ASME SA240 304H Stainless Steel Plate | SA240 Type 304H

As a professional stainless steel plate supplier and China Mill-Direct Supply / Mill Direct Exporter, SHH STEEL is pleased to present ASME SA240 304H Stainless Steel Plate, also known as SA240 Type 304H.

ASME SA240 Type 304H is the higher-carbon version of the classic 18-8 austenitic stainless steel family. While standard Type 304 has a maximum carbon content of 0.08% and Type 304L is limited to 0.030%, Type 304H is deliberately specified with a carbon range of 0.04–0.10%. This controlled higher carbon content provides significantly improved strength at elevated temperatures, particularly in the range of 500°C to 800°C, making it the preferred choice for pressure vessels, boilers, heat exchangers and piping systems that operate continuously at high temperature.

The grade retains the fundamental advantages of the 300-series austenitic stainless steels: excellent toughness, good fabricability, non-magnetic behavior in the annealed condition, and reliable corrosion resistance in many oxidizing environments. However, the higher carbon level means that greater care must be taken regarding sensitization and intergranular corrosion when the material is exposed to the temperature range of approximately 450–850°C for prolonged periods.

SHH STEEL supplies ASME SA240 304H stainless steel plate as true Mill Direct Supply, sourcing directly from major Chinese stainless steel producers. This supply model enables competitive mill pricing, consistent quality, full traceability and shorter lead times. We offer thicknesses from 3 mm up to 100 mm (thicker plates available on request), widths up to 2000–3000 mm, and lengths up to 12000 mm or cut-to-length according to project requirements. Material can be supplied in the hot-rolled annealed and pickled condition (No.1 finish) or with additional surface processing as needed.

Because of its optimized high-temperature strength, ASME SA240 304H is frequently dual-certified or cross-referenced with ASTM A240 Type 304H and is widely accepted under the ASME Boiler and Pressure Vessel Code for elevated-temperature construction.

Chemical composition of ASME SA240 Type 304H is tightly controlled to balance high-temperature strength with adequate corrosion performance.

Heat Analysis (Ladle Analysis)

Product Analysis

The controlled carbon range of 0.04–0.10% is the most important distinction of Type 304H. This level of carbon provides the necessary solid-solution strengthening and contributes to improved creep and stress-rupture properties at elevated temperatures. At the same time, the carbon content remains low enough to allow the grade to be fabricated and welded with reasonable care.

Room-Temperature Mechanical Properties (Annealed Condition)

Elevated-Temperature Performance

ASME SA240 304H is specifically intended for service at elevated temperatures. The higher carbon content delivers noticeably better tensile and yield strength above approximately 500°C compared with Type 304L, and better long-term creep strength than both 304 and 304L. It is commonly used in the temperature range of 500–800°C where higher allowable stresses are required by the ASME Code.

Physical Properties

• Density: 7.93 g/cm³
• Melting Range: approximately 1400–1450°C
• Magnetic: Non-magnetic in the annealed condition

When the design temperature requires higher allowable stresses, ASME SA240 304H is often selected instead of 304 or 304L. For applications that combine high temperature with aggressive welding or cyclic thermal exposure, stabilized grades such as astm a240 type 321 stainless steel sheet plate or astm a240 type 347 stainless steel sheet plate may be preferred. For general welded service at lower temperatures, astm a240 type 304l stainless steel sheet plate remains the most economical and widely used option.

Japanese equivalents frequently requested include jis g4305 sus304 steel plate (closest standard grade) and related high-carbon variants when dual certification is needed.

The higher carbon content that gives ASME SA240 304H its elevated-temperature strength also increases its susceptibility to sensitization. When the material is held for extended periods between approximately 450°C and 850°C, chromium carbides can precipitate at grain boundaries, depleting the adjacent areas of chromium and reducing resistance to intergranular corrosion.

In continuous high-temperature service where the environment is not corrosive, this is usually not a problem. However, if the equipment will be exposed to corrosive media during shutdowns, start-ups, or in process streams that can attack sensitized material, additional precautions (stabilized grades, post-weld heat treatment, or careful temperature control) should be considered.

