What is 316H Stainless Steel Grade (UNS S31609)

Stainless steel is wide range amalgamations of ferrous and other alloying agents. It is composed of iron, carbon and chromium. It has stable passive layer of chromium oxide which protects it against corrosive agents. It has vast benefits and famous peculiarity of resisting corrosion. Stainless steel is an ideal choice for outdoor structures, water, and high temperature uses.

Its benefits include corrosion and heat resistance, strength, ductility, formability and weldability. Stainless steel requires less maintenance and it economical in long use.

Stainless steel is big family, comprises of multiple grades. The most common stainless steel grades are Ferritic, Austenitic, Martensitic, and Duplex stainless steel. Different grade are designed to enhance its qualities. The compositions of carbon and alloying agents vary with each grade.

Austenitic is the most commercial produced grade. It represents the grade 300 series. Grade 316 Stainless Steel is the second most commercial available grade after 304. It is the distinctive, molybdenum holding grade and provides resistance to a certain type of corrosive environment. Its core alloying elements are iron, chromium, nickel, and molybdenum. Molybdenum is the element that distinguishes Grade 316 from other grades. The presence of molybdenum significantly enhances corrosion resistance in the chloride exposed environment.

316H is a higher carbon version of grade 316 stainless steel. It is suitable for applications that required a higher temperature.

OVERVIEW

Grade 316H stainless steel is a higher carbon version of 316 stainless steel. This alloy can be used at elevated temperatures. Increased carbon content provides higher tensile and yields strength. The austenitic microstructure gives toughness even at cryogenic temperature. It offers moderate corrosion resistance in chloride environments. 316H is non-magnetic in nature. It cannot be hardened by heat treatment and can be easily welded and fabricated.

It is ideal for industrial boilers, heat exchangers, and pressure vessel at an elevated temperature at 500°C. 316H is widely used in the petrochemical and oil industry.

CHEMICAL COMPOSITION

316H is a high-carbon austenitic stainless steel derived from 316 with elevated carbon for better high-temperature strength.

Element	Range (%)
Carbon (C)	0.04–0.10
Chromium (Cr)	16.0–18.0
Nickel (Ni)	10.0–14.0
Molybdenum (Mo)	2.0–3.0
Manganese (Mn)	≤2.0
Silicon (Si)	≤0.75
Phosphorus (P)	≤0.045
Sulfur (S)	≤0.030
Iron (Fe)	Balance

MECHANICAL PROPERTIES

Property	Typical Value
Tensile Strength	≥ ~515 MPa
Yield Strength (0.2% offset)	≥ ~205 MPa
Elongation	≥ ~40 %
Hardness (HRB)	≤ ~95 HRB (~217 HB)
Modulus of Elasticity	~200 GPa

PHYSICAL PROPERTIES

Property	Value
Density	~7.98–8.00 g/cm³
Melting/Range	~1370–1400 °C
Electrical Resistivity	~74 µΩ·cm @ 20 °C
Thermal Conductivity	~16–21 W/m·K (varies with temp.)
Coefficient of Thermal Expansion	~16–18×10⁻⁶ /°C

MAGNETIC PROPERTIES

Grade 316H is austenitic stainless steel and non-magnetic in nature.

HEAT TREATMENT

Grade 316 H cannot be hardened by heat treatment. It can be hardened by cold working. 316H can be formed easily and cold working operations can enhance its strength and hardness.

CORROSION RESISTANCE

Grade 316H offers corrosion resistance comparable to grade 316 most of the time. Grade 316H provides corrosion resistance in sulfur and chloride containing environments. It also performs well in providing good corrosion resistance to pitting in phosphoric and acetic acids.

Grade 316H provides corrosion resistance in freshwater with high levels of chlorides. It is famous for providing excellent corrosion resistance in marine environments.

PRE (Pitting resistance equivalent) is 24
CPT (Corrosion pitting temperature) is 20±2
CCT (Critical crevice corrosion temperature) is <0

WELDABILITY

Grade 316 can be easily welded by standard processes. Post weld treatment is not required with Grade 316 H

MACHINABILITY

Grade 316H can undergo deformation during hardening and is prone to chip breaking. Better machinability can be obtained with slower speed, lubrication, and appropriate tooling.

APPLICATIONS

Grade 316H is broadly used in the following industries.

Petro-chemical industry:
Pressure vessels, tanks, heat exchangers, piping systems, flanges, valves, and pumps.
Oil industry
Chemical industry
Pharmaceutical industries
Food and beverage industry
Marine
Pulp and paper industry
Water treatments
Textiles