AMS 5628 Forging Parts | China Professional Forged Steel Manufacturer

AMS 5628 Material — Deep Metallurgy & Why It Outperforms Standard 410

Jiangsu Liangyi Co., Limited is an ISO 9001:2015 certified specialist manufacturer of AMS 5628 open die forgings and seamless rolled rings. With over 25 years of hands-on production experience in high-alloy stainless forgings, we have produced AMS 5628 components ranging from 30 kg valve spindles to 18-tonne nuclear pump casings, delivering to customers in more than 50 countries through Shanghai Port and Ningbo-Zhoushan Port.

AMS 5628 is a martensitic stainless steel whose design philosophy is best understood in the context of its principal competitor, AMS 5612 (standard 410). Both alloys share a chromium backbone of 11.5–16.5%, which generates the passive Cr₂O₃ surface oxide layer responsible for stainless steel corrosion resistance. The critical difference lies in what happens during solidification. Standard 410 solidifies through a dual-phase ferritic-austenitic path. As it cools, some of that primary ferrite — called delta ferrite — fails to fully transform and remains as elongated stringers in the final microstructure, oriented parallel to the forging direction. Under transverse loading or impact, these stringers act as pre-existing crack initiation sites: the engineering equivalent of a hidden fault line through the material. For room-temperature static applications, this is tolerable. For rotating aerospace components, nuclear coolant pump seals, or subsea valve bodies subjected to cyclic loading and sub-zero temperatures, it represents an unacceptable risk.

AMS 5628 solves this with a targeted nickel addition of 2.0–3.0%. Nickel is a powerful austenite stabiliser. Added at this level, it shifts the alloy's solidification path to suppress delta ferrite formation entirely in the final tempered martensite microstructure. The result is a fully martensitic single-phase structure with refined lath packet size — the fundamental microstructural unit controlling toughness in martensitic steels. Smaller lath packets mean more grain boundaries per unit volume, which deflect crack propagation paths and consume more energy per unit of crack extension. In measurable terms, this pushes the ductile-to-brittle transition temperature (DBTT) of AMS 5628 approximately 50–80°F lower than equivalent 410 — enough to make the difference between passing and failing a Charpy impact test at −73°C (−100°F) for safety-critical applications.

The carbon range of 0.12–0.17% is tightly controlled for a specific reason: carbon content in martensitic stainless steel is the primary lever controlling hardness and strength via the martensite carbon content after quenching. Too low (below 0.12%) and the martensite lacks sufficient hardness for the application; too high (above 0.17%) and the risk of carbide precipitation at grain boundaries during tempering increases, producing a sensitised microstructure with locally reduced chromium and impaired corrosion resistance. The AMS 5628 window was established by decades of fatigue and fracture testing to optimise this balance for aero-engine and nuclear service.

The martensite start temperature (Ms) for AMS 5628 is approximately 270°C (518°F). This value is critical for the forging process: all hot working must be completed above Ms to avoid forming brittle untempered martensite during deformation. The martensite finish temperature (Mf) sits near ambient for this composition, meaning the transformation to martensite is essentially complete upon cooling to room temperature after austenitizing — unlike some higher-alloy grades that retain significant austenite and require sub-zero cooling to complete transformation.

AMS 5628 International Equivalents — EN, JIS, GOST & Critical Differences

Global procurement engineers regularly encounter AMS 5628 requirements on drawings from aerospace OEMs, nuclear EPCs, and oil field operators, often with a footnote allowing substitution with "equivalent international standard." Understanding where equivalency is genuine and where it creates material non-conformance risk is one of the most practically important skills in this alloy class. The table below presents the five most commonly cross-referenced standards with measurable specification differences highlighted.

AMS 5628 Physical & Thermal Properties — Complete Data for Design Engineers

The physical property data below is essential for finite element analysis (FEA), thermal stress calculations, heat exchanger design, and selection of compatible fasteners and housings. Most competitor datasheets omit these values entirely, forcing engineers to use generic "stainless steel" assumptions that can introduce significant error in critical calculations. The values presented here are based on our in-house measurement data and published metallurgical reference data for this alloy class, representing the hardened and tempered (H+T) condition at standard composition (Cr 16%, Ni 2.5%, C 0.14%).

