Tesco Steel & Engineering manufactures ASTM A105 lap joint flanges — the lap joint bench's most-produced material, in two roles. The first is the straightforward one: matched carbon-steel pairs for utility and process lines, chosen for the pattern's rotation and dismantling virtues. The second is the famous one: the universal cheap half of the alloy economy — because on this pattern the backing flange never touches the fluid, a 316L, duplex or Hastelloy line needs its expensive metal only in the stub end, with A105 carrying the bolts behind every alloy on the site — plain, primed or hot-dip galvanised for the marine deck, the EEMUA collar tradition's finish. Made per ASME B16.5 in ½″–24″ NB, Classes 150–2500, with carbon stub ends (A234 WPB per B16.9) or any alloy stub end supplied against the same order — pairs certified together. The honest notes: cold climates read A350 LF2, and heavy loads read the weld neck bench. Every lot with EN 10204 3.1/3.2 MTC. ISO 9001:2015, made in Mumbai, India — exported to 50+ countries.
ASTM A105 Lap Joint Flanges — Specifications at a Glance
What is an ASTM A105 Lap Joint Flange?
The pattern's workhorse, in two roles. An ASTM A105 lap joint flange is the loose backing flange of the two-piece system: it slides over the pipe, spins free behind the stub end's lap, and carries the entire bolt load — never touching the fluid. Role one: matched carbon pairs for utility and process lines. Role two: the universal cheap backing flange behind stainless, duplex and nickel stub ends — the alloy economy that defines the pattern. Per ASME B16.5, ½″–24″ NB, Classes 150–2500; plain, primed or galvanised; stub ends per B16.9. EN 10204 3.1 on every pair.
Also searched as: A105 backing flange, carbon steel loose flange, A105 LJ flange, CS lap joint flange, galvanised backing flange, A105N lap joint — all this page's product. Related pages: the lap joint hub (the pattern's full story), the impact-tested cousin — A350 LF2 lap joint — the A105 bench — weld neck / slip-on / long weld neck — and the alloy stub ends this flange backs: F316L / F51 / Monel 400 / 90/10 CuNi.
The Joint, Drawn — Four Parts, Two Metals If You Want
The Lap Joint Connection — 1: Backing Flange (this page's A105) · 2: Stub End (any metal the line needs) · 3: Butt Weld · 4: Pipe
Read the diagram with the economics in mind: part 2 (the stub end) touches the fluid and follows the line's metallurgy; part 1 (this page's flange) touches only bolts and atmosphere — which is why one cheap grade backs every expensive line on the site. And the site lesson: slide part 1 on before welding part 2.
What A105 Brings to the Pattern
The Universal Cheap Half
Behind every alloy stub end on the bench — one grade backing 316L, duplex, Monel and Hastelloy lines alike, at a fraction of solid-alloy flange cost.
Honest Plain Carbon Steel
Killed, deoxidised, residual-capped — 485/250 MPa with a 187 HB cap: generous numbers for a part that works in bolting and bending, never in chemistry.
Three Finishes for Three Atmospheres
Plain for painted systems, primed for site coating, hot-dip galvanised for the deck — the finish is the flange's real corrosion story.
Pairs Certified Together
One EN 10204 document covers flange and stub end — even when the two halves are different metals, the traceability arrives as one record.
Specification Notes — Getting A105 Lap Joints Right
Three honest notes.No impact guarantee: plain A105 carries no low-temperature toughness requirement — sustained sub-zero duty reads A350 LF2, the impact-tested cousin with its own lap joint page. The atmosphere is the enemy: the flange never sees process fluid, but it rusts on deck like any carbon steel — specify the finish (plain / primed / galvanised) alongside the stub end's alloy, every time. And the pattern's own boundaries apply: heavy external loads, severe vibration and high-moment positions read the weld neck bench in any grade — the hub page states them fully.
How Our A105 Lap Joint Flanges Are Manufactured
1
Material — certified A105 forgings (A105N normalised on request), heat-number transfer at the first operation.
2
Machining — B16.5 lap joint dimensions: OD, thickness, bolt circle to class; bore and shoulder turned to suit the stub end's lap.
3
Shoulder dressing — the radius dressed to bear evenly on the back of the lap: the detail that spreads bolt load instead of concentrating it at the lap's edge.
4
Testing & marking — hardness checked against the 187 HB cap; marked with grade, size, class and heat number.
