1.7335 (13CrMo4-5) Forged Parts | China Professional Forging Manufacturer

 Jiangsu Liangyi Co.,Limited is a professional manufacturer based in China, holding ISO 9001:2015 certification. We make premium1.7335 (13CrMo4-5, 13CrMo45, 13CrMo4.5) open die forging parts and seamless rolled steel forged rings. Equipped with advanced melting and forging machines, we follow strict quality control standards and fully meet European EN and American ASTM standards. We provide custom 13CrMo4-5 forged parts for all industrial buyers across power generation, petrochemical, oil & gas, nuclear power, valve manufacturing and other fields, exporting our products to more than 50 countries around the world.

1.7335 (13CrMo4-5) Alloy Steel — In-Depth Material Overview

EN 1.7335  (also known as 13CrMo4-5 and often written as 13CrMo45 or 13CrMo4.5)  is a low-alloy chromium‑molybdenum heat-resistant steel suitable for long-term use at high temperatures. Ordinary carbon steel loses its ability to resist creep above 350°C, while 1.7335 contains 0.7–1.15% chromium and 0.4–0.6% molybdenum.These added elements form stable carbide particles along grain boundaries, which block internal metal sliding that causes creep. So that the steel can keep its structural strength steady up to 500°C under continuous load.

Why the Cr-Mo Combination Matters for High-Temperature Forging

Chromium in this concentration range serves a dual role: it contributes to oxidation resistance by forming a thin chromium oxide surface layer, and it stabilizes the ferritic matrix, keeping the steel in a favorable microstructural condition during long-term thermal cycling. Molybdenum complements this by increasing the recrystallization temperature of the steel — meaning that even after repeated thermal cycles, the grain structure remains refined and uniform rather than coarsening. This synergy is precisely why 1.7335 is the preferred choice over plain carbon steel or lower-alloy grades for boilers and pressure vessels that must operate for 200,000+ hours without creep failure.

Weldability: The Engineering Advantage of 1.7335 Over Higher Cr-Mo Grades

One of the most commercially important properties of 13CrMo4-5 is its genuinely excellent weldability — a characteristic that higher Cr-Mo grades like 10CrMo9-10 (1.7380) or 12CrMo9-10 do not share to the same degree. With a carbon equivalent (CE) value typically in the range of 0.55–0.65 for forged sections, 1.7335 can be welded with standard low-hydrogen electrodes and requires only moderate pre-heat (typically 150–200°C for section thicknesses above 25mm). Post-weld heat treatment (PWHT) at 690–710°C is standard practice for stress relief, and the steel consistently produces high-quality, crack-free welds in qualified procedures. This combination — high-temperature strength plus field-weldability — makes 1.7335 uniquely practical for installation in large-scale plant construction where welding is unavoidable.

Standard Delivery Condition and What It Means for Your Application

All our 1.7335 forged parts are supplied in the normalized and tempered (N+T) condition as standard. Normalizing at 910–940°C refines the forging-induced coarse grain matrix, removes forging stresses and produces a consistent ferritic-pearlitic microstructure throughout the section. Tempering at 650–720°C then improves the balance between yield strength, tensile strength and toughness — achieving the property levels required by EN 10222-2 and related standards. The result is a forging that has stable, predictable properties immediately upon receipt, without the need for the buyer to perform additional heat treatment before installation.

International Equivalent Grades for Cross-Reference

For procurement engineers who source goods from supply chains with mixed standards, these grade matches offer easy practical reference. ASTM A182 Grade F11 Class 2 is the closest American match for forged flanges and fittings, with nearly the same chromium (1.0–1.5%) and molybdenum (0.44–0.65%) content.ASTM A387 Grade 11  applies to pressure vessel plates made with the same equivalent material composition.

The British standard BS 1503 621-490 and the older German designation 13CrMo44 (DIN 17175) are also directly equivalent. When substituting 1.7335 for A182 F11 material in a mixed European-American project, always verify that the specific heat and mechanical test data meet both EN and ASTM minimum requirements — our MTC format includes both sets of values on request.

