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X6NiCrTiMoVB25-15-2 Threaded Rod
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Name: X6NiCrTiMoVB25-15-2 Threaded Rod
Standard: EN10269
Material: X6NiCrTiMoVB25-15-2
Size: 1-7/8 inch
Lenght: 420 mm
Temperature: 650-700℃
Surface: Natural color
Standard: EN10269
Material: X6NiCrTiMoVB25-15-2
Size: 1-7/8 inch
Lenght: 420 mm
Temperature: 650-700℃
Surface: Natural color
Quantity
X6NiCrTiMoVB25-15-2 Threaded Rod is manufactured to EN 10269. Diameter 1-7/8 in., length 420 mm; after solution treatment and ageing the tensile strength is ≥ 900 MPa and excellent resistance to relaxation and oxidation is retained at 650–700 °C. The natural bright finish resists high-temperature sulphidic attack without any additional coating, making it the ideal high-strength fastening element for ultra-super-critical steam cylinders, nuclear steam generators and heavy-duty gas turbines.
Which elements must be watched when X6NiCrTiMoVB25-15-2 Threaded Rod is analysed by optical emission (OES) or X-ray fluorescence (XRF)?
The purpose of the analysis is “quantitative grade confirmation and mix-up prevention”, so the elements that fix the alloy family must be measured accurately. In order of importance they fall into three groups:
The purpose of the analysis is “quantitative grade confirmation and mix-up prevention”, so the elements that fix the alloy family must be measured accurately. In order of importance they fall into three groups:
1. Matrix and main alloying elements (to be reported to 0.01 %)
- Carbon/alloy steels: C, Mn, Si, Cr, Ni, Mo
- Stainless steels: Cr, Ni, Mo, Cu, N (N mandatory for duplex grades)
- High-temperature alloys such as X6NiCrTiMoVB25-15-2 Threaded Rod: Ni, Cr, Ti, Mo, V, B, Al, Nb
- Carbon/alloy steels: C, Mn, Si, Cr, Ni, Mo
- Stainless steels: Cr, Ni, Mo, Cu, N (N mandatory for duplex grades)
- High-temperature alloys such as X6NiCrTiMoVB25-15-2 Threaded Rod: Ni, Cr, Ti, Mo, V, B, Al, Nb
2. Minor control elements (affect heat treatment and high-temperature behaviour, normally ≤ 0.1 %)
B, V, Nb, Ti, Al, N, Co
B, V, Nb, Ti, Al, N, Co
3. Residual/harmful impurities (to verify they are below the maximum allowed)
P, S, Pb, Sn, As, Sb, Bi (nuclear and defence orders often limit the “five harmful” elements to ≤ 0.010 %)
P, S, Pb, Sn, As, Sb, Bi (nuclear and defence orders often limit the “five harmful” elements to ≤ 0.010 %)
Taking X6NiCrTiMoVB25-15-2 Threaded Rod as an example, the points to watch during composition testing are as follows.
X6NiCrTiMoVB25-15-2 Threaded Rod (EN 10269 designation, the same as material 660) is an iron–nickel-base super-alloy strengthened by γ′ precipitates. After solution treatment and ageing it still gives Rp0.2 ≥ 550 MPa and Rm ≥ 900 MPa at 700 °C, and its resistance to relaxation is better than that of 25 Cr-20 Ni austenitic steels.
X6NiCrTiMoVB25-15-2 Threaded Rod (EN 10269 designation, the same as material 660) is an iron–nickel-base super-alloy strengthened by γ′ precipitates. After solution treatment and ageing it still gives Rp0.2 ≥ 550 MPa and Rm ≥ 900 MPa at 700 °C, and its resistance to relaxation is better than that of 25 Cr-20 Ni austenitic steels.
Acceptance testing by OES/XRF is therefore centred on “five major plus three minor” elements with the following internal limits (mass fractions, %):
1. Nickel Ni 24.0–27.0
Fixes the γ-austenite matrix and guarantees microstructural stability at 650–700 °C. Below 24 % σ-phase may precipitate; above 27 % hot-workability drops and cost rises.
Fixes the γ-austenite matrix and guarantees microstructural stability at 650–700 °C. Below 24 % σ-phase may precipitate; above 27 % hot-workability drops and cost rises.
