Chrome Plated 42CrMo Tube

The Chrome Plated 42CrMo Tube is precision-ground and hard chrome plated from premium 42CrMo chromium-molybdenum alloy structural steel (AISI 4140 / 42CrMo4) seamless tube in a non-heat-treated condition. Thanks to the combined strengthening of chromium and molybdenum, 42CrMo steel possesses exceptionally high hardenability and base strength, significantly outperforming plain carbon and common alloy steels. As a hollow piston rod or cylinder barrel tube, it maintains superior OD accuracy and surface performance while considerably reducing weight and enabling internal fluid passage. This product is engineered for ultra-high-pressure, heavy-load and high-fatigue hydraulic systems in large mining equipment, heavy construction machinery, marine hydraulics, and other extreme applications requiring maximum tube strength with weight or flow optimization—a high-performance solution combining ultimate 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: ≤260 HB (approx. 200–260 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: Very poor (high carbon equivalent severely impairs weldability; if welding is unavoidable, the chrome layer must be mechanically removed, and strict high-temperature preheating, interpass control, and immediate post-weld stress-relief tempering must be followed; welding in load-bearing areas is strictly prohibited)

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

• Hollow structure achieves significant weight reduction, lowering equipment load and energy consumption, perfectly aligning with heavy-duty lightweight design trends

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

• 42CrMo chromium-molybdenum alloy base delivers top-tier strength and hardenability, effortlessly handling ultra-high-pressure and extreme fatigue conditions

• Strict f7 OD tolerance and low ovality guarantee precise sealing and smooth operation even under extreme working conditions

• Hard chrome layer at 850–1150 HV provides excellent wear, scratch and corrosion resistance

• 96-hour salt spray rating 9 withstands highly corrosive environments such as sea salt spray and acidic mine water

• Top-tier non-heat-treated alloy steel tube perfectly integrating lightweight design with ultra-high load-bearing capacity

• Supports in-depth, comprehensive customization of wall thickness, internal bore, heat treatment and surface finishing to flexibly meet stringent high-end 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.