Available 13CrMo4-5 Forged Product Forms: Dimensions, Tolerances & Selection Guide

We manufacture the complete range of 1.7335 (13CrMo4-5) forging products across all standard and custom shapes, from single prototype forgings to mass production runs of thousands of pieces. Every product is manufactured from in-house melted ingots with full traceability, guaranteeing that the material properties of the finished forging are directly traceable to the original heat analysis. Below is a detailed guide to each product form, including dimensional capability, typical tolerances and the specific engineering considerations that determine the right form for your application.

Open Die Forged Bars, Rods & Custom Shafts

Our 1.7335 open die forged bars are produced by repeated hot compression between flat dies, achieving a minimum forging ratio of 4:1 to guarantee thorough closure of internal porosity and significant grain refinement throughout the entire cross-section. Available forms include round bars (diameter range: 80mm–1,200mm), square bars, rectangular flat bars and hexagonal bars. Shaft-type forgings include simple stepped shafts, eccentric shafts, turbine rotor blanks, gear shaft preforms and spindles, with lengths up to 12,000mm.

Dimensional tolerances for forged bars are held to EN 10243-1 (open die forgings) as standard, with tighter tolerances available for pre-machined surfaces. Surface condition is supplied as forged (black surface) with decarburization layer removed on machined surfaces. For shaft forgings, we routinely achieve straightness within 2mm per meter of length on bars above 300mm diameter after heat treatment — a specification that significantly reduces downstream machining waste for our customers.

Seamless Rolled Rings — Flanges, Swivel Rings & Custom Profiles

Seamless ring rolling is one of our main specializations, with 1.7335 rolled rings available from 200mm to 6,000mm outer diameter, wall thicknesses from 30mm to 800mm, and ring heights from 50mm to 2,500mm. The ring rolling process provides a continuous, unbroken grain flow that follows the circumference of the ring — a significant mechanical advantage over rings machined from plate or forged disc, where grain flow cuts across the important hoop stress direction.

Common ring products include weld-neck flanges, slip-on flanges, blind flanges, swivel flanges (for rotating offshore applications), valve seat rings, gear ring blanks, bearing ring blanks, slewing ring blanks and custom profiled rings. We can roll near-net-shape profiles (rectangular, trapezoidal, T-section, L-section) that reduce machining time and material waste by up to 35% compared to starting from a flat ring blank. All rings are 100% ultrasonically tested per EN 10228-3 before dispatch.

Hollow Forgings, Thick-Walled Cylinders & Pressure Vessel Shells

For hollow forgings — including pressure vessel shells, reactor body sections, thick-walled cylinders, tubing barrels and sleeve forgings — we use a combination of open die forging with a mandrel-assisted punching and elongation process. This technique ensures that the forging ratio is kept across the full wall thickness, not just the outer surface, which is critical for large-diameter, thick-walled parts where center porosity and segregation are the primary quality risks.

Our hollow forging capability covers outer diameters from 300mm to 3,000mm, wall thicknesses from 50mm to 600mm, and lengths up to 8,000mm. Typical applications include reactor pressure vessel body sections, high-pressure column shells for distillation towers, cylinder liners for large reciprocating compressors and hydraulic cylinder body blanks. UT acceptance class for hollow forgings is standard EN 10228-3 Class 3 (which requires rejection of echoes above 50% of the reference reflector from any Ø2mm FBH), with Class 4 available for important pressure applications where higher cleanliness is specified by the customer.

Forged Discs, Plates, Tube Sheets & Blind Flanges

1.7335 forged discs and tube sheets are essential parts in heat exchanger and pressure vessel construction. The main engineering requirement for tube sheets is that the material must retain sufficient strength at the tube-to-tubesheet joint even after the thermal cycling of welding and PWHT operations — 1.7335's combination of weldability and high-temperature strength makes it particularly well-suited. We produce forged discs from 300mm to 4,500mm diameter and tube sheets from 200mm to 3,500mm diameter, with bore and face machining available.

