CN101362243A

CN101362243A - Large-sized iron casting fracture arc cold-welding repair method

Info

Publication number: CN101362243A
Application number: CNA2007100778893A
Authority: CN
Inventors: 黄初皓
Original assignee: Jiangxi Copper Corp
Current assignee: Jiangxi Copper Corp
Priority date: 2007-08-07
Filing date: 2007-08-07
Publication date: 2009-02-11

Abstract

The invention provides a cold welding fracture recovery method for a large-scale cast iron piece. Non cast iron welding material is selected, a layer of metal is scraped off on the fracture surface along the crack direction, so as to form a V-shaped groove; steel screws are screwed in the two sides of the groove, and a direct current welder is used for multi-layer welding. The technique of the invention carries out welding repair to the fracture of the large-scale cast iron piece under the condition of not being influenced by climate, the technique is simple, and the welding effect is good.

Description

Large-sized iron casting fracture arc cold-welding repair method

Technical field:

The present invention relates to a kind of method of REPAIR WELDING large-sized iron casting fracture, belong to the Metal Material Welding technical field.

Background technology:

Cast iron belongs to difficult welding material, though the welding method to ironcasting has multiple, but, all be to adopt half hot weld method usually: promptly will treat earlier to weld again after weldment is preheating to 400 ℃ before the weldering, and be incubated slow cooling again after welding finishes to the soldering of large-sized iron casting fracture.But this welding method can't be carried out by the restriction of environmental condition sometimes, for example at the season or the extremely frigid zones of cold, under the situation that does not have special heat tracing facility, preheat temperature is that instability is unbalanced again, postwelding is not accomplished slow cooling yet, causes welding point to produce white structure, and weld seam and heat affected area crack, whole welding line can strip down from mother metal, causes the welding failure.

Summary of the invention:

Purpose of the present invention is exactly in order to overcome the deficiency of above-mentioned technology, to provide a kind of to large-sized iron casting fracture arc cold-welding repair method, and this welding method is not subjected to the restriction of above-mentioned objective condition, and very strong adaptability and versatility are arranged.

The inventive method is as follows:

1, select welding rod: the cast iron arc cold-welding adopts non-cast iron type welding material Z308, and this welding base metal chemical analysis (%) is C ≦ 2.0, Si ≦ 2.5, Mn ≦ 1.0, S ≦ 0.03, Fe ≦ 8.0, Ni ≧ 9.2.The mechanical performance of weld seam is: weld metal tensile strength 28～40kgf/mm ², grey cast-iron butt joint intensity 15～20kgf/mm ², weld metal hardness HV130～170, grey cast-iron heat affected area hardness HV200～300.

2, prepare before the weldering: (1) checks crack length, for preventing the crackle expansion, is boring a stop hole from 5mm place, crackle end; (2) dig layer of metal at the fracture section along direction of check, form a V-butt, groove depth is as the criterion can't see the crackle vestige on weldment; (3) dry by the fire burning at groove part distance of positions face of weld 150～200mm place with blowtorch, the greasy dirt of weldment inside, moisture content are burnt, till flue gas takes over, but it is unsuitable too high to heat, and not scalding with feel serves as suitably, otherwise causes that easily mother metal is out of shape; (4) because large-sized iron casting is stressed very big, and the bevel for welding size is generally bigger in addition, thus at each groove both sides drilling and tapping, be screwed into the steel screw, to improve strength of joint; (5) remove the groove face residual impurity, and with carbon tetrachloride (CCl ₄) clean, beginning welding after the cleaning immediately, the time of shelving is unsuitable oversize, in order to avoid pollute once more, especially at wet weather, prevent that groove face from getting rusty; (6) before the welding welding rod was placed in the baking oven about 150 ℃ baking 2 hours, leave in then preserve in 80 ℃ of left and right sides baking ovens stand-by.

3, welding program and method: (1) uses DC welder, and welding rod one end adopts anodal; (2) adjust electric current, on other test specimen, the electric current of welding machine is adjusted in certain scope, adjust the foundation of electric current: the one, carry out coarse adjustment according to used core diameter size, its reference current such as following table:

Core diameter (mm)	2.5	3.2	4.0	5.0
Core diameter (mm)	2.5	3.2	4.0	5.0	Electric current (A)	65～90	90～110	120～150	160～190

