and stainless steel stud bolt materials for low-temperature service.

Each alloy under ASTM A320 shall conform to prescribed chemical requirements. The material, as represented by the tension specimens, shall conform to specific requirements in terms of tensile strength, yield strength, elongation, and hardness. The stud bolt material shall meet the prescribed impact energy absorption requirements and the target test temperature.

According to the ASTM A320 specification, manufacturers shall execute at least the following mechanical tests on the material: impact test, tension test, and hardness test.

The most common stud bolt materials under ASTM A320 are listed below (low-temperature service):

• ASTM A320 L7: Alloy steel, AISI 4140/4142 Quenched and tempered
• ASTM A320 L7M
• ASTM A320 L43: Alloy steel, AISI 4340 Quenched and tempered
• ASTM A320 B8 Class 1: Stainless steel, AISI 304, carbide solution treated
• ASTM A320 B8A
• ASTM A320 B8T
• ASTM A320 B8TA
• ASTM A320 B8C
• ASTM A320 B8M: Class 1 Stainless steel, AISI 316, carbide solution treated
• ASTM A320 B8MA
• ASTM A320 B8cl2: Stainless steel, AISI 304, carbide solution treated, strain hardened
• ASTM A320 B8Mcl2: Stainless steel, AISI 316, carbide solution treated, strain hardened

ASTM A320: Mechanical Properties

Grade	Diameter	Tensile (ksi min)	Yield (ksi min)	Charpy Impact @ Temp	Elong. (% min)	RA (% min)
A320 L7	Up to 2-1/2	125	105	20 ft-lbf @ -150°F	16	50
A320 L43	Up to 4	125	105	20 ft-lbf @ -150°F	16	50
A320 B8 Class 1	All	75	30	N/A	30	50
A320 B8M Class 1	All	75	30	N/A	30	50
A320 B8 Class 2	Up to 3/4	125	100	N/A	12	35
A320 B8 Class 2	7/8 to 1	115	80	N/A	15	35
A320 B8 Class 2	1-1/8 to 1-1/4	105	65	N/A	20	35
A320 B8 Class 2	1-3/8 to 1-1/2	100	50	N/A	28	45
A320 B8M Class 2	Up to 3/4	110	95	N/A	15	45
A320 B8M Class 2	7/8 to 1	100	80	N/A	20	45
A320 B8M Class 2	1-1/8 to 1-1/4	95	65	N/A	25	45
A320 B8M Class 2	1-3/8 to 1-1/2	90	50	N/A	30	45

ASTM A182 (Duplex and Super Duplex)

Duplex Steel Grade

Chemical Composition:

Grade	C	Mn	Si	P	S	Cr	Mo	Ni	N
Duplex 2205 (S31803)	0.03 max	2.0 max	1.0 max	0.03 max	0.02 max	21.0-23.0	2.5-3.5	4.5-6.5	0.08-0.20
Duplex 2205 (S32205)	0.03 max	2.0 max	1.0 max	0.03 max	0.02 max	22.0-23.0	3.0-3.5	4.5-6.5	0.14-0.20

Mechanical Properties:

Grade	Tensile Strength (ksi min)	Yield Strength 0.2% (ksi min)	Elongation (%)	Hardness (HB max)
2205	90	65	25	217

Physical Properties:

Temperature	Density (lbm/in³)	Thermal Conductivity (BTU/hr·ft·°F)	Heat Capacity (BTU/lbm·°F)	Electrical Resistivity (in x 10⁻⁶)
68°F	0.278	8.7	0.112	27.6
212°F	-	9.2	0.119	26.1
392°F	-	9.8	0.127	25.4
572°F	-	10.4	0.134	24.9

Super Duplex Grade

Chemical Composition:

Element	C	Cr	Ni	Mo	N	S
%	0.02	25	7	4	0.27	0.001

Mechanical Properties:

Property	Value
Ultimate Tensile Strength (ksi)	116 min
0.2% Offset Yield Strength (ksi)	80 min
0.1% Offset Yield Strength (ksi)	91 min
Elongation in 2 inches (%)	15 min
Hardness (Rockwell C)	32 max
Impact Energy (ft-lbs)	74 min

Physical Properties:

Property	Unit	Value
Density	lb/in³	0.28
Modulus of Elasticity	psi x 10⁶	29
Coefficient of Thermal Expansion (68-212°F)	x10⁻⁶/°F	7.2
Thermal Conductivity	BTU/h·ft·°F	8.7
Heat Capacity	BTU/lb·°F	0.12
Electrical Resistivity	Ω-in x 10⁻⁶	31.5

Coatings for Stud Bolts

Coating materials for stud bolts enhance corrosion resistance, reduce galling risk, and in some cases provide electrical insulation or color-coding for traceability.

