CS216660B2 - Method of thermal working the band of the welded pieces of the silicon steel influenced by the welding heat - Google Patents

Abstract

A process for improving the mechanical properties of welded lengths of silicon steel. The weld heat affected area of welded lengths of silicon steel is heat treated with the welded lengths clamped so as to restrain movement thereof.

Description

The invention relates to a method of heat treating a zone of welded pieces of silicon steel affected by welding heat, in particular in the case of boron-containing silicon steel.

The heat developed during the processing of boron-containing silicon steels often causes brittleness of the steel in the welding heat-affected zone and, therefore, means have been sought and developed to improve the mechanical properties of metals in the welding heat-affected zone. Heat treatment after welding was tested but resulted in thermal warping and weld cracks.

It is an object of the present invention to provide a method for improving the mechanical properties of a metal in a zone affected by welding heat. This zone, which has been influenced by the welding heat, is thermally processed, the pieces of welded steel being clamped so as to reduce or reduce the heat. suppressed their movement. By such a clamping of the welded pieces, the invention provides means for improving the mechanical properties without any thermal warping and the formation of weld cracks that were characteristic of previously known heat treatment attempts after welding.

The invention therefore relates to a method of heat treating a zone of welded pieces of silicon steel influenced by welding heat, which is based on the fact that in order to improve mechanical and technological properties, the zone affected by welding heat is treated by heating means on the weld at above 815 ° C, but below the critical temperature that promotes grain growth, with the pieces of steel being fixedly fixed.

The heat treatment of the metal while clamping the pieces of steel according to the invention achieves an improvement of the mechanical properties in the zone affected by the welding heat, without thermal collapse and the formation of weld cracks. In most cases, the pieces of steel are clamped in the same fixture used to clamp the piece of steel during welding. Electric arc welding is generally used. Typical examples of electric welding are tungsten arc flame welding, metal arc flame welding, and submerged arc welding. As a heat source, a non-consumable electrode used in flame welding of the tungsten arc can be passed through the weld.

An electric arc is then formed between the electrode and the welded pieces of steel.

Alternatively, a burner may be used, e.g. an oxy-acetylene burner. The heat treatment is carried out at a temperature below the temperature at which the growth of the additional grains occurs in the heat-affected weld zone. The exact temperature cannot be given as it depends. the chemical composition of the steel as well as the time it is,. Steel exposed to this temperature. Since it is assumed that the embrittlement phase forms during welding, it is also contemplated that the time and temperature should be such as to allow the embrittlement phases to be dissolved again. Practically speaking, temperatures should be - - higher - - than - 815 degrees Celsius and lower than the critical - temperature that supports grain growth.

A novel effect of the invention is that, as has already been said, - mechanical properties such as bending strength are improved and further improved technological properties are obtained, e.g. no edge cracks occur during the subsequent cold rolling; eliminates - thermal - - warping - - weld - and - - - eliminates the formation of weld cracks. This effect has never been achieved in the prior art. It is believed that these improvements in the properties of the weld zone steel are likely to be achieved by redissolving those phases that cause - embrittlement - of the material. and- which ·? - formed during welding.

The following - exemplary - embodiments of the method of the invention illustrate some essential features and objects of the present invention. Although - - - - these - particular - embodiments - relate to - - boron-containing silicon steels of up to 0.06% by weight carbon, 0.015 to 0.15 why, manganese, 0.01 to -0.05% Substances from the group consisting of sulfur and selenium, 0,00006 to 0,008: -% - boron, - to - to - -0,01 - -% nitrogen, up to - to 1 -% - copper, - 2,5 to 4 - - ^: silicon - and supplementary - - amount of - - iron, - - the method - - the refinement ^: - properties - - according to - of the invention - can be applied to - silicon - other steel - composition, - in which - during the welding process - phases - causing embrittlement - occur. ·

APPENDIX .Two - steel - pieces - ex - welded - tungsten electric - arc. - The electrode - moved - - - at - welding - at a speed of 1 m / min - was used - - electric arc - at a current of 200 A. - Steel - - exhibited - nominal thickness -2- mm. 'Other - welding parameters - are - - listed - in - the following:

Protective gas - atmosphere:.

Helium -'760 - mVhod. Curing copper - rod: -; 3.1 - mm ^: -x - 0.2- ·· mm --depth- - grooves.-Copper clips: í

6.35- -mm- - spacing - -

Electrode:

tungsten - diameter 2,4 mm containing 2 -% - thorium.