All forged discs and tube sheets are produced with a minimum forging reduction ratio of 3:1 measured from ingot to finished forging, with the additional requirement that the forging direction is documented and included in the MTC. This is important for tube sheets, where the through-thickness properties (Z-direction) must meet specific requirements to resist lamellar tearing during the tube-expanding and welding process.

Custom Special-Shaped & Near-Net Forgings

Beyond standard shapes, our engineering team works directly with customers to design optimized forging preforms for complex geometries. Common special-shaped 1.7335 forgings include: impeller blanks for high-temperature centrifugal pumps, valve body blanks (globe, gate, check, ball valve), transition cone sections for pressure vessel nozzles, BOP (blowout preventer) body blocks, tee-shaped forgings and elbow preforms. For complex shapes, we provide a DFM (Design for Manufacturability) review at quotation stage, suggesting parting line placement, draft angle requirements and material allocation that minimizes finishing machining while ensuring full sound metal in all important areas.

1.7335 Forging Parts: Industry Applications, Design Considerations & Project Experience

Understanding why 1.7335 (13CrMo4-5) is specified in a given application — rather than simply listing end-use industries — is what distinguishes a genuine engineering partner from a commodity supplier. Below, we explain the specific design requirements that drive 1.7335 selection in each main industry, alongside real production experience from our 25+ years of global supply.

Power Generation & Utility Boiler Industry: Creep Life Management

In thermal power generation, the design life target for a supercritical boiler pressure part is typically 200,000 to 300,000 hours of continuous operation. Over this period, even small amounts of creep deformation accumulate and can lead to failure if the material is not correctly specified. 1.7335 (13CrMo4-5) is the standard material for boiler headers, steam drum nozzle necks, tube-to-header weld connections and superheater outlet collector forgings operating in the 400–500°C range — below the optimal range for higher-alloy grades like P91, but well above where plain carbon steel is reliable.

Our supply experience in this sector includes tube sheet forgings up to 2,800mm diameter for shell-and-tube heat exchangers, drum nozzle forgings for 600MW and 1000MW supercritical boiler projects, and custom channel flanges for feedwater heater assemblies. A main engineering point we communicate to our customers: for boiler forgings above 100mm section thickness, the normalizing and tempering temperatures must be carefully controlled to ensure the center of the section reaches full transformation temperature — a quality control step we verify using embedded thermocouples in our furnaces and document in the heat treatment record delivered with every MTC.

Petrochemical & Pressure Vessel Industry: High-Pressure Hydrogen Service

One of the most demanding applications for 1.7335 forgings is in high-pressure hydrogen service — hydrocracking reactors, hydrotreating vessels and catalytic reformer equipment where the combination of high temperature, high hydrogen partial pressure and cyclic loading creates conditions for hydrogen embrittlement, temper embrittlement and stress corrosion cracking. The Nelson Curves (API 941) define the safe operating limits for Cr-Mo steels in hydrogen service, and 1.7335 — with its 0.7–1.15% Cr — sits in the appropriate zone for hydrogen partial pressures up to approximately 70 bar at 500°C when in the normalized and tempered condition.

Our petrochemical forging experience includes reactor shell ring sections, transition cone forgings connecting cylindrical shells to ellipsoidal heads, large nozzle forgings (DN300–DN600) for reactor inlet/outlet connections, and heat exchanger channel head forgings. For hydrogen service applications, we offer additional testing on request: step cooling tests for temper embrittlement screening, absorbed hydrogen measurement, and J-factor (J = Si+Mn × P+Sn ×10,000) calculation to verify resistance to temper embrittlement — supporting our customers' compliance with API 934-A requirements.

Industrial Valve Manufacturing: Dimensional Precision & Pressure Rating

Valve body forgings in 1.7335 must meet two demanding requirements simultaneously: tight dimensional precision in the bore areas and nozzle openings (typically ±0.5mm for CNC-finish machined components) and excellent structural integrity in the thin-wall regions between the flow passage and the outer pressure boundary. The challenge is that the forging process inherently creates variable grain flow patterns around complex internal passages — for valve bodies with multiple intersecting bores, the die design must ensure that the primary grain flow remains aligned with the principal stress direction in service.

