CN101138802B - Composite arc-welding method - Google Patents

Abstract

A complex arc welding method is characterized in that a joint bevel and surface around the joint bevel is cleaned up prior to welding; groups of work pieces are spaced out 2 to 2mm apart. Point is fixed. The fixed point is polished. Process of welding adopts MAG welding method: electric current for a first welding seam is 260 to 280 A and voltage is 28 to 30V; with welding completed, interlamination cleaning is practiced and interlamination temperature is not below 200 DEG C; the electric current for a second welding seam is 260 to 280 A and voltage is 28 to 30V; with welding completed, interlamination cleaning is practiced and interlamination temperature is not below 200 DEG C; the electric current for a third welding seam is 260 to 280 A and voltage is 28 to 30V; with welding completed, interlamination cleaning is practiced and interlamination temperature is not below 200 DEG C; after the third welding seam is cooled for 2 to 3 hours until the temperature of the third welding seam is the same with room temperature; a position of welding seam is polished. TIG cladding is adopted for re-melting the position of welding seam with current being 85 to 100A. The present invention is able to reduce hardening organization of the welding seam, make grains refined and enhance strength of the welding seam, thereby avoiding or decreasing occurrence of cold cracks and tearing at the junction end of a tube plate.

Description

A kind of composite arc-welding method

Technical field

The present invention relates to a kind of welding method, especially relate to a kind of composite arc-welding method.

Background technology

Ubiquity pipe-plate banjo fixing butt jointing pattern adopted the MAG welding method when various flap seats and crossbeam welded in the domestic subway bogie frame, and the polishing of welding back is rounding off also.Because flap seat is stressed concentrated position, under the effect of long-term dynamic loading, tends to occur cold crack in the end that pipe and plate have a common boundary and vertically expand, even tear phenomenon along weld seam.

Summary of the invention

Technical problem to be solved by this invention is to be prone to cold crack and vertically to expand along weld seam at end, tube sheet boundary, even tear phenomenon, propose a kind ofly can reduce the weld seam hardened structure, make grain refinement, increase welding seam toughness, thereby avoid or reduce the composite arc-welding method that the cold crack phenomenon appears in end, tube sheet boundary, to overcome the defective that background technology exists.

Welding method of the present invention is as follows:

Prepare before the weldering: remove on butt joint groove and near surface thereof before the welding;

The workpiece group is right: group is to gap 2～3mm, and point is solid, will put the Gu Chu polishing smoothly;

Welding process: MAG welding method, ground floor weld seam electric current 260～280A, voltage 28～30V, postwelding, the interlayer cleaning, interlayer temperature is not less than 200 ℃, second layer weld seam electric current 240～250A, voltage 26～28V, postwelding, the interlayer cleaning, interlayer temperature is not less than 200 ℃, the 3rd layer of weld seam electric current 240～250A, voltage 26～28V, postwelding, interlayer cleaning, interlayer temperature is not less than 200 ℃, and the 3rd layer of postwelding cooled off 2～3 hours, until cool to room temperature;

The weld seam welding toe polishes smooth, and adopts the TIG cladding, with the welding toe remelting, and electric current 85～100A.

MAG is meant the mixed gas arc welding of consumable electrode oxidisability.

TIG is meant the non consumable arc welding electrode inert gas-shielded arc welding.

The present invention can reduce the weld seam hardened structure, makes grain refinement, increases welding seam toughness, thereby avoids or reduce end, tube sheet boundary cold crack occurring even tearing phenomenon.

Description of drawings

Fig. 1 is a S355 fine-grained steel original structure shape appearance figure;

Fig. 2 is MAG welding point heat affected area metallographic structure figure;

Fig. 3 is MAG+TIG welding point heat affected area metallographic structure figure.

Further specify effect of the present invention below by test example.

Test example 1

1, test material and method:

Test steels is selected S355 fine-grained steel (thickness of slab 12mm), and its chemical composition sees Table 1, and main performance index sees Table 2, and the original structure pattern is seen Fig. 1.

The chemical composition (ω %) of table 1S355 fine-grained steel

Table 1 Chemical material contents of S355 fine grained steel

Table 2S355 main performance index

Table 2 Main mechanical properties of S355 fine grained steel

Adopt MAG welding method and MAG+TIG complex welding method to weld in the test respectively, the weldment groove type is a V-type, and bevel angle is 60 degree, and concrete welding procedure sees Table 3.

Table 3 welding procedure

Table?3?Process?of?welding

Welding method number of plies welding current weldingvoltage power supply kind gage of wire

(A) (V) class (mm)

1 260～280 28～30 direct current φ 1.2

MAG 2 240～250 26～28 direct current φ 1.2

3 240～250 26～28 direct current φ 1.2

TIG 1 85～100 direct currents

2, test results and analysis

2.1 the metallographic structure of welding point heat affected area

Welding piece under two kinds of welding conditions in the table 3 is made into the metallographic structure that metallographic specimen carries out the welding point heat affected area observes, observed result is seen shown in Fig. 2 (MAG weldering), Fig. 3 (MAG+TIG weldering).