Elevated Temperature Strength Retention

One of the most frequent engineering questions we receive is: how does AMS 5628 strength degrade with temperature, and what is the practical upper service temperature limit? Unlike austenitic grades that maintain reasonable strength up to 800°C, martensitic stainless steels are limited by carbide coarsening and martensite recovery processes that begin significantly above the tempering temperature. The following data represents the approximate strength retention profile for AMS 5628 in the standard H+T condition:

Our AMS 5628 Forging Process — Step-by-Step from Ingot to Finished Part

Most AMS 5628 pages list chemical compositions and quote the standard. What they rarely explain is how the material must be processed to achieve the specified properties — and what happens when the process goes wrong. After producing over 8,000 tonnes of AMS 5628 forgings since 2005, our process engineers have developed a production sequence that consistently delivers first-article approval, even for the most demanding nuclear and aerospace customers.

1. Ingot Selection & Melting Process Verification We confirm the required melting route based on the application before material is ordered. For standard industrial forgings, we procure VIM+VAR double-melted ingots from approved Chinese special steel mills, with incoming chemical OES analysis and macro-etch inspection on every heat. For aerospace, nuclear, and subsea applications, we source VIM+ESR+VAR triple-melted ingots, verified to have sulphur below 0.008% and non-metallic inclusion ratings below B1.5 / C1.5 per ASTM E45. Each incoming ingot is assigned a unique traceability number that follows the forging through every subsequent production stage.
2. Ingot Heating & Homogenization Soak AMS 5628 ingots are charged into our gas-fired forging furnaces at a controlled rate to avoid thermal shock cracking, then heated to a soaking temperature of 1,180–1,220°C (2,156–2,228°F). Soaking time is critical: we apply a minimum of 1 hour per 100mm of ingot diameter, plus a mandatory 30-minute furnace equalisation period at the set temperature. This dissolves carbide networks that form during solidification — premature forging of an under-soaked ingot produces carbide streaks that pass chemical analysis but create preferential fatigue crack initiation sites. This is one of the most common — and most invisible — quality failures in low-cost AMS 5628 forgings.
3. Primary Breakdown Forging (Ingot-to-Billet) Using our 6,000-ton hydraulic press, the ingot undergoes primary breakdown to a billet with a minimum area reduction ratio of 4:1 for bar and shaft products, and 3.5:1 for ring preforms. This simultaneously closes residual solidification porosity, breaks the coarse as-cast dendritic grain structure, and elongates any oxide inclusions into detectable stringers for subsequent UT. Multiple press passes with 90° rotation between each pass are applied to ensure directional uniformity of the refined microstructure.
4. Intermediate Reheat & Temperature-Monitored Forging For large forgings requiring multiple sequences, billets are reheated to 1,100–1,150°C between passes. All forging is completed above the martensite start temperature (Ms ≈ 270°C) to prevent brittle untempered martensite formation during deformation — a crack initiation risk unique to martensitic steels. Our press operators use calibrated optical pyrometers to monitor billet surface temperature at every stage, with automatic data logging included in the production record for customer review.
5. Finish Forging & Ring Rolling For seamless rings, the billet is punched and transferred to our 1-metre or 5-metre radial-axial ring rolling machines. Feed rate, rolling speed, and axial pressure are controlled to achieve simultaneous radial and axial elongation, maintaining a homogeneous ASTM No. 5 or finer grain size throughout the ring cross-section. This circumferential grain alignment gives ring forgings superior hoop-direction mechanical properties compared to cut-and-welded or fabricated alternatives. For shafts and bars, finish forging to near-net shape preserves the forged grain flow aligned with the primary stress axis, maximising the fatigue and impact performance in service.
6. Controlled Post-Forge Cooling This step is absent from most competitor process descriptions, yet it is where many martensitic forging failures originate. After finish forging, AMS 5628 must be cooled at a controlled rate to avoid thermal gradient-induced cracking. We cool forgings in sand-insulated cooling pits or perform a controlled furnace cool from 800°C to below 200°C at a maximum rate of 30°C/hour for sections above 200mm. Sections below 100mm may be air cooled. Forgings that cool too rapidly from the forging temperature will develop through-thickness thermal cracks that only appear during final UT inspection — causing costly rejections and delays that could have been entirely avoided.
7. Austenitizing, Quench & Double Tempering Full parameters are detailed in the dedicated Heat Treatment section below. In summary: austenitize at 980–1,050°C with minimum soak time of 1 hour per 25mm section, oil quench within 20 seconds of leaving the furnace, then double temper at 580–650°C with a minimum of 2 hours per 25mm section per temper cycle, with a minimum 24-hour ambient hold between temper cycles for sections above 150mm. All furnace work is performed in our ten computer-controlled continuous furnaces, calibrated and regularly maintained, with ±5°C temperature uniformity and full furnace chart recording.
8. Full Non-Destructive & Mechanical Testing Every AMS 5628 forging is individually ultrasonically tested using straight-beam and angle-beam probes before release. For aerospace and nuclear grade parts, the acceptance standard is ASTM A388 Zone I: zero indications exceeding a 3mm equivalent flat-bottom hole, and no complete loss of back-wall echo. Mechanical test specimens are taken from representative test prolongations on the same forging lot, with tensile, hardness, and Charpy impact tests performed by our qualified NDT inspectors in our in-house laboratory.

