CN105014200A

CN105014200A - Steel casting loose defect welding method

Info

Publication number: CN105014200A
Application number: CN201510464221.9A
Authority: CN
Inventors: 陈得润; 曹鹏; 雷永红
Original assignee: Kocel Steel Foundry Co Ltd
Current assignee: Kocel Steel Foundry Co Ltd
Priority date: 2015-07-31
Filing date: 2015-07-31
Publication date: 2015-11-04

Abstract

The invention relates to a steel casting defect welding method, in particular to a steel casting loose defect welding method. The method is characterized in that firstly, a defect is dug away, and then the edge of the defect is preheated; the defect is placed in the horizontal position or a slope climbing position to be welded after being preheated; a small-specification welding rod with the diameter phi being 3.2 mm or 4.0 mm; a single track is welded manually and does not swing; by means of continuous arc welding backing, it is guaranteed that a weld joint is continuously welded, and welding is achieved at a time as much as possible; postwelding stress relief has to be conducted within eight hours after each time of welding; and the furnace temperature is required to be not lower than 200 DEG C before the defect enters a furnace, and the cooling speed is controlled within 60 DEG C per hour. The method is unique, prevents the loose defect from tearing in a layer shape in the welding process, increases the defect repair yield, and reduces the number of times of repair.

Description

A kind of steel-casting loosens the welding method of class defect

Technical field

The present invention relates to a kind of welding method of cast steel part defect, especially relate to a kind of steel-casting and to loosen the welding method of class defect.

Background technology

Along with the fast development of National Industrial, the demand of some key industrys to large-scale steel-casting is increasing, and the single casting weight of requirement is increasing, also more and more higher to the requirement of product quality.The quality of heavy castings depends on the quality of liquid metal and the design of casting process scheme to a great extent.Foundry goods, after solidification of molten steel terminates, easily produces the problem such as gross segregation, coarse grains at the thick and large section of rising head root or foundry goods, is referred to as material rarefaction defect.

Material is loosened, and the crystal grain referring to be formed in casting solidification process is comparatively thick, the structure of association non-metallic inclusion, is often detected with shrinkage porosite, strip defective form.But belong to non-broad perspectives defect due to this shortcoming, usually all cannot be detected by outward appearance, magnetic or infiltration, can not be removed completely when defect processing.

This kind of problem is particularly serious in thick and large section casting parts, and during casting defect process, need reprocess repeatedly, cause reprocessing low qualified, increase production cost, the production cycle lengthens, and incurs loss through delay delivery.

Also do not overcome the method for above-mentioned defect at present.

Summary of the invention

The object of the invention is the defect overcoming prior art, provide a kind of method unique, avoid loose class defect to produce lamellar tearing in welding process, improve faults repair qualification rate, a kind of steel-casting reducing number of rewelding loosens the welding method of class defect.

The present invention realizes in the following way:

A kind of steel-casting loosens the welding method of class defect, it is characterized in that: first the method for excavate defect, then preheating is carried out to Defect Edge, after preheating, defect is placed in horizontal level or the welding of climbing position, employing diameter is the small dimension welding rod of Φ 3.2mm or Φ 4.0mm, manual welding single track does not swing, the arc-welding bottoming of the company of employing, and ensure that one weld seam welding is uninterrupted, as much as possible once complete, stove must be entered after each welding completes in 8 hours and carry out postwelding stress-removal, enter stokehold and require that furnace temperature must not lower than 200 DEG C, and cooling velocity is controlled within reduction per hour 60 DEG C,

It is described that to excavate defect be to the state of the invisible defect of naked eyes by foundry goods rarefaction defect position gouge, then 10 ~ 20mm is removed in the gouge process of bottom groove and both sides, excavate material weaker zone, finally by inner for defect reconditioning rounding off, avoid cusped edge wedge angle iso-stress centrostigma;

Described preheating adopts combustion of natural gas to carry out preheating to Defect Edge, preheat temperature is higher than 30 ~ 50 DEG C of welding procedure temperature, preheating is kept more than 2 hours after reaching preheat temperature, but be no more than 6 hours, guarantee welding region and neighboring area homogeneous temperature, temperature difference≤40 DEG C within the scope of defect periphery 100mm in guarantee welding process, during stopping weldering, weld zone keeps minimum preheat temperature.

