Industrial-grade ferrochromium nitride alloy powder

01

Choose the chromium and nitrogen grade and residual limits

ASTM A101 covers ferrochromium in high-carbon and low-carbon types, the low-carbon type including nitrogen-bearing and vacuum grades, available in different sizes and required to conform to limits for chromium, carbon, silicon, sulfur, phosphorus and nitrogen. [1]

Westbrook Resources lists two nitrided ferrochrome grades, both with 63–68% chromium, at most 1.50% silicon, 0.03% phosphorus, 0.03% sulfur and 0.5% manganese, and with either 3–4% or 6–9% nitrogen. It states carbon of around 0.05–0.07% for special steels that need tight carbon control. [2]

China's ferrochrome standard, GB/T 5683-2024 (issued 25 April 2024, in force 1 November 2024, replacing the 2008 edition and modified from ISO 5448:1981), covers ferrochrome for alloying steel and castings, including micro-, low-, medium- and high-carbon grades and new low-nitrogen low-carbon and low-nitrogen medium-carbon grades. It raises the number of grades from 28 to 68, changes the particle size and non-metallic inclusion requirements, and adds a distillation separation and Nessler reagent spectrophotometric method for nitrogen (Appendix C). Its scope does not list nitrided ferrochrome, so a nitrogen-bearing grade bought in China needs its chemistry and size written into the contract or a maker's own specification. [3]

Editorial note: name the nitrogen test method in the order; GB/T 5683-2024 gives a spectrophotometric method, and the supplier and your laboratory should use the same one when the lot is checked. [3]

Westbrook describes production as exposing ferrochrome to a nitrogen-rich atmosphere at up to 1,300 °C, then cooling and crushing it to size. [2]

Give the supplier the steel grades and melt practice, chromium and nitrogen grade, maximum carbon, silicon, phosphorus, sulfur and other residuals, size range (lump, granule or powder with a stated distribution), packaging, lot size, and the analysis certificate required with each shipment.

02

Set size, packing and expected nitrogen recovery

Westbrook supplies nitrided ferrochrome sized 5–100 mm, in drums on pallets or 25 kg bags, with other packing on request. It says nitrogen recovery, the share of added nitrogen that dissolves in the steel, depends on steel grade and melting temperature, and quotes 70–95% recovery from nitrided ferrochrome against 20–70% from nitrogen gas, because the nitrogen is released gradually as the alloy dissolves and chromium raises nitrogen solubility. [2]

Westbrook adds that too much nitrogen can reduce ductility, weldability, toughness and formability, and that nitrogen is an austenite stabiliser in stainless steels. [2] For powder or granule sizes below its listed 5 mm minimum, ask the supplier for the particle size distribution, fines content and how the material is packed to limit oxidation and dust.

Editorial calculation: 1 kg of a 6–9% N grade carries 60–90 g of nitrogen; at 70–95% recovery, about 42–86 g dissolves in the steel. [2]

03

See how published melts add nitrided ferrochrome and what nitrogen they reach

Two open-access studies from Chinese steel research groups describe nitrided ferrochrome as the nitrogen carrier in vacuum induction melting (VIM) and report the nitrogen that ended up in the steel. They show where in the melt sequence the alloy goes in and the nitrogen levels buyers of this product are aiming at.

In a 50 kg VIM furnace, researchers melting T91 heat-resistant steel charged pure iron and pure metals, melted them under a vacuum below 10 Pa, deoxidised with Ni-Mg, added graphite, then back-filled the furnace with argon to 30,000 Pa before adding ferrochromium nitride. The finished heats held 9.05–9.36 wt.% Cr and 0.039–0.066 wt.% N. The authors state that T91 is held to Al of no more than 0.02 wt.% with N/Al of at least 4, so nitrogen added through the alloy also sets the permissible aluminium. [4]

For a 00Cr20Ni18Mo6CuN super austenitic stainless steel, another group added ferrochrome nitride after breaking the vacuum, deoxidised with Ni–Mg, then forged and hot-rolled the ingots at 1150 °C to 5 mm sheet; the five heats analysed 20.02–20.37 wt.% Cr and 0.194–0.235 wt.% N. [5]

Editorial calculation: putting 0.2 wt.% N into a 50 kg heat needs 100 g of dissolved nitrogen; with a 6–9% N grade and the 70–95% recovery Westbrook quotes, that is roughly 1.2–2.4 kg of nitrided ferrochrome. [2] [5]

04

Lot analysis, size distribution and REACH status to ask any nitrided ferrochrome supplier for

Ask any supplier for the standard or specification met, lot analysis for Cr, N, C, Si, P, S and Mn, size distribution, packaging, REACH registration where needed, lead time and minimum order.

05

Chromium, nitrogen, carbon, residuals and size

Carbon matters as much as nitrogen in this alloy: Westbrook gives around 0.05–0.07% carbon for special steels, and ASTM A101 places its nitrogen-bearing grades under the low-carbon type. [2] [1]

06

Chromium, nitrogen, carbon, sulfur and phosphorus, and size distribution for a nitrided ferrochrome order

Size is the row to settle with the supplier: Westbrook lists 5–100 mm, so a powder or granule order needs its own distribution, and the reviewed sources give no bulk density, flow or oxygen value for powder. [2]

07

Send the grade, residual and size data together

Paste it into your enquiry below or into an email to a maker, then replace every bracket.

Grade: [Cr %; N 3–4% or 6–9%]
Limits: [C; Si; P; S; Mn]
Specification: [ASTM A101 or other]
Size: [lump; granule; powder distribution]
Packing: [drums; 25 kg bags; big bags]
Use: [steel grades; addition method]
Quantity: [t per shipment]

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