40-XC Alloy Steel Bar 40X-C Round Bars 40-XC Rods

Product Description

40-XC (40XC) / 40X-C Alloy Steel Overview

40-XC (often written as 40XC in GOST standards or 40X-C in specific commercial catalogs) is a high-quality Chromium-Silicon (Cr-Si) alloy structural steel. It is recognized for its high fatigue strength, excellent wear resistance, and high elastic limit.

Unlike standard carbon steels, the addition of Silicon ($\text{Si}$) and Chromium ($\text{Cr}$) enhances the material's hardenability and resistance to tempering, making it ideal for parts subjected to high alternating loads.

Chemical Composition (%)

The "40" represents approximately 0.40% Carbon, while the "X" and "C" denote Chromium and Silicon respectively.

Mechanical Properties (Quenched & Tempered)

When properly heat-treated, 40-XC achieves a superior balance of hardness and impact toughness:

• Tensile Strength ($R_m$):$\ge$ 1100 MPa

• Yield Strength ($R_e$):$\ge$ 950 MPa

• Elongation ($A_5$):$\ge$ 10%

• Impact Strength ($KCU$):$\ge$ 590 kJ/m²

• Hardness (after heat treatment): Typically 45–52 HRC depending on tempering temperature.

International Equivalents

This grade is primarily found in Eastern European and CIS industrial sectors (under GOST 4543), but it aligns with specific high-silicon chromium steels elsewhere:

Key Characteristics

1. High Elasticity: The high silicon content increases the yield-to-tensile ratio, making it resistant to permanent deformation under heavy stress.

2. Wear Resistance: Chromium improves surface hardness and depth of hardening, which is vital for components involving friction.

3. Hardenability: It has excellent through-hardening properties compared to simple carbon steels like C40 or 1040.

4. Weldability:Poor. This steel is prone to cold cracking and temper brittleness. Welding should generally be avoided; if necessary, significant pre-heating (above 250°C) and immediate stress-relieving are mandatory.

Common Available Formats

• Round Bars: Supplied in hot-rolled or forged conditions. These are frequently used for machining heavy-duty shafts and spindles.

• Rods: Often used for high-strength springs, fasteners, and small-diameter structural pins.

• Plates/Sheets: Used for wear-resistant liners or structural plates in heavy machinery.

Common Applications

• Heavy Machinery: High-load gears, worm shafts, and transmission splines.

• Automotive: Steering knuckles, axle shafts, and high-tensile bolts.

• Tooling: Mandrels and structural parts of die sets where high rigidity is required.

• Energy Sector: Fasteners and structural pins for oil and gas equipment.

Thermal Processing Data

• Forging: 800°C – 1220°C.

• Normalizing: 860°C – 880°C.

• Hardening: 850°C – 870°C (Oil quench is standard to prevent cracking).

• Tempering: 400°C – 600°C (Adjusted based on required final hardness).