We supply valve forging blanks to valve manufacturers across Europe, North America and the Middle East, in pressure ratings from ANSI Class 150 through Class 4500. Product range covers gate valve bodies (sizes DN15–DN600), globe valve bodies, check valve bodies, ball valve body halves, valve bonnet forgings and valve yoke arms. For ASME VIII pressure-containing valve forgings, we provide the full material traceability documentation including A182 F11 grade cross-reference alongside the EN 1.7335 mill certificate on request. Valve forgings are among our highest-volume product categories and a core part of our regular production schedule.

Nuclear Power Industry: Secondary Loop Applications & Documentation Support

1.7335 forged parts for nuclear plant secondary loop systems — including heat exchanger tube sheets, feedwater heater shells, and secondary piping flanges — are non-nuclear-safety class in most plant designs, but are still subject to improved quality documentation requirements from the equipment manufacturer. These requirements typically include full material heat traceability, documented and witnessed heat treatment, and third-party inspected MTCs (EN 10204 Type 3.2).

We supply 1.7335 forgings to equipment manufacturers who hold the relevant nuclear supply qualifications for their specific projects, providing them with EN 10204 3.2 certified forgings with full chemistry traceability, complete heat treatment records, and third-party witnessed UT and MPI inspection. Our ISO 9001:2015 quality management system — with its documented process control, non-conformance tracking, and full heat-number traceability — provides the quality evidence framework that equipment manufacturers need when auditing material suppliers for nuclear-related projects. We welcome customer quality audits and can provide our quality system documentation upon request.

Oil & Gas Industry: Subsea & High-Pressure Well Service

Blowout preventer (BOP) bodies represent one of the most demanding forging applications in the oil and gas sector: they must withstand working pressures up to 138 MPa (20,000 PSI) for deepwater applications, survive impact loading from rapidly closing rams, and function reliably at temperatures ranging from -29°C (subsea ambient in cold water) to +121°C (produced fluid temperature). The 1.7335 material in BOP applications is specified to API 6A requirements, with material property requirements that often exceed the standard EN values — particularly in terms of Charpy impact toughness at low temperature (-60°C for certain subsea applications).

Our BOP forging experience covers wellhead housing forgings, BOP ram block forgings, annular BOP body forgings and high-pressure valve block forgings, supplied to oil and gas equipment manufacturers across the Middle East, North America and Southeast Asia. For subsea applications with low-temperature impact requirements, we select ingot heats with the lowest possible phosphorus and sulphur content (P ≤ 0.010%, S ≤ 0.003%) and apply a specialized quench and temper heat treatment optimized for toughness rather than the standard normalize and temper cycle.

Pump & Rotating Machinery: Fatigue Performance & Dimensional Stability

For rotating parts — impellers, pump shafts, bearing housings and compressor disc blanks — the engineering requirements shift from static high-temperature strength to fatigue life, dynamic balance tolerances and dimensional stability after final machining. 1.7335 forgings for rotating applications are produced to tighter hardness uniformity requirements (max variation 20 HB across any cross-section) and are given additional magnetic particle inspection to detect any surface cracks or laps that could serve as fatigue crack initiation sites. For large pump casings, we perform rough machining at our facility, followed by a stress-relief heat treatment at 620–650°C before the final precision machining — eliminating the dimensional creep that occurs when internal stresses are released during heavy material removal.

Production Standards, Melting Technology & Why In-House Steel Making Matters

All our 1.7335 (13CrMo4-5) forged steel products are manufactured based on the applicable international standards shown below. However, meeting a standard is a minimum threshold, not a quality target. What distinguishes our 1.7335 forgings from many market alternatives is our in-house steel making capability — we melt our own ingots from certified scrap and alloying materials, rather than purchasing commercial billets of unknown or variable internal quality. This vertical integration is the foundation of our quality guarantee and the reason we can provide full traceability from liquid steel to finished forging.

