SU1668081A1 - Composition for welding up cracks - Google Patents

Abstract

The invention relates to welding, in particular to materials for welding cracks in body cast iron engine parts by gas-thermal welding. The purpose of the invention is to improve the quality of the cladding due to the convergence of hardness values and linear expansion coefficients of the base and weld metal. The composition contains, wt%: boron 0.003 - 0.005

carbon 0,2 - 0,6

silicon 2.3 - 2.8

iron 0.1 - 0.5

copper 8-12

silicocalcium 0.5 - 1.0

borax 1.5 - 2.0

nickel - the rest. The introduction of silicocalcium and borax contributes to a better deoxidation of alloying elements and iron in the fusion zone. The specified ratio of components provides high-quality welding of defects in the hull cast-iron parts. 1 tab.

Description

The invention relates to welding, in particular to welding materials, and can be used for welding cracks in body cast-iron parts of engines using the method of thermal thermal welding.

The purpose of the invention is to improve the quality of the weld seam due to the approximation of the hardness values and the linear expansion coefficient of the base and weld metal.

With the proposed ratio of components, the best adhesion to gray cast iron is observed, there is no cracking of the seam in the zone of welded cracks, and the quality of the weld seam is improved.

An increase in the copper content contributes to a decrease in hardness, an increase in plasticity, and a convergence of the values of the linear expansion coefficients of the weld metal of this composition and gray iron.

A decrease in the boron content leads to a decrease in the contamination with borides and an increase in the density of the weld metal.

An increase in the iron content contributes to a better combination of the filler material with the core in the fusion zone.

The use of borax and silicocalcium contributes to a better deoxidation of alloying elements and iron in the fusion zone.

The table lists examples of the five formulations studied.

As a result of metallographic studies of the structure of the deposited metal of gray cast iron, the materials of various chemical compositions based on nickel-based self-fluxing powders on nickel found the following.

In the metal deposited by compounds 1 - 3. there is no dendritic structure. Metal structure - fine-grained, absent (L

WITH

about (with about

with

pores and slag inclusions. There are no cracks in the weld metal and in the zone of fusion with the base metal, there is a deep deoxidation of the weld metal and the zone of fusion. In the fusion zone, there is a lower carbon content in the base metal, as well as silicon in the fusion zones and the thermal effect of the base metal. Crystallization of the alloy follows the diagram of the stable system Fe – C. There is no gray iron cast iron in the heat affected zone. The hardness and coefficient of linear expansion of the deposited layer and the base metal are close in magnitude and are for compositions 1-3: a 10-11-106, 1 / ° C: HB 180-210.

The structure of the metal deposited by composition 4 is dendritic, coarse-crystalline. The structure in the fusion zone and in particular about the heat-affected zone of the metallic cast iron base contains a large amount of coarse-grained free ferrite. A large amount of metal oxides is observed in the weld metal and in the zone of fusion with the base metal. Coagulation and growth of graphite plates are observed in the fusion zone and areas of the heat affected zone adjacent to it. The hardness of the weld metal is significantly higher than the hardness of the base metal of a-iron (H B 200-280). The linear expansion coefficient of the weld metal is a (8.5 - 9.5) -, 1 / ° C. There are cracks and pores in the weld metal and in the heat-affected zone. The crystallization of the metal in individual volumes occurs according to a metastable Re-Plc diagram. In the structure of the fusion zone and adjacent areas of the heat-affected zone, the appearance of a solid phase, cementite, is observed.

When using composition 5, there is a high contamination of the deposited and base metals with powdered boron compounds, as well as an increased carbon content in the fusion zone and the presence of coarse-grained graphite. There are microcracks in the fusion zone. In the weld metal in the fusion zone - a large number of slag inclusions. The iron metal base grains have a predominantly pearlitic structure in the fusion zone. The weld metal has a hardness lower than the hardness of cast iron (HB 140-170). The coefficient of linear expansion of the deposited layer is (11.5 - 12) -10 6, 1 / ° C. The structure of the weld metal and the fusion zone are contaminated with silicon, calcium, sodium oxides, etc.

The linear expansion coefficient is measured by a standard method on a DCM differential dilatometer, hardness is measured on a TS hardness meter.

Claims (1)

Claims A composition for welding cracks in body cast-iron parts of engines using gas-thermal welding, containing boron, carbon, silicon, iron, copper, nickel, differing in that. that, in order to improve the quality of the weld seam due to the approximation of the hardness values and the linear expansion coefficient of the base and weld metals, it additionally contains silicocalcium and borax in the following ratio, wt.%: Lices 0.003-0.005 0.2-0.6 2.3-2.8 0.1-0.5 8-12 0.5-1.0 1.5-2.0, Else