Submerged Arc Welders (SAW) — MZ Series High-Deposition Welding Systems
A submerged arc welding machine joins thick steel by burning an electric arc beneath a blanket of granular flux. The flux completely covers the arc and the molten weld pool, which is where the process gets its name: subm
The MZ series is BrightWelding's line of submerged arc welding equipment, covering 630 A to 1250 A. SAW is an automated or mechanized process rather than a manual one, so the machine set includes not only the power source but the carriage or tractors that move the welding head. This page explains how the process works, why its deposition rates are substantially higher than manual arc welding, what the MZ range offers, and what importers and distributors need to know about specification, certification and ordering.
What Is Submerged Arc Welding?
Submerged arc welding is an arc welding process in which the arc is struck beneath a layer of granular flux material. The flux is fed continuously from a hopper ahead of the welding head, covers the joint, and the arc burns within it. [source: en.wikipedia.org]
The visible characteristic of the process is that there is no visible arc. An operator watching the head move sees a bright glow through the flux, a molten slag pool at the trailing edge, and un-fused flux being recovered ahead of and beside the weld — but not the arc itself. That is the process working as intended.
Where SAW sits among the arc processes
Submerged arc welding hides its arc beneath a layer of granular flux, which gives it the highest deposition rates and deepest penetration of any common arc process. [source: westermans.com]
That combination — very high deposition, deep penetration, fully covered arc — is what makes SAW the standard process for long, heavy weld runs in controlled conditions: pressure vessels, storage tanks, structural beams and similar work where thick sections are joined over substantial lengths.
What SAW is not
SAW is not a general-purpose process. It is normally restricted to flat and horizontal positions, because the granular flux has to stay in place over the joint. It is a mechanized process rather than a manual one, so it suits work that can be brought to a fixture or where the welding head can be carried along the joint. For vertical, overhead or constrained-access work, other processes are used instead.
Why "Submerged"? The Function of the Flux
The granular flux is not merely a shield. It performs several functions simultaneously, and understanding them explains both the process's capabilities and its consumable logistics.
Function 1: Arc shielding
The flux blankets the arc and the molten pool, excluding the atmosphere. Because the shield is a granular layer rather than a gas envelope, it is unaffected by draughts and does not require a supply of shielding gas. [source: en.wikipedia.org]
Function 2: Arc stabilisation
The flux ionises in the arc and helps maintain a stable, continuous arc at high current. This stability is part of what allows SAW to run at the current levels that produce its deposition rates.
Function 3: Slag formation and weld protection
A portion of the flux melts and forms slag on the weld pool. The slag protects the cooling weld from oxidation, shapes the bead, and is removed after cooling. Unlike the slag from a stick electrode, SAW slag comes off in a continuous shell along the weld.
Function 4: Alloying
The flux composition can contribute alloying elements to the weld, which is one of the reasons flux selection is matched to the parent material and the required weld properties rather than treated as a generic consumable.
Function 5: Thermal insulation
The flux blanket slows the cooling rate of the weld, which affects the weld's microstructure and helps reduce the risk of certain cracking mechanisms in thick sections.
Recovery of un-fused flux
Because the flux is granular, the portion that does not melt is recovered — typically by a vacuum or mechanical recovery unit that returns it to the hopper. This is one of the ways SAW keeps consumable costs manageable despite the volume of flux the process appears to consume.
The SAW Process: Wire, Flux and Molten Pool
The setup
A submerged arc welding system comprises:
- A welding power source — capable of sustained high current output
- A welding head — feeding the wire into the joint
- A flux hopper and feed system — delivering granular flux ahead of the arc
- A wire feed unit — driving the electrode wire at the required speed
- A carriage, tractor or column-and-boom — moving the head along the joint
- A flux recovery system — collecting and returning un-fused flux
The welding head moves along the joint while the flux powder is supplied by the hopper, followed by the filler wire, with the arc beneath the flux layer. [source: en.wikipedia.org]
Multiple wires
Higher-productivity configurations use two or more wires feeding into the same weld pool. Multiple-wire setups increase deposition further and allow the weld profile to be controlled by arranging the wires in-line or in tandem. They are common in heavy fabrication where the volume of welding justifies the additional equipment.