Applicable International Standards

• EN 10028-2: 2009 — Flat products made of steels for pressure purposes. Defines chemical composition, mechanical properties and testing requirements for 13CrMo4-5 in plate form. Our forging MTCs include property values cross-referenced to this standard when plate-equivalent products are requested.
• EN 10222-2: 2000 — Steel forgings for pressure purposes, ferritic and martensitic steels with specified elevated temperature properties. This is the primary standard governing our forged bars, rings, discs and hollow forgings in 1.7335. It specifies the normalized + tempered delivery condition and the minimum elevated-temperature yield strength values.
• EN 10216-2: 2014 — Seamless steel tubes for pressure purposes, non-alloy and alloy steel tubes with specified elevated temperature properties. Referenced when our hollow forgings and thick-walled tubular products are supplied as tube-equivalent stock.
• EN 10253-2: 2007 — Butt-welding pipe fittings, non-alloy and ferritic alloy steels with specific inspection requirements. Governs material requirements for 1.7335 forged elbow preforms, tee-forgings and transition cone forgings used in pressure piping systems.
• EN 10273: 2007 — Hot rolled weldable steel bars for pressure purposes with specified elevated temperature properties. Referenced for forged bar supply where customers are manufacturing pressure parts by machining from bar stock.

Additional standards our material can be cross-referenced to on request: ASME SA-182 F11 (pressure vessel and piping flanges and fittings), API 6A material requirements (wellhead and Christmas tree equipment), API 16A material requirements (drill-through equipment including BOPs), NACE MR0175/ISO 15156 sour service material requirements, and EN 13480 (industrial piping). For products being incorporated into assemblies that need PED 2014/68/EU compliance or CE marking, we can provide the material traceability documentation and EN 10204 3.1/3.2 certificates required by the equipment assembler who holds legal responsibility for CE marking. For projects with RCC-M or ASME NQA-1 documentation requirements, please contact us at inquiry stage to confirm what additional traceability or witness inspection arrangements are required.

Our In-House Melting Technology: The Difference Between Raw Material and Real Quality

Many forging suppliers purchase commercial billets or bar stock and forge from purchased material — meaning they have no visibility into how the steel was made, what the ingot structure looked like, or how the chemistry was controlled during melting. We operate our own complete steelmaking facility, and for 1.7335, every ingot starts with our controlled melting process:

• 60-tonne Electric Arc Furnace (EAF), 40 MVA power — Primary melting with controlled atmosphere, eliminating bulk impurities and establishing base composition. Our EAF operation monitors melt chemistry continuously with optical emission spectrometry, allowing real-time composition adjustment before tapping.
• 2 × Ladle Furnace (LF) — Secondary metallurgical treatment for precise alloy trimming, desulfurization (achieving S ≤ 0.003% routinely, well below the EN maximum of 0.010%) and temperature homogenization. The LF stage is where we achieve our tighter-than-standard chemistry control ranges — particularly important for the Cr:Mo ratio that determines high-temperature creep performance.
• 2 × VD/VOD Tank Degassing — Vacuum degassing to get hydrogen levels below 1.5 ppm and oxygen levels below 15 ppm. For large forgings where hydrogen-induced cracking is a risk during cooling after forging, this ultra-low dissolved gas content is essential — it eliminates the need for a slow-cooling or hydrogen bake-out treatment that would otherwise add 48+ hours to the production cycle.
• Bottom Pouring Pits — Controlled bottom pouring produces ingots with lower oxide inclusions (no top-pouring splashing and re-oxidation) and better ingot surface quality, resulting in less surface defect conditioning required before forging and a higher yield of clean metal.
• ESR Plant (max 32-tonne ingot weight) — Electroslag Remelting for the most critical applications where inclusion content must be minimized to the absolute lowest level achievable. ESR-remelted 1.7335 ingots show inclusion ratings consistently at A0-B0 level (per ASTM E45 Chart I) — well beyond the capability of conventional cast ingots. ESR material is specified for nuclear applications, subsea BOP forgings and other safety-important parts where no compromise on cleanliness is acceptable.

For more details about our production facilities, please visit our Equipment page. For our full range of available alloy steel grades, please visit our Materials page.

