Process Technology for Inner Wall Surfacing of Flange Forging Blanks

Literature Overview

This paper published in "Hot Working Technology" (2005, Vol. 34, No. 5, pp. 67-68) by Chen Sunyi from Sinopec Maoming Petrochemical Machinery Factory addresses the technical challenges encountered during inner wall surfacing of stainless steel layers on composite flanges. The paper proposes alternative blank geometries and deformation control measures to improve the process economics and quality of overlay-welded flange manufacturing.

Core Technical Content

The traditional approach to manufacturing composite flanges involves overlay welding stainless steel layers on the inner wall of a conventional ring-shaped forging blank. This approach encounters two major challenges: significant overlay welding deformation and ultrasonic testing requirements for the blank material. The paper proposes two alternative blank geometries that are more economical than the traditional ring blank: a profile-matched blank and a columnar neck blank. For the profile-matched blank approach, four preventive deformation measures and one post-correction measure are proposed, with comparative analysis of advantages and disadvantages for each method.

Approach	Blank Type	Deformation Control Method	Advantages	Limitations
Traditional	Ring blank	Standard measures	Familiar process	High material cost, significant deformation
Alternative 1	Profile-matched blank	Four preventive measures	Economic, reduced deformation	Requires specialized blank design
Alternative 2	Columnar neck blank	Modified process	Different geometry advantages	May require process adaptation
Post-correction	Applied after welding	One correction measure	Flexible, applicable to existing parts	Additional processing step required

Technical Analysis

The deformation problem in inner wall overlay welding of flanges arises from the asymmetric heat input and the constrained geometry of the ring-shaped component. During overlay welding of the inner wall, the deposited material undergoes thermal expansion and subsequent contraction during cooling, generating significant residual stresses that cause the flange to warp or distort. This deformation is particularly problematic for flanges that require precise dimensional accuracy and flatness for bolted joint sealing.

The ultrasonic testing requirement for the forging blank adds another layer of complexity. The traditional ring blank must be fully inspected for internal defects before overlay welding, and any defects detected may require extensive repair or rejection of the entire blank. The proposed alternative blank geometries address this issue by reducing the material volume and potentially improving the solidification quality, thereby reducing the probability of internal defects.

The four preventive deformation measures for the profile-matched blank approach likely include strategies such as preheating control, welding sequence optimization, backing ring design, and拘束装置 (restraint fixture) design. The post-correction measure may involve mechanical straightening or thermal correction after welding. The comparative analysis of these methods provides engineers with a toolkit for selecting the most appropriate approach based on specific production requirements, available equipment, and cost constraints.

Engineering Practice Integration

In the petrochemical industry, composite flanges with stainless steel overlay layers are widely used for connecting process piping systems that handle corrosive or high-purity media. The overlay provides corrosion resistance on the inner surface while the carbon steel forging provides the mechanical strength required for pressure containment. The process challenges described in this paper are directly relevant to any manufacturer producing composite flanges, and the proposed solutions offer practical improvements to process efficiency and quality.

For pipe and fitting manufacturers, the concepts presented here are transferable to other overlay welding applications where deformation control is critical. The systematic approach of proposing alternative blank geometries combined with multiple deformation control measures reflects a comprehensive engineering methodology that can be applied to similar problems in the manufacturing of overlay-welded components of various geometries.

Study Insights and Implications

This research demonstrates the practical engineering approach to solving manufacturing challenges through systematic analysis and multiple solution development. The proposal of alternative blank geometries represents a design-for-manufacturability philosophy that addresses process problems at the design stage rather than relying solely on process modifications. For engineers in the pipe and fitting industry, this paper serves as a reminder that material and process design should be considered together, and that sometimes the most effective solution to a manufacturing problem lies in modifying the component design rather than the manufacturing process itself.