Dongfeng Xinjiang truck flat frame Left step beam welding assembly 8405369-KXGG02Y

Crafted from Q345B low-alloy high-strength steel—a premium material for truck frame and step components—the assembly delivers exceptional load-bearing capacity tailored to commercial use. This steel exhibits a minimum yield strength of 345 MPa, tensile strength of 470–630 MPa, and impact toughness of 34 J at -40°C (critical for Xinjiang’s frigid winters). The step beam’s main body features a box-type cross-section (80mm×50mm, 4mm wall thickness) that enhances bending resistance by 50% compared to open-channel designs, enabling it to withstand a static load of up to 800 kg (exceeding the 500 kg design requirement for heavy-duty truck steps). After shot blasting (SA 2.5 grade) to remove surface impurities, the steel undergoes stress relief annealing at 600°C—eliminating welding-induced internal stress and preventing crack formation under cyclic loads (e.g., repeated boarding or minor road impacts)

The assembly’s critical joints—including the step plate-to-main beam connection and mounting bracket-to-frame interface—are welded using the MIG (Metal Inert Gas) welding process, complying with AWS D1.1 automotive welding standards. Each weld features a 6mm leg height and full penetration, ensuring weld strength ≥320 MPa (matching the base material’s strength) and resisting separation under heavy loads. All welds undergo 100% quality inspection: visual testing (VT) to check for surface defects like porosity or undercutting, and ultrasonic testing (UT) to detect internal flaws. The step plate (5mm-thick Q345B steel) is attached with continuous fillet welds (no spot welds), preventing water, dust, or sand from accumulating in gaps—critical for avoiding corrosion in Xinjiang’s  - prone environment

Designed to resist corrosion from Xinjiang’s harsh environmental conditions—road salt in winter, sandstorms in spring, and high humidity in summer—the step beam undergoes a three-stage protective coating process:

Zinc Phosphate Coating (50μm): Forms a crystalline base layer that improves adhesion of subsequent coatings and provides initial protection against salt spray corrosion.

Electrophoretic Primer (70μm): Seals micro-pores in the steel surface, blocking moisture and dust intrusion and preventing electrochemical corrosion.

Polyester Powder Coating (80μm): Baked at 180–200°C to form a hard, scratch-resistant finish (Mohs hardness ≥5H) that resists diesel stains, UV degradation, and sand abrasion. It passes 1,500 hours of neutral salt spray testing without rust or coating peeling.

This system ensures the step beam maintains structural integrity and appearance for 5+ years, even in extreme temperatures (-35°C to 45°C)

The assembly integrates user-friendly features to enhance safety for drivers and simplify maintenance for fleet teams:

Anti-Slip Step Surface: The step plate is punched with 12mm-diameter anti-slip holes (spaced 30mm apart) that provide secure traction even in wet, icy, or dusty conditions—reducing fall risks by 70% compared to smooth surfaces.

Drainage Channels: Two 10mm-wide drainage channels along the step’s edges direct rainwater or melting snow away from the beam, preventing freeze-thaw damage in winter and water accumulation-related corrosion.

Tool-Free Installation: The package includes 4 grade 8.8 high-strength bolts (M12×40mm) and lock nuts (pre-lubricated with anti-seize compound), requiring only a 19mm socket for installation. No specialized tools or frame modifications are needed.

Installation takes 30–40 minutes: clean the frame’s mounting surface, align the step beam’s holes with the frame, torque bolts to 85 N·m (per Dongfeng’s specifications), and verify step stability. Each unit undergoes load testing (800 kg static load for 24 hours), dimensional inspection via CMM, and coating adhesion checks, backed by a 36-month warranty against defects (e.g., weld cracking, coating peeling, structural deformation)