5
Finish — plain (oiled), primed, or hot-dip galvanised with bores cleared of excess zinc.
6
Pairing & certification — matched to carbon (A234 WPB) or alloy stub ends where ordered; one EN 10204 3.1 document per pair (3.2 witnessed on request); packed sea-worthy.
Where A105 Lap Joint Flanges Are Used
Everywhere the pattern lives: behind stainless and duplex stub ends across chemical and process plants (the alloy economy's daily bread), behind copper-nickel laps on ships and platforms in the galvanised collar tradition, on matched carbon pairs in utility air, water and low-pressure process systems, on strainer and filter stations that dismantle monthly, and on prefabricated spools whose bolt holes must align at site. Production and supply below:
A105 Backing Flanges — Production Batch at Our WorksA105 Lap Joint Flange, 6″ Class 150 — Black Protective FinishA105 Lap Joint Flanges — Protective Black FinishThe System This Flange Backs — Stub Ends in Any Metal the Line Needs
A105 Lap Joint Flange Dimensions
Flange dimensions are class-governed per ASME B16.5; stub ends per B16.9 / MSS SP-43. Full class-by-class charts:
Example: “Lap Joint Flange, 3″ NB, ASME B16.5 Class 150, ASTM A105 hot-dip galvanised, to back 316L Sch 40S stub ends (B16.9 Type A long, supplied together), pairs certified on one MTC, EN 10204 3.1 — 25 sets.” Quotations normally within 24 hours with price, unit weights (both parts) and delivery.
A105 Lap Joint Flanges — Frequently Asked Questions
What is an ASTM A105 lap joint flange?
An ASTM A105 lap joint flange is the loose backing flange of the two-piece lap joint system, machined in the flange world's carbon steel workhorse. It slides over the pipe before the stub end is welded, sits free behind the stub end's flared lap, and when bolted presses the lap against the mating gasket — carrying the entire bolt load without ever touching the line fluid. A105 is the pattern's most-produced material because it serves two roles at once: the matched pair for carbon-steel utility and process lines, and the universal cheap backing flange behind stainless, duplex and nickel-alloy stub ends — the alloy economy that defines the lap joint pattern. Manufactured per ASME B16.5 in ½" to 24" NB, Classes 150 to 2500, supplied plain, primed or hot-dip galvanised, with EN 10204 3.1/3.2 certification.
How does a lap joint flange work with a stub end?
By splitting the two jobs a flange normally does — sealing and bolting — between two parts. The stub end butt-welds to the pipe: its flared lap provides the gasket sealing face and does all the fluid contact. The lap joint flange never welds and never wets: it slides on the pipe, spins freely until the bolts enter, and transmits bolt load through its shoulder onto the back of the lap. The assembly order is the classic site lesson — flange onto the pipe first, then weld the stub end. Two virtues follow: bolt holes always align, because the flange rotates until the joint is made; and the flange's material can differ from the line's, because it never touches the process. The diagram on this page shows the four parts of every lap joint connection: backing flange, stub end, butt weld, and the pipe or fitting behind them.
Why is A105 the lap joint pattern's most-produced material?
Because the pattern's famous economy runs through this grade. On a lap joint the backing flange never touches the fluid — so a 316L, duplex, Monel or Hastelloy line needs its expensive metallurgy only in the stub end, with A105 carbon steel carrying the bolts behind it at a fraction of solid-alloy cost. Every alloy family on this site therefore consumes A105 lap joint flanges: the stainless wing, the duplex twins, the whole nickel bench — one cheap grade backing them all, which is why our A105 lap joint production outruns every alloy backing flange combined. The second role is the straightforward one: matched A105 pairs on carbon utility and process lines, where the pattern is chosen for its rotation and dismantling virtues rather than its economics. The one discipline in the alloy-economy role: the flange's outside still faces the environment — a bare A105 flange on an offshore deck rusts — so the finish (plain, primed or galvanised) is specified alongside the stub end's alloy.
What is the chemical composition of ASTM A105?
Carbon ≤0.35%, manganese 0.60-1.05%, silicon 0.10-0.35%, phosphorus ≤0.035% and sulphur ≤0.040% — with residual caps of copper ≤0.40%, nickel ≤0.40%, chromium ≤0.30%, molybdenum ≤0.12% and vanadium ≤0.08%, plus combined-residual limits in the specification. Read it plainly: this is honest plain carbon steel — the manganese strengthens and manages sulphur, the silicon window (note its floor) marks killed, deoxidised steel, and the residual caps exist to keep stray alloying from disturbing weldability and hardenability. For the lap joint pattern the chemistry matters least of all the site's grades: the flange never touches the process, so its metallurgy serves structure and atmosphere only — which is exactly why the cheap grade can back the expensive lines. Chemistry is verified per heat and travels on the EN 10204 3.1 MTC.