Sequence of operation
- Flux is deposited ahead of the welding head on the joint
- The wire feeds into the joint and the arc strikes beneath the flux
- The arc melts the wire, the parent metal and a portion of the flux
- The weld pool forms and the molten slag floats on top
- The head advances; flux continues to be deposited ahead
- Un-fused flux is recovered behind the head by the recovery unit
- The slag shell solidifies and is removed
Operating parameters
The parameters that govern weld quality are current, voltage, travel speed, wire feed speed, wire diameter and electrode stick-out. Because these are set on the machine rather than controlled by hand, SAW produces consistent results once a procedure is established — which is a major part of its attraction for repetitive heavy work.
MZ Series Specifications at a Glance
| Model | Rated Current | Input Power | Position |
|---|---|---|---|
| MZ-630 | 630 A | 35 kVA | Flat, horizontal |
| MZ-800 | 800 A | 45 kVA | Flat, horizontal |
| MZ-1000 | 1000 A | 57 kVA | Flat, horizontal |
| MZ-1250 | 1250 A | 72 kVA | Flat, horizontal |
The MZ-1000 is the model in the current catalogue with published parameters; the 630 A, 800 A and 1250 A variants appear in the series comparison documentation.
Shared characteristics: IGBT inverter technology, three-phase 380 V input, and integration with a mechanized carriage or tractor system. Flux recovery and wire feed arrangements are specified as part of the system rather than as separate purchases.
> Note on specifications. Parameters differ by model, and the figures above are intended for range-level comparison. Detailed parameter sheets, including wire and flux compatibility for specific models, are available on request.
Model-by-Model Guide
MZ-630 — entry point for mechanized heavy welding
At 630 A with a 35 kVA input requirement, the MZ-630 is the lightest configuration in the range. It suits shops moving from manual or semi-automatic processes into mechanized welding for the first time, and for moderate-thickness work where the full deposition capability of the larger models is not required.
MZ-800 — general heavy fabrication
The MZ-800 delivers 800 A at 45 kVA. It targets general heavy fabrication — structural steel, medium-thickness vessel work and similar applications where a single wire and standard travel speeds produce adequate deposition.
MZ-1000 — the standard heavy-fabrication configuration
The MZ-1000 delivers 1000 A at 57 kVA in a 120 kg package. It is specified for heavy fabrication, pressure vessel and tank work, and applications where thick plate is welded over substantial lengths. This is the model most frequently specified for the applications that define the SAW process — long, heavy, repetitive seams.
MZ-1250 — maximum deposition
At 1250 A with a 72 kVA input requirement, the MZ-1250 is the highest-output configuration. It is intended for the heaviest fabrication work where maximum deposition rate justifies the power supply requirement. The higher input capacity means the plant supply must be assessed accordingly before specification.
Wire and Flux Selection
SAW uses a separate wire and flux combination rather than a single self-contained consumable. Both must be selected together, and for the material being welded.
Wire selection
Wire type follows the parent material. Wire diameter is selected against the current level and the deposition rate required: larger diameters permit higher current and higher deposition but require more current to melt cleanly.
Flux selection
Flux is supplied in two broad forms — fused and agglomerated — and classified by its chemical behaviour. The practical distinction for buyers is that flux chemistry varies in how much it contributes to the weld composition, and therefore in how tightly it must be matched to the wire and the parent material. Flux selection is normally determined by the welding procedure rather than chosen independently.
Matching wire and flux
Wire and flux are specified as a combination, typically against a published classification that pairs a wire grade with a flux type for a given application. Substituting one component without reviewing the pairing affects the weld's chemical composition and mechanical properties.
Materials welded with SAW
Submerged arc welding is used on carbon steels (structural and vessel construction), low alloy steels, stainless steels and nickel-based alloys, as well as for surfacing applications — wear-facing, build-up and corrosion-resistant layers. [source: en.wikipedia.org]
Flux handling and storage
Because flux is hygroscopic to varying degrees depending on its type, storage conditions matter. Moisture in flux affects weld quality and can produce porosity. Buyers should note the storage requirements for the specific flux selected, and distributors should consider this when advising end users — particularly in humid markets.
Deposition Rate: SAW Compared with Manual Processes
The deposition rate advantage is the primary commercial argument for SAW, and it is substantial.
