CH631100A5 - Weld filler metal for the heterogeneous fusion welding of cast iron - Google Patents

Description

The invention relates to a welding filler material for heterogeneous fusion welding of cast iron, in particular of spheroidal graphite cast iron, consisting essentially of a nickel-based alloy which, in addition to carbon, silicon and manganese, contains a carbide-forming element from the series titanium, niobium / tantalum and zirconium.

A number of proposals are known for welding cast iron, in particular spheroidal graphite cast iron, so-called nodular cast iron. A basic distinction can be made between solutions in which a homogeneous weld metal is sought, i.e. a weld metal in which the carbon is predominantly in the form of spheroidal graphite and those solutions in which a material consisting of nickel and in particular nickel-iron alloys, that is to say a heterogeneous weld metal, is formed.

The present invention is concerned with an improvement in heterogeneous fusion welding, that is to say the last-mentioned welding method, because the solutions known hitherto have brought about certain improvements with regard to the technological parameters of the pure weld metal, the main disadvantage of welding, namely the unfavorable influence on the heat of the peripheral zones, but could only be improved by subsequent heat treatment of the welded parts. There was therefore an urgent need to create a welding filler material, the application of which produces welding results in which fully satisfactory technological parameters transverse to the welding direction can also be achieved in the edge area of the welding zone without special heat treatment of the welded parts.

It is known from DE-AS 2 437 247 that with modified nickel-iron electrodes relatively high elongation values in the order of magnitude of about 25% can be determined when taking longitudinal tensile specimens from multilayer welds. If you test such welding

However, bonds transverse to the direction of welding (transverse tensile tests), the breakage usually occurs at very low elongation values in the transition zone between the weld metal and the base material, these elongation values generally being less than 5%.

The invention solves the above-mentioned problem with a welding filler material which essentially consists of a Nik-kel-based alloy which, in addition to carbon, silicon and manganese, contains a carbide-forming element from the series titanium, niobium / tantalum and zirconium; The material is characterized in that, based on the weight of the alloy components, it contains the following alloy elements:

at least 75% Ni,

Max. 2.0% C,

0.05 to 5.0% Si,

0.1 to 20.0% Mn,

0.5 to 5.0% Ti, Nb / Ta and / or Zr, 2.0 to 20.0% Co,

Max. 15.0% Fe

According to preferred embodiments of the invention, the welding filler material contains 0.05 to 3.0% Si or 0.1 to 10.0% Mn.

The decisive factor in solving the problem is the composition of the welding filler material according to the invention, which in the case of bare wires or rods intended for gas-shielded arc welding practically coincides with that of the weld metal. It is known and familiar to the experts in the field of welding which adaptations or modifications are to be made in order to use different bands, for example in the case of coated stick electrodes, which may also contain part of the alloy components in the sheath, in the case of sweat bands by means of a corresponding band / powder Combination or in the case of cored wire welding to achieve the desired weld metal.

When using the welding filler material according to the invention, the cobalt content in the weld metal is so noticeable that the carefully coordinated alloy composition surprisingly inhibits the formation of brittle structural components in the heat-affected transition zone of the base material, so that there is no premature break in this zone comes in. As extensive tests have shown, the transverse tensile specimens, in which strain values in the order of magnitude of 15 to 20% are reached, break in the base material outside the transition zone after a correspondingly high degree of deformation.

The invention is explained in more detail below on the basis of exemplary embodiments:

example 1

For comparison, welded joints (V-seams) were produced with 15 mm thick nodular cast iron plates using the inert gas welding process with bare wires of 1.2 mm diameter, welding being carried out without preheating and without post-treatment. The pure weld metal practically corresponding to the wire composition had the chemical composition given in the following table, from which it follows that

that samples 1 and 2 contained cobalt in the Fe / Ni alloys only as part of an unwanted contamination, while sample 3 corresponds to the definition of the invention:

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

Table 1

631 100

rehearse

Alloy composition

No.

C.

Si

Mn

Ti

Nb

Fe

Co

Ni

1

0.18

0.43

1.31

0.04

1.12

31.4

0.08

rest

2nd

0.25

1.09

0.56

0.33

0.36

49.1

0.11

rest

3rd

0.15

0.47

2.81

0.15

3.10

1.72

5.91

rest

The nodular cast iron had the following chemical composition: 3.48% C, 2.41% Si, 0.17% Mn, 0.022% P, 0.003% S, 0.047% Mg, balance: Fe.

The yield strength crs was 343 n / mm2, the tensile strength crB was 465 N / mm2; the elongation at break 8S was found to be 19.2%.

Round tensile samples were taken from the welded plates at right angles to the weld seam and tested for their properties. The following values were obtained:

15

Table 2

Sample No.

1

2nd

3rd

Yield point <tS

N / mm2

330 327 339

Tensile strength a B

N / mm2

Elongation at break

55

%

411 390 471

1.7 1.3 17.0

Break in the transition zone in the transition zone in the base material outside the transition zone

Example 2

In this case, connection welds were carried out as (core wire diameter 4 mm), whereby fol-V seams with the 15 mm 30 gauze plates described above in Example 1, largely thick with the core wire composition and with thick rod nodular cast iron plates with covered rod electrodes, showed an analysis of the pure weld metal:

Table 3

Sample No.

Si

Alloy composition Mn Zr Nb Fe

Co

Ni

0.12

0.39

1.51

0.42

2.85

3.2

6.25

rest

The examination of the round tensile tests taken in accordance with Example 1 gave the following result:

Table 4

Sample No.

Yield point <* s

N / mm2

Tensile strength elongation at break crB S5

N / mm2%

fracture

358

463

18.5

in the base material outside the transition zone s

Claims (3)

631100 2. welding filler material according to claim 1, characterized in that the silicon content is 0.05 to 3.0% Si. 2.0 to 20.0% Co, Max. 15.0% Fe 2.0% C, 0.05 to 5.0% Si, 0.1 to 20.0% Mn, 0.5 to 5.0% Ti, Nb / Ta and / or Zr, 2nd PATENT CLAIMS 1. Welding filler material for heterogeneous fusion welding of cast iron, in particular of spheroidal graphite cast iron, consisting essentially of a nickel-based alloy, which contains carbon, silicon and manganese as well as a carbide-forming element from the series titanium, niobium / tantalum and zirconium. characterized in that the material, based on the weight of the alloy components, contains the following alloy elements: at least 75% Ni, Max. 3. welding filler material according to claims 1 and 2, characterized in that the manganese content is 0.1 to 10.0% Mn.