What are the mechanical properties of A105 lap joint flanges?
Tensile strength 485 MPa (70 ksi) minimum, yield strength 250 MPa (36 ksi) minimum, elongation 22% minimum, with a hardness cap of 187 HB in the specification. For the backing-flange duty these numbers are generous: the flange works in bending and bolt-load transmission through its shoulder onto the lap, and A105's yield comfortably carries every class's bolt loads at the B16.5 dimensions — the class tables, not the certificate, govern the joint's rating as everywhere on the site. Where the flange serves outdoors in cold climates, note that plain A105 carries no impact-test requirement: for genuinely low-temperature service the impact-tested A350 LF2 backing flange takes over, exactly as on the welded bench — its own lap joint page carries the story. A105N (normalised) is supplied on request where a specification asks for the refined-grain condition.
What finishes are available — plain, primed and galvanised?
Three standard finishes, because the backing flange's enemy is the atmosphere, not the process. Plain (mill finish, rust-preventive oiled) suits indoor and painted-system duty where the piping contractor coats the assembled line. Primed (red-oxide or specified primer) arrives ready for the site's paint system. Hot-dip galvanised is the marine and offshore answer — the finish that makes the alloy economy work on deck: a galvanised A105 backing flange behind a copper-nickel or duplex stub end is the classic shipboard and platform pattern, standardised in EEMUA 145's collar tradition. The galvanising notes worth knowing: threads and bores are cleared of excess zinc after dipping, the coating adds thickness the fitter should expect at the bore, and where a specification forbids zinc near stainless welding (zinc embrittlement risk in a fire), the primed finish substitutes. State the finish on every enquiry — it costs little and decides the flange's service life outdoors.
What stub ends pair with A105 lap joint flanges?
Whatever the line demands — that is the pattern's whole point. For carbon-steel lines, the matching stub end is wrought carbon steel to ASME B16.9, commonly ASTM A234 WPB — the fitting grade that pairs with A105 forgings across the piping world — welded with the line's own carbon-steel procedure. For alloy lines, the stub end follows the fluid: 304L/316L and the stainless wing, duplex F51/F53/F55, Monel, Inconel, Incoloy, Alloy 20, Hastelloy or copper-nickel — every one backed by this page's A105 flange in the alloy economy, with MSS SP-43 light-pattern stainless stub ends serving the lower-pressure corrosion-resistant duty. The matching rules are dimensional, not metallurgical: the stub end's lap OD must suit the flange's shoulder, its schedule must match the line bore, and flange and stub end are best bought as a matched pair — as we supply them, certified together on one document even when the two halves are different metals.
What is the difference between an A105 lap joint flange and an A105 slip-on flange?
The weld — and everything that follows from it. An A105 slip-on flange slides over the pipe and is fillet-welded front and back: fixed in orientation forever, wetted at its bore, one piece, welded by a qualified procedure. An A105 lap joint flange never welds: the stub end takes the weld, the flange spins free, and the joint dismantles by sliding the flange back. In plain carbon systems the cost runs close — the lap joint adds a stub end but simplifies the flange — so the choice follows the virtues: slip-on for simple fixed process piping where the joint is made once; lap joint where erection speed, bolt-hole alignment and frequent dismantling matter, and always where the flange must be cheaper than the line. The shared honest boundary: neither pattern reinforces like a weld neck's tapered hub, so heavily-loaded and severe cyclic services read the weld neck bench in any grade.
Where should A105 lap joint flanges NOT be used?
The pattern's boundaries plus the grade's own two. From the pattern: high external loads and bending belong to weld necks (the loose flange bears on a narrow lap shoulder), severe vibration makes the lap-to-flange face a fretting interface, and the annular crevice at the bore deserves thought in corrosive atmospheres. From the grade: plain A105 carries no low-temperature impact guarantee — sustained sub-zero duty reads A350 LF2, whose lap joint page carries the impact-tested story; and A105's atmosphere resistance is a coating story, not a metallurgy story — the finish FAQ's discipline applies wherever the flange lives outdoors. None of this narrows the pattern's real territory: dismantleable utility and process piping, and the universal backing role behind alloy stub ends, where A105 serves in greater numbers than every other grade combined.
