Elsevier

Materials Letters

Volume 42, Issue 5, February 2000, Pages 311-320
Materials Letters

Study of restoration by welding of pearlitic ductile cast iron

https://doi.org/10.1016/S0167-577X(99)00204-9Get rights and content

Abstract

The objective of this investigation is to study the restoration and/or hardfacing by welding of worn-out parts manufactured from pearlitic ductile cast iron. The work may be divided into two sections. The first deals with studying the weldability of pearlitic ductile cast iron by means of five different types of filler material, namely, pure Ni, Fe–Ni alloy, Ni–Cu alloy, stainless steel and ferritic steel. Particular attention was directed towards the parameters affecting welding by ferritic steel filler metal. This material is attractive because of its low cost. In addition, weldments produced are characterized by excellent colour match, satisfactory hardness and the variety of austenitic transformation products which occur on cooling. Process variables such as preheating, heat input, post weld heat treatment (PWHT), multipass and multilayer techniques, and hardfacing process were studied in detail. Microstructural analysis, microhardness distribution of the melt region (MR) and heat affected zone (HAZ), and nondestructive evaluation were all applied to assess the weldment quality.

Introduction

Ductile cast iron is an important cast material to the designer which combines the advantages of cast iron, such as cheapness, ease of machining, low melting temperature, good fluidity, good wear resistance properties, high damping capacity, excellent heat resistance properties and those of steel, such as high strength, ductility, toughness, hot workability and hardenability [1], [2], [3]. Therefore, such material can economically replace steel in a very wide variety of applications.

The poor weldability of ductile cast iron can be attributed to two factors, the formation of martensite in the heat affected zone (HAZ), and the development of hard, brittle iron carbide in the zone of partial fusion [4], [5], [6]. Most of the welding performed on cast iron is repair welding. It is either the repair of discontinuities produced during the casting process or those developed in the cast component itself while in service [7]. Despite this, the welding of this material has always been proven difficult and continues to require specialised knowledge and techniques [8].

The aim of this work is to restore the surface or to improve the surface properties of iron casting damaged by spalling or wear. This can be achieved by welding repair and/or hardfacing.

Section snippets

Experimental work

Pearlitic ductile cast iron base metal test plates 20×20×60 mm were machined from Y-blocks casting and prepared for welding by employing the manual shield metal arc welding (SMAW). The chemical composition is given in Table 1. The specimens were surfaced, single pass bead on-plate welds were deposited on the flat position using manual SMAW process, the level of preheat was 200°C for 1 h, the interpass temperature should be not less than 200°C. After the welding was performed, the specimens were

Results and discussion

The microstructure of the as-received ductile iron plate is shown in Fig. 1. The structure consists of graphite nodules surrounded by ferrite rings and the darker lamellar structure in the matrix is pearlite. This typical structure is described as a bull's eye pattern. Fig. 2 shows the optical micrographs of the weld metal and HAZ of the specimens surfaced by using different filler materials. The various phases detected in both the melt region (MR) and HAZ are listed in Table 4. It is clear

Conclusions

  • 1.

    The problems associated with welds with pure Ni, Ni–Fe alloy, Ni–Cu alloy and stainless steel are also present to various extent in welds made with ferritic steel filler metal.

  • 2.

    Preheating to 300°C appears as the best option when welding by ferritic steel filler metal. This is reflected in narrow MR, discontinuous carbide areas and bainitic HAZ.

  • 3.

    Higher heat input allows smaller MR and pearlitic HAZ.

  • 4.

    PWHT slightly reduces the maximum hardness of the HAZ.

  • 5.

    Multipass welding exhibits a smaller MR and

References (20)

  • The Joining and Fabrication of Nodular Iron Casting by Welding, S.G. Iron Produces Association, London (970), pp....
  • Castolin Societe Anongome, ‘Cast Iron’ Technical Report, 1985, pp....
  • E.E. Huke et al.

    Welding metallurgy of nodular cast iron

    Weld. J.

    (1953)
  • E.F. Nippes

    The heat affected zone of arc welded ductile iron

    Weld. J.

    (1960)
  • G.R. Pease

    The welding of ductile iron

    Weld. J.

    (1960)
  • H. Megahed

    Effect of weld heat input, number of passes and interpass temperature on the mechanical and structural properties of ductile cast iron

    J. Eng. Appl. Sci., Fac. Eng., Cairo University

    (1995)
  • S.D. Kiser et al.

    Unraveling the mysteries of welding cast iron

    Weld. J.

    (1993)
  • C.L.M. Coltrell

    Welding Cast Iron

    (1985)
  • S.D. Kise

    Production welding of cast iron

    AFS Trans.

    (1977)
  • X.Y. Zhang

    A newly developed nickel–iron electrode with superior hot cracking resistance of high strength properties for welding

    Weld. J.

    (1995)
There are more references available in the full text version of this article.

Cited by (59)

  • Mechanical behavior of bimetallic stainless steel and gray cast iron repairs via directed energy deposition additive manufacturing

    2023, Journal of Manufacturing Processes
    Citation Excerpt :

    A temperature controller utilized real-time thermocouple data to maintain the substrate at 300 °C during the print and during cooldown. This temperature has been previously identified as ideal for cast iron repair [3,4]. The groove repair was completed by depositing stainless steel in four layers to completely fill the void.

View all citing articles on Scopus
View full text