The comparison
Deposition rates depend heavily on how the process is set up, so the figures have to be compared like for like. In a conventional single-wire setup, a 4 mm wire at 700 A deposits approximately 9 kg/h at a normal 32 mm electrode stickout, rising to about 14 kg/h at a long stickout; the long-stickout configuration is used mainly for cladding and surfacing, where deposition rate matters more than precise wire positioning. [source: twi-global.com]
Multi-wire systems go considerably higher. Tandem and multiple-wire arrangements — up to five wires in high-deposition work such as pipe mills — are what push the process toward the reported upper bound: deposition rates approaching 45 kg/h (100 lb/h) have been reported for submerged arc welding. That figure represents the high-deposition end of the process rather than a typical single-wire rate. [source: en.wikipedia.org]
Against this, shielded metal arc welding — the stick process — deposits on the order of 5 kg/h (10 lb/h) at maximum. [source: en.wikipedia.org]
The efficiency difference shows up in heat as well as in filler. SAW reaches thermal efficiency as high as 60% because the arc is completely covered by flux and heat loss is very low, where manual metal arc achieves about 25%. [source: twi-global.com]
In practical terms: a conventional single-wire SAW setup deposits roughly two to three times as much filler per hour as manual arc welding, and high-deposition multi-wire arrangements widen that gap considerably further. On thick sections with long seams, that difference translates directly into labour hours.
Where the advantage applies
The deposition advantage is realised when three conditions hold:
- The work is long enough — setup time is amortised over the weld
- The work is flat or horizontal — so the flux stays in place
- The work is repetitive enough — to establish and reuse a procedure
Where any of these fails, the advantage narrows. This is why SAW dominates tank and vessel fabrication but plays little role in site work or repair.
The wider cost picture
Deposition rate alone does not determine cost per metre. SAW's economics also depend on:
- Flux consumption and recovery rate — recovered flux lowers consumable cost
- Setup and fixture cost — mechanized welding requires the work to be presented consistently
- Operator skill profile — SAW operation differs from manual welding skills; the operator sets and monitors rather than manipulates an arc
- Defect rates — a stable mechanized process produces consistent results once established
For high-volume heavy work, the combination typically favours SAW decisively. For one-off work and site welding, manual or semi-automatic processes remain more practical.
Automation: Tractors, Carriages and Column-and-Boom
SAW is a mechanized process, and the equipment that moves the head is as central to the system as the power source.
Tractor systems
A self-propelled tractor carries the welding head, flux hopper and wire feed unit, running on a track or directly on the workpiece. Tractor systems suit long straight seams on plate and on structural sections, and they are portable between jobs.
Column and boom
A column-and-boom manipulator carries the welding head on an articulated arm mounted to a rotating column. This arrangement supports vessel and tank welding, where the work is rotated beneath a fixed head or the head is positioned over the joint. Column-and-boom systems are common in pressure vessel fabrication.
Gantry systems
A gantry spans the workpiece and carries one or more welding heads. Gantry systems suit large fabrications and allow multiple simultaneous welds, which is why they appear in heavy structural and shipbuilding applications.
Fixturing and positioning
For any of these arrangements, the workpiece must be presented so that the joint stays flat and the flux stays in place. Rotators, positioners and turning rolls are therefore part of a complete SAW installation — a point worth confirming at order stage, since a quotation covering the power source and head alone may not reflect what a shop needs to become operational.
Head and control integration
Modern systems integrate wire feed speed, travel speed, current and voltage control at a single panel. Programmable systems allow a procedure to be stored and recalled, which supports consistency across shifts and between operators.
Applications
Pressure vessels and tanks
Pressure vessel and storage tank fabrication is the classic SAW application: thick plate, long longitudinal and circumferential seams, and a flat or rotated joint position. The high deposition and deep penetration suit the thick sections involved.
Structural steel and H-beams
Beam fabrication involves long longitudinal welds on thick web and flange material, frequently produced with tractor systems running along the joint. Deposition rate and consistency are the drivers.
Wind towers and large-diameter pipe
Large-diameter fabrication — wind tower sections, heavy pipe and penstock work — involves circumferential and longitudinal seams on thick material, positions well suited to mechanized SAW with rotators.
Shipbuilding and heavy plate
Shipyard panel lines use SAW for butt and fillet welding of stiffened panels, where the volume of welding justifies gantry-based systems.
Surfacing and hardfacing
Submerged arc is also used for surfacing: applying wear-resistant or corrosion-resistant layers to a base material. [source: en.wikipedia.org] This application uses the process for deposition of a specific alloy rather than for joining.
Materials
Carbon steels for structural and vessel construction, low alloy steels, stainless steels and nickel-based alloys are all within the process's scope. [source: en.wikipedia.org]
Weld Quality and Defect Control
SAW's consistency is one of its advantages, but the process has characteristic defect modes that operators monitor for.
Porosity
Porosity in SAW welds most commonly traces to moisture or contamination. Flux storage, joint cleanliness and the condition of the wire all contribute. This is why flux handling procedures matter more in SAW than in processes using gas shielding alone.
