CN105728963A - Repair welding technology for grey cast iron - Google Patents

Abstract

The invention discloses a repair welding technology for grey cast iron. The technology mainly comprises the steps of 1) materials and preparations before welding and 2) the repair welding technology, wherein (1) a work piece is placed in an inclined manner, and welding seams are located at the positions for uphill welding or half-vertical welding, so that a melting-mixing ratio is reduced; (2) peripheries of a groove are preheated before welding at a temperature of 200-250 DEG C, so that a temperature difference between the welding seams and the work piece is reduced; (3) welding rods made of cast iron 308 are selected, the diameters D are 3.2 mm and 4 mm, and the welding rods shall be baked for 2h at a temperature of about 150 DEG C; (4) the welding rods with D of 3.2 mm are used for welding of the first, second and third layers of welding beads with the current of 90-100 A, the welding rods with D of 4 mm are used for the last two layers of welding beads with the current of 130-160 A, and direct current positive connection is adopted; (5) slag is removed after the welding of each layer; and (6) after the welding, the area within a scope of 200 mm around a welding area is heated to the temperature of 300-350 DEG C, the temperature is kept for 30 min, and the area is covered by asbestos powder for slow cooling. The technology disclosed by the invention has the advantages that processes are rational; manufacture cost is low; matching of different parameters is rational and harmonious; and product quality and production efficiency can be increased effectively.

Description

A kind of repair welding of grey cast-iron

Technical field

The present invention relates to the repair welding of a kind of grey cast-iron.

Background technology

The repair welding of existing grey cast-iron exists that procedure arrangement is unreasonable, operation is various, and technological parameter selects unreasonable, and the collocation of each technological parameter is unreasonable and higher to operator's skill requirement so that production cost is higher, product quality is on the low side, yield rate is the highest.

Summary of the invention

Because the drawbacks described above of prior art, the technical problem to be solved be to provide a kind of operation rationally, the repair welding of the grey cast-iron of low cost of manufacture.

For achieving the above object, the invention provides

The repair welding of a kind of grey cast-iron, comprises the steps:

1), prepare before material and weldering；The cylinder body of a certain product, material is HT20-40 grey cast-iron, and thickness is 18 mm.Crackle degree: and horizontal, longitudinally staggered, has and penetrates and do not penetrate；

(1) stop hole is bored: at distance crack-tip 2～3 mm, bore the stop hole of a diameter of 6～8 mm；To through wall flaw, stop hole to be beaten；To non-penetrative crackle, stop hole is deep 2～3 mm than crackle；

(2) bevel: use mechanical means, dig groove at crack initiation position；To through wall flaw, crackle to be got rid of during bevel, in garden arcuation bottom groove；

(3) preweld cleaning: by the greasy dirt around groove, the foul such as rust is removed clean, until exposing gloss；

2), repair welding

(1) by workpiece slant setting, weld seam is made to be in uphill welding or half vertical position welding, to reduce penetration ratio；

(2) will preheat around groove before weldering, temperature is 200～250 DEG C, to reduce the temperature difference of weld seam and workpiece；

(3) selection of electrodes casting 308, diameter D3.2 mm and 4 mm；Welding rod should be bakeed 2 h through about 150 DEG C before weldering；

Selecting D3.2 mm welding rod during (4) the 1st, 2,3 layers of welding bead welding, electric current is 90～100 A；Rear two-layer welding bead, selects D4 mm welding rod, electric current 130～160A；Use straight polarity direct current；

(5) every layer of clear slag of postwelding；

(6) postwelding, around weld zone in the range of 200 mm, is heated to 300～350 DEG C, is incubated 30 min, is covered with flake asbestos and is allowed to slow cooling；

(7) welding points for attention are:

1. in groove both sides for reducing fusion penetration, the most not weave bead welding can be taked；And can slightly swing in the middle of weld seam, but amplitude of fluctuation is little；

2., when repair welding workpiece is thicker, groove section is relatively big, uses multi-pass welding；Section of weld joint is relatively big, and the shrinkage stress of generation is very strong, easily forms weld seam and peels off；Therefore use rational welding sequence (1,2,3)；

3. short section of weldering, discontinuous welding, dispersion weldering, backstep welding are used；Short section of weldering, i.e. every segment length about 10～40 mm；Stop a moment after discontinuous welding, i.e. weldering one section, when workpiece is as cold as 50～60 DEG C, weld down one weld seam again, to prevent heat from concentrating；Dispersion weldering, arrives the welding of another position after a position welds one section again, to reduce the temperature difference, reduces stress；Backstep welding, it is compared with sequential welding, the tension peak value of weld seam can be made to have the biggest attenuating, therefore desirably prevent the generation of bead crack；

4. hammering weld seam；During hammering weld seam, temperature should be carried out above at 400 DEG C, with small round head hammering weld seam, makes weld metal extend, the stress in loose soldering district；Welding ground floor and last layer do not want hammering； After using process above repair welding, through weldquality inspection, shape good, do not find crackle and Seepage, reached prescription.

The invention has the beneficial effects as follows: operation of the present invention is reasonable, low cost of manufacture, each parameter collocation reasonable coordination, it is possible to be effectively improved product quality and production efficiency.

