Use A105 for common carbon steel flange requirements when project conditions allow
ASTM A105 vs A350 LF2 Flanges
ASTM A105 and ASTM A350 LF2 are both common forged flange materials, but they should not be treated as interchangeable. Service temperature, impact testing, heat treatment, standard basis and certificate requirements should be confirmed before quotation. This guide also carries the third-party type-test report on one of our own low-temperature weld neck flanges, so the notch-toughness claim on this page can be checked against the source document. The tested grade is 16MnD and not A350 LF2, and that difference is stated in full below.
Key Points
Use A350 LF2 when low-temperature service and impact testing are specified
Confirm normalized condition, certificate wording and inspection documents
Attach the project specification when material selection is controlled by the end user
Read notch-toughness evidence as grade-specific: impact results belong to the grade that was tested
Engineering Selection Notes
The practical decision between A105 and A350 LF2 is rarely made by price alone. It is usually made by the project line class, minimum design metal temperature, certificate wording and whether impact evidence must be visible in the document package. If the buyer only sends a material name, the supplier may quote the right shape but the wrong verification route.
A105 and A105N are familiar carbon-steel flange words in many ASME RFQs, but normalized condition still needs to be stated when the project requires it. LF2 carries a different purchasing signal: the buyer is usually asking for low-temperature suitability and notch-toughness evidence, so the RFQ should say exactly what impact test, heat treatment and MTC 3.1 records are expected.
For export quotation, the safest approach is to quote the material exactly as written first, then discuss alternatives separately. That keeps the commercial offer, MTC wording, heat treatment route and inspection plan aligned with the end-user approval path.
The outside evidence on this page for the low-temperature half of this comparison is one report, and it has to be read precisely. The Zhejiang Academy of Special Equipment Science ran a type test on a WN 200-150 RF STD weld neck flange taken from our shop floor and issued report YSY202450080. Six Charpy specimens broken at -45 °C returned 175.0 to 283.0 J against the 47 J minimum printed in the report, and the tensile and chemistry rows sit inside their printed limits as well. The material on that report is 16MnD, a Chinese low-temperature carbon-manganese forging grade tested to NB/T 47009-2017. It is used for the same kind of low-temperature duty that A350 LF2 is used for, but it is a different grade under a different specification and the measured numbers belong to 16MnD alone. What the report evidences is that this shop can put a low-temperature forging several times over its notch-toughness requirement. It is not an LF2 test result and must not be read as one. Measured A350 LF2 values of ours are on a different document: our A350 LF2 flange page shows TÜV SÜD inspection certificate 348229, for one order, with Charpy results at -46 °C. Those values belong to that certificate and are neither repeated nor combined here.
First-Hand Evidence
One third-party report, published whole: the figure shows the page the measured values on this guide are taken from, and the link under it opens the complete PDF - cover, declaration, contents and all five report pages. The report is on a 16MnD low-temperature flange, not on an A350 LF2 flange, and the answers below state exactly what that does and does not prove.
Evidence 1
Nothing on this page is redacted. The report carries no customer, contract or order reference - it is a type test on our own production sample - and the inspector signatures are part of what makes the document valid. The two buttons below open and download the complete report PDF, not only this page.
Direct Answers with Evidence
Has anyone outside the factory measured low-temperature impact toughness on a flange you forged?
Yes. The evidence on this page is one type-test sample set: six Charpy specimens cut from a WN 200-150 RF STD weld neck flange broke at 175.0 to 283.0 J at -45 °C against the 47 J minimum printed in the report - the lowest of the six is 3.7 times the requirement.
Evidence
- Report YSY202450080, section III, report page 5 of 5, impact row: specimen 23XS5127-001 reads 175.0 J, 206.5 J and 210.0 J; specimen 23XS5127-002 reads 180.0 J, 236.5 J and 283.0 J; the requirement column reads at least 47 J on both lines and the remark column records the test temperature as -45 °C
- The report was issued by the Zhejiang Academy of Special Equipment Science under type-test rules TSG D7002-2023, against material standard NB/T 47009-2017 for alloy steel forgings used in low-temperature pressure equipment; testing signed 2023-12-28, review signed 2024-01-11
- It belongs to type-test certificate TSXY741010027202450009, whose printed material scope names alloy steels with a design temperature below -40 °C
Applies when
The sample was a DN200 (NPS8) CL150 raised-face weld neck flange in 16MnD, forging grade IV, batch 2023-BCKC-0082, forged and sampled 2023-12-26. Two pieces were tested out of a five-piece sampling base, three impact specimens per piece.