Double Melt vs Triple Melt for AMS 5628 — Engineering Decision Guide

The melt route choice is one of the most impactful — and most frequently misunderstood — decisions in AMS 5628 procurement. It directly affects inclusion cleanliness, fatigue life, fracture toughness, lead time, and cost. Here is how our technical team evaluates this decision for every new customer inquiry.

The ESR Step — Why It Makes the Difference

Electroslag Remelting works by slowly remelting a consumable electrode through a molten slag pool. As the steel passes through the slag, the slag reacts chemically with sulphur in the steel to form CaS, which remains trapped in the slag rather than re-entering the solidifying ingot. This is why ESR is the only commercially practical way to achieve sulphur below 0.008% in large-tonnage melts — VIM and VAR alone cannot reach this level without extraordinary process constraints. The CaS removal eliminates the MnS inclusions that are the primary Type B inclusion family in the ASTM E45 rating, which are also the most damaging to fatigue life because their elongated morphology after forging presents a large projected area perpendicular to tensile stresses.

Full Range of AMS 5628 Forged Steel Products & Maximum Size Capabilities

Our integrated facility — with presses from 800 to 6,000 tonnes, hammers from 0.75 to 9 tonnes, and ring rollers up to 5 metres — gives us the widest single-source AMS 5628 production envelope available from China. All products below are available in double-melt or triple-melt AMS 5628, with EN 10204 3.1 or 3.2 mill test certificates, dimensional inspection reports, and full NDT records as standard.

For all products, we can arrange protective surface coating (rust-preventive oil, VCI film, wooden crate with desiccant) for sea freight, and full export documentation including commercial invoice, packing list, certificate of origin, EUR.1 form, mill test certificate, inspection release note, and bill of lading. Incoterms available: EXW, FOB Shanghai/Ningbo, CFR, CIF, DDP.

AMS 5628 Global Applications & Six Real Engineering Case Studies

The following case studies are drawn from actual Jiangsu Liangyi projects since 2010. Customer names are replaced with industry and region descriptors per our standard confidentiality agreements, but all technical parameters — material specifications, test results, dimensions, and delivery conditions — are factual production data.

AMS 5628 Chemical Composition, Mechanical Properties & Extended Material Data

The tables below present the full AMS 5628 standard limits alongside Jiangsu Liangyi's aim chemistry targets. Our policy is to target the centre of every specification window — not the edges — to provide maximum margin against process variation and incoming material variability. Engineers designing to AMS 5628 should use the standard minimum values for conservative calculations, not our typical achieved values.

Chemical Composition — Standard Limits, Aim Chemistry & Element Function

Mechanical Properties — Standard Requirements vs Jiangsu Liangyi Typical Achieved

AMS 5628 Heat Treatment — Complete Parameter Guide for Engineers

Heat treatment is where AMS 5628 forgings either achieve or fall short of their specified properties. The parameters below are not textbook generalisations — they are production-proven settings refined through thousands of heats and hundreds of first-article inspection submissions over 25 years.