The following coatings are commonly used on stud bolts:

1. Zinc Coatings

Zinc coatings come in three main forms. Electroplated zinc offers baseline corrosion resistance but can cause hydrogen embrittlement in high-strength steels. Hot-dip galvanizing (where bolts are dipped into molten zinc) produces a thicker, more durable protective layer. Zinc flake coatings (Dacromet, Geomet) provide corrosion protection in a thin layer without the hydrogen embrittlement risk.

2. Cadmium Coatings

Cadmium provides excellent corrosion resistance and natural lubricity. However, its toxicity has led to widespread restrictions, and it is increasingly replaced by zinc-nickel and other alternatives.

3. PTFE (Polytetrafluoroethylene) Coatings (Teflon)

PTFE provides excellent chemical resistance and low friction, reducing the torque required during tightening and preventing galling between mating threads.

4. Phosphate Coatings

Phosphate coatings serve as a primer for painting or as temporary corrosion protection. They also reduce friction during tightening.

5. Chromium Coatings

Electroplated chromium offers hardness and corrosion resistance but is relatively rare on stud bolts due to cost. Chromium overlays are sometimes specified for severely corrosive environments, though they remain less common than zinc-based coatings.

6. Nickel Coatings

Electroplated nickel provides good corrosion resistance and performs well in high-temperature service. Nickel-alloy coatings (nickel-cobalt, nickel-iron) offer enhanced properties for specific environments.

7. Aluminum Coatings

Applied through aluminizing processes, these coatings provide high-temperature oxidation resistance.

8. Ceramic Coatings

Ceramic coatings offer high-temperature resistance and are sometimes used in exhaust systems and similar thermal applications.

9. Silver Coatings

Silver is used in high-temperature and anti-galling applications. It has excellent conductivity and lubricity.

10. Molybdenum Disulfide Coatings

Molybdenum disulfide acts as a lubricant coating that withstands high pressures and helps prevent galling during tightening.

11. Epoxy Coatings

Epoxy provides durable, corrosion-resistant protection and can also serve as color coding for material identification.

12. Xylan 1070/1024 & Xylar 1

Xylan and Xylar coatings for stud bolts have multiple advantages:

• Lower frictions vs. uncoated bolts (CoF is as low as 0.02)

• Increased wear resistance for the bolt even under extreme pressures.

• Strong corrosion and chemical resistance in most demanding environments

• Increased resistance to adverse weather conditions (such as extreme sunlight, salt-water exposure to chemicals)

• Wider operating range in terms of temperature (from -420° to +550°F, i.e. -250° to 285°C).

• Color coding for easier traceability

• Pliability: Xylan coatings bend easily and repeatedly and do not break

• Machinability: multiple Xylan coatings can be applied to the stud bolts

• Strong adhesion to bolting materials

Stud Bolts Coating Selection Considerations:

When choosing a coating, evaluate the following factors:

Factor	Consideration
Corrosion environment	Presence of moisture, salts, chemicals, and the required service life of the bolt in that environment
Temperature	High-temperature applications narrow the range of viable coatings
Friction and galling	Some coatings reduce friction and prevent galling, particularly important for stainless steel fasteners
Electrical properties	Some applications require non-conductive or conductive coatings
Regulatory compliance	Environmental regulations may restrict certain materials such as cadmium or lead

Stud Bolts and Nuts Material Selection

The material to use for stud bolts depends on multiple factors, the main ones are the material of the flanges and the pipeline design temperature:

DESIGNTEMPERATURE	FLANGE MATERIAL	STUD BOLT	HEAVY HEX STEEL NUTS
-195° to 102°C	ASTM A 182 Gr. F304, F304L, F316, F316L, F321, F347	A320 Gr. B8 Class 2	A194 Gr. 8A
-101° to -47°C	ASTM A 350 Gr. LF3	A 320 Gr. L7	A 194 Gr. 7
-46° to -30°C	ASTM A 350 Gr. LF2	A 320 Gr. L7	A 194 Gr. 7
-29° to 427°C	ASTM A 105	A 193 Gr. B7	A 194 Gr. 2H
428° to 537°C	ASTM A 182 Gr. F11, F22	A 193 Gr. B16	A 194 Gr. 2H
538° to 648°C	ASTM A182 Gr. F11, F22	A 193 Gr. B8 Class 1	A 194 Gr. 8A
649° to 815°C	ASTM A182 Gr. F304 H, F316 H	A 193 Gr. B8M Class 1	A 194 Gr. 8A