What sizes and pressure classes do A105 lap joint flanges come in?
½" to 24" NB per ASME B16.5 in Classes 150, 300, 400, 600, 900, 1500 and 2500, with larger diameters machined to B16.47 or drawing — and the full class-by-class lap joint dimension charts are on this site. The order book concentrates where the pattern's virtues live: Classes 150 and 300 in 1"-8" NB dominate — utility systems, alloy-economy process lines, marine backing duty — with the higher classes appearing where a dismantling-friendly joint is wanted on rated systems. B16.5's tables assign the class ratings as everywhere (the A105 material group's curves), with the pattern note the hub page explains: high-energy joints overwhelmingly weld, so lap joints above Class 600 are the exception that a specification names deliberately. State size, class, finish and the stub-end question together, and our quotation returns price, unit weight and delivery per class.
How much does an A105 lap joint flange weigh?
Slightly less than the same slip-on flange — the loose flange has no weld prep and a plain shouldered bore. Representative Class 150 figures for the flange alone: 1" roughly 0.8 kg, 2" roughly 2 kg, 3" roughly 3.5 kg, 4" roughly 5.5 kg, 6" roughly 9 kg, 8" roughly 14 kg — climbing steeply with class. The carbon stub end adds its own mass by schedule and pattern (a 2" Sch 40 long-pattern stub end roughly 0.5 kg). On matched carbon pairs the freight counts both parts; on alloy-economy orders the arithmetic favours the buyer twice — the heavy part is the cheap metal, and only the light stub end carries alloy price and alloy freight class. Our quotations state unit and consignment weights per line item, flange and stub end separately, and the site's flange weight chart carries the full reference tables.
How are your A105 lap joint flanges manufactured?
From certified A105 forgings, machined to the pattern's one critical detail. Forged blanks are machined to B16.5's lap joint dimensions — OD, thickness, bolt circle drilled to class — with the bore and shoulder turned to suit the stub end's lap, and the shoulder radius dressed so it bears evenly on the back of the lap: the detail that decides whether bolt load spreads across the lap or concentrates at its edge. Heat-number marking transfers at the first operation; hardness is checked against the 187 HB cap; and the finish — plain, primed or hot-dip galvanised with bores cleared — is applied to order. Where the order includes stub ends (carbon A234 WPB or any alloy), the pair is dimensionally matched and certified together on one EN 10204 3.1 document (3.2 witnessed on request). Faces and laps are protected and the consignment packed sea-worthy.
What details are needed to get an accurate A105 lap joint flange quotation?
Seven elements plus commercial terms: (1) size and dimensional standard — e.g. 3" NB ASME B16.5; (2) pressure class — 150 to 2500; (3) finish — plain, primed or hot-dip galvanised, per the atmosphere the flange will live in; (4) the stub end — carbon A234 WPB matched pair, an alloy stub end for the economy pattern (state its grade and schedule), or 'flange only' where the laps exist; (5) quantity as pairs or pieces — the two-piece system ships as matched sets unless ordered separately; (6) certification — EN 10204 3.1 (our standard) or 3.2 witnessed, pairs certified together; (7) destination and delivery expectations. Add the service where it helps — cold climates steer the A350 LF2 question, marine atmospheres steer the galvanising — and quotations normally return within 24 hours with price, unit weights for both parts, and delivery.
Who manufactures ASTM A105 lap joint flanges in India?
Tesco Steel & Engineering is an ISO 9001:2015 certified flange manufacturer based in Mumbai, India, producing ASTM A105 lap joint (lapped joint) flanges per ASME B16.5 from ½" to 24" NB (larger to B16.47 or drawing) in Classes 150-2500 — each machined from certified A105 forgings with the shoulder dressed to bear evenly on the lap, hardness-checked against the specification's cap, supplied plain, primed or hot-dip galvanised, heat-number marked, and certified to EN 10204 3.1/3.2. Matched carbon stub ends (A234 WPB per B16.9) and every alloy stub end on the site's bench — stainless, duplex, Monel, Inconel, Incoloy, Alloy 20, Hastelloy, copper-nickel — are supplied against the same order, pairs certified together on one document. Alongside the complete A105 range — weld neck, slip-on, socket weld, threaded, blind and long weld neck — and the full lap joint grade bench. Exported to more than 50 countries.