AMS 5628 Corrosion Resistance & Service Environment Guide

Corrosion resistance is frequently the most misunderstood aspect of AMS 5628. Engineers sometimes over-specify the material's corrosion capability (treating it as equivalent to austenitic stainless steel in aggressive environments) or under-specify it (assuming it corrodes like carbon steel). The following guide is based on our 25 years of customer feedback, published corrosion data for chromium-nickel martensitic stainless steels, and the specific NACE and ISO standards governing corrosion-critical applications.

Pitting Resistance Equivalent (PRE) Calculation

The PRE is the standard index for comparing pitting corrosion resistance between stainless steel grades in chloride environments. For AMS 5628:

PRE = %Cr + 3.3 × %Mo + 16 × %N

At aim chemistry (Cr 16.0%, Mo 0.15%, N 0.05%):

PRE ≈ 16.0 + (3.3 × 0.15) + (16 × 0.05) ≈ 17.3

This places AMS 5628 significantly below austenitic 316L (PRE ≈ 24) and duplex 2205 (PRE ≈ 35), confirming that AMS 5628 is not a substitute for these grades in aggressive chloride or process fluid environments. Its corrosion resistance is appropriate for the environments listed below.

Passivation — Why It Is Mandatory After Machining

When AMS 5628 is machined, the cutting process mechanically disrupts the surface passive oxide layer and may embed iron-rich particles (from tooling or fixturing contact with carbon steel) into the surface. These embedded iron particles form galvanic cells with the underlying stainless steel, initiating localised corrosion that appears as rust staining — often mistaken for bulk material corrosion. Passivation per ASTM A967 removes these iron contaminants and restores the Cr₂O₃ passive layer through a controlled nitric acid or citric acid chemical treatment. Jiangsu Liangyi performs passivation per ASTM A967 on all finish-machined AMS 5628 parts as standard, with a free-iron detection test (water break test or ferroxyl test) to confirm surface cleanliness before final packaging. For customers preferring to perform passivation after their own machining operations, we recommend ASTM A967 Method B (citric acid, 4–8% concentration, 60–71°C, 4 minutes minimum immersion) as the safest procedure for high-strength martensitic stainless steels.

AMS 5628 Machining & Fabrication Guidelines — Cutting Parameters, Tools & Common Pitfalls

AMS 5628 in the hardened and tempered condition (248–302 HB) is considerably more machinable than austenitic stainless grades such as 316L or 310S, because it does not work-harden as aggressively during cutting. This means tool life is longer and surface finish is more consistent between tool changes — an advantage that procurement engineers should factor into total machined-part cost comparisons. However, AMS 5628 does present specific machining challenges that arise from its high hardness and moderate abrasivity. The guidance below is based on our in-house CNC machining experience with AMS 5628 forgings and feedback from customers who machine our rough-forged blanks.

Tool Geometry Recommendations

The insert geometry is as important as the grade selection for consistent AMS 5628 machining. Key recommendations from our production machining experience:

• Rake angle: Positive rake 5–10° for turning and milling. Positive geometry reduces cutting force and heat generation, both of which increase tool life and surface finish in hard stainless steels.
• Clearance angle: 8–12° primary clearance. Insufficient clearance causes rubbing rather than cutting, generating excess heat and work-hardening the surface layer — creating progressively harder material for the next tool pass.
• Nose radius: 0.4–0.8mm for finishing operations. Larger nose radius (1.2mm+) improves surface finish but increases radial cutting force, causing deflection in slender shafts. Use smaller nose radius for length-to-diameter ratios above 5:1.
• Chip breaker: Use a moderate chip breaker geometry — the medium work-hardening of AMS 5628 produces chips that are controllable but will nest if the chip breaker is too open. Tangled chips in internal bore machining are the most common cause of surface damage in AMS 5628 hollow forging machining.
• Edge preparation: A light hone (T-land 0.05–0.10mm) on the cutting edge is recommended for intermittent cuts (irregular forging surfaces in early passes). Avoid sharp edges on interrupted cuts, as AMS 5628's hardness in the H+T condition can micro-chip sharp carbide inserts at scale-to-clean surface transitions.

AMS 5628 Machinability Comparison vs Similar Alloys

AMS 5628 Surface Treatment & Post-Processing Options

The base AMS 5628 forging in the H+T condition provides a defined combination of hardness, strength, and corrosion resistance. For specialised applications requiring enhanced surface properties — lower friction, higher wear resistance, improved fatigue life, or enhanced corrosion protection — several proven surface treatment options are applicable. The following guide covers the options we routinely specify or arrange for our customers, with the engineering rationale for each.

