1. Plan Overview

1. Applicable scenarios

Data center cold plate/CDU circulation piping, industrial equipment water-cooled piping, precision liquid cooling piping inside cabinets; Mainstream pipes: 316L thin-walled stainless steel (0.8-3.0mm), a small amount of 304L stainless steel; Media: deionized coolant, pure water circulation medium; Core objectives: zero leakage, no oxidation on inner walls, no weld cake impurities, corrosion resistant, and no pipeline blockages during long-term operation.

2. Core Industry Pain Points (Targeted Solutions for Solutions)

1. Thin-walled pipes are prone to welded penetration, deformation, or misalignment of the edges and exceeding standards

2. Oxidation and blackening of the weld seams on the inner wall of the pipe, shedding of oxide scale, blocking filters and cold plate runners

3. Poor consistency in manual welding, frequent defects such as leakage, porosity, and unpenetrated welds

4. Welding impurities contaminate deionized water, causing electrochemical corrosion of the system

5. On-site full-position welding is highly challenging, with a high rate of batch rework

2. Overall Process Selection (Recommended by Working Condition)

Priority is given to graded welding techniques; ordinary manual electric welding is strictly prohibited

1. Batch prefabrication / standard straight pipes: fully automatic closed track TIG autofuse welding (preferred)

Single-sided welding with double-sided forming, inner wall mirror forming, no welding slag, standard liquid cooling industry process. For example, the Suzhou Line Energy XF series

2. Narrow spaces/on-site special-shaped elbows: Pulse manual TIG welding (backup) Low
current, low heat input, deformation control, only used for a few emergency repair points

3. Ultra-high precision thin-walled piping: laser precision welding with minimal
heat input, almost no deformation, suitable for ultra-thin water-cooled piping of 0.5-1.0mm

4. Prohibitions: Electrode arc welding and shielded welding; Weld beads are prone to slag inclusion and impurities, which do not meet liquid cooling cleanliness standards

3. Complete Construction Process (Pre-welding, In-Welding, Post-weld closed-loop control)

(1) Pre-welding preparation (key to successful liquid cooling welding, accounts for 70% of quality control weight)

1. Control of materials and welding materials

• Base material: unified 316L low-carbon stainless steel pipe, no carbon steel mixed use; The pipes must have no cracks, peeling, or rust

• Welding material: ER316L high-purity stainless steel welding wire; Store sealed and moisture-proof; wipe with anhydrous ethanol before use to remove oil

• Gas: 99.99% high-purity argon (5N), equipped with a gas drying filter to remove water vapor impurities

2. Pipeline assembly standards

• Bevel: 60° V-shaped bevel, blunt edge 0.5\1.0mm; Joint gap is 0.1\0.2mm

• Edge misalignment: ≤ pipe wall thickness is 10%, maximum not exceeding 0.3mm; fixed with stainless steel self-centering fixtures

• Pipeline concentricity error ≤0.05mm, preventing local uneven melting and welding penetration

3. Comprehensive Clean Treatment (Mandatory Standard)

• Weld seams on both sides of 30mm inner and outer pipe walls, acetone/anhydrous ethanol for degreasing and dust removal; Do not touch the welding area with your bare hands

• Sectional high-purity argon purge of the entire pipeline removes iron filings and dust inside the pipes; Idle pipe openings are fully sealed throughout

4. Back Protection Inflatable Fixture Arrangement: A sealed argon protection chamber is established inside the
pipeline; Pre-inflate for 5-10 minutes before welding to reduce the oxygen content inside the tube to below 20 ppm; Maintain a slight positive pressure inside the pipe to prevent air backflow

(2) Welding Construction Process Standards

1. Environmental Control: Wind shelters are set up in the
construction area, with an ambient wind speed of ≤1.5m/s; Reliable grounding of welding machines to eliminate current fluctuation defects; A dust-free construction environment on site

2. Standard welding parameters (for 316L stainless steel)

• Wall thickness 0.5-1.0mm: pulse TIG, current 25-45A, arc length 1-2mm

• Wall thickness 1.0-3.0mm: pulse TIG, current 45-75A; fully automatic welding machine rotates at constant speed for welding

• External argon flow: 8-12L/min; Rear protection flow rate inside the tube: 4-6L/min

3. Core process: Dual gas delay protection. After the
welding torch extinguishes the arc, continuously aerate the inner and outer argon channels for 3-5 minutes, waiting for the weld to cool below 80°C before shutting off the gas source; Completely prevents oxidation and blackening of high-temperature welds

4. Full-position welding control: For
vertical and overhead welding positions at elevation/cabinet positions, reduce welding current by 10%-15%, decrease heat accumulation, and prevent molten pool sagging and inner wall weld bulges

(3) Post-weld standardized treatment

1. Appearance shaping: Remove minor external welding slag; do not grind to damage the passivated layer of the weld base material

2. Pickling and passivation: All welds and heat-affected zones undergo unified passivation treatment, forming a corrosion-resistant passivation film to prevent iron ion precipitation and contaminating the coolant

3. Closed-loop pipeline flushing: Pure water circulation flush the pipeline for more than 6 hours to remove fine welding particles on the inner wall

4. Finished product protection: seal both ends of the finished pipeline to prevent secondary dust contamination

4. Special Inspection and Acceptance System (Level 4 Testing, Zero Leakage Release)

1. Grade 1: Visual inspection of appearance -
weld silver white / light golden yellow; No blackening, welded welds, or depressions on the inner wall; Weld remainder ≤ 0.2mm

2. Level 2: 100% penetrant flaw detection (PT) to
check for surface microcracks, pinholes, and pores; all welds must be inspected

3. Level 3: Pressure sealing test

• Low-pressure liquid cooling system: 0.8MPa airtight pressure holding for 2 hours, no pressure drop, no leakage

• High-pressure industrial liquid cooling system: 1.5x design water pressure holding for 30 minutes; high-end computing system adds helium leak detection, leak rate ≤ 10⁻⁹Pa·m³/s

4. Level 4: Internal Inspection of the Endoscope -
Randomly inspect the inner wall of the pipeline for forming, no oxide scale, no diameter reduction, and the flow cross-section meets standards

5. Solutions for Common Welding Defects

6. On-site Construction Management Plan

1. Personnel management: Certified welders must be on duty; Precision liquid cooling pipelines prioritize automated equipment operations, reducing manual intervention

2. Equipment control: priority is given to the installation of enclosed automatic pipe welding machines; Compact workstations are equipped with water-cooled small argon arc welding guns

3. Process control: Prefabricated welding → on-site assembly→ flaw detection → pressure testing→ system flushing→ completion acceptance, irreversible process construction

4. Quality red line: Welds that have blackened the inner wall must be directly reworked; If the flaw detection fails, the next process is strictly prohibited

7. Advantages and Benefits of the Solution

1. The welding rework rate has been reduced from 15%-20% in the industry to within 3%.

2. Long-term zero leakage in welds, meeting the data center's 7*24 hour uninterrupted operation standards

3. Pipeline cleanliness meets standards to prevent cold plate and pump blockage failures

4. Standardized processes can be replicated in batches, greatly improving on-site construction delivery efficiency

5. Enhances the overall corrosion resistance of pipelines, matching the design service life of liquid cooling systems for over 10 years

(Note: Some content may be AI-generated)