Limits
The tested grade is 16MnD, not A350 LF2 - these joules are not an LF2 result and cannot be quoted as one. Six values from two pieces of one batch are not a guarantee for your batch, and a type test is not batch release. The report records no heat-treatment temperature, soak time or cooling medium, so it evidences the outcome on those two pieces and nothing about the recipe that produced it. The tested article is DN200 CL150 only; a Class 900 or an NPS 24 low-temperature flange sits outside what was sampled.
Is 16MnD the same thing as ASTM A350 LF2?
No. They are built for the same job - forged piping components for low-temperature service - but they are different grades under different specifications, and nothing in this report is written in A350 LF2 wording.
Evidence
- Report YSY202450080 names the material as 16MnD and the material standard as NB/T 47009-2017; ASTM A350/A350M appears nowhere in the report
- The requirement column on that report is the NB/T 47009-2017 limit set for 16MnD: C 0.13-0.20, Si 0.20-0.60, Mn 1.20-1.60, P max 0.020, S max 0.010, Cr max 0.25, Ni max 0.40, Cu max 0.20, Nb max 0.030 - measured 0.17, 0.27, 1.30, 0.011, below 0.0050, 0.095, 0.025, 0.023 and 0.019 respectively
- LF2 appears in our documentation on a different piece of paper: Annex I of the TÜV NORD ASME Section II Part A conformity certificate lists SA-350/SA-350M grades LF2, LF3 and LF6, and that is a material scope statement, not a measurement
Applies when
Use the 16MnD figures when the question is whether this shop can forge and pass a low-temperature flange at all. Use the Annex I row when the question is whether LF2 is inside the material scope an outside body has assessed here.
Limits
Do not read across the two documents. Our published A350 LF2 impact values are on a third document - TÜV SÜD inspection certificate 348229 on our A350 LF2 flange page, for one order and one heat - and they say nothing about 16MnD, just as this report says nothing about LF2. If your line class calls for LF2, the acceptance values, the test temperature and the certificate wording come from A350/A350M and belong in an MTC written to that specification for your heat. Treat 16MnD as evidence of process capability on low-temperature carbon-manganese forgings and nothing more.
What else did the type-test body measure on that flange, and what did it leave untested?
Chemistry, tensile, dimensions, geometry, sealing-face roughness, marking and appearance were all measured and all passed. Hardness, metallography, reduction of area and grain size were not tested at all, and the ultrasonic line is our own UT report reviewed by the test body rather than UT they performed.
Evidence
- Tensile on specimens 23XS5127-001 and -002, report page 5: Rp0.2 383 and 412 MPa against a 305 MPa minimum, Rm 529 and 551 MPa against a 480-630 MPa band, elongation A 25.5% and 27.0% against 20%
- Report page 4 carries the first half of the chemistry and the dimensional and geometric checks to HG/T 20615-2009 - flange outside diameter 346.1 mm and 346.5 mm against 345 mm +4.0/-1.0, thickness 27.3 mm and 27.8 mm against 27 +3.0/-0, flange height 100.2 mm and 100.8 mm against 100 plus or minus 1.6, facing parallelism 0.6 and 0.7 degrees against a 1 degree limit, sealing-face roughness Ra 5.8 and Ra 5.9 against Ra 3.2-6.3
- Non-destructive testing is recorded as piece-by-piece ultrasonic examination to NB/T 47013.3-2015 Class I, with the result column stating that our own UT report was reviewed and confirmed by the test body
Applies when
All of it applies to the two sampled pieces of batch 2023-BCKC-0082 only, measured at the test body's Haining and Hangzhou sites between 2023-12-28 and 2024-01-11.
Limits
Both hardness rows are dashes - there is no hardness number in this report, even though the verdict cell on that row reads pass, so nothing here supports a hardness cap. The metallographic row is empty. Reduction of area Z and grain size are not listed at all. The ultrasonic result is a review of our report, so it cannot be quoted as UT performed by a third party. And the heat-treatment line on the document-review page is a conformity verdict with no temperature or soak time behind it.
Is there third-party paper that covers A105 and LF2 themselves?
Yes, as a material scope statement rather than as test results: our forged flange and forging materials are certified to ASME Section II Part A by TÜV NORD, and Annex I of that certificate lists SA-105/SA-105M and the SA-350/SA-350M grades LF2, LF3 and LF6 on the same page.