The 2nd, carry out fine tuning according to weldment thickness and complex-shaped degree, thickness is bigger, simple shape, electric current is got the big value of coarse adjustment; Otherwise, get the little value of coarse adjustment; (3) striking: be selected in the striking of welding zone center, prevent the groove side bump the hair, singe, influence welding quality; (4) because bevel for welding is bigger, should adopt multilayer welding.Like this, back layer weld seam has thermal processes act to anterior layer weld seam and heat affected area, and the joint average hardness is reduced.But the weld seam shrinkage stress is bigger during multilayer welding, need prevent to produce the fissility crackle.Therefore, on welding procedure, should accomplish: weld around the steel screw earlier, again between the welding steel matter screw, and adopt the weldering of short section, discontinuous welding, dispersion weldering, the segmentation modes such as weldering that fall back, weldering speed is wanted soon, to reduce fusion penetration, during the long 30mm of each weld seam, should stop immediately and knock weld seam rapidly with hand hammer, purpose is the elimination internal stress, small spaces and dead angle are filled up in the refinement metallographic structure.(about 60 ℃) weld next time again when treating that weld seam is cooled to touch with hand, to reduce welding stress; (5) in welding process, as find shrinkage cavity or pore, can not make up again after the hammering, then need to remove one deck weld metal, more particularly use ironcasting for many years with the chisel engraving tool, some tissues are more loose, baking is burnt also and may not necessarily be hung out oil, the water of ensconcing the metal structure depths fully before the weldering, also pore can occur after the weldering once, must carve to fall to reweld, carry out repeatedly, till welding.

Technology of the present invention can not be subjected to can to carry out REPAIR WELDING to large-sized iron casting fracture effectively under the climatic influences, and technology is simple, and welding effect is good.

Description of drawings: Fig. 1 is a bevel for welding schematic diagram of the present invention

The specific embodiment:

Contrast Fig. 1 must dig layer of metal along direction of check at the fracture section as can be known before the present invention welds, form a V-butt 1, and each groove both sides drilling and tapping is screwed into steel screw 2 again.

Claims

1. large-sized iron casting fracture cold-welding recovery method, its method is as follows:

Select welding rod: the cast iron arc cold-welding adopts non-cast iron type welding material Z308, and this welding base metal chemical analysis is C ≦ 2.0, Si ≦ 2.5, Mn ≦ 1.0, S ≦ 0.03, Fe ≦ 8.0, Ni ≧ 9.2, the mechanical performance of weld seam is: weld metal tensile strength 28～40kgf/mm ², grey cast-iron butt joint intensity 15～20kgf/mm ², weld metal hardness HV130～170, grey cast-iron heat affected area hardness HV200～300;

Prepare before the weldering: a: boring a stop hole from 5mm place, crackle end; B: dig layer of metal at the fracture section along direction of check, form a V-butt, groove depth is as the criterion can't see the crackle vestige on weldment; C:, in groove part distance of positions face of weld 150～200mm place baking burning the greasy dirt of weldment inside, moisture content are burnt with blowtorch, till flue gas takes over, but it is unsuitable too high to heat, and it serves as suitable not scalding with feel; D:, be screwed into the steel screw at each groove both sides drilling and tapping; E: remove the groove face residual impurity, and clean, begin welding after the cleaning immediately with carbon tetrachloride; F: before the welding welding rod was placed in the baking oven about 150 ℃ baking 2 hours, leave in then preserve in 80 ℃ of left and right sides baking ovens stand-by;

Welding program and method: a: use DC welder, welding rod one end adopts anodal; B: adjust

Electric current is adjusted to the electric current of welding machine in certain scope on other test specimen, adjusts the foundation of electric current: the one, carry out coarse adjustment according to used core diameter size, the 2nd, carry out fine tuning according to weldment thickness and complex-shaped degree, thickness is bigger, simple shape, and electric current is got the big value of coarse adjustment; Otherwise, get the little value of coarse adjustment; C: striking: be selected in the striking of welding zone center; D: adopt multilayer welding, on welding procedure, should accomplish: weld around the steel screw earlier, again between the welding steel matter screw, and adopt the weldering of short section, discontinuous welding, dispersion weldering, the segmentation modes such as weldering that fall back, weldering speed wants fast, during the long 30mm of each weld seam, should stop immediately and knock weld seam rapidly, treat that weld seam welds next time again when being cooled to touch with hand with hand hammer; E: in welding process, as find shrinkage cavity or pore, can not make up again after the hammering, then need to remove one deck weld metal, more particularly use ironcasting for many years with the chisel engraving tool, some tissues are more loose, baking is burnt also and may not necessarily be hung out oil, the water of ensconcing the metal structure depths fully before the weldering, also pore can occur after the weldering once, must carve to fall to reweld, carry out repeatedly, till welding.