General Core Process Specifications for Electric Welding
Release time：2026-01-30
I. Pre-Welding Preparation Process
- Base metal cleaning Clean the welding area of the welded components using methods such as angle grinders, wire brushes, and sandblasting. Within a range of 20-30 mm on both sides Remove impurities such as rust, oxide scale, oil stains, moisture, and paint layers until the metallic luster is exposed. Before joining the base materials, they must be aligned to ensure a uniform joint gap and an edge misalignment no greater than 10% of the base material thickness, with a maximum allowable misalignment of 3 mm.
- Bevel machining The groove form shall be determined based on the thickness of the base metal: For thicknesses less than 6 mm, an I-groove (no groove) may be used; for thicknesses between 6 mm and 30 mm, a V-groove is recommended; and for thicknesses exceeding 30 mm, an X-groove (double-sided) is required. Groove preparation can be carried out by gas cutting, milling, or turning. After machining, burrs and slag at the groove edges must be removed. The groove angle should be controlled within 60° ± 5°, the root face height should be 1–2 mm, and the butt joint gap should be 1–3 mm.
- Welding Material Preparation The welding electrodes/wires must be compatible with the base metal material (e.g., use E43 series electrodes for Q235 base metal, and E50 series electrodes for Q355 base metal). Before use, welding electrodes must be dried according to specified requirements: acidic electrodes should be dried at 150–200℃ for 1–2 hours, while basic electrodes should be dried at 350–400℃ for 2–3 hours. After drying, store the electrodes in a thermal container and take them out as needed to prevent moisture absorption. Welding wires must have their surface oil and oxide scale removed, and the purity of shielding gases (such as carbon dioxide or argon) must be ≥99.5%.
- Workwear fixed Perform tack welding on the welded components. The electrodes used for tack welding shall be identical to those used for the final weld. The length of each tack weld should be 30–50 mm, with a spacing of 200–300 mm. Tack welds must be free of defects such as cracks and porosity. If any defects are found, they must be immediately removed and the weld re-done. For large welded components, use jigs and fixtures to secure the parts and prevent deformation during welding. If necessary, add additional process supports or tie rods.
- Preheating treatment For medium- and high-carbon steels, low-alloy high-strength steels, or when the base metal thickness exceeds 25 mm and the ambient temperature is below 5°C, the weld area must be preheated to a temperature ranging from 80 to 200°C. The preheating zone should extend at least 100 mm on either side of the weld seam. Use a thermometer to monitor the temperature continuously and ensure uniform preheating. II. Core Welding Operation Procedures
(1) General Process Parameter Control
| Welding Applicable Thickness (mm) | Welding current (A) | Arc voltage (V) | Welding speed (cm/min) |
|---|---|---|---|
2-5 | 60-90 | 20-24 | 10-15 |
5-12 | 90-130 | 22-26 | 12-18 |
12-25 | 130-180 | 24-28 | 15-20 |
25 and above | 180-230 | 26-30 | 18-22 |
Note For automatic and semi-automatic welding, the wire feeding and protective gas supply processes must be synchronized to match the process rhythm, ensuring that the current density is appropriately matched with the welding speed. |
(2) Basic Manipulation Techniques
- Arc initiation Use the scratch-start or direct-strike method to initiate the arc. When using the scratch-start method, lightly touch the surface of the base metal and then quickly lift the electrode 2–4 mm away. When using the direct-strike method, strike the base metal perpendicularly and immediately lift the electrode afterward to prevent sticking. If sticking occurs, quickly separate the electrode by making a swinging motion and then re-initiate the arc.
- Move the electrode After initiating the arc, maintain arc stability and complete the rod movement simultaneously. Uniform feed, reasonable oscillation, and smooth forward movement. Three key actions: Match the feed speed with the melting rate to ensure a constant arc length (arc length ≈ electrode diameter); select the weaving pattern according to the groove width—use a straight-motion technique for narrow grooves, and adopt a saw-tooth, crescent, or triangular motion for wide grooves. During weaving, pause for 0.5–1 second on each side of the groove to prevent undercutting. Maintain a steady forward travel speed to avoid welding defects: too fast may result in incomplete penetration, while too slow could lead to excessive weld reinforcement or burn-through.