Detailed description of the invention

Below in conjunction with embodiment, the invention will be further described:

The repair welding of a kind of grey cast-iron, comprises the steps:

1), prepare before material and weldering；The cylinder body of a certain product, material is HT20-40 grey cast-iron, and thickness is 18 mm.Crackle degree: and horizontal, longitudinally staggered, has and penetrates and do not penetrate；

(1) stop hole is bored: at distance crack-tip 2～3 mm, bore the stop hole of a diameter of 6～8 mm；To through wall flaw, stop hole to be beaten；To non-penetrative crackle, stop hole is deep 2～3 mm than crackle；

(2) bevel: use mechanical means, dig groove at crack initiation position；To through wall flaw, crackle to be got rid of during bevel, in garden arcuation bottom groove；

(3) preweld cleaning: by the greasy dirt around groove, the foul such as rust is removed clean, until exposing gloss；

2 repair weldings

(1) by workpiece slant setting, weld seam is made to be in uphill welding or half vertical position welding, to reduce penetration ratio；

(2) will preheat around groove before weldering, temperature is 200～250 DEG C, to reduce the temperature difference of weld seam and workpiece；

(3) selection of electrodes casting 308, diameter D3.2 mm and 4 mm；Welding rod should be bakeed 2 h through about 150 DEG C before weldering；

Selecting D3.2 mm welding rod during (4) the 1st, 2,3 layers of welding bead welding, electric current is 90～100 A；Rear two-layer welding bead, selects D4 mm welding rod, electric current 130～160A；Use straight polarity direct current；

(5) every layer of clear slag of postwelding；

(6) postwelding, around weld zone in the range of 200 mm, is heated to 300～350 DEG C, is incubated 30 min, is covered with flake asbestos and is allowed to slow cooling；

(7) welding points for attention are:

1. in groove both sides for reducing fusion penetration, the most not weave bead welding can be taked；And can slightly swing in the middle of weld seam, but amplitude of fluctuation is little；

2., when repair welding workpiece is thicker, groove section is relatively big, uses multi-pass welding；Section of weld joint is relatively big, and the shrinkage stress of generation is very strong, easily forms weld seam and peels off；Therefore use rational welding sequence (1,2,3)；

3. short section of weldering, discontinuous welding, dispersion weldering, backstep welding are used；Short section of weldering, i.e. every segment length about 10～40 mm；Stop a moment after discontinuous welding, i.e. weldering one section, when workpiece is as cold as 50～60 DEG C, weld down one weld seam again, to prevent heat from concentrating；Dispersion weldering, arrives the welding of another position after a position welds one section again, to reduce the temperature difference, reduces stress；Backstep welding, it is compared with sequential welding, the tension peak value of weld seam can be made to have the biggest attenuating, therefore desirably prevent the generation of bead crack；

4. hammering weld seam；During hammering weld seam, temperature should be carried out above at 400 DEG C, with small round head hammering weld seam, makes weld metal extend, the stress in loose soldering district；Welding ground floor and last layer do not want hammering；

After using process above repair welding, through weldquality inspection, shape good, do not find crackle and Seepage, reached prescription.

Claims (1)

1. a repair welding for grey cast-iron, is characterized in that: comprise the steps:

1), prepare before material and weldering；The cylinder body of a certain product, material is HT20-40 grey cast-iron, and thickness is 18 mm；

Crackle degree: and horizontal, longitudinally staggered, has and penetrates and do not penetrate；

(1) stop hole is bored: at distance crack-tip 2～3 mm, bore the stop hole of a diameter of 6～8 mm；To through wall flaw, stop hole to be beaten；To non-penetrative crackle, stop hole is deep 2～3 mm than crackle；

(2) bevel: use mechanical means, dig groove at crack initiation position；To through wall flaw, crackle to be got rid of during bevel, in garden arcuation bottom groove；

(3) preweld cleaning: by the greasy dirt around groove, the foul such as rust is removed clean, until exposing gloss；

2 repair weldings

(1) by workpiece slant setting, weld seam is made to be in uphill welding or half vertical position welding, to reduce penetration ratio；

(2) will preheat around groove before weldering, temperature is 200～250 DEG C, to reduce the temperature difference of weld seam and workpiece；

(3) selection of electrodes casting 308, diameter D3.2 mm and 4 mm；Welding rod should be bakeed 2 h through about 150 DEG C before weldering；

Selecting D3.2 mm welding rod during (4) the 1st, 2,3 layers of welding bead welding, electric current is 90～100 A；Rear two-layer welding bead, selects D4 mm welding rod, electric current 130～160A；Use straight polarity direct current；

(5) every layer of clear slag of postwelding；

(6) postwelding, around weld zone in the range of 200 mm, is heated to 300～350 DEG C, is incubated 30 min, is covered with flake asbestos and is allowed to slow cooling；

(7) welding points for attention are:

1. in groove both sides for reducing fusion penetration, the most not weave bead welding can be taked；And can slightly swing in the middle of weld seam, but amplitude of fluctuation is little；

2., when repair welding workpiece is thicker, groove section is relatively big, uses multi-pass welding；Section of weld joint is relatively big, and the shrinkage stress of generation is very strong, easily forms weld seam and peels off；Therefore use rational welding sequence (1,2,3)；

3. short section of weldering, discontinuous welding, dispersion weldering, backstep welding are used；Short section of weldering, i.e. every segment length about 10～40 mm；Stop a moment after discontinuous welding, i.e. weldering one section, when workpiece is as cold as 50～60 DEG C, weld down one weld seam again, to prevent heat from concentrating；Dispersion weldering, arrives the welding of another position after a position welds one section again, to reduce the temperature difference, reduces stress；Backstep welding, it is compared with sequential welding, the tension peak value of weld seam can be made to have the biggest attenuating, therefore desirably prevent the generation of bead crack；

4. hammering weld seam；During hammering weld seam, temperature should be carried out above at 400 DEG C, with small round head hammering weld seam, makes weld metal extend, the stress in loose soldering district；Welding ground floor and last layer do not want hammering； After using process above repair welding, through weldquality inspection, shape good, do not find crackle and Seepage, reached prescription.