Welding Handbook for Stainless Steel Pipe

1 Overview

Installed capacity: 2x 150T/h+2x30MW, this unit's steam generator sealed oil pipeline, material is 1Cr18Ni9Ti.

Project name: stainless steel pipe welding operation guide

2 Basis for preparation:

2.1 Design drawings

2.2 "Technical Specifications for Welding of Thermal Power Plants" DL/T 869-2004

2.3 "Firepower I Quality Inspection and Evaluation Standards (Welding)" 1996 edition

2.4 "Welder Technical Assessment Regulations"

2.5 "Safety Regulations for Electric Power Construction"

3 Construction preparation:

3.1 Materials and equipment

3.1.1 Welding materials

Welding wire: H1Cr18Ni9Ti φ2.5. The welding wire should have the quality certificate of the manufacturer, and the welding consumable manager will collect and issue it.

Management. The welding wire should be cleaned of oil rust and other contaminants before use, exposing the metallic luster.

3.1.2 Argon: The factory qualified label should be affixed to the argon cylinder, the purity is >99.95%, the flow rate used is 6-9 liters/min, the cylinder

The argon gas cannot be used up, and the residual pressure in the bottle should not be lower than 0.5MPa to ensure the purity of argon filling.

3.2 Construction equipment

3.2.1 Use DC welding machine.

3.2.2 Select children L-15 argon decompression flowmeter. The flowmeter should open and close freely, without air leakage. Remember not to open the flow first

The meter and the research cylinder cause the high-pressure airflow to go directly to the low pressure, damaging the flowmeter; when closing, first turn off the flowmeter 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 instead

Use, the length does not exceed 30 meters.

3.2.4 Worker tools: Welders should be equipped with hand hammer, sandpaper, flat shovel, wire brush, electric grinder I, etc., to prepare for slag removal and elimination.

4 process

4.1 The welder must pass the examination of the corresponding test piece in accordance with the "examination regulations" and then weld to the post.

4.2 It is strictly forbidden to bow freely on the surface of the welded parts | burning arc, test current or welding temporary support, etc.

4.3 The argon arc welding handle and argon decompression flowmeter used by the welder should be checked frequently to ensure that the argon gas is laminar when the argon arc welding is sealed status.

4.4 Before the alignment, the oil, paint, scale and rust on the surface of the groove and the inner and outer walls of the base material should be cleaned up until the metal shines.

The cleaning range is 10-15mm on each side, and the gap between the counterparts is 2.5~3.5mm.

4.5 The deviation of the centerline of the pipe counterpart should not exceed 1/100, the gap between the counterparts should be straight, strong counterparts are prohibited, and the value of the misalignment of the inner wall should be small

At 10% of the wall thickness, the embryo is greater than 1 mm.

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

4.7 After the counterpart is qualified, the points of the pipe diameter should be 2-3 points, the material of the spot welding should be the same as the formal welding, the length of the spot welding is 10-

15mm, thickness 3-4mm.

4.8. When welding the pipes, there must be no wind passing through the pipes, the pipes should not be shaken, and windproof measures should be taken.

4.9 After the priming is completed, the quality of the bottom weld should be carefully checked, and the argon arc welding cover welding should be performed after the qualification is confirmed.

4.10 Arc starting and closing must be carried out in the groove. The closing arc should fill the molten pool and extinguish the arc bow towards the groove.

4.11 Spot welding, argon arc welding, cover welding, if defects occur, must be removed with an electric grinder I, and then continue to weld, not heavy

The double melting method eliminates defects.

4.12 Attention should be paid to the quality of the joint and the arc closing, and the joint fusion should be good, and the molten pool should be filled when the arc is closed. To ensure the tightness of the weld,

All welds should be welded in at least two layers, which cannot be completed all at once, and the joints between layers should be staggered by more than 10mm, in order to reduce the oxidation process of the bottom welding pass

Degrees, should be adapted to reduce the temperature between floors.

4.13 After completion, the surface of the weld should be cleaned of slag and spatter in time. After passing the self-test, the self-code is marked near the weld

Stencil.

4.14 Welding seams are subject to non-destructive inspection. If there are defects exceeding the standard, they can be repaired by digging and repairing. The number of digging and repairing in the same position should not exceed

After three times, and do:

a. Thoroughly understand the defects.

b. When repair welding, the original process requirements shall be followed.

5 control points:

5.1 The counterpart assembly inspection is qualified before spot welding or welding is performed, which is a witness point on site.

5.2 After the welding is completed, the steel stamp code of the welder is marked by the self-inspection, which is a witness point on site.

6Quality standards:

6.1 The internal quality is evaluated according to the DL/T5069-96 standard, and the grade I is qualified.

6.2 The surface quality of the welding seam shall be inspected in accordance with the provisions of "Quality Inspection and Evaluation Standards for Thermal Power Application I (Welding)" (1996 edition)

Check, the surface quality standards (good grade) of welded joints are as follows:

Weld seam forming: the weld seam is too smooth and straight, and the joint is good

Reinforced surface height: 0- 3mm

Weld seam width difference: ≤3mm

Staggered: outer wall ≤0.1δ, and ≤4

Bending: ≤1/200

Undercut: h≤0.5, 2 I≤0.1L and ≤40

Cracks, craters, pores, slag inclusions: none

6.3. Check

6.3.1 Self-inspection: The welder shall perform 100% self-inspection after welding, fill in the self-inspection record, and send the shift (team) leader to the construction team for re-inspection.

6.3.2 Re-inspection of the construction team: the welding quality inspector shall submit the welder self-inspection form according to the squad (group).

The re-inspection shall be carried out, the surface quality grade of the welded joint shall be preliminarily assessed, and the result shall be filled in the "Sub-item I-process welded joint surface quality inspection.

Rating Form"

6.3.3 The technician shall entrust the non-destructive inspection with the proportion specified in the “welding chapter”.

6.3.4 Initial evaluation of the construction team: According to the provisions of the "Welding Chapter" standard, the surface quality grade and tightness of the welded joint are evaluated by experiment

The rating of each test report provided by the grading and test department, fill in the sub-item I-process welding comprehensive quality rating table, and begin

Step to evaluate its welding comprehensive quality grade and send it to the company's quality inspection department for evaluation.

6.3.5 The company's quality inspection section shall conduct preliminary evaluation on the surface quality and comprehensive quality of the welded joints provided by the construction team in accordance with the provisions of the "Welding Chapter"

Sampling. The Huitong construction team and relevant personnel jointly assessed the comprehensive quality level of sub-item I welding.

6.3.6 The technician makes construction records.

7 Safety technical measures

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

7.2 Welders must abide by the regulations for safe and civilized construction.

7.3 Working at height must wear a safety belt, and the scaffolding should be safe, reliable and easy to weld.

7.4. Welders take protective measures when using electric grinder tools. Before use, check whether the grinding wheel of the electric grinder I is loose or not.

Change the wheel.

7.5 It is forbidden to weld oil in the pipeline.

7.6 The air counterpart is when there are flammable and explosive materials under the working area, measures should be taken to prevent the splash from falling.

7.7 The rabbit welding wire should be connected to the equipment with induction coil, and the connection part of the welding wire and welding clamp should be placed reliably to avoid work.

The arc strikes the pipe or equipment during operation.

7.8 When welding, care should be taken to avoid damage to the equipment by splashing or arcing, splashing or welding slag falling into the cleaned pipeline.