- Interlayer welding For thick base metals, a multi-layer, multi-pass welding process is employed. After each weld pass is completed, the surface slag and spatter are thoroughly removed, and the weld surface is ground smooth before proceeding to the next pass. The interpass temperature is maintained within the preheating range; if the temperature exceeds the specified limit, welding is temporarily halted and allowed to cool naturally to the prescribed temperature before resuming, thereby preventing coarse grain formation in the weld that could compromise its strength.
(3) Key operational points for different welding positions
- Flat weld Maintain a welding electrode-to-base-metal angle of 70°–80°, use a short-arc welding technique, and keep the electrode movement speed moderate. Ensure that the weld bead has a full and rounded appearance, with the excess height controlled within 2–4 mm. If the excess height exceeds this range, it should be ground down.
- Vertical welding Primarily use upward vertical welding, with the electrode held at an angle of 60° to 70° relative to the base metal. Employ a short-arc, low-current welding process, using a saw-tooth weaving motion with reduced oscillation amplitude and a slightly faster forward travel speed to prevent molten metal from sagging and forming weld bumps.
- Horizontal welding The welding rod should be held at a horizontal angle of 70°–80° relative to the base metal and a vertical angle of 10°–15°. Use a short arc, low current, and a short-distance zigzag weaving motion. Slightly pause on the upper side of the groove and quickly pass through the lower side to prevent molten metal from sagging, which could lead to undercutting on the upper side of the weld and weld buildup on the lower side.
- Overhead welding The welding process is the most challenging. Use a short arc and the minimum possible current. Maintain a 60°–70° angle between the electrode and the base metal, and move the electrode in small, saw-tooth or crescent-shaped motions. Strictly control the size of the weld pool, and slightly increase the travel speed to prevent the molten metal from sagging. This ensures a smooth and even weld bead formation.
III. Post-Weld Treatment Process
- Post-weld cleaning After the weld has cooled to room temperature, thoroughly remove surface slag, spatter, and weld scars. Grind the weld edges until smooth, ensuring that the weld appearance is free of burrs and sharp corners and that the transition between the weld and the base metal is smooth and seamless.
- Stress-relief treatment For welded joints made of medium- and high-carbon steels, low-alloy high-strength steels, or large and complex welded structures, stress-relief treatment should be performed after welding. This can be achieved either through natural aging (by leaving the weldment at room temperature) or by uniformly or locally heating the weldment to 200–300°C, holding it at that temperature for a specified period, and then allowing it to cool slowly. Such treatment effectively eliminates internal stresses generated during the welding process, thereby preventing deformation and cracking of the welded components.
- Defect Inspection and Handling Perform an visual inspection of the weld seam to ensure that it is free from defects such as porosity, slag inclusions, cracks, incomplete penetration, and undercut. The weld reinforcement and width should be uniform and consistent. If any surface defects are detected, promptly remove them and perform repair welding, strictly adhering to the original welding process parameters and operational techniques during the repair welding.
- Molding and trimming According to the requirements for the welded component, the weld seam shall be ground and smoothed to ensure it is flush with the surface of the base material, thereby guaranteeing a neat appearance of the welded component and meeting the requirements for subsequent machining or assembly.
IV. General Process Requirements
- During the welding process, ensure that the working environment is well-ventilated and dry. Avoid outdoor welding in windy, rainy, or humid conditions. If outdoor work is necessary, take measures to protect against wind, rain, and moisture.
- During welding, strictly adhere to the process parameters and do not arbitrarily adjust the current, voltage, or welding speed to ensure a stable welding process.
- During multi-layer, multi-pass welding, the welding direction of each weld pass can be adjusted appropriately to reduce welding stresses and deformation.
- After the weld is completed, prepare detailed process records that include information such as the base material being welded, the welding location, process parameters, and post-weld treatment, thereby ensuring traceability.
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