Chrome Plated 27SiMn Tube

The Chrome Plated 27SiMn Tube is precision-ground and hard chrome plated from premium 27SiMn silicon-manganese alloy structural steel seamless tube in a non-heat-treated condition. Through the combined strengthening of silicon and manganese, 27SiMn steel already achieves high strength and good toughness, offering superior mechanical properties over plain carbon steels. As a hollow piston rod or cylinder barrel tube, it maintains high OD accuracy and surface performance while significantly reducing weight and enabling internal fluid passage. It is widely used in ultra-high-pressure, heavy-duty hydraulic systems, mining machinery, construction equipment and hydraulic supports demanding both high tube strength and weight reduction—an ideal solution combining high strength 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: Fair (moderate to high carbon equivalent limits weldability; strict preheating and post-weld stress-relief tempering are mandatory if welding is necessary; welding on critical load-bearing areas should be avoided)

• 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

• 27SiMn silicon-manganese alloy steel base delivers high strength in non-treated condition, meeting mechanical demands in ultra-high-pressure and heavy-duty applications

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

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

• 96-hour salt spray rating 9 meets corrosion protection requirements in aggressive mining, underground and outdoor environments

• Good heat treatment adaptability allows upgrade to Q&T, Induction Hardening and other strengthened conditions

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