ASTM A355 Forgings — Nitralloy-Family Aluminum-Bearing Steel Specifically Alloyed for Superior Nitriding Response, Class A, B & C
Shivam Forge manufactures forgings in ASTM A355 (Nitralloy-family) steel, Class A/B/C — an aluminum-chromium-molybdenum alloy steel specifically formulated for the nitriding case hardening process, forming particularly hard, stable aluminum nitrides that general-purpose steel grades cannot match under the same nitriding treatment. Rajkot, India. Call +91-9265772827.
Nitriding is a case hardening process that works by diffusing nitrogen into a steel's surface, but the case hardness that process actually achieves depends heavily on what alloying elements are present in the base steel to react with that diffusing nitrogen — and this is precisely the gap ASTM A355 Nitralloy-family steel is engineered to fill. General-purpose alloy steels can be nitrided and will develop some case hardness improvement, since nitrogen forms nitride compounds with iron and with common alloying elements like chromium to a useful degree, but ASTM A355's defining compositional feature is a deliberate aluminum addition (typically around 1.0-1.5%), specifically because aluminum forms aluminum nitride (AlN) precipitates that are both considerably harder and more thermally stable than the iron and chromium nitrides that form in general-purpose nitriding-capable steel. This means the same nitriding process — same time, same temperature, same nitrogen potential — produces a meaningfully harder, more wear-resistant case in ASTM A355 material than it does in a general-purpose alloy steel, which is exactly why A355 (encompassing the Nitralloy 135, Nitralloy 135M, and Nitralloy N compositions corresponding to its Class A, B, and C designations) became the standard specification whenever a component's design case hardness requirement genuinely depends on nitriding delivering its maximum achievable case hardness, rather than settling for the more modest case hardness improvement nitriding a general-purpose steel grade would provide. Selecting ASTM A355 is therefore a deliberate upstream material decision made specifically because nitriding is the intended case hardening route — choosing the wrong base steel and then nitriding it produces a functional but meaningfully softer, less wear-resistant case than the same process applied correctly to Nitralloy-family material.
Forged ASTM A355 gear blanks for applications requiring maximum achievable nitrided case hardness at the tooth flank and root, leveraging the alloy's aluminum content for superior wear resistance and bending fatigue strength beyond what general-purpose nitriding steel achieves.
Forged A355 shaft blanks for precision shaft applications requiring both the dimensional stability nitriding's low-temperature, no-quench process provides and the maximum case hardness the aluminum-bearing composition enables.
Forged A355 components for cylinder liner and precision bore applications where maximum wear resistance at the working surface, achieved through nitriding's characteristic hard case, is a governing design requirement.
Forged A355 valve stem and trim component blanks for applications combining precision dimensional requirements with maximum nitrided wear resistance at critical sealing and guiding surfaces.
Chemistry verification against the specific ASTM A355 class ordered — Class A (Nitralloy 135), Class B (Nitralloy 135M), or Class C (Nitralloy N) — since these compositions differ in secondary alloying content tuned to specific core mechanical property requirements.
Quench-and-temper core heat treatment performed prior to nitriding, developing the base mechanical properties the component's core requires before the nitriding case hardening treatment is applied to the surface.
Manufacturing coordinated with the customer's or our partner's nitriding process, ensuring the forged and pre-heat-treated component is prepared correctly for the gas or plasma nitriding treatment that will develop the aluminum-nitride-strengthened case.
Material test certificates confirming chemistry and core mechanical properties, issued as standard for every batch supplied into nitriding-dependent component manufacturer supply chains.
Nitriding's effectiveness as a case hardening process depends on more than just process parameters like temperature and treatment time — it depends fundamentally on what alloying elements are present in the base steel to actually react with the nitrogen diffusing into the surface, and this is the specific gap ASTM A355 Nitralloy-family steel exists to fill. While most alloy steels can be nitrided and will develop some useful case hardness improvement, the maximum achievable case hardness a nitriding treatment can deliver depends directly on the base steel's alloy content, and this is precisely why component designs that depend on nitriding delivering its full potential case hardness specify A355 rather than a general-purpose nitriding-capable grade.
A355's defining compositional feature is a deliberate aluminum addition, typically 1.0-1.5%, and the reason this specific element matters so much traces to basic nitride chemistry: aluminum forms aluminum nitride (AlN) precipitates that are considerably harder and more thermally stable than the iron and chromium nitrides that form when nitrogen reacts with a general-purpose alloy steel's more conventional composition. This means identical nitriding process parameters — same furnace temperature, same treatment duration, same nitrogen potential — produce a meaningfully harder, more wear-resistant case in A355 material than in general-purpose steel, a difference that traces entirely to what the base material offers the nitriding process to work with.
This makes selecting ASTM A355 a deliberate upstream material decision, made specifically because nitriding has already been chosen as the component's case hardening route, rather than a generic alloy steel selection made independently of the surface treatment plan. A355 encompasses three related compositions — Class A (Nitralloy 135), Class B (Nitralloy 135M), and Class C (Nitralloy N) — sharing the aluminum addition responsible for superior nitride formation while differing in secondary alloying content tuned to specific core mechanical property requirements, giving component designers flexibility in matching base material core properties to application load requirements while retaining the superior nitriding response the aluminum content provides across all three classes.
For gear manufacturers, precision shaft producers, and component manufacturers whose designs depend on nitriding achieving its maximum case hardness potential, Shivam Forge manufactures ASTM A355 forgings with pre-nitriding core heat treatment coordinated to your specified nitriding process. Contact our engineering team at +91-9265772827 or sales@shivamforge.com with your drawing and specification for a manufacturability review and quotation.
ASTM A355 covers Nitralloy-family steel (Class A, B, and C, corresponding to Nitralloy 135, 135M, and N compositions) specifically alloyed with aluminum, typically 1.0-1.5%, because aluminum forms aluminum nitride precipitates that are considerably harder and more thermally stable than the iron and chromium nitrides that form when nitriding general-purpose alloy steel.
Nitriding works by diffusing nitrogen into the steel surface, where it reacts with alloying elements to form hard nitride compounds. Aluminum nitride (AlN) is meaningfully harder and more stable than the nitrides formed with iron or chromium alone, so the same nitriding process produces a harder, more wear-resistant case in aluminum-bearing A355 material than in general-purpose steel.
Yes, most alloy steels can be nitrided and will develop some case hardness improvement from nitrogen reacting with iron and elements like chromium. But the case hardness achieved is meaningfully lower than what the same process delivers in A355's aluminum-bearing composition, which is why A355 is specified whenever a component's design case hardness requirement genuinely depends on nitriding reaching its maximum achievable hardness.
The three classes correspond to Nitralloy 135, Nitralloy 135M, and Nitralloy N respectively, differing in secondary alloying content tuned to specific core mechanical property requirements — the aluminum addition responsible for superior nitriding response is common across all three classes.
We manufacture and pre-heat-treat A355 forgings to prepare them correctly for nitriding, coordinating with the customer's specified nitriding process or our nitriding services partner to ensure the aluminum-nitride-strengthened case develops as designed. Discuss your specific process flow requirement with our engineering team.
Why Choose Shivam Forge
Shivam Forge delivers precision hot-forged components from our integrated Shapar, Rajkot facility — covering forging, CNC machining, heat treatment, and quality inspection under one roof.