13CrMo4-5 (1.7335) Chemical Composition: Element-by-Element Engineering Analysis

The chemical composition of 1.7335 is not an arbitrary set of numbers — each element plays a specific, quantified role in getting the material's characteristic combination of weldability, high-temperature strength and toughness. Knowing these roles helps procurement engineers evaluate MTCs  and identify out-of-specification or borderline heats before they become field problems. Following are our standard EN-range values alongside our tighter production control targets, with an explanation of why each element matters.

Carbon Equivalent (CE) Note: For weldability assessment, engineers should calculate the Pcm (Process Composition for cold cracking) or the IIW CE value from the actual MTC values, not assumed midpoint values. Our 1.7335 production heats typically get CE (IIW) in the range of 0.52–0.62 for sections up to 300mm, confirming the material's position as genuinely weldable with standard low-hydrogen procedures and appropriate pre-heat.

Mechanical Properties of 1.7335 Forged Steel: Understanding the Numbers

Mechanical property tables for 1.7335 are published in EN 10222-2 and widely reproduced — but the numbers themselves only have meaning when understood in the context of how they were obtained and what they imply for your application. The values below represent minimum requirements for the normalized and tempered condition. Our actual production results consistently exceed these minima, and we provide the actual measured values — not simply "≥ standard" statements — on every MTC. This distinction matters when customers perform fitness-for-service calculations that require the actual lower-bound properties of the specific heat delivered, rather than a standard minimum assumption.

Room Temperature Mechanical Properties (Normalized + Tempered, EN 10222-2)

Elevated Temperature Yield Strength (Rp0.2 Min)

Design Note on Elevated-Temperature Properties: The values in the table above are minimum Rp0.2 values for the normalized and tempered condition per EN 10222-2. Designers should note that these values are derived from short-time tensile tests at temperature, not from long-term creep tests. For design of parts with design life above 100,000 hours, creep rupture strength values (Rm/100,000h and Rp1%/100,000h from EN 10302 or equivalent) should be used rather than the short-time proof strength, as they represent the actual limiting failure mode for long-term elevated-temperature service. Contact our technical team for creep rupture data applicable to specific operating temperatures and design life requirements.

Heat Treatment of 1.7335 Forgings: Process Stages and Engineering Rationale

Heat treatment is the step that transforms a raw forging — with its uneven deformation-induced microstructure and residual thermal stresses — into a consistent, predictable engineering material. For 1.7335 (13CrMo4-5), the heat treatment sequence is not merely a quality assurance step; it is where the final mechanical properties are fundamentally established. Understanding the physical basis of each treatment helps engineers evaluate whether a supplier's process is genuinely optimized or simply the minimum required to pass a specification test.

Softening Annealing (600–700°C): When Pre-Machining Requires Softer Material

Softening annealing is an optional first step, applied when customers require a pre-machined condition for complex shapes where large material removal is planned. Heating to 600–700°C partially spheroidizes the pearlite phase, reducing hardness from the as-forged 220–260 HB range to approximately 160–185 HB, significantly improving machinability and reducing tool wear. Cooling rate through this range must be slow (furnace cool at max 20°C/hour through 400°C) to avoid re-introducing residual stresses. This treatment is not part of the standard normalized + tempered sequence — it is an additional cycle applied to specific orders only.

Normalizing (910–940°C): Grain Refinement and Microstructural Homogenization

The normalizing treatment is the most important first step of the standard N+T cycle. Heating above the Ac3 transformation temperature (approximately 870°C for 1.7335) fully austenitizes the steel, dissolving all prior carbide precipitates and eliminating the coarse forged grain matrix. The target temperature of 910–940°C is selected to be high enough to guarantee complete austenitization even in the centre of large-section forgings, while avoiding excessive grain coarsening that occurs above 960°C in this grade. Holding time is calculated at 2 hours per 100mm of maximum section thickness (minimum 4 hours), with temperature verified by three independent thermocouples placed to bracket the actual cold-section zone of the furnace charge.