First by flat for the weldering of the defect bottom during described defect welding, then manual electric arc welding bottoming at least three layers is adopted, timely scarfing cinder after every layer of welding completes, and polished in the bulky grain splash produced in welding process, concavo-convex welding position, dead angle and groove both sides, guaranteeing to adopt less welding current in good confluent situation during bottoming welding; Other welding methods such as gas shielded arc welding can be used to carry out shunting welding during packed layer welding, welding swing width≤30mm, and welding process guarantees rounding off all the time, avoid existing stress to concentrate and cause cracking, pneumatic shovel hammer mode is adopted to eliminate welding stress, timely hammering after requiring except ground floor and last one deck all the other every layer welding to complete;

During described depth of defect > 100mm, welded at twice, depth of defect >=150mm time-division three times has welded, and has welded all to carry out reconditioning detection afterwards at every turn, ensures that each stage welding portion meets Requirements of Nondestructive Testing.

The present invention has following effect:

1) method is unique: first method provided by the invention for excavate defect, then preheating is carried out to Defect Edge, after preheating, defect is placed in horizontal level or the welding of climbing position, employing diameter is the small dimension welding rod of Φ 3.2mm or Φ 4.0mm, manual welding single track does not swing, the arc-welding bottoming of the company of employing, and ensure that one weld seam welding is uninterrupted, as much as possible once complete, stove must be entered after each welding completes in 8 hours and carry out postwelding stress-removal, enter stokehold and require that cooling velocity lower than 200 DEG C, and must not control within reduction per hour 60 DEG C by furnace temperature.

2) avoid loose class defect to produce lamellar tearing in welding process: the present invention adopts expansion borderless manner to remove material rarefied zone to greatest extent, reduce the secondary cracking because mother metal reason causes.By improving preheat temperature, reducing welding point, increase the buffering of join domain, increase process detection number of times and carry out the measures such as postwelding stress-removal in time and tear tendency to reduce mother metal, greatly reduce the accumulative peak value of welding stress, reduce cracking amount more than 40%.Adopt multi-pass welding, restriction weld width, reduce to weld the defect caused.Adopt gradation welding+postwelding stress-removal mode to eliminate welding stress in time, reduce cracking situation;

3) improve faults repair qualification rate, reduce number of rewelding: use welding procedure of the present invention, one time solder yield can reach more than 95%, integral solder qualification rate improves more than 30%.Foundry goods welding times reduces 2 ~ 3 times than before, and the production cycle shortened at least 1 week.

Accompanying drawing explanation

Fig. 1 multi-pass welding welding sequence schematic diagram.

Detailed description of the invention

Steel-casting loosens the welding procedure of class defect, comprises the full-flow process excavating preheated weld and stress-removal from defect, comprises the steps:

1) defect is excavated

By foundry goods rarefaction defect position gouge to the state of the invisible defect of naked eyes, then 10 ~ 20mm is removed in the gouge process of bottom groove and both sides, excavate material weaker zone.Finally by inner for defect reconditioning rounding off, avoid cusped edge wedge angle iso-stress centrostigma.

2) preheated weld

1. preheat temperature is improved

Adopt combustion of natural gas to carry out preheating to Defect Edge, require that preheat temperature is higher than 30 ~ 50 DEG C of welding procedure temperature.Keep preheating after reaching preheat temperature more than 2 hours, less than 6 hours, guarantee welding region and neighboring area homogeneous temperature.Temperature difference≤40 DEG C within the scope of defect periphery 100mm in guarantee welding process, during stopping weldering, weld zone keeps minimum preheat temperature.

2. reduce welding point, the buffering increasing join domain tears tendency to reduce mother metal

Defect is placed in horizontal level or the welding of climbing position, employing diameter is the small dimension welding rod of Φ 3.2mm or Φ 4.0mm, and manual welding single track does not swing, the arc-welding bottoming of the company of employing, and ensures that one weld seam welding is uninterrupted, as much as possible once completes.

