DD134209B1 - CHANGED ELECTRODE FOR THE COLD WELDING OF CAST IRON - Google Patents

Description

Field of application of the invention

The invention relates to a coated electrode for cold welding of cast iron with lamellar or globular graphite.

Characteristic of the known technical solutions

The mechanical properties of cast iron depend on its chemical composition, the shape and distribution of the graphite and the formation of the basic structure. Moreover, in the welding of old castings, the general condition is important, especially with regard to mechanical impurities, e.g. Sooting with oil and its change due to thermal influences.

It is known that the welding of cast iron can be carried out in the hot and in the cold state. For the hot welding of cast iron, cast gray cast iron or with flux additives can be autogenously melted or as coated electrodes by means of electric arc.

It is also known to use covered electrodes comprising a low alloy steel wire or a steel wire which is up to 1.6 % C and a sheath comprising predominantly graphite in an amount of 10-75 # and 10-50 % Si contains, own (CH-PS 272 635).

Furthermore, it is known to use coated electrodes for the welding of cast iron, which contain a high Si-containing (5-12 # Si) steel wire as the core and whose cladding has larger proportions of graphite and silicon carbide (FH-PS 1 267 053 ).

In addition, still coated electrodes are known, which can be used for welding cast iron in the preheated state, the core of non-alloyed special steel with at most 0.05 fo C and the sheaths have, as essential components silicon alloys, aluminum, magnesium and over 20 Weight proportions contain graphite · These electrodes deposit a weld metal which, depending on the thermal aftertreatment, has a ferritic or pearlitic basic structure (DT-GM 1 885 763).

Used for the cold welding of cast iron coated electrodes whose core material consists of nickel, nickel-nickel or nickel-iron alloys.

In addition, in DT-OS 1 533 539 a coated electrode for the cold welding of cast iron is known, the melted weld metal has a high content of vanadium (5-11 #) »but not always soft machinable transitions are achieved.

Vfeiterhin is known from DT-AS 1 296 932, that the properties of the weld metal to be improved by larger additions of iron oxide in the envelope. In addition, according to the OE-PS 251 370 and DT-OS 2 162 313 attempts to prevent the hardening of Schv / Eißgutes or the transition thereby, that by using coated jacket or tube electrodes of the Y / poor input during welding kept as low as possible. It is also evident from the aforementioned patents that the described electrodes have lime-basic coatings which contain fluorspar and alkaline-earth carbonates as slag formers.

Of particular importance, however, in the cold welding of cast iron, the transition from the weld metal to the base material, which should be possible without continuous on curing zone if possible.

In the cold welding of cast iron is not always guaranteed that the connection of the remote weld metal with the base material without defects, such as voids and cracks occurs. In addition, the bondability of the melted weld metal is often impaired by a too large surface tension, resulting in training

of convex welds «The core material required for the production of the aforementioned electrodes is high-quality and expensive metals and metal alloys.

Object of the invention

The solution according to the invention should make it possible, when welding cast iron with coated electrodes, to reduce the proportion by weight of coils of up to 25 # of the previous requirement.

Explanation of the essence of the invention

The invention has for its object to develop for repair welding and maintenance an electrode in which the Mckelanteil in the weld metal is replaced by cheaper raw materials and which combines well with the cast iron during cold welding, at the same time mechanically weldable weld transitions can be achieved. The features of the invention are that in the lime-basic coating of the electrode in addition to fluorspar, calcite and barium carbonate as slag forming agent, the following components are included:

5 - 15 % graphite 25 - 60 % iron powder

Using iron-nickel alloy core material with 30-70 $ iron adds an additional 5-15 $ of ferro-silicon to the cladding.

The thickness of the cladding may be 1.5-2.2 times the core wire diameter. The melted weld metal has an average hardness of 180 kp / mm (HB 30) and contains up to

2 % C

0.3 - 0.8 fo Mn to 2.0 $ Si less than 0.025 $ P less than 0.02 % S 50-70 % Fe 35 - 45 fo m

When using core material made of pure nickel, the melted weld metal contains up to

0.3 - 0.8 # Mn less than 0.5 # Si less than 0.025 tf P less than 0.02 # S

15 - 25 * Fe and the Best Ui

and has an average hardness of 155 kp / mm (HB 30). During the cold welding of cast iron with the electrodes according to the invention, maximum hardness values of 225 kp / mm (HB 30) occurred in the transition to the weld metal, which permit perfect mechanical processing. The strength of the weld metal corresponds to that of the base material and has no appreciable color differences compared to cast iron.

embodiment

The invention will be explained in more detail by way of example. Repair welds were performed on cast iron with globular graphite. In this case, the electrode according to the invention with a core wire made of an iron-nickel alloy (50 <$> Pe and 50 # Ni) was used. The melted weld metal had a hardness of 170 kp / mm (HB 30) and contained

1.52 <b С 0.32 <$> Mn 1.78 % Si 0,010 * P 0,004 # S 40.8 % Ni

and the rest iron

In repair welding of cast iron with lamellar graphite, the electrode according to the invention was used with a core wire of pure nickel (at least 98 # Ni).

The melted weld metal had a hardness of 145 kp / mm ² (HB 30) and contained

1.60 * C fewer as 0.1 Я • Mn 0.17 *   Si $ 0.010 P 0.004 # S 79.60 %   Ni and the Best iron.

The thickness of the cladding was 1.75 times the core wire diameter for both electrodes.

Claims (1)

Invention claim: Wrapped electrode for cold welding of cast iron with lamellar or globular graphite, which has a nickel core material and whose sheath contains fluorspar, calcite and barium carbonate as slag forming agent, characterized in that the sheath 5 - 15 # graphite 25 - 60 # iron powder when using a core material of an iron-nickel alloy having 30-70 # iron 5 - 15 # ferro-silicon, the thickness of the cladding is 1.5-2.2 times the core wire diameter. Documents considered: DE-AS 1296932 (49 h _r 36/36)
DE-OS 1533539 (B 23 k, 35/30)
DE-OS 2162313 (B 23 k, 35/30)
AT-PS 251370 (48 b, 4/40)