Undercut
Undercut at the weld toe is influenced by travel speed, current and electrode angle. Because these are machine-set parameters, correcting undercut is a matter of procedure adjustment rather than operator technique.
Incomplete fusion
Incomplete fusion between passes or at the sidewall traces to insufficient heat input, incorrect electrode position, or poor joint preparation. Deep penetration is a SAW characteristic, but it depends on the parameters being correct.
Slag inclusion
Slag trapped between passes occurs where slag from a previous pass has not been fully removed. Between-pass cleaning is therefore part of the procedure, even though SAW slag removes cleanly in most cases.
Distortion
The high heat input that gives SAW its penetration also produces distortion on long welds. Sequence planning, fixturing and, where appropriate, balanced welding sequences manage this. Thick-section work benefits from the process's ability to complete a joint in few passes.
Procedure qualification
Because SAW is a mechanized process, weld quality depends heavily on procedure rather than operator skill. Establishing and qualifying a welding procedure before production is standard practice in applications where the weld is subject to code requirements, and the machine's parameter control is what makes that procedure repeatable.
Sourcing a Submerged Arc Welding Machine
Because SAW systems are specified rather than bought off a shelf, the sourcing process differs from buying a portable welding machine. The points below cover what buyers raising enquiries typically need to establish.
What to compare between suppliers
Equipment from different submerged arc welding machine manufacturers is not directly comparable on price alone, because the scope of supply varies. When comparing quotations, establish whether each covers:
- The power source only, or the power source plus head and wire feed
- The carriage, tractor or column-and-boom — often quoted separately
- The flux hopper and feed system
- The flux recovery unit — frequently listed as an option rather than standard
- Wire and flux — consumables, normally sourced separately
- Rotators or positioners — required for circumferential work, but not needed for straight seams on plate
A quotation that appears lower may simply exclude items another supplier includes. Requesting an itemised scope avoids the comparison problem.
What determines price
Among submerged arc welding machine suppliers, price is driven primarily by rated output current, the automation scope included, and control system capability. The MZ range spans 630 A to 1250 A with input capacity from 35 kVA to 72 kVA — the higher-output configurations require more substantial power electronics and a correspondingly higher plant supply.
Buyers evaluating submerged arc welding machine price information should therefore establish the current and system scope required before comparing figures. Pricing for a 630 A power source alone and for a 1250 A system including carriage and flux recovery are not comparable numbers.
Questions worth putting to any supplier
- Which materials and thicknesses is the proposed configuration rated for?
- What wire and flux combination is recommended for my application?
- What input supply does the machine require, and does my plant support it?
- What is included in the quotation, and what is supplied separately?
- What is the production lead time, and what documentation accompanies shipment?
Our engineering team can review these against your application. Parameter sheets for specific MZ models, including wire and flux compatibility, are available on request.
Terminology
Buyers encountering this equipment in catalogues will see it listed as a submerged arc welding machine, a sub arc welding machine, or a subarc welding machine — the three describe the same process. Where "saw welding machine" appears, that is also the same equipment rather than a machine for cutting timber.
The variation in naming is worth noting during sourcing, because search results for the shorter forms return a different mix of suppliers than the full term does, and quotations gathered under different names may cover equipment that is not equivalent. Confirming the process, the rated current and the system scope in writing resolves the ambiguity before commercial terms are discussed.
Certifications and Export Compliance
BrightWelding products carry CE certification across the product lines, with CSA certification available for North American markets. The company operates an ISO 9001 quality management system. [source: brightwelding.com]
Documentation accompanying shipments typically includes a Certificate of Origin (Form E, Form F or general, depending on destination), a CE Declaration of Conformity, a commercial invoice and packing list in English, and the bill of lading or airway bill. Test reports and inspection certificates are supplied on request. [source: brightwelding.com]
Where welds are subject to code requirements, the applicable welding standard governs procedure qualification and consumable selection. Our Welding Machine Certifications guide covers the equipment certification side, and the Certifications page lists the documentation available.
OEM and Private Label Options
The MZ range is available with OEM and private-label customization for distributors and brand owners. [source: brightwelding.com]
Customization scope typically covers:
- Body colour matched to the distributor's brand
- Control panel overlay and layout
- Logo and labelling on machine and packaging
- Voltage configuration for the destination market
- System configuration — carriage type, flux recovery arrangement and head count specified to the application
Minimum order quantity starts at 20 units for mixed models, with trial orders accepted at as few as 5 units per model and volume pricing at container quantities. The OEM Service page describes the process from artwork through first-article approval.
