Technical knowledge
Monel K-500: age hardened strength with Monel corrosion resistance
Monel K-500 composition, ageing response, strength advantage over Monel 400, risks in stagnant seawater and specification notes for shafts, fasteners and high strength flanged components.
How K-500 develops strength
Aluminium and titanium form coherent gamma prime precipitates during ageing, which raise strength without a large loss of ductility. The alloy is normally solution annealed, formed or machined, then aged. Because the ageing response depends on time, temperature and prior cold work, the thermal history must be recorded and reported.
| Item | Monel 400 | Monel K-500 aged |
|---|---|---|
| UNS number | N04400 | N05500 |
| Aluminium | Not specified | 2.30 - 3.15 % |
| Titanium | Not specified | 0.35 - 0.85 % |
| Hardening | Solid solution only | Age hardenable |
| Typical yield strength | About 170 MPa | Well above 400 MPa |
| Seawater, flowing | Excellent | Excellent |
| Seawater, stagnant | Good | More susceptible |
Risks that should be on the specification
- Stagnant or polluted seawater. Aged K-500 can suffer localised attack where flow stops or where sulphide contamination occurs.
- Cathodic protection. Hydrogen generated at a protected surface can contribute to cracking in high strength aged material. Review the protection design voltage.
- Hardness limits. For sour service, state the maximum hardness and require actual readings.
- Fabrication sequence. Welding in the aged condition destroys the properties of the heat affected zone; solution anneal and re-age the component if full strength is required.
Typical uses in piping and equipment
K-500 is most often selected for pump shafts, impellers, fasteners, springs, doctor blades and valve trim rather than for whole piping systems. Where a flanged joint needs higher strength than Monel 400 can give, it is a practical upgrade provided the environment remains flowing and free of oxidising contaminants.
Questions about this topic
Can K-500 be used in place of Monel 400?
Yes where higher strength is required and the environment is flowing and non oxidising. It is not a universal upgrade: in stagnant seawater and in strongly cathodically protected systems, Monel 400 is often the safer choice.
Does K-500 need a post weld heat treatment?
Welding overages and softens the heat affected zone. If the joint must develop full strength, the component should be solution annealed and re-aged, which is only practical before final machining.
Is K-500 suitable for hydrofluoric acid?
Yes, it retains the hydrofluoric acid resistance of Monel 400 and adds strength. Confirm the specific concentration, temperature and contaminant levels with the process licensor before specifying.
Questions about our products
What products does Hangbo Alloy supply?
Four product families, all available in nickel-based alloys, titanium, duplex and special stainless steel: flanges, butt weld pipe fittings, elbows, and seamless tube and pipe. Flanges cover weld neck, long weld neck, slip-on, blind, socket weld, threaded and lap joint patterns. Fittings and elbows cover concentric and eccentric reducers, equal and reducing tees, caps, stub ends, and 45°, 90° and 180° returns in both long and short radius, plus 3D and 5D bends for piggable lines. Seamless tube and pipe is supplied cold drawn or hot finished from 6 mm to 630 mm outside diameter.
Which alloy grades are available for these products?
More than 90 grades are published in our grade library. The most requested are Inconel 625, 718, 600 and X-750, Hastelloy C-276, C-22 and B-2, Monel 400 and K-500, Incoloy 800H, 825 and 925, duplex 2205 and super duplex 2507, 316L, 904L and 254SMO stainless steel, and titanium Grade 2 and Grade 5. Nickel-based grades can also be supplied with VIM plus ESR double melting where cleanliness or fatigue life is critical.
What sizes, wall thicknesses and pressure classes can you supply?
Flanges run from NPS ½ to NPS 24 to ASME B16.5 and from NPS 26 to NPS 60 to ASME B16.47 Series A or B, in pressure classes 150 through 2500. Butt weld fittings and elbows run from NPS ½ to NPS 48 (DN 15 to DN 1200) in wall thickness Schedule 5S through XXS. Seamless tube and pipe covers 6 mm to 630 mm outside diameter, in random lengths of about 5 to 7 metres or fixed lengths up to 12 metres. Non-standard and intermediate sizes are quoted on request.
Which material and dimensional standards do you work to?
Forged flanges to ASTM B564, B381 and A182 with dimensions to ASME B16.5 and ASME B16.47. Butt weld fittings and elbows to ASTM B366 and A403 with dimensions to ASME B16.9 and MSS SP-43. Seamless tube and pipe to ASTM B444, B423, B622, B163, B167, B861, A312, A213 and A790. Marking follows MSS SP-25 and the applicable product standard. If your project is governed by EN, DIN, JIS or a company specification, send the document and we will confirm equivalence before quoting.
Is there a minimum order quantity?
There is no minimum for standard sizes and grades held in stock, and prototypes, spares and small trial batches are accepted. Made-to-order melts and special forgings carry a minimum weight that depends on the alloy and the route, typically from about 500 kg for special grades.
What inspection and certification is issued with the goods?
Every shipment carries an EN 10204 3.1 mill test certificate quoting the actual chemical and mechanical results for the specific heat lot, together with dimensional records and heat treatment data where applicable. Testing is carried out in house by optical emission spectrometry, tensile, impact and hardness testing, plus ultrasonic and eddy current examination, with hydrostatic pressure and intergranular corrosion testing to ASTM G28 or A262 Practice E where the specification requires it. Third party inspection by SGS or another recognised agency can be arranged, and their report is issued alongside the shipment.
What are typical lead times?
Standard stock items ship within days. Common production grades such as Inconel 625 or duplex 2205 are typically a few weeks. Special chemistries, larger forgings and items that require third party inspection take longer and are quoted individually against the requirement.
How are the products packed for export?
Flanges and fittings receive a rust preventive coating, are individually wrapped and are packed in plywood cases secured with steel banding. Tube ends are capped and bundles are strapped. Packing lists quote heat numbers so every case can be cross-checked against the mill certificate on arrival. We quote EXW, FOB, CFR, CIF and DAP, and mixed-alloy orders can be consolidated into one shipment with a single documentation package.
How do I request a quotation or a sample?
Send the grade or UNS number, the dimensions including schedule or wall thickness, the governing material and dimensional standards, quantity, any heat treatment or NDT scope and the certificate type you need; a drawing is ideal for special flanges and fittings. Email demi@nickel-alloy.com or message us on WhatsApp +86 15618279078 and we normally issue a formal quotation within 24 hours on working days. Samples and previous test reports can be arranged before the first order.
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