Evidence
- TÜV NORD Certificate of Conformity No. CER-IND1105842412004001 Rev. A, ASME BPVC Section II Part A, product line 'Forged Steel Flanges and Forgings', certification type type approval plus factory inspection
- Annex I prints SA-105/SA-105M with a dash in the grades cell, SA-350/SA-350M with LF2, LF3 and LF6, and SA-765/SA-765M with Grade I to V; one merged size cell applies thickness max 550 mm and weight max 7000 kg to every row
- The certificate states its own dates - issued 25.02.2025, valid to 24.02.2028, subject to annual surveillance audit
Applies when
Useful at vendor-registration or prequalification stage, when the question is which material standards an outside body has already assessed at our plant rather than what a particular flange measured.
Limits
The certificate says in its own words that it is based on the evaluation of samples, that it does not imply an assessment of the production of the product, and that it does not permit use of a TÜV NORD mark - which is why the fact is stated here in text and no TÜV badge appears anywhere on this site. It is a material conformity certificate: not an ASME Code stamp authorization, not a quality-system certificate and not a per-order release. Its validity is conditional on the annual surveillance audit, so ask for the current signed annex page if your approval process has to see it. Above all, a grade appearing in Annex I is a scope line, not evidence that any particular flange met that grade.
Source Basis
- Type-test report YSY202450080 - complete PDF (Zhejiang Academy of Special Equipment Science) - every measured value quoted on this page comes from section III, report pages 4 and 5
- Special equipment type-test certificate TSXY741010027202450009 - the certificate the report belongs to; its material scope names alloy steels with a design temperature below -40 °C
- ASME BPVC Section II Part A material conformity certificate issued by TÜV NORD - Annex I lists SA-105/SA-105M and the SA-350/SA-350M grades LF2, LF3 and LF6, with one size limit covering every row
Measured values against the limits printed in type-test report YSY202450080 (16MnD, WN 200-150 RF STD)
| Property | Limit printed in the report | Measured value | Verdict |
|---|---|---|---|
| C | 0.13-0.20% | 0.17% | within range |
| Si | 0.20-0.60% | 0.27% | within range |
| Mn | 1.20-1.60% | 1.30% | within range |
| P | max 0.020% | 0.011% | within limit |
| S | max 0.010% | below 0.0050% | within limit |
| Cr | max 0.25% | 0.095% | within limit |
| Ni | max 0.40% | 0.025% | within limit |
| Cu | max 0.20% | 0.023% | within limit |
| Nb | max 0.030% | 0.019% | within limit |
| Yield strength Rp0.2 (two specimens) | min 305 MPa | 383 MPa / 412 MPa | passes with margin |
| Tensile strength Rm (two specimens) | 480-630 MPa band | 529 MPa / 551 MPa | inside the band, not only above a floor |
| Elongation A (two specimens) | min 20% | 25.5% / 27.0% | passes with margin |
| Impact energy at -45 °C, specimen 23XS5127-001 | min 47 J | 175.0 J / 206.5 J / 210.0 J | lowest of the three is 3.7 times the requirement |
| Impact energy at -45 °C, specimen 23XS5127-002 | min 47 J | 180.0 J / 236.5 J / 283.0 J | lowest of the three is 3.8 times the requirement |
| Sealing face roughness (two specimens) | Ra 3.2-6.3 | Ra 5.8 / Ra 5.9 | within range |
| Ultrasonic examination | piece-by-piece UT to NB/T 47013.3-2015 Class I | our UT report reviewed and confirmed by the test body | accepted - the test body did not run the UT itself |
| Hardness | no requirement entered in this report | not tested, both hardness rows are dashes | no hardness data exists for this sample, even though the verdict cell on that row reads pass |
| Metallographic examination | no requirement entered in this report | not tested, the row is dashes | no metallographic data exists for this sample |
| Reduction of area Z and grain size | neither is listed in the report | not tested | not available |
| Heat-treatment parameters | not recorded anywhere in the report | the document-review page marks heat treatment as conforming, with no temperature, soak time or cooling medium given | no process values to quote from this document |
Published ASTM Scope Check
| Scope item | ASTM A105 | ASTM A350 LF2 | RFQ implication |
|---|---|---|---|
| Published use | Forged carbon steel piping components for ambient- and higher-temperature pressure systems | Carbon and low-alloy steel forged or ring-rolled flanges, fittings and valves intended primarily for low-temperature service | Do not treat the grades as interchangeable without project or end-user approval |
