Stainless Steel Welding Operation Manual

1. Overview

Installed capacity: 2 × 150T/h+2 × 30MW. The sealing oil pipeline of the turbine generator in this unit is made of 1Cr18Ni9Ti material.

Project Name: Stainless Steel Pipe Welding Operation Guide

2. Compilation basis:

2.1 Design drawings

2.2 Welding Technical Specification for Thermal Power Plants DL/T 869-2004

2.3 "Quality Inspection and Evaluation Standards for Thermal Power Construction (Welding Section)" 1996 Edition

2.4 Welder Technical Assessment Regulations

2.5 Safety Work Regulations for Electric Power Construction

3. Construction preparation:

3.1 Materials and equipment

3.1.1 welding material 

Welding wire: H1Cr18Ni9Ti φ two point five

Welding wire should have a quality certificate from the manufacturer, and the issuance and issuance should be managed by the welding material administrator. Welding wire should be cleaned of oil rust and other dirt before use to expose its metallic luster.

3.1.2 argon 

The argon gas cylinder should be labeled with a factory qualified label, with a purity of ≥ 99.95% and a flow rate of 6-9 liters/minute. The argon gas in the cylinder cannot be used up, and the residual pressure inside the cylinder should not be less than 0.5MPa to ensure the purity of argon filling.

3.2 Construction equipment

3.2.1 Using a DC welding machine.

3.2.2 Select JL-15 argon pressure reducing flowmeter. The flow meter should open and close freely without any air leakage. Remember not to open the flow meter first and then the gas cylinder, as it may cause high-pressure airflow to directly flow into the low-pressure area and damage the flow meter; When turning off, first turn off the flow meter and then turn off the argon cylinder.

3.2.3 Rubber hoses for transporting argon gas shall not be used in series with rubber hoses for transporting other gases. New oxygen rubber hoses can be used as substitutes, with a length not exceeding 30 meters.

3.2.4 Other tools and instruments

Welders should be equipped with hammers, sandpaper, flat shovels, wire brushes, electric grinding tools, etc., to prepare for slag removal and defect elimination.

4. Process

4.1 Welders must pass the corresponding specimen examination in accordance with the "examination regulations" before they can start welding on the job.

4.2 It is strictly prohibited to ignite arcs, test currents, or weld temporary supports on the surface of the welded parts at will.

4.3 The argon arc welding handle and argon pressure reducing flow meter used by the welder should be regularly inspected to ensure that the argon gas is in laminar flow state during the argon arc welding sealing.

4.4 Before aligning, the surface of the groove and the inner and outer walls of the base material should be cleaned of oil, paint, rust, etc. until a metallic luster appears. The cleaning range is 10-15mm on each side, and the gap between the alignments is 2.5-3.5mm.

4.5 The deviation value of the centerline of the pipe alignment should not exceed 1/100, the alignment gap should be uniform and straight, and strong alignment is prohibited. The misalignment value of the inner wall should be less than 10% of the wall thickness and not more than 1mm.

4.6 When the local gap of the weld is too large, it should be repaired and it is strictly prohibited to add plugs within the gap.

4.7 After the alignment is qualified, 2-3 points should be welded according to different pipe diameters. The material for spot welding should be the same as the formal welding, with a length of 10-15mm and a thickness of 3-4mm.

4.8 When welding pipes, there should be no ventilation inside the pipes, the pipes should not shake, and windproof measures should be taken.

4.9 After the completion of the base welding, the quality of the base welding seam should be carefully checked and confirmed to be qualified before proceeding with argon arc welding cover welding.

4.10 Arc ignition and arc extinguishing must be carried out within the groove. Arc extinguishing must fill the molten pool and direct the arc towards the groove to extinguish the arc.

4.11 Spot welding, argon arc welding, and cover welding. If defects occur, they must be ground off with an electric grinding tool before continuing welding. Repetitive melting methods are not allowed to eliminate defects.