2. Chromium Cr 13.5–16.0
Gives an oxidation-mass-gain limit ≥ 0.3 mg/(cm²·h) (700 °C, 100 h) by forming a continuous Cr₂O₃ film. Below 13.5 % the film is discontinuous and grain-boundary oxidation occurs; above 16 % residual δ-ferrite appears and impact toughness after ageing falls by more than 30 %.
Gives an oxidation-mass-gain limit ≥ 0.3 mg/(cm²·h) (700 °C, 100 h) by forming a continuous Cr₂O₃ film. Below 13.5 % the film is discontinuous and grain-boundary oxidation occurs; above 16 % residual δ-ferrite appears and impact toughness after ageing falls by more than 30 %.
3. Molybdenum Mo 1.00–1.50
Provides solid-solution strengthening and raises the creep activation energy. Together with Cr it increases the pitting potential by 60–80 mV. Above 1.5 % Mo-rich μ-phase may form and cause notch sensitivity.
Provides solid-solution strengthening and raises the creep activation energy. Together with Cr it increases the pitting potential by 60–80 mV. Above 1.5 % Mo-rich μ-phase may form and cause notch sensitivity.
4. Titanium Ti 1.90–2.30
Main former of γ′ Ni₃(Ti,Al). Keeping Ti/Al between 5 and 7 gives a γ′ volume fraction of 12–15 % and a creep life ≥ 120 h at 700 °C under 200 MPa. Below 1.9 % strengthening is insufficient; above 2.3 % massive η-Ni₃Ti appears and fatigue-crack-initiation resistance drops.
Main former of γ′ Ni₃(Ti,Al). Keeping Ti/Al between 5 and 7 gives a γ′ volume fraction of 12–15 % and a creep life ≥ 120 h at 700 °C under 200 MPa. Below 1.9 % strengthening is insufficient; above 2.3 % massive η-Ni₃Ti appears and fatigue-crack-initiation resistance drops.
5. Vanadium V 0.10–0.50
Refines grain-boundary carbides and improves notched creep strength. V(C,N) pins boundaries, reducing grain-growth rate at 700 °C by about 40 %. Above 0.5 % V-rich phases form and machinability deteriorates.
Refines grain-boundary carbides and improves notched creep strength. V(C,N) pins boundaries, reducing grain-growth rate at 700 °C by about 40 %. Above 0.5 % V-rich phases form and machinability deteriorates.
6. Boron B 0.003–0.010
Grain-boundary micro-alloy element; a segregation level of 10–20 ppm raises grain-boundary diffusion activation energy by ~15 % and doubles creep ductility. Upper limit 0.01 % avoids low-melting boride eutectics.
Grain-boundary micro-alloy element; a segregation level of 10–20 ppm raises grain-boundary diffusion activation energy by ~15 % and doubles creep ductility. Upper limit 0.01 % avoids low-melting boride eutectics.
7. Aluminium Al 0.35–0.65
Enters γ′ and raises its solution temperature by 15–20 °C. Below 0.35 % ageing hardness is too low; above 0.65 % it competes with Ti and brittle Ni₂Al may form.
Enters γ′ and raises its solution temperature by 15–20 °C. Below 0.35 % ageing hardness is too low; above 0.65 % it competes with Ti and brittle Ni₂Al may form.
8. Niobium Nb 0.50–1.00
Supplements γ′ strengthening and forms some NbC that inhibits grain-boundary sliding. Above 1 % acicular δ-Ni₃Nb appears and room-temperature impact energy falls by more than 20 J.
Supplements γ′ strengthening and forms some NbC that inhibits grain-boundary sliding. Above 1 % acicular δ-Ni₃Nb appears and room-temperature impact energy falls by more than 20 J.
Analytical tolerances are taken from EN 10269 Table D.1: major elements Ni, Cr ±1 % relative; Mo, Ti ±5 % relative; micro-element B ±0.001 % absolute. For on-site PMI, spark-OES with a 6 s pre-burn and 3 s integration is recommended; use multi-line averaging for Ti and Al, select the 249.677 nm line for B with matrix-matched correction, and keep the repeatability error ≤ 0.0005 %.
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