Stainless Steel Strip Electrode Overlay Welding on Hydraulic Sulfurization Tank Plungers

Literature Overview

This paper by Jiao Jianguo from Jilin Chemical Industry Company Chemical Equipment Factory, published in Welding journal in 1998, addresses a specific industrial problem: the corrosion and surface degradation of plungers in rubber vulcanization hydraulic tanks. The plungers, operating in prolonged contact with water under pressure, suffer from severe rusting and surface scoring that damages the sealing components of the working cylinder. The proposed solution employs a strip electrode overlay welding technique to deposit a stainless steel layer on the plunger surface, offering a cost-effective and technically sound alternative to full material replacement.

Problem Analysis and Failure Mechanism

The hydraulic sulfurization tank is a critical piece of equipment in rubber processing, where plungers are subjected to cyclic pressure loads, constant water immersion, and mechanical sliding contact with cylinder seals. The failure mechanism follows a progressive degradation pattern:

Initial rust formation on the carbon steel plunger surface due to water contact
Surface roughening and scoring from seal interaction with corroded areas
Accelerated material loss through combined corrosion-abrasion synergy
Seal damage and eventual hydraulic leakage
Complete functional failure requiring plunger replacement or overhaul

The economic implications are substantial, as unplanned replacements disrupt rubber production schedules and require expensive downtime. The overlay welding approach directly addresses the root cause by providing a corrosion-resistant surface layer that maintains smoothness and dimensional accuracy.

Strip Electrode Overlay Welding Technology

Process Description

The strip electrode overlay welding method differs fundamentally from conventional electrode or wire-based surfacing. A continuous stainless steel strip serves as both the filler material and the welding electrode, producing a uniform, dense overlay layer with excellent surface quality. The process parameters and material specifications are as follows:

Parameter	Specification
Base material	Carbon steel plunger (typically 45 steel or 50 steel)
Overlay material	304 or 316 stainless steel strip
Strip thickness	1.5-2.0 mm
Strip width	20-30 mm
Pre-machining tolerance	Nominal diameter minus 4-6 mm
Surface roughness (pre-weld)	Ra 12.5 μm
Overlay layer thickness	2-3 mm
Post-weld machining	To nominal diameter, Ra 0.8-1.6 μm

Process Sequence

The manufacturing sequence follows a carefully controlled workflow:

Mechanical preparation of the plunger surface to the specified roughness and dimensional tolerance
Cleaning and degreasing to remove all contaminants
Application of the stainless steel strip overlay using the strip electrode welding process
Post-weld inspection for surface quality and defect detection
Final machining to achieve the required dimensional accuracy and surface finish
Surface hardness and adhesion testing

Welding Process Parameters

Process Variable	Typical Value
Arc voltage	22-28 V
Welding current	200-320 A
Travel speed	300-500 mm/min
Shielding gas	Argon or Ar-CO2 mixture
Strip feed speed	Matched to travel speed
Overlap between passes	30-50%
Number of passes	2-3

Quality Characteristics and Performance Advantages

The strip electrode method offers several distinct advantages over conventional overlay welding approaches for this application:

Uniformity: The continuous strip provides consistent composition and thickness across the entire overlay, eliminating the stringer bead profile variations common with wire electrodes.
Speed: The process achieves significantly higher deposition rates compared to manual electrode welding, reducing manufacturing time by 40-60%.
Surface quality: The overlay surface requires minimal post-weld machining, preserving dimensional accuracy and reducing material waste.
Bond strength: The metallurgical bond between the stainless steel overlay and carbon steel substrate achieves shear strengths exceeding 250 MPa when proper preheating and interpass temperature control are maintained.

Defect Analysis and Process Control

Defect	Cause	Prevention
Cracking at strip-substrate interface	Carbon diffusion from base to overlay, excessive heat input	Use appropriate preheat (150-200°C), control interpass temperature below 250°C
Lack of fusion	Insufficient arc penetration, contaminated surface	Verify surface cleanliness, adjust current to ensure proper wetting
Surface porosity	Gas entrapment during rapid solidification	Ensure adequate shielding, clean strip surface before welding
Uneven thickness	Inconsistent travel speed, strip feed variation	Use mechanized equipment with speed control

Study Insights and Engineering Implications

This paper demonstrates a practical engineering philosophy: solving a corrosion problem through surface engineering rather than wholesale material substitution. The strip electrode technique represents a mature application of advanced surfacing technology in the chemical equipment sector. The key insight is that the overlay must be thick enough to provide long-term corrosion protection yet thin enough to permit final machining to precise tolerances required for hydraulic sealing applications.

The approach also illustrates the importance of surface preparation in overlay welding success. The specification of Ra 12.5 μm roughness for the pre-weld surface ensures adequate mechanical interlocking while avoiding excessive surface irregularities that would compromise the final machined finish. This balance between weldability and final dimensional quality is a critical engineering consideration that is often overlooked in specification documents.