Copper-Steel Connecting Tube

Quick Fit Guide

Why Replace Copper Piping Now?

Copper has long been the default for cooling and refrigerant lines, but two pressures are pushing engineers and buyers toward alternatives.

Rising Copper Cost and Price Volatility

Copper prices have moved sharply and unpredictably in recent years. That copper price volatility turns into budget uncertainty on every project. Building the main run from stainless steel reduces how much of your bill of materials is exposed to the copper market, while keeping copper only where it is actually needed—at the joints.

Corrosion and Leaks in Glycol and Mixed-Metal Systems

In systems that circulate glycol-based coolant, copper can corrode over time, and corrosion eventually means leaks, lost efficiency and downtime. In a mixed-metal system, copper in contact with other metals can also drive galvanic corrosion at the interface. Stainless steel holds up far more predictably against these coolants, which is why many cooling designs now specify stainless steel to replace copper—and why the next question becomes how to connect it.

Specifications and Sizes

Before reviewing the joining method, most buyers need to confirm whether the tube can match their project size. Common copper-steel tube sizes are listed below in stainless grades S30403, S30408 and SUS316. Sizes shown are typical; custom sizes are available to specification.

Common Copper-Steel Connecting Tube Sizes (unit: mm)
Tube OD (D)	Flared ID (d)	Length (L)	Stainless wall thickness	Insulation sleeve
15.88	16.04	3000 / 2000	1.0	20 / 30
19.05	19.21	3000 / 2000	1.0	20 / 30
22.2	22.36	3000 / 2000	1.0	20 / 30
25.4	25.56	3000 / 2000	1.0	20 / 30
28.6	28.76	3000 / 2000	1.0	20 / 30
31.8	31.96	3000 / 2000	1.2	20 / 30
34.9	35.06	3000 / 2000	1.2	20 / 30
38.1	38.26	3000 / 2000	1.2	20 / 30
41.3	41.46	3000 / 2000	1.5	20 / 30
44.5	44.66	3000 / 2000	1.5	20 / 30
50.8	50.96	3000 / 2000	1.5	20 / 30
54.1	54.26	3000 / 2000	1.5	20 / 30

General Parameters
Stainless tube material	S30403, S30408, SUS316
Stainless wall thickness	1.0–2.5 mm
Copper end wall thickness	1.5–3.0 mm
Diameter coverage	approx. Ø16–159 mm
Standard length	2000 mm / 3000 mm per piece
End form	One flared end, one straight end for direct butt-brazing
Factory joining	Stainless-to-copper joint by TIG (argon-arc) welding and special brazing
Testing	Leak-tested before delivery
Insulation	Optional insulation sleeve, 20 mm / 30 mm
Custom sizes	Available to specification; final values per project specification (MTC)

The Connection Problem — and How a Copper-Steel Transition Tube Solves It

The moment a team considers switching to stainless, a practical objection appears: stainless is harder to join. Brazing stainless directly needs additional flux and tight cleanliness control, and heating a copper-to-stainless joint directly can aggravate galvanic corrosion at that point. For many installers, that connection difficulty is the real obstacle—not the material itself.

The copper-steel connecting tube is built to remove that obstacle. Each tube carries pre-fabricated copper ends, so on site your crew only has to braze copper-to-copper—a butt-brazed joint made with the workmanship they already trust. There is no need to weld stainless in the field at all.

The difficult dissimilar-metal connection—copper to stainless—is completed in the factory by TIG (argon-arc) welding together with a special brazing process at the copper joint, and every tube is leak-tested before it ships. One end is supplied as a flared end and the other as a straight end, so the tube butt-joins cleanly into an existing copper system. The hardest, most failure-prone joint is made and tested under controlled factory conditions, while the field crew works only with proven copper-to-copper technique.

Aspect	Welding stainless in the field	Copper-steel connecting tube (braze copper ends)
Field skill required	Stainless welding, flux, cleanliness control	Standard copper-to-copper brazing
Joint and leak risk	Higher; more field variables	Critical joint made and leak-tested in factory
Batch consistency	Depends on each installer	Controlled, repeatable and traceable
Connects to existing copper	Needs a separate transition method	Direct butt-braze, copper to copper

Best fit: projects that already want stainless steel for corrosion control, but cannot leave the copper-to-stainless connection to uncertain field workmanship. If you only need commodity copper pipe, soft AC hose or a retail repair fitting, this is not the right product.

Data Center Liquid Cooling

As AI and high-performance computing drive rack densities up, data centers are moving from air cooling to liquid cooling, and copper is being replaced with stainless steel in many coolant loops because copper corrodes in glycol and dielectric coolant service.

Here the copper-steel connecting tube works as exactly that—a connecting tube that joins a stainless run into an existing copper interface or a coolant loop. It is a transition component, not a complete CDU or cooling skid. Because a leak in a liquid-cooled rack can mean downed servers and a broken SLA, the factory-made, leak-tested joint is the point of the product: the highest-risk connection is never left to the field. The stainless body and the working pressure of each tube are supplied to suit the coolant and operating conditions of your loop, confirmed against your project specification before production.

Check what to send for a liquid-cooling RFQ →

HVAC & Refrigeration Connecting Pipe

For central air conditioning, heat pumps and multi-split (VRF) systems, the copper-steel connecting tube serves as the refrigerant line and water-loop connecting section between indoor and outdoor units—a direct way to replace copper refrigerant line runs.

Pressure is the first question for any ACR application. The tube is supplied to a working pressure rating matched to refrigerant service, including high-pressure refrigerants such as R410A; the exact rating is confirmed against your system requirement and issued on the material certificate. On site, the advantage is practical: crews braze copper-to-copper instead of welding stainless, which cuts both labor and the number of potential leak points. The flared end joins straight into existing copper, and an insulation sleeve of 20 mm or 30 mm can be fitted where condensation control is needed. Replacing the main run with a stainless body also lowers your exposure to copper price swings.

Check what to send for an HVAC RFQ →

Industrial Fluid and General Copper Replacement

Beyond cooling and refrigeration, the same tube replaces copper in industrial cooling and fluid transfer lines, where corrosion resistance and reliable joints matter more than copper's conductivity. The stainless body resists corrosion, the copper ends keep installation simple where a line meets existing copper, and sizes are available to specification for the run you need.

Quality Checks and Documents

For project supply, the tube is confirmed by drawing or specification before production. Chalco can confirm material grade, tube dimensions, end form, insulation requirement and the service conditions you provide. The factory-made stainless-to-copper joint is leak-tested before delivery, and final documents are prepared according to the order requirement.

For applications where leakage or batch consistency is a concern, inspection can be planned around the points that usually matter most: incoming material verification, weld appearance, dimensional recheck, air-tightness or sealing test, and traceability records for project batches.

Manufacturing and Testing Details

Frequently Asked Questions