After normalizing, forgings are withdrawn from the furnace and cooled in calm (still) air. This is not simply "air cooling" — for thick sections (above 200mm), we use controlled cooling booths with monitored airflow to ensure that the cooling rate through the 800–500°C range is kept within 1.5–3.0°C/second. Too-slow cooling produces coarse pearlite with insufficient strength; too-fast cooling risks martensite formation in thick sections that could cause cracking during subsequent tempering loading.

Tempering (650–720°C): Optimizing the Strength-Toughness Balance

The tempering treatment following normalizing reduces the brittleness of the as-normalized matrix by allowing controlled carbide precipitation and recovery of the dislocation substructure. For 1.7335, the tempering temperature selection within 650–720°C critically affects the final property balance: lower tempering temperatures (650–670°C) produce higher strength at some cost in toughness, while higher tempering temperatures (700–720°C) optimize toughness and ductility at the cost of yield strength. For impact-critical applications requiring high Charpy energy (≥50J at 0°C), we use the higher end of the tempering range. For API 6A oil and gas forgings requiring high yield strength (≥515 MPa), the lower end is appropriate. The specific tempering temperature is agreed with the customer at the order confirmation stage and documented in the heat treatment record on the MTC.

Stress Relief Annealing (660–710°C): Post-Weld and Post-Machining Treatment

Stress relief annealing (PWHT) is performed after welding when customers purchase 1.7335 forgings that will be welded into fabricated assemblies. At 660–710°C, residual stresses from welding are reduced to below 20% of the yield strength without significantly altering the base material microstructure or properties. We can perform PWHT in our furnaces before dispatch, providing a stress-relieved, ready-to-use forging. For customers performing PWHT in their own facilities, we provide the recommended thermal cycle parameters including maximum heating rate (≤100°C/hour for sections above 50mm), soak time (typically 1 hour per 25mm of weld throat, minimum 2 hours) and maximum cooling rate (≤100°C/hour through 400°C).

Hardening and Tempering (Q+T): For High-Strength Pressure Applications

The quench and temper (Q+T) cycle is an alternative to N+T for applications requiring significantly higher yield strength — for example, API 6A forgings where 75K (515 MPa YS) or 110K (758 MPa YS) material grades are needed. For Q+T, 1.7335 is austenitized at 890–930°C, then rapidly quenched (water cooling for sections ≤150mm; oil cooling or forced air for larger sections) to produce a predominantly martensitic microstructure, then tempered at 650–700°C. The Q+T cycle produces significantly higher strength than N+T for equivalent section thickness, but needs more careful process control to avoid quench cracking in complex shapes — particularly at section changes, holes and undercuts.

Quality Inspection System: What We Test, How We Test It, and Why It Matters

Quality inspection in forging is not a single test at the end of the production process — it is a cascade of interconnected controls from liquid steel to finished part. At each stage, a specific defect type is being targeted by the most appropriate detection method. Below, we describe our full inspection system for 1.7335 forgings, with an explanation of what each test detects and why it is necessary for the product types we manufacture.

In-Process Chemistry Control: OES and Vacuum Spectrometry

Chemistry verification begins in the ladle, not after casting. During melting, we take multiple ladle samples at 10-minute intervals during the LF treatment, analyzing each by optical emission spectrometry (OES) with a 60-second turnaround time. This allows real-time adjustment of alloy additions before the heat is tapped. After casting, a product analysis sample is taken from the actual ingot and analyzed by vacuum spectrometry for trace elements including tin (Sn), arsenic (As), antimony (Sb) and lead (Pb) — elements not specified in EN standards but relevant to temper embrittlement susceptibility. Both ladle and product analyses appear on the MTC.

Ultrasonic Testing (UT): Volumetric Integrity of the Forging

Ultrasonic testing per EN 10228-3 is performed on 100% of our 1.7335 forgings after final heat treatment and before any machining beyond the initial surface preparation. The UT examination uses contact straight-beam (compression wave) scanning at 2 MHz or 4 MHz to detect internal planar defects (cracks, cold shuts, segregation bands), volumetric defects (porosity clusters, inclusions) and laminations. Inspection class is standard EN 10228-3 Class 3 (which requires rejection of echoes above 50% of the reference reflector from any Ø2mm flat-bottomed hole) with Class 4 available for more demanding applications where customers specify a higher cleanliness requirement. For ring forgings above 1,500mm diameter, we perform UT from multiple directions — including axial, radial and circumferential scanning — to ensure no significant defect orientation is missed by single-direction scanning.

