RJ Ring Connection Sealing Surface Surfacing Process Technology

Literature Overview

This paper, authored by Yang Meikun from Xi'an Nuclear Equipment Co., Ltd. and published in China Chemical Equipment (2020, Vol. 22, Issue 1, pp. 45-48), provides a detailed discussion of the surfacing process technology for RJ (Ring Joint) sealing surfaces on flanges and connectors used in chemical equipment manufacturing. RJ flanges are widely used in high-pressure and high-temperature service where a metal-to-metal seal is required, and the quality of the surfacing layer on the sealing surface is critical to ensuring leak-tight performance.

Process Specification and Manufacturing Standards

The RJ sealing surface surfacing process must comply with relevant manufacturing codes and technical specifications. The typical process flow involves the following steps:

Step	Activity	Key Requirement
1	Base metal machining	Surface flatness within 0.05 mm, roughness Ra ≤ 6.3 μm
2	Surface preparation	Cleaning, degreasing, preheating
3	Transition layer deposition	Compatible alloy, low dilution
4	Surface layer deposition	Final alloy composition, required hardness
5	Post-weld machining	Final flatness within 0.02 mm, roughness Ra ≤ 1.6 μm
6	Non-destructive testing	MT or PT inspection
7	Final dimensional verification	Ring diameter, groove geometry

The two-layer surfacing approach (transition layer followed by surface layer) is a critical process feature. The transition layer ensures metallurgical compatibility between the base metal and the final overlay alloy, reducing the risk of cracking and ensuring adequate bond strength.

Process Parameters and Quality Control

The surfacing process parameters are determined through formal welding procedure qualification (WPS/PQR) in accordance with applicable codes. Key parameters include:

Parameter	Transition Layer	Surface Layer
Welding process	GTAW or SAW	GTAW or SAW
Current	100–180 A	80–150 A
Travel speed	50–100 mm/min	40–80 mm/min
Wire diameter	1.6–2.4 mm	1.2–2.0 mm
Shielding gas	Argon or Ar-He mix	Argon or Ar-He mix
Preheat temperature	150–250 °C	100–200 °C
Interpass temperature	≤ 250 °C	≤ 200 °C

Non-destructive testing is performed after each layer deposition. Magnetic particle testing (MT) or penetrant testing (PT) is used to detect surface and near-surface defects such as cracks, porosity, and lack of fusion. Any detected defects must be repaired and re-inspected before proceeding to the next layer.

FMEA Analysis of Critical Process Steps

An FMEA (Failure Mode and Effects Analysis) approach can be applied to identify the most critical failure modes in the RJ sealing surface surfacing process:

Failure Mode	Effect	Severity	Occurrence	Detection	RPN	Countermeasure
Crack in transition layer	Sealing failure	10	3	2	60	Optimize preheat and interpass temperature
Excessive dilution	Hardness below spec	8	4	3	96	Use low-dilution process, verify composition
Surface porosity	Leak path	9	3	2	54	Ensure clean surface and proper gas flow
Inadequate flatness	Seal contact failure	8	3	2	48	Control machining after surfacing
Hardness below specification	Wear and deformation	7	4	3	84	Verify alloy composition and heat treatment

Study Insights and Practical Recommendations

This paper provides a comprehensive and practical guide for engineers responsible for the manufacture of RJ flanges and connectors in chemical equipment. The emphasis on the two-layer surfacing approach, systematic process qualification, and rigorous non-destructive testing reflects the high reliability requirements of chemical process equipment. The paper also highlights the importance of post-weld machining in achieving the precise dimensional tolerances required for RJ sealing surfaces, a step that is sometimes overlooked in process planning.

For engineers in the nuclear and chemical equipment sectors, this paper underscores that the quality of RJ sealing surfaces is determined by the entire manufacturing chain, from base metal preparation through final machining and inspection. Each step must be controlled to specification, and any deviation must be documented and evaluated for its impact on the final product quality.

The five literature studies collectively demonstrate the breadth and depth of surfacing welding technology as applied to modern industrial manufacturing. From equipment retrofit for continuous cylindrical surfacing to data-driven dilution rate prediction, from alloy design for thermal fatigue resistance to large-scale industrial applications and precision sealing surface manufacture, these papers illustrate the diverse challenges and solutions that engineers encounter in practice. The common thread is that successful surfacing welding requires a systematic integration of metallurgical understanding, process parameter optimization, equipment capability, and quality control. Engineers who master this integration can deliver reliable, high-performance surfacing solutions across a wide range of industrial applications.