| Typical product form | Flanges, fittings, valves and similar forged piping parts | Forged or ring-rolled flanges, forged fittings and valves | Send the exact flange type and dimensional standard with the material grade |
| Temperature clue | Common carbon-steel pressure service where the project permits A105 / A105N | Low-temperature service where notch toughness testing is required | State design temperature and any MDMT / impact-test wording from the project specification |
| Certificate evidence | MTC 3.1 with chemistry, mechanical values and heat treatment when required | MTC 3.1 plus impact-test / notch-toughness evidence when specified | List certificate and test-report scope before quotation |
| Substitution risk | May not satisfy a low-temperature line class or end-user material note | May be over-specified for ordinary service if LF2 is not required | Ask whether substitution or alternative grade review is allowed |
Rows of Annex I that bear on this comparison (TÜV NORD certificate CER-IND1105842412004001 Rev. A)
| Standard code as printed | Grades printed in Annex I | Size limit printed in Annex I | What the row does and does not say |
|---|---|---|---|
| SA-105 / SA-105M | the grades cell is a dash - this standard is not subdivided into grades | thickness max 550 mm, weight max 7000 kg | the standard sits inside the assessed material scope; the row is not a test result on any particular flange |
| SA-350 / SA-350M | LF2, LF3, LF6 | same limit - Annex I prints one merged size cell covering every row | LF2 sits inside the assessed material scope; the certificate carries no measured value for it |
| SA-765 / SA-765M | Grade I, II, III, IV, V | same merged size cell | the low-temperature-toughness forging standard is inside the assessed scope as well |
A105 vs LF2 RFQ Decision Table
| Decision point | ASTM A105 / A105N | ASTM A350 LF2 | RFQ action |
|---|---|---|---|
| Service temperature | General carbon steel pressure service | Low-temperature service with impact expectations | State design/service temperature |
| Impact testing | Not always part of standard RFQ scope | Often requested for low-temperature use | List Charpy requirement explicitly |
| Heat treatment | Normalizing may be specified as A105N | Heat treatment route tied to LF2 requirement | Confirm condition on MTC |
| Typical flange shapes | WN, blind, SO, threaded, socket weld | Same shapes, different material basis | Do not compare only by shape |
| Documents | MTC 3.1, dimensional report | MTC 3.1 plus impact/heat-treatment evidence | Add document scope before quote |
Practical Checklist
- Project service temperature and material specification
- Flange standard, pressure class, size and facing
- A105, A105N, A350 LF2 or other required material wording
- Heat treatment, impact test and low-temperature test requirements
- Minimum design metal temperature, plus the impact acceptance value your specification sets and the temperature it is measured at
- MTC 3.1, chemical and mechanical values, and heat number traceability
- Whether impact testing has to be run per heat on the delivered material, or whether a qualification-stage type-test record is enough
- PMI, UT, MT, PT or third-party inspection if required
- Destination country and any end-user approval requirement
Common RFQ Mistakes
- Using A105 for low-temperature service without checking the project specification
- Not stating whether A105N or normalized condition is required
- Requesting A350 LF2 but omitting impact test or certificate requirements
- Approving a material substitution before the end user confirms the low-temperature design basis
- Quoting LF2 without checking whether the impact-test record must be witnessed or only reported
- Reading an impact result measured on one low-temperature grade as evidence for a different grade
- Treating a supplier type-test report as the material certificate for the delivered heat
FAQ
Can ASTM A105 be substituted for A350 LF2?
Do not substitute from the material name alone. A350 LF2 is used when low-temperature service and notch toughness testing are specified, so any substitution needs project or end-user approval.
What should an A350 LF2 flange RFQ state clearly?
State the flange standard, size, pressure class, service temperature, impact test requirement, heat treatment condition, MTC 3.1 scope and any third-party inspection hold point.
When is A105N wording important?
A105N usually signals that normalized condition is required by the buyer or project specification. Put the exact material wording in the RFQ so heat treatment and certificate language are priced correctly.
Do you have third-party impact data on a low-temperature flange you actually made?