AMS 5628 Industry Standards Cross-Reference — Where This Material Is Accepted

Engineers and procurement professionals working on regulated projects — aerospace, nuclear, oil and gas, defense — need to confirm that AMS 5628 material is explicitly accepted by the governing design code for their application. The following cross-reference summarises the major international standards and codes that reference or accept AMS 5628 martensitic stainless steel, along with the specific clauses or conditions that apply. This is information that most forging supplier websites do not provide — we publish it here because we believe informed engineers make better purchasing decisions.

12-Stage Quality Assurance & Testing System for AMS 5628 Forgings

Our quality control philosophy for AMS 5628 is built on a single principle: every defect found in our inspection department is significantly less costly than the same defect found in the field. We operate a documented 12-stage quality gate system from raw material receipt through final shipment release, with no stage bypassed under any commercial or schedule pressure. All inspections are performed by our trained and qualified in-house NDT inspection team, with inspectors qualified to ASNT SNT-TC-1A guidelines.

Test Certificate Contents — EN 10204 3.1 Standard Package

Every shipment of AMS 5628 forgings from Jiangsu Liangyi includes a complete EN 10204 3.1 mill test certificate containing: heat number and melt route confirmation (double or triple melt, with ingot producer name); full OES chemical analysis with traceability to source ingot; all individual mechanical test results (tensile, hardness survey, Charpy with specimen identification and test machine calibration certificate number); macro and micro inspection results with photographic documentation where specified; complete UT scan record with probe calibration confirmation and rejection criteria used; MT inspection record with magnetisation method and sensitivity confirmation; heat treatment record including actual furnace chart traces showing time-temperature profile; dimensional inspection report referencing customer drawing revision; and certificate signatory and company authorisation stamp. EN 10204 3.2 (third-party witness by SGS, BV, TUV, DNV, or Lloyd's Register) is available at no additional surcharge when TPI access is arranged in advance of production start.

5 Common AMS 5628 Specification Mistakes Engineers Make — and How to Avoid Them

After reviewing thousands of customer drawings and purchase orders over 25 years, our technical team has identified five recurring specification errors. We share these openly because informed customers make better purchasing decisions — and because fixing specification errors before production begins costs nothing, while fixing them after Final Inspection costs everyone.

About Jiangsu Liangyi — Specialist AMS 5628 Forging Manufacturer Since 1997

Established in 1997 in Jiangyin City, Jiangsu Province, Jiangsu Liangyi Co., Limited has grown from a regional open die forging operation into one of China's leading specialists in high-alloy forged steel for critical industrial applications. Our 80,000 m² integrated facility lies in the Yangtze River Delta manufacturing corridor — 90 minutes from Shanghai Pudong International Airport and 2 hours from both Yangshan Deep Water Port (Shanghai) and Ningbo-Zhoushan Port, giving us direct access to the world's two highest-volume container shipping hubs for competitive global freight rates and reliable transit times to every major market.

We hold ISO 9001:2015 certification and manufacture in full compliance with ASTM, AMS, AISI, API 6A, API 17D, DIN, EN, JIS, and NORSOK standards. Our factory is fully open to third-party inspection by internationally recognised agencies including SGS, Bureau Veritas, TUV Rheinland, Lloyd's Register, and DNV GL — customers may arrange witness inspections and third-party testing through any of these bodies at our Jiangyin facility. We support customer QA audits and supplier surveys at our facility. Our technical team includes forging process engineers, heat treatment specialists, and materials engineers with direct AMS 5628 production experience across oil and gas, power generation, marine, and industrial projects.

14 Frequently Asked Engineering Questions About AMS 5628 Forgings

Request Your Custom AMS 5628 Forging Quotation — Response Within 24 Hours

Our technical sales team includes engineers with direct AMS 5628 forging production experience across aerospace, nuclear power, oil and gas, marine, and defense programmes. We are ready to review your drawing, assess the appropriate melt route and heat treatment condition for your application, confirm applicable standard compliance, and provide a detailed quotation with a confirmed delivery schedule. No minimum order quantity. No obligation. Full technical support from initial inquiry through delivery and beyond.