ASTM A105 vs A350 LF2 Flanges

Summary

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.

Use A105 for common carbon steel flange requirements when project conditions allow

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

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.

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

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

Use this list before sending drawings or line items for quotation review.

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

MTC 3.1, chemical and mechanical values, and heat number traceability

PMI, UT, MT, PT or third-party inspection if required

Destination country and any end-user approval requirement

Common RFQ Mistakes

These points often cause repeated clarification, price revisions or document mismatch.

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

FAQ

Short answers for buyers preparing this RFQ topic.

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.

PDF Datasheets for RFQ Review

Use these direct PDF links with the article before sending line items. The PDFs are generated from published product-page RFQ scope tables and do not invent standard dimensions.

ASTM A105 Flanges RFQ Datasheet

Use this PDF when the RFQ is for carbon steel A105 or A105N forged flanges.

Download PDF

A350 LF2 Flanges RFQ Datasheet

Use this PDF when low-temperature service, impact testing or LF2 certificate wording is part of the RFQ.