SS 440C — Stainless Steel (SS) Grade Specification, Properties & Equivalents

SS 440C stainless steel is a high-carbon, high-chromium martensitic stainless steel renowned for its exceptional hardness, strength, and wear resistance after heat treatment. Widely utilized in demanding applications across India, SS 440C finds its niche in industries requiring superior performance under abrasive conditions. Its unique combination of properties makes it a preferred choice for manufacturing critical components such as ball bearings, valve seats, pump shafts, surgical instruments, and high-quality cutting tools. Procurement engineers and QC professionals in India value SS 440C for its predictable performance and durability. The Indian market, with key suppliers in major industrial hubs like Mumbai, Pune, and Chennai, ensures reliable availability of SS 440C for various project scales, from small fabrications to large-scale industrial productions. Understanding the specific attributes of SS 440C is crucial for maximizing its potential in diverse engineering challenges.

Chemical Composition of SS 440C

SS 440C Stainless Steel Chemical Composition

Element	Per ASTM A276	Per SS 440C
Carbon (C)	0.95 - 1.20 %	1.07 %
Manganese (Mn)	1.00 % max	0.45 %
Silicon (Si)	1.00 % max	0.30 %
Chromium (Cr)	16.00 - 18.00 %	17.20 %
Molybdenum (Mo)	0.75 % max	0.40 %
Phosphorus (P)	0.040 % max	0.025 %
Sulfur (S)	0.030 % max	0.015 %

Mechanical Properties of SS 440C

SS 440C Stainless Steel Mechanical Properties (Hardened & Tempered Condition)

Property	Value (Typical)	Standard Reference
Ultimate Tensile Strength (UTS)	1500 - 2000 MPa	ASTM A276 / A582
Yield Strength (YS) @ 0.2% Offset	1300 - 1800 MPa	ASTM A276 / A582
Elongation at Break	8 - 15 %	ASTM A276 / A582
Hardness (HRC)	54 - 62	ASTM A276 / A582
Modulus of Elasticity	190 - 200 GPa	General Data
Density	~7.75 - 7.85 g/cm³	General Data

SS 440C Stainless Steel Available Forms in India

Shape	Typical Sizes	Standard Length/Form
Round Bars	5 mm to 100 mm diameter	3-6 meters (custom lengths available)
Wire Rod	0.5 mm to 10 mm diameter	Coils / Spools
Sheet & Plate	0.5 mm to 50 mm thickness	1m x 2m, 1.2m x 2.4m (cut to size)
Forgings	Custom diameters and shapes	As per order

SS 440C Stainless Steel Real-world Applications

Bearings: High-precision ball and roller bearings requiring extreme hardness and wear resistance.
Valves: Valve seats, balls, and stems in corrosive or abrasive environments.
Cutting Tools: High-quality knives, surgical scalpels, and industrial blades demanding superior edge retention.
Pump Components: Shafts, impellers, and wear rings subjected to friction and corrosion.
Aerospace: Components requiring high strength and resistance to wear.
Food Processing: Equipment parts needing hardness and corrosion resistance.
Textile Machinery: Components exposed to abrasive fibers.
Injection Molds: Components benefiting from wear resistance and polishability.

SS 440C Stainless Steel Machinability & Weldability

Machining SS 440C requires careful consideration due to its high carbon content and tendency to harden. In the annealed condition, SS 440C is readily machinable, but once hardened, it becomes very difficult to machine, often necessitating grinding or specialized tooling. For turning and milling operations in the hardened state, use carbide tools with slow speeds (e.g., 30-60 SFM) and ample coolant. Heavy-duty drilling might require slow speeds and high feed rates with robust drill bits. Grinding is the preferred method for achieving final dimensions and surface finish in the hardened condition, using appropriate grinding wheels. Welding SS 440C is generally not recommended if maximum hardness and corrosion resistance are critical, as welding can lead to cracking and compromise properties. If welding is unavoidable, preheating to 200-300°C and post-weld heat treatment (PWHT) involving slow cooling and potentially a tempering cycle are essential to mitigate cracking risks. Low-hydrogen electrodes or filler metals, such as those matching the base metal composition (e.g., 420 or 410 type), are suggested.

