Lesson 6: Methods that meet today’s requirements – surface reinforcement

In this lesson, we will delve into Surface Reinforcement by Open Arc Welding and the Repair of Special Parts Using Special Welding Procedures.

  1. SURFACE REINFORCEMENT BY OPEN ARC WELDING

Introduction

  • Surface reinforcement involves applying a hard, abrasion-resistant layer to protect the base surface.
  • This technique is highly effective in extending the lifespan of various components.

Tools and Materials

  • Tubular wire with specific functions like arc stabilization, deoxidization, fluidization, carbide forming, and additives for desired properties.
  • Common diameter range: 2-4 mm (e.g., 2.8 mm).
  • Applications include low carbon, non-alloyed, Mn, Mn-Cr alloy structural steels, and more.

Process

  • Surface preparation involves cleaning and defect type assessment.
  • Rounding edges and corners and marking crack traces.
  • Application of the tubular wire to create a hard, abrasion-resistant layer.
  • Considerations for specific material compositions and requirements.

Applications

  • Ideal for reinforcing low carbon and alloyed structural steels.
  • Butt and fill-up welding of medium carbon alloy steels.
  • Suitable for forming stainless steel surfaces (Cr, Mn, Ni).

  1. REPAIR OF SPECIAL PARTS USING SPECIAL WELDING PROCEDURES

Machine Frames, Frame Structures, Leaf Springs

  • Common failures include cracking, fracture, and embrittlement.
  • Risk of indentation or annealing during welding due to material composition.
  • Recommended hardness test in the weld area before reuse.

Welding Technology

  • Direct current with positive polarity.
  • Electrode materials with high Cr, Ni, and Mn content for adequate elasticity and tensile strength.
  • Target tensile strength of the weld: 800-850 MPa.

Minor Chipping, Fracture of Pinions, Sprockets, Rib Shafts

  • Components subjected to frequent and unpredictable conditions.
  • Preheating to 500-600°C required before welding.
  • Use of a fluxing agent for proper flaw space filling.
  • Selection of welding rod characteristics: Cr, Ni, Si alloys, low melting point, high hardness.

Highly Stressed Cutting Edges for Machine Tools

  • Carbide filling and sharpening methods.
  • Suitable welding processes and bonding methods.
  • Deposition of materials with excellent abrasion resistance, containing metal carbides, nitrides, and borides.

Self-Sharpening Concept

  • The concept explained in the context of carbide charging, ensuring the effectiveness and longevity of tool surfaces.

Coated-Electrode Manual Arc Welding

  • Performed with direct current and bonded with positive polarity.
  • Preparation steps include removing previous armor, preheating, and applying a flexible pad layer if needed.

Conclusion

  • Surface reinforcement and special welding procedures are essential in prolonging the life of components subjected to harsh conditions.
  • Understanding these methods is crucial for professionals involved in the maintenance and repair of specialized parts.

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