Ordering, Lead Time and Shipping
Order process. Orders begin with a specification: model, quantity, voltage configuration, wire and flux specification for the intended application, carriage or tractor configuration, and any OEM requirements. Because SAW systems comprise several components, agreeing the scope of supply at quotation stage is particularly important.
Lead time. Standard production lead time runs 15 to 30 days depending on order size. Sea freight transit typically adds 15 to 35 days depending on destination; air freight is available for urgent orders. [source: brightwelding.com]
Payment terms. Standard first-order terms are a 30% deposit by T/T on order confirmation with the 70% balance before shipment. Letters of credit at sight and Alibaba Trade Assurance are accepted for eligible orders, and terms are negotiable for established customers. [source: brightwelding.com]
Packaging. Machines ship in export-grade packaging with protective inserts, loaded onto fumigated ISPM 15-compliant wooden pallets for container shipment. Because SAW systems include carriages and auxiliary equipment, the packing configuration is confirmed against the agreed system scope.
Support. Wire and flux selection for a specific application can be reviewed against your material and procedure before order stage.
Frequently Asked Questions
What is submerged arc welding used for? Long, heavy weld runs on thick steel in flat or horizontal positions — pressure vessels, storage tanks, structural beams, large-diameter pipe and wind tower sections. It is also used for surfacing and hardfacing. [source: en.wikipedia.org]
Why is it called submerged arc welding? Because the arc is completely covered, or submerged, beneath a layer of granular flux while it burns. The arc is not visible to the operator during welding. [source: en.wikipedia.org]
What are the disadvantages of submerged arc welding? It is restricted to flat and horizontal positions, because the granular flux must stay in place over the joint. It is a mechanized process, so the work must be presented to the welding head — which makes it unsuitable for site work, repair and constrained-access joints. Setup and fixturing add cost that is only recovered on work of sufficient volume.
What is the function of flux in submerged arc welding? The flux shields the arc and weld pool from the atmosphere, stabilises the arc, forms a slag that protects and shapes the weld, contributes alloying elements, and slows the weld's cooling rate. Un-fused flux is recovered and reused. [source: en.wikipedia.org]
How does the deposition rate compare with manual welding? Deposition rates approaching 45 kg/h (100 lb/h) have been reported for SAW, against approximately 5 kg/h (10 lb/h) maximum for shielded metal arc welding. [source: en.wikipedia.org]
What materials can be welded with SAW? Carbon steels, low alloy steels, stainless steels and nickel-based alloys, as well as surfacing applications. [source: en.wikipedia.org]
Can submerged arc welding be used outdoors? The flux blanket is not affected by wind in the way that gas shielding is, but the process requires flat or horizontal positioning and mechanized movement of the head. In practice SAW is used in controlled fabrication environments — shop or yard — rather than in field conditions.
What is the difference between SAW and FCAW? Both use flux, but differently. SAW covers the arc with a separate granular flux fed from a hopper, and is mechanized. FCAW uses a tubular wire containing flux and is a semi-automatic, hand-held process. Their deposition characteristics and applications differ accordingly.
What is the difference between a sub arc welding machine and a saw welding machine? They are the same equipment — "sub arc" and "subarc" are common contractions of submerged arc, and "saw welding machine" is a frequent search phrasing for the same process.
Do I need a rotator or positioner? For circumferential welding on vessels, pipe and tank sections, yes — the work must be rotated to keep the joint in position. For long straight seams on plate or structural sections, a tractor system running along the joint may be sufficient. The requirement follows from the geometry of the work.
What input power does an MZ series machine require? The MZ series runs on three-phase 380 V input, with rated input capacity from 35 kVA to 72 kVA depending on model. The plant supply should be assessed against the specific model before specification.
What is the minimum order quantity? Standard MOQ is 20 units for mixed models, with trial orders accepted at as few as 5 units per model. [source: brightwelding.com]
How long is the warranty? All machines carry a one-year free warranty. After that period spare parts are supplied at cost, with local repair support through our dealer network in key markets. [source: brightwelding.com]
Request a Quotation
Tell us the models, quantities, voltage configuration and the system scope you need — power source, carriage or tractor, flux recovery, and any wire and flux specification for your application. We will return a quotation with lead time and shipping options, and our engineering team can review process parameters against your materials and joint configuration.
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Models in this series
Each model page lists rated output, input requirements, duty cycle and the applications the machine is specified for.