Chrome Plated 40Cr Tube

The Chrome Plated 40Cr Tube is precision-ground and hard chrome plated from premium 40Cr alloy structural steel (AISI 5140) seamless tube in a non-heat-treated condition. Containing chromium, 40Cr steel offers superior hardenability and significantly higher base strength than plain carbon steel tubes. As a hollow piston rod or cylinder barrel tube, it maintains high OD accuracy and surface performance while substantially reducing weight and enabling internal fluid passage. It is widely used in heavy-duty hydraulic equipment, construction machinery, mining machinery, and medium-to-high-pressure hydraulic systems requiring high tube strength with weight or flow optimization—a high-performance solution balancing superior load-bearing capacity and lightweight design.

• Outer Diameter: Mainly φ25–300 mm, larger custom sizes accepted

• Length: ≤8000 mm, custom lengths available

• Straightness: ≤0.2 mm/M

• Tolerance Grades: IT6–IT9

• OD Tolerance: According to ISO f7/f8/g6/h7/h8/h9; customized tolerances available upon request

• Ovality: Half of the tolerance value ISO f7

• Heat Treatment: None; customization options include Quenched & Tempered, Induction Hardening, and QPQ

• Core Hardness: ≤250 HB (approx. 200–250 HB)

• Surface Treatment: Hard Chrome Plated; customization options: EN Plating / Zinc Plating / Laser Cladding / Nitriding / QPQ / Thermal Spraying / Ceramic Coating

• Chrome Thickness: ≥10 μm, mainly 20–40 μm; can be over 100 μm for high-standard requirements

• Chrome Layer Hardness: 850–1150 HV (Vickers 100 gf)

• Surface Roughness: Ra≤0.2 μm, Rt≤2 μm

• Cohesion: No cracks, breaking or detaching after thermal shock (warming up at 300 ℃ and cooling in water)

• Porosity: Tested according to ISO 1456/1458, evaluation according to ISO 10289 rating 8–10. Under 10× magnification, no more than 30 micro white pin-holes per 1000 mm², with diameter not greater than approx. 0.1 mm

• Corrosion Resistance: Tested in neutral salt spray according to ISO 9227/ASTM B117 – 96 hours, rating 9 per ISO 10289

• Weldability: Poor (alloying elements reduce weldability compared to carbon steels; strict preheating, interpass temperature control, and post-weld slow cooling or stress relieving are mandatory if welding is necessary; welding in critical load-bearing areas is not recommended)

• Packing: Anti-rust oil + cardboard tube/plastic sleeve + wooden case

• Hollow structure effectively reduces weight, lowering equipment load and energy consumption, supporting lightweight design trends

• Can serve as a hydraulic fluid passage, simplifying system design and saving space and piping costs

• 40Cr alloy steel base offers higher strength and good hardenability to meet demanding mechanical requirements in medium-to-high-pressure applications

• Strict f7 OD tolerance and low ovality ensure precise sealing and smooth operation

• Hard chrome layer at 850–1150 HV delivers reliable wear and corrosion resistance

• 96-hour salt spray rating 9 meets corrosion protection requirements for severe industrial and outdoor environments

• A high-performance, non-heat-treated alloy steel tube combining lightweight design with high load-bearing capacity

• Full customization of wall thickness, internal bore, heat treatment and surface finishing to meet diverse OEM requirements

In addition to standard specifications, we offer:

• Custom OD, ID and wall thickness

• Custom lengths

• Tolerance grades and non-standard OD tolerances

• Higher straightness and internal bore precision requirements

• Heat treatment options: Q&T, Induction Hardening, QPQ

• Surface treatment alternatives: zinc plating, electroless nickel, laser cladding, nitriding, thermal spray, ceramic coating

• Special chrome layer thickness

• Enhanced corrosion resistance and dedicated packing solutions

Limits and Fits Table

The table below provides shaft deviation values for commonly used tolerance grades f7, f8, g6, h7, h8, and h9 to assist your selection according to seal fits.

Chemical Composition

The table presents the standard chemical composition of frequently used materials such as CK45, 25Mn, 20#, ST52, 40Cr, 42CrMo4, 20MnV6 and 38MnVS6 for your reference.

Mechanical Properties

The following table lists reference tensile strength, yield strength, elongation and impact energy values for CK45 (hot-rolled, cold-drawn, Q&T), 25Mn, 20#, ST52, Q345D, 40Cr, 42CrMo4, 20MnV6 and 38MnVS6 under various conditions.