Yes. The one on this page is a type-test sample set: the Zhejiang Academy of Special Equipment Science tested a WN 200-150 RF STD weld neck flange from our shop and issued report YSY202450080: six Charpy values from 175.0 to 283.0 J at -45 °C against a 47 J minimum, with Rm 529 and 551 MPa and every reported element inside its printed limit. The full PDF is linked on this page. The tested grade is 16MnD, a Chinese low-temperature forging grade, not A350 LF2, so it evidences our low-temperature forging capability rather than LF2 performance - and it is a type test on two samples from one batch, not a batch release. Separately, our A350 LF2 flange page shows TÜV SÜD inspection certificate 348229 with Charpy results at -46 °C for one A350 LF2 order.
Can A350 LF2 be used in place of A105?
On strength it can: both specify a 485 MPa (70 ksi) minimum tensile strength and a 250 MPa (36 ksi) minimum yield, and ASME B16.5 puts both in material group 1.1. On paper it cannot by itself: if the line class says A105, the flange needs either the end user's written approval of LF2 or a dual A105/A350 LF2 certificate. Do not ship LF2 against an A105 line item without one of the two.
What is a dual-certified A105 / A350 LF2 flange?
A flange from one heat that meets both specifications at once: chemistry inside both sets of limits, the heat treatment A350 requires, the mechanical minimums of both, and the LF2 Charpy test at its specified temperature. The MTC then names both A105 and A350 LF2 with the LF2 class. Ask for it in the RFQ - it cannot be added after production, because the heat treatment and impact test have to be done for that heat.
Does a dual-certified A105 / LF2 flange weigh the same as an A105 flange?
Yes. Weight follows the dimensions, and both grades are carbon steels of practically the same density. Dual certification changes the chemistry window, heat treatment and testing, not the dimensions, so the same standard, size, class and facing give the same nominal weight.
Do A105 and A350 LF2 flanges have the same pressure rating?
Under ASME B16.5, yes: both are material group 1.1, so their ratings come from the same table - in ASME B16.5-2025, 19.6 bar for Class 150, 51.0 bar for Class 300 and 102.0 bar for Class 600 at up to 38 °C. What differs is how cold the flange may be used, and that follows from the impact test and your piping code, not from the B16.5 rating table.
Is A105N the same as A350 LF2?
No. A105N is A105 supplied in the normalized condition. Normalizing does not add an impact test, so an A105N flange is not LF2 unless it is also tested and certified to A350 LF2.
Author & Verification
Written by: Tom Fan, Sales Director, BLD Forge Direct (Shanxi Baolongda Forging Co., Ltd.)
Reviewed by: BLD QC Engineering Team - in-house laboratory, CNAS L24083
Last verified: 2026-09-19
Revision log
- 2026-10-21 - Corrected four sentences that still said our shop had no published A350 LF2 impact value, or only one outside impact test: since 2026-09-23 our A350 LF2 flange page shows TÜV SÜD inspection certificate 348229 (Charpy at -46 °C, one order). Its values are not repeated here; the 16MnD report remains the only measured evidence on this page.
- 2026-10-10 - Added five FAQs on the questions buyers were searching for when this guide appeared in Bing: using LF2 in place of A105, dual A105/A350 LF2 certification, weight, the shared ASME B16.5 group 1.1 rating and A105N. No test value was added; the 16MnD report remains the only measured evidence on the page.
- 2026-09-19 - Added the third-party low-temperature evidence: type-test report YSY202450080 (Zhejiang Academy of Special Equipment Science) on our WN 200-150 RF STD 16MnD weld neck flange, its data page as evidence 1 with the complete PDF attached, the measured-against-limit table, the Annex I rows covering SA-105 and SA-350 LF2, four evidence units and this block. The tested grade is 16MnD and not A350 LF2; that distinction is stated in the intro, in the figure caption and in every limits paragraph instead of being smoothed over. What the report does not contain - hardness, metallography, reduction of area, grain size, heat-treatment parameters - is written into the table rather than left out.
- 2026-06-13 - ASTM A105 vs A350 LF2 comparison, published-scope table and FAQ baseline version.
PDF Datasheets for RFQ Review
ASTM A105 Flanges RFQ Datasheet
Use this PDF when the RFQ is for carbon steel A105 or A105N forged flanges.
A350 LF2 Flanges RFQ Datasheet
Use this PDF when low-temperature service, impact testing or LF2 certificate wording is part of the RFQ.
Send your RFQ or drawing directly to BLD Forge Direct.
Email quote@bldforgedirect.com with standard, drawing, material, quantity and inspection requirements.