In the properly annealed condition, ASME SA240 304H offers corrosion resistance comparable to standard Type 304 in most atmospheric, fresh-water and oxidizing acid environments. It performs well in nitric acid and many organic compounds. Its resistance to pitting and crevice corrosion in chloride media is similar to that of 304 and inferior to molybdenum-bearing grades such as 316L.

Because of the higher carbon content, the risk of intergranular corrosion is greater than with 304L if the material is sensitized. For this reason, 304H is primarily selected for high-temperature mechanical strength rather than for maximum corrosion resistance in the as-welded condition.

ASME SA240 304H can be welded by all standard fusion and resistance welding methods. Matching filler metals (E308H / ER308H) are recommended when high-temperature strength of the weld metal is also required. Standard E308 / ER308 or E308L fillers are sometimes used when corrosion resistance of the weld is the primary concern.

Due to the higher carbon level, the heat-affected zone is more prone to sensitization than in 304L. For critical corrosive service after welding, post-weld solution annealing may be necessary. In many high-temperature non-corrosive applications, the material is used in the as-welded condition.

ASME SA240 304H is supplied in the solution-annealed condition. Proper heat treatment is essential to achieve optimum corrosion resistance, ductility and microstructure.

Solution Annealing Parameters

• Temperature range: 1050 – 1150°C (typically 1080 – 1120°C is used in practice)
• Holding (soaking) time: – For plates up to 25 mm thick: minimum 10–15 minutes at temperature after the entire section has reached the target temperature – For plates 25–50 mm thick: minimum 20–30 minutes – For plates above 50 mm: approximately 30–60 minutes or longer, depending on thickness and furnace loading, to ensure uniform temperature throughout the cross-section
• Cooling: Rapid cooling is mandatory. Water quenching is preferred for thicker plates to avoid re-precipitation of carbides. Accelerated air cooling may be acceptable for thinner sections.

The purpose of the relatively high annealing temperature and rapid cool is to dissolve any chromium carbides that may have formed and to retain carbon in solid solution, restoring maximum corrosion resistance and ductility.

Stress relieving, if required, should be performed outside the sensitization range or followed by full solution annealing when corrosion resistance is critical.

Dimensional tolerances for ASME SA240 304H plate follow ASME SA240 and the referenced ASTM A480 standards. Thickness, width, length and flatness tolerances are strictly controlled. Tighter tolerances can be arranged for specific project requirements.

Related grades that are often evaluated together with ASME SA240 304H include astm a240 type 304 stainless steel sheet plate, astm a240 type 304l stainless steel sheet plate, astm a240 type 321 stainless steel sheet plate and astm a240 type 347 stainless steel sheet plate.

ASME SA240 304H is specifically chosen for equipment that operates at elevated temperatures where higher allowable stresses are required:

SHH STEEL is a China Mill-Direct Supply and Mill Direct Exporter of stainless steel plate. We maintain long-term strategic relationships with major Chinese stainless steel mills and supply ASME SA240 304H with the following advantages:

• Competitive mill-direct pricing
• Consistent quality and complete heat traceability
• Full Mill Test Certificates (EN 10204 3.1 / ASME /EN 10204 3.2 )
• Flexible thickness, width and length combinations
• Professional export packaging and worldwide logistics support
• Technical assistance on material selection for high-temperature service

ASME SA240 304H Stainless Steel Plate (SA240 Type 304H) is the high-carbon austenitic grade optimized for elevated-temperature strength while retaining the fundamental corrosion resistance and fabricability of the 18-8 family. It is the material of choice when design conditions demand higher allowable stresses at temperatures above approximately 500°C.

As a professional China Mill-Direct Supply and Mill Direct Exporter, SHH STEEL provides reliable ASME SA240 304H plate with competitive pricing, full certification and complete technical support.

Contact SHH STEEL today for stock availability, detailed technical data or a competitive quotation for your high-temperature stainless steel requirements.

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