Chrome Hollow Bar

—Cost-effective power transmission shaft solution-Baokun

Chrome Hollow Bar is a high-precision, lightweight engineering material manufactured through cold drawing/hot rolling process, with hard chrome plating (thickness 5-30μm), which is widely used in high-strength, wear-resistant scenes such as hydraulic systems, automation equipment, and engineering machinery. Core advantages: high strength/weight ratio, excellent torsion resistance, surface finish Ra≤0.4μm, can replace traditional solid shafts, and reduce system energy consumption and material costs.

Core features of Hollow Bar

1.Lightweight design:

The hollow structure reduces weight by 30%-50% (compared with a solid shaft with the same outer diameter), reduces inertial load, and improves dynamic response speed.

2.Torsional strength:

Through the optimization of the annular section, the torsional stiffness is increased by 15%-20% compared with the solid shaft (at the same weight).

3.Wear and corrosion resistance:

The hard chrome plating (HV 800-1000) reduces the friction coefficient (μ≤0.12), and the salt spray test is ≥500h (ASTM B117).

4.Processing flexibility:

The inner hole can be pre-processed (tolerance H7-H9), supporting secondary fine grinding (dimensional accuracy ±0.02mm), drilling, and tapping integration.

5.High straightness:

The cold drawing process ensures a straightness of ≤0.3mm/m, reducing the cost of subsequent straightening processes.

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Products Categories

Honed Tube/SRB Tube

Special-shaped Tube

Chrome Plated Rod/Hollow Bar

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Chrome Plated Hollow Bar Description

Material

grade

Standard

system

Characteristics

Applicable

CK45

DIN

17200

Medium carbon steel, quenched and tempered,

hardness 28-32HRC, high fatigue resistance

General mechanical transmission shaft,

gearbox support shaft

ST52

10025

Low alloy high strength steel,

yield strength ≥355MPa, good weldability

Engineering machinery hydraulic cylinder,

structural parts

SAE4140

ASTM

A322

Chromium-molybdenum alloy steel, strong hardenability,

impact resistance + corrosion resistance

Heavy-duty gear shaft,

oil drilling equipment

SCM440

JIS

G4105

High hardenability,

hardness ≥55HRC after high-frequency quenching

Precision machine tool spindle,

automobile steering knuckle

42CrMo4

ISO

683-1

Ultra-high strength (tensile strength ≥1000MPa),

high temperature creep resistance

Wind power spindle,

aerospace components

Hollow Chrome Plated Bar Technical Sheet

Hollow chrome shaft vs Solid chrome shaft

Comparison items	Hollow Chrome Bars	solid chrome-plated shaft
Weight	30%-50% lighter (same outer diameter)	fully solid
Torsional strength	15%-20% higher (same weight)	dependent on diameter increase
Material cost	save 20%-40% steel	high cost
Heat dissipation performance	inner hole can pass cooling medium	only surface heat dissipation
Designability	can integrate hydraulic oil circuit/wiring	single function
Ultimate load	suitable for dynamic load	more suitable for static overload

Technical Parameters

Item	Parameter Range
Outer diameter	Φ20mm – Φ300mm
Wall thickness	5mm – 50mm
Length	3m – 12m (customizable)
Coating thickness	5-30μm (customizable)
Straightness tolerance	≤ 0.3mm/m
Tensile strength	600MPa – 1200MPa
Surface hardness	Chrome layer HV ≥ 800, base material HB 200-320
Surface roughness	Ra ≤ 0.4μm

The Hollow Chrome Plated Rods Applications

1.Engineering machinery

Hydraulic cylinder piston rod, excavator arm pin (ST52 material + 30μm chrome plating).

2.Automobile manufacturing

Gearbox drive shaft (SAE4140 quenching and tempering), new energy vehicle motor output shaft (42CrMo4).

3.Mold industry

Injection molding machine guide column (SCM440 high-frequency quenching), stamping mold guide shaft (CK45 hard chrome plating).

4.Automation equipment

Industrial robot joint shaft (high-precision grinding + Ra≤0.2μm).

5.Ship heavy industry

Steering gear drive shaft (salt spray resistant chrome plating + 42CrMo4 base material).

Quality inspection process

1.Chemical composition analysis

Spectrometer detects material elements.

2.Hardness test

Rockwell/Brinell hardness tester multi-point detection.

3.UT flaw detection

Detect internal cracks/inclusions.

4.Dimension detection

Full-size scanning with three-coordinate measuring machine.

5.Surface inspection

White light interferometer detects roughness/coating uniformity.

6.Torque test

Simulate actual working conditions and load to 1.5 times rated torque.

7.Salt spray test

Customized according to customer needs.

FAQS

Q1: How to choose the material?

According to the load type: dynamic impact select SAE4140/42CrMo4; static heavy load select ST52/CK45.

Q2: Can the hollow shaft replace the solid shaft?

It can be replaced in the scene with high torsional strength requirements and weight sensitivity (the working condition parameter calculation verification is required).

Q3: How to control the risk of chromium plating falling off?

Adopt micro-crack chromium process (crack density ≤80/cm²), combined with sandblasting activation treatment of substrate before electroplating.

Q4: Does it support non-standard customization?

Customizable special-shaped cross-section (hexagonal/spline), inner hole step structure, special plating (nickel-based alloy).

Q5: How long is the delivery ?

7-15 days for standard specifications and 20-30 days for customized products.