After - - welding - the - - - both - - welded - '- pieces - - after a slight - bend -' separated ^: and - 'weld - - burst.

Two -Other 'pieces welded _-: Steel · - heat treated at - vzájemném- for clamping -účelem constraints' respectively. suppression of movement. The pieces to be welded were held in a clamping which was used to weld them. The parameters - welding - were the same as in the previous paragraph. The heat treatment was carried out by passing the welding electrode above the weld at a reduced current value to. -60 - A. - - The welding electrode passed four times at a speed of - 0.82 m / min above the weld. After the heat treatment, they were welded. pieces - bent - around the bar - diameter - 7.62 centimeters. Weld during this - bending did not crack. After the heat treatment of the steel pieces - even according to the invention - a noticeable improvement was found. Heat warping and - weld ... cracks - were negligible. /

The welded and heat treated pieces were then cold rolled to a nominal thickness of - 0.25 - - - - mm. - No - - edge - cracks were observed. This is a significant advance in this industry.

Example II

Two pieces of steel were welded with tungsten flame; - arc. - The welding electrode was moving at a speed of 0.64 m / min. A current of 21 - A was used. - The steel had a nominal thickness of 0.6 mm. Other welding parameters were as follows:

O.chraná - plynová-. atmosphere:

Helium 760 cm3 / hour

Curing copper rod:

2.4 mm width x 0.13 mm groove depth. Měděné- tack to ^^ ^{^:;} -

6.35 - mm - distance.

Electrode:/

1,6 -mm - -s - 2 -% - thorium content. ' - - '' ^:

After - welding - '- - both - -''welded ¹ - pieces - - in - - - weld - - cracked - and - separated - - already -' at very - 'slight ¹ bend. - c ·

Example '-' 2

Two - - other · - pieces - - welded - steels - were - heat-treated - - clamped - for - the purpose of - limitation, respectively. suppression of movement. The pieces to be welded were - held - in - clamped, which were used to weld them; - - The parameters - welding ^{1 -} were the same as - - in the previous- - - paragraph. The heat treatment was carried out at a welding electrode above the weld at a reduced current of 10 · A. > -Welding - - - - electrode - passed - above - - weld '- twice - ¹ at - - speed' motion - '0,83' - m '/ min. - ¹ After - heat- - - processing - -were - pieces - - welded - - '- steel - bent -o o- · -90 °. - - During - - this - - bend - no - rupture - - weld. The heat treatment of the welded pieces according to the invention achieved a significant improvement. Thermal breakdown ^; appreciate - - and - weld - cracks - were negligible

The welded - and - heat-treated - pieces - were then cold rolled to a thickness of 0.25 millimeters. No edge cracks were observed, again indicating significant progress in this sector.

Example 3

Two pieces of steel were welded under the flux. The steel was nominally 2 mm thick. Welding was carried out with a carbon steel electrode with a high manganese content and a copper coating. The electrode ranged from 1.27 m / min. up to 1.65 m / min. An electrical current of 350 to 400 A was used.

After welding, the steel was heat-treated while clamping the pieces to reduce or reduce the heat. suppression of movement.

Welded pieces of steel were clamped in the clamping that was used to weld them. The heat treatment was carried out with an oxy-acetylene burner moving above the weld at a rate of 0.25 m / min. The burner was placed at a height of 2.54 cm above the zone affected by the welding heat.

Welded and heat treated pieces of steel were successfully cold rolled to a nominal thickness of 0.25 mm. No edge cracks were observed. Heat treatment significantly improved the properties of the steel produced.

The above specific embodiments of the method of the invention do not preclude application to other various modifications of the steel composition and welding conditions.

Claims (4)

Method for heat treating a zone of welded pieces of silicon steel affected by welding heat, characterized in that, in order to improve the mechanical and technological properties, the zone affected by welding heat is treated by heating means on the weld at a temperature greater than 815 ° C but lower than a critical temperature that promotes grain growth, with the pieces of steel immobilized. vynalezu 2. Method according to claim 1, characterized in that the pieces of steel are clamped in the same fixture used for welding the pieces. 3. Method according to claim 1 or 2, characterized in that the heating means is a non-consumable electrode forming an arc with welded pieces of steel. 4. A method according to claim 1 or 2, wherein the heating means is a burner, e.g. an oxyacetylene burner.