4.12 Attention should be paid to the quality of joints and arc extinguishing, and the fusion of joints should be good. The molten pool should be filled when arc extinguishing. To ensure the tightness of the weld seam, all welds should be welded in at least two layers and not completed in one pass. The interlayer joints should be staggered by more than 10mm. To reduce the degree of oxidation of the base weld, it is necessary to adapt to reducing the interlayer temperature.

4.13 After the covering is completed, the surface of the weld seam should be cleaned of slag and spatter in a timely manner. After passing the self inspection, the welding seam should be stamped with its own code steel seal near it.

4.14 After non-destructive testing of the weld seam, if there are defects that exceed the standard, they can be repaired by patching. However, the number of patching times at the same position shall not exceed three, and the following measures shall be taken:

a. Thoroughly identify defects.

B. When repairing welding, it should be carried out according to the original process requirements.

5. Control points:

5.1 Spot welding or welding can only be carried out after passing the inspection of the matching assembly, which is an on-site witness point.

5.2. After welding is completed and self inspection is qualified, the welder's own steel seal code is marked, which is an on-site witness point.

6. Quality standards:

6.1 The internal quality is evaluated according to the DL/T5069-96 specification, and it is qualified at level I.

6.2 The surface quality of welded joints shall be inspected in accordance with the provisions of the "Quality Inspection and Evaluation Standards for Thermal Power Construction (Welding Section)" (1996 Edition). The surface quality standards (excellent level) for welded joints are as follows:

Welding seam formation: The welding seam is excessively smooth and straight, and the joint is good

Strengthening surface height: 0-3mm

Weld seam width difference: ≤ 3mm

Misalignment: Outer wall ≤ 0.1 δ， And ≤ 4

Bending: ≤ 1/200

Undercut: h ≤ 0.5, ∑ I ≤ 0.1L and ≤ 40

Cracks, arc pits, pores, slag inclusions: None

6.3 inspect

6.3.1 Self inspection

Welders shall perform 100% self inspection after welding, fill out self inspection records, and submit them to the construction team for re inspection by the shift (team) leader.

6.3.2 Construction team re inspection

The welding quality inspector shall conduct re inspection according to the proportion and standards specified in the "Welding Section" based on the welder self inspection form submitted by the team, preliminarily evaluate the surface quality level of the welding joint, and fill the results in the "Sub item Engineering Welding Joint Surface Quality Inspection and Evaluation Form".

6.3.3 Non destructive testing shall be commissioned by technicians in accordance with the proportion specified in the welding section.

6.3.4 Preliminary evaluation of construction team

According to the regulations of the "Welding Section" standard, the surface quality level, tightness test evaluation level, and various test report evaluation levels of the welded joint shall be filled in the comprehensive welding quality level evaluation form of the sub project, and its comprehensive welding quality level shall be preliminarily evaluated and submitted to the company's quality inspection department for evaluation.

6.3.5 The company's quality inspection department conducts spot checks on the surface quality and comprehensive quality evaluation results of the welding joints provided by the construction team in accordance with the "Welding Section" regulations. Collaborate with the construction team and relevant personnel to evaluate the comprehensive welding quality level of the sub project.

6.3.6 Technicians keep construction records.

7. Safety technical measures:

7.1 Welders must wear work clothes, insulated gloves, and insulated shoes when working.

7.2 Welders must comply with safety and civilized construction regulations.

7.3 High altitude operations must wear safety belts, and scaffolding erected at heights should be safe, reliable, and easy to weld.

7.4 Welders take protective measures when using electric grinding tools. Before use, check if the grinding wheel of the electric grinding tool is loose and if it needs to be replaced.

7.5 Welding with oil inside the pipeline is prohibited.

7.6 When there are flammable and explosive materials below the work area, measures should be taken to prevent splashes from falling.

7.7 Welding wires should be avoided from being connected to equipment with induction coils. The connection between welding wires and welding tongs should be placed reliably to prevent arc damage to pipes or equipment during operation.

7.8 When welding, attention should be paid to avoiding splashing or arc damage to equipment, splashing or welding slag falling into cleaned pipelines.