Duplex Steel S31803 Stud Bolts

Duplex steel S31803 stud bolts are high-strength fasteners used in heavy-duty industrial applications. This material is called 'duplex' because it has a dual-phase microstructure. It consists of roughly equal parts of ferrite and austenite. This specific balance gives the bolts better corrosion resistance than standard stainless steel, like 304 or 316. These stud bolts are commonly used in environments where chloride stress corrosion cracking is a risk. They provide a combination of high yield strength and good fatigue resistance.

Price of Duplex Steel S31803 Stud Bolts

The price of these fasteners changes frequently. Market rates for raw materials like nickel and chromium move up and down, which affects the final cost of the bolts.

Approx Price Range

Standard sizes will cost you anywhere between ₹1000 and ₹1500 per kilogram. Additional costs will apply for custom lengths and coatings. Small batches are always more expensive than bulk orders.

Price Per Unit / Kg

Buying by the kilogram is standard for large projects. For small maintenance jobs, you might buy per unit. A single M20 stud bolt might cost ₹85 to ₹250 as per the length and the nuts included.

Factors Affecting Price

The primary reason is the raw material cost. The Duplex Steel S31803 stud bolts price is directly impacted by the prices of molybdenum and nickel in the London Metal Exchange. Other factors include the thread precision, the type of finish required, and shipping costs from the factory.

Types of Duplex Steel S31803 Stud Bolts

There are several versions of these bolts designed for different connection types in piping and structural work.

S31803 Fully Threaded Stud Bolts
S31803 Tap End Stud Bolts
S31803 Double End Stud Bolts
S31803 Flange Studs
S31803 Custom Machined Studs

Specifications of Duplex Steel S31803 Stud Bolts

The table below shows Duplex Steel S31803 Stud Bolts specifications like standards, dimensions, sizes, etc.

Property	Details
Specifications	ASTM A479 / ASME SA479
Diameter	1/4"–3", Metric: M3 to M72 in length 2000 mm
Dimensions	DIN 975/976, ASME B18.2.1, B18.31.3, B16.5
DIN Standard	B.S. DIN 931, DIN 933, DIN 912, DIN 934, DIN 6923, DIN 603, DIN 7981, DIN 970, DIN 916, DIN 7982, DIN 7985, DIN 913
UTS	NPT, UNS, UNF, UNC, UNEF, NPTF
ISO	ISO 4033, ISO 4032, ISO 7380, ISO 4017, JIS standards
Threads	ASME B1.1 2A/3A – 2B/3B Inch Unified Threads and B1.13M 6h-6G Metric Coarse Threads
Type	Cold Forged, Hot Forged, Bar Stock Machined, Bar Stock Milling

Chemical Properties of Duplex Steel S31803 Stud Bolts

The chemical composition is what gives S31803 its strength. The high chromium content is particularly important for preventing rust in salty or acidic conditions.

Element	Composition
Carbon (C)	0.030 max
Manganese (Mn)	2.00 max
Silicon (Si)	1.00 max
Phosphorus (P)	0.030 max
Sulfur (S)	0.020 max
Chromium (Cr)	22.0 – 23.0
Molybdenum (Mo)	3.0 – 3.5
Nickel (Ni)	4.50 – 6.50
Nitrogen (N)	0.14 – 0.20
Iron (Fe)	63.72 min

Mechanical Properties Duplex Steel S31803 Stud Bolts

The table given below displays the mechanical strength of S31803 stud bolts.

Property	Value
Density	7.8 g/cm³
Melting Point	1350 °C (2460 °F)
Tensile Strength	Psi – 116000, MPa – 800
Yield Strength (0.2% Offset)	Psi – 80000, MPa – 550
Elongation	15%

Physical Properties Duplex Steel S31803 Stud Bolts

These properties are useful for engineers who need to calculate the weight of the assembly or how the bolt reacts to heat.

Property	Value
Density	7.8 g/cm³
Melting Point	1385 - 1440 °C
Thermal Conductivity	19.0 W/m-K (at 100°C)
Specific Heat	450 J/kg-K
Electrical Resistivity	0.80 µΩ-m

Dimension Chart Of Duplex Steel S31803 Stud Bolts

Dimensions follow ASME B18.31.2 or DIN 976 standards. The diameter and length are the two most important measurements you need to provide when ordering.

Nominal Diameter	Thread Pitch (Metric Coarse)	Nut Flat Width (Heavy Hex)
M12	1.75 mm	21 mm
M16	2.00 mm	27 mm
M20	2.50 mm	34 mm
M24	3.00 mm	41 mm
M30	3.50 mm	50 mm
M36	4.00 mm	60 mm

Size Chart of Duplex Steel S31803 Stud Bolts

We provide a wide range of sizes. Most suppliers keep standard metric sizes in stock, but imperial sizes for the oil and gas industry are also common.

Size (Inches)	Size (Metric Equivalent)
1/2"	~12.7 mm
5/8"	~15.8 mm
3/4"	~19.0 mm
1"	~25.4 mm
1 1/2"	~38.1 mm
2"	~50.8 mm

Torque Charts of Duplex Steel S31803 Stud Bolts

Correct torque is necessary to ensure the bolt doesn't loosen or snap. These values are estimates for bolts in "as-received" condition. Using lubricants will change these numbers significantly.

Bolt Size	Suggested Torque (Nm) - Unlubricated	Suggested Torque (Nm) - Lubricated
M12	85	60
M16	210	150
M20	410	290
M24	710	500
M30	1450	1000

Key Features of Duplex Steel S31803 Stud Bolts

These bolts are picked for specific reasons. They handle tough jobs that would ruin regular steel bolts quickly.

Pitting Resistance
High Strength
Stress Corrosion Resistance
Thermal Expansion
Erosion Resistance

Applications of Duplex Steel S31803 Stud Bolts

You will find these bolts in industries where failure is not an option, and the environment is harsh.

Oil and Gas
Chemical Processing
Desalination Plants
Marine Engineering
Paper and Pulp
Pollution Control

How to Choose the Right Duplex Steel S31803 Stud Bolts?

Selecting the right bolt is more than just picking a size. You have to think about where it is going and who is making it.

Supplier Selection Criteria

When looking at Duplex Steel S31803 stud bolts suppliers, check their history. Ask how long they have been working with duplex grades. It is harder to machine than regular steel, so experience matters. Make sure they can provide full traceability for the metal they use. If they cannot tell you which mill the steel came from, do not buy from them.

Technical Considerations

Consider the temperature. S31803 is usually good up to about 300°C. Above that, the metal can become brittle. Also, check the thread type. The metric is standard in Europe, but many oil and gas projects still use Imperial (UNC/UNF) threads.

Quality & Certification Check

Always ask for a Mill Test Certificate (MTC). This document proves that the chemical and mechanical properties match the standards. It should be an EN 10204 3.1 certificate at a minimum. For very critical jobs, you might want a 3.2 certificate, which involves an independent inspector.

Procurement Tips for Bulk Orders

If you are buying a lot, ask for a sample first. Check the fit of the nuts on the studs. They should be free to turn, but not loose. Also, watch for "galling" when the threads lock up on tightening. This can be avoided with a PTFE coating and may be worth the extra cost for large projects.