SS 440C Stainless Steel Heat Treatment & Processing

The heat treatment of SS 440C is critical to achieving its optimal properties. Typically supplied in the annealed condition (softened for machinability), SS 440C requires hardening and tempering for its high-performance applications. Annealing involves heating to 870-900°C, holding, and then slow furnace cooling to achieve a maximum hardness of around 241 HB. For hardening, SS 440C is austenitized at 1010-1065°C, followed by rapid quenching in oil or air to achieve its martensitic structure. Tempering is performed at temperatures ranging from 150°C to 370°C, depending on the desired hardness and toughness balance. Higher tempering temperatures (e.g., 300-370°C) result in higher toughness and ductility but lower hardness (around 54-58 HRC), while lower temperatures (e.g., 150-200°C) maximize hardness (up to 60-62 HRC) at the expense of toughness. Normalizing is not a standard heat treatment for this grade. Careful control of temperatures and cooling rates is paramount to avoid distortion and achieve the specified mechanical properties for SS 440C.

SS 440C Stainless Steel Sourcing in India

SS 440C stainless steel is readily available through various Indian manufacturers and stockists, with primary sourcing hubs located in Maharashtra (Mumbai, Pune) and other industrial centers like Chennai and Gujarat. Major Indian steel producers like Jindal Stainless and SAIL may offer SS 440C, though it

SS 440C Stainless Steel International Equivalents

Standard	Code
ASTM	A276 Type 440C, A582 Type 440C
EN	X105CrMo17 (approximate), 1.4124 (approximate)
JIS	SUS440C
UNS	S44004
DIN	X105CrMo17, 2.4603

FAQs about SS 440C

What is the primary advantage of SS 440C stainless steel?

The primary advantage of SS 440C stainless steel is its exceptional combination of high hardness, strength, and wear resistance after heat treatment. This makes SS 440C ideal for applications demanding superior resistance to abrasion and deformation, such as bearings, cutting tools, and valve components, ensuring extended service life and reliable performance in critical Indian industrial settings.

Is SS 440C suitable for corrosive environments?

While SS 440C offers good corrosion resistance due to its high chromium content (16-18%), its corrosion resistance is lower compared to austenitic stainless steels like 304 or 316. The high carbon content, necessary for hardness, slightly compromises its overall corrosion performance. SS 440C is best suited for mildly corrosive environments or where hardness and wear are the primary concerns. Thorough cleaning and maintenance are recommended for SS 440C in any environment.

What are the typical applications for SS 440C in India?

In India, SS 440C is extensively used for manufacturing high-precision ball bearings, valve seats and balls, pump shafts, surgical instruments, and high-quality knives and cutting tools. Its ability to achieve extreme hardness makes SS 440C the material of choice for components subjected to significant wear and stress in industries ranging from automotive and aerospace to medical and food processing.

How is SS 440C typically supplied in India?

SS 440C is commonly supplied in India in the annealed condition, making it easier to machine into desired shapes. After fabrication, it undergoes hardening and tempering heat treatments to achieve its characteristic high hardness and strength. Buyers can procure SS 440C in various forms like round bars, wire, sheets, and plates from major stockists and manufacturers across India, often with Mill Test Certificates (MTC) available.

What is the hardness range of SS 440C after heat treatment?

After proper heat treatment (hardening and tempering), SS 440C typically achieves a Rockwell hardness (HRC) in the range of 54 to 62. This exceptional hardness allows SS 440C to resist wear, abrasion, and indentation effectively, making it suitable for demanding applications where surface durability is paramount. The exact hardness achieved via SS 440C depends on the specific tempering temperature applied.

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