First by flat for the weldering of the defect bottom during defect welding, then adopt manual electric arc welding bottoming at least three layers, timely scarfing cinder after every layer of welding completes, and polished in the bulky grain splash produced in welding process, concavo-convex welding position, dead angle and groove both sides.Guaranteeing to adopt less welding current, welding current parameter lookup table 1 in good confluent situation during bottoming welding.

Other welding methods such as gas shielded arc welding can be used to carry out shunting welding during packed layer welding, welding swing width≤30mm, and welding process guarantees rounding off all the time, as shown in Figure 1, avoids existing stress and concentrates and cause cracking.

Pneumatic shovel hammer mode is adopted to eliminate welding stress, timely hammering after requiring except ground floor and last one deck all the other every layer welding to complete.

Table 1 welding current parameter lookup table

Core diameter mm	Welding current A
		Φ3.2	90～120
Φ4.0	130～170
		Φ5.0	170～210

3. the process that increases detects number of times

During depth of defect > 100mm, welded at twice, depth of defect >=150mm time-division three times has welded, and has welded all to carry out reconditioning detection afterwards at every turn, ensures that each stage welding portion meets Requirements of Nondestructive Testing.

3) post weld heat treatment requirement

Stove must be entered after each welding completes in 8 hours and carry out postwelding stress-removal, enter stokehold and require that cooling velocity lower than 200 DEG C, and must not control within reduction per hour 60 DEG C by furnace temperature.

In Fig. 1,1 is prime coat; 2 is packed layer; 3 is gradation welding boundary line; 4 is capping layer.

Claims

1. a steel-casting loosens the welding method of class defect, it is characterized in that: first the method for excavate defect, then preheating is carried out to Defect Edge, after preheating, defect is placed in horizontal level or the welding of climbing position, employing diameter is the small dimension welding rod of Φ 3.2mm or Φ 4.0mm, manual welding single track does not swing, the arc-welding bottoming of the company of employing, and ensure that one weld seam welding is uninterrupted, as much as possible once complete, stove must be entered after each welding completes in 8 hours and carry out postwelding stress-removal, enter stokehold and require that furnace temperature must not lower than 200 DEG C, and cooling velocity is controlled within reduction per hour 60 DEG C.

2. a kind of steel-casting as claimed in claim 1 loosens the welding method of class defect, it is characterized in that: described in excavate defect be to the state of the invisible defect of naked eyes by foundry goods rarefaction defect position gouge, then 10 ~ 20mm is removed in the gouge process of bottom groove and both sides, excavate material weaker zone, finally by inner for defect reconditioning rounding off, avoid cusped edge wedge angle iso-stress centrostigma.

3. a kind of steel-casting as claimed in claim 1 loosens the welding method of class defect, it is characterized in that: described preheating adopts combustion of natural gas to carry out preheating to Defect Edge, preheat temperature is higher than 30 ~ 50 DEG C of welding procedure temperature, preheating is kept more than 2 hours after reaching preheat temperature, but be no more than 6 hours, guarantee welding region and neighboring area homogeneous temperature, temperature difference≤40 DEG C within the scope of defect periphery 100mm in guarantee welding process, during stopping weldering, weld zone keeps minimum preheat temperature.

4. a kind of steel-casting as claimed in claim 1 loosens the welding method of class defect, it is characterized in that: first by flat for the weldering of the defect bottom during described defect welding, then manual electric arc welding bottoming at least three layers is adopted, timely scarfing cinder after every layer of welding completes, and polished in the bulky grain splash produced in welding process, concavo-convex welding position, dead angle and groove both sides, guaranteeing to adopt less welding current in good confluent situation during bottoming welding; Other welding methods such as gas shielded arc welding can be used to carry out shunting welding during packed layer welding; welding swing width≤30mm; and welding process guarantees rounding off all the time; avoid existing stress to concentrate and cause cracking; pneumatic shovel hammer mode is adopted to eliminate welding stress, timely hammering after requiring except ground floor and last one deck all the other every layer welding to complete.

5. a kind of steel-casting as claimed in claim 1 loosens the welding method of class defect, it is characterized in that: during described depth of defect > 100mm, weld at twice, depth of defect >=150mm time-division three times has welded, all carry out reconditioning detection after each welding completes, ensure that each stage welding portion meets Requirements of Nondestructive Testing.