Magnetic Particle Inspection (MPI): Surface and Near-Surface Crack Detection

MPI per EN 10228-1 is applied to all 1.7335 forgings after heat treatment and after any rough machining that exposes new surfaces. MPI detects surface-breaking and near-surface (≤2mm depth) linear defects — primarily hot tears, forging laps, grinding burns and quench cracks — that are not reliably detected by UT due to their thin planar geometry. We use the wet fluorescent technique (WFMT) with UV-A (365 nm) illumination, which provides significantly better sensitivity than the dry powder or wet visible methods commonly used by less specialized suppliers. Fluorescent MPI can detect cracks as narrow as 1 μm at the surface — a capability that is particularly important for valve body forgings where any surface crack is an absolute rejection criterion.

Mechanical Property Testing: Tension, Hardness and Impact

Mechanical testing is performed on test coupons machined from sacrificial material attached to each forging heat lot (for bars and rings) or from a prolongation of each individual forging (for large one-piece pressure vessel parts). This ensures that test results reflect the actual thermal and mechanical history of the forging being supplied, not just the heat of steel.

• Tensile Testing (ASTM E8/E8M or EN ISO 6892-1): Room-temperature testing for ultimate tensile strength (UTS), 0.2% proof strength (Rp0.2), elongation (A%) and reduction of area (Z%). Test specimens are machined parallel to the main forging direction. For section thicknesses above 200mm, we test at both surface and ¼-thickness locations to demonstrate property uniformity through the section.
• Charpy Impact Testing (EN ISO 148-1): Standard testing at 0°C on three V-notch specimens per test location, reporting individual and average absorbed energy values. For low-temperature applications, we routinely test at -20°C and -40°C, with -60°C testing available for subsea and arctic applications.
• Brinell Hardness (ASTM E10 / EN ISO 6506-1): Surface hardness mapping at a minimum of 5 evenly distributed locations per forging. For 1.7335 in N+T condition, acceptable hardness range is typically 135–190 HBW for standard pressure applications. Hardness variation within a single forging of more than 30 HBW triggers re-inspection of the heat treatment record.
• Elevated-Temperature Tensile Testing (EN 10002-5): Performed at customer request for boiler and pressure vessel applications, typically at 200°C, 300°C, 400°C and 500°C, providing actual Rp0.2 values at service temperature for design verification.

EN 10204 3.1/3.2 Mill Test Certificate: What Is Actually Included

Our standard MTC for every 1.7335 forging delivery is a Type 3.1 certificate (prepared and signed by our authorized Inspector, independent from the manufacturing department) covering: heat number, ingot number, forging serial number, order reference; full product analysis (not just ladle analysis) including 20+ elements; actual measured mechanical test results (not "conforms to standard" statements); heat treatment cycle records with actual furnace temperatures, holding times and cooling rates from embedded thermocouples; UT and MPI inspection results with acceptance class reference; dimensional inspection report with actual measured values; and material designation to EN 10222-2 (or dual-certified to ASTM A182 F11 where required). Type 3.2 co-inspection by a customer-nominated third-party inspector (Bureau Veritas, Lloyd's, SGS, TÜV, DNV etc.) is available for all orders above 5 tonnes.

Why Source 1.7335 Forgings from Jiangsu Liangyi: A Supplier Evaluation Guide

We encourage our customers to evaluate forging suppliers rigorously — not to accept generic claims of "best quality and price" without verification. Below, we provide specific, verifiable differentiators that distinguish our 1.7335 forging capability from the typical market alternatives. These are the questions we recommend asking any forging supplier before placing an order.

Our 1.7335 Custom Forging Production Process: Step-by-Step

Frequently Asked Questions (FAQ) About 1.7335 (13CrMo4-5) Forgings