By Fig. 2, Fig. 3 as can be seen: welding point heat affected area crystal grain all has significantly and grows up under two kinds of welding conditions; Compare much smaller under the width of MAG+TIG welding point heat affected area and grain growth trend and the simple employing MAG welding rod spare.In multi-pass welding seam welding technical process, bottom layer tissue mostly is tiny ferrite and pearlitic structrure, and its toughness is bigger, and this is because the back layer has Effect of annealing to last, so that crystal grain is able to is tiny, toughness, plasticity increase.But repeatedly big heat input that multi-pass welding connects makes weld heat-affected zone roomy, and crystal grain is thick, and the fragility of heat affected area is bigger, this phenomenon the skin of weld seam embody comparatively obvious.But, use TIG remelting welding procedure, can make the outer tissue refinement, the crystal grain nodularization.

2.2 the welding point mechanical performance detects

After finishing welding by the welding procedure in the table 3, respectively the test specimen under two kinds of welding conditions is processed into tensile sample and impact specimen (the detection position is the overheated zone) carries out Performance Detection, testing result sees Table 4.

Table 4 welding point mechanical performance testing result

Fig?4?Character?test?results?of?welding?joints

From table 4 welding point mechanical performance testing result as can be seen: 1. the welding point yield strength is compared all with mother metal with tensile strength and is significantly decreased under the MAG welding rod spare, and the welding point yield strength is not compared with mother metal with tensile strength and obviously descended under the MAG+TIG welding rod spare.This be because: though TIG and MAG belong to arc-welding, the two has difference in essence.TIG compares with MAG, and it approximately is tens times of MAG that its sweating heat is gone into amount.Again because TIG sweating heat input than comparatively dense, and the input of MAG sweating heat is relatively evacuated, and causes the MAG weld affected zone bigger, organizes thickly, fragility is big.So, use TIG surface cladding principle, outer weld seam toe of weld is carried out the TIG remelting, can crystal grain thinning, the effect that improves welding seam toughness, plasticity.

3, conclusion

The welding point yield strength is compared all with mother metal with tensile strength and is significantly decreased under the MAG condition, and the welding point yield strength is compared not obviously decline with tensile strength under the MAG+TIG welding rod spare with mother metal, and joint toughness is than MAG welding rod spare height.

Pipe sheet weld joint adopts the MAG+TIG complex welding method can improve the welding point structure property.

Embodiment 1

Prepare before the weldering: remove on butt joint groove and near surface thereof before the welding;

The workpiece group is right: group is to gap 2mm, and point is solid, will put the Gu Chu polishing smoothly;

Welding process: MAG welding method, ground floor weld seam electric current 260A, voltage 28V, postwelding, the interlayer cleaning, interlayer temperature is not less than 200 ℃, second layer weld seam electric current 240A, voltage 26V, postwelding, the interlayer cleaning, interlayer temperature is not less than 200 ℃, the 3rd layer of weld seam electric current 240A, voltage 26V, postwelding, interlayer cleaning, interlayer temperature is not less than 200 ℃, and the 3rd layer of postwelding cooled off 2 hours, until cool to room temperature;

The weld seam welding toe polishes smooth, and adopts the TIG cladding, with the welding toe remelting, and electric current 85A.

Embodiment 2

Prepare before the weldering: remove on butt joint groove and near surface thereof before the welding;

The workpiece group is right: group is to gap 3mm, and point is solid, will put the Gu Chu polishing smoothly;

Welding process: MAG welding method, ground floor weld seam electric current 280A, voltage 30V, postwelding, the interlayer cleaning, interlayer temperature is not less than 200 ℃, second layer weld seam electric current 250A, voltage 28V, postwelding, the interlayer cleaning, interlayer temperature is not less than 200 ℃, the 3rd layer of weld seam electric current 250A, voltage 28V, postwelding, interlayer cleaning, interlayer temperature is not less than 200 ℃, and the 3rd layer of postwelding cooled off 3 hours, until cool to room temperature;

The weld seam welding toe polishes smooth, and adopts the TIG cladding, with the welding toe remelting, and electric current 100A.

Embodiment 3

Prepare before the weldering: remove on butt joint groove and near surface thereof before the welding;

The workpiece group is right: group is to gap 2.5mm, and point is solid, will put the Gu Chu polishing smoothly;

Welding process: MAG welding method, ground floor weld seam electric current 270A, voltage 29V, postwelding, the interlayer cleaning, interlayer temperature is not less than 200 ℃, second layer weld seam electric current 245A, voltage 27V, postwelding, the interlayer cleaning, interlayer temperature is not less than 200 ℃, the 3rd layer of weld seam electric current 245A, voltage 27V, postwelding, interlayer cleaning, interlayer temperature is not less than 200 ℃, and the 3rd layer of postwelding cooled off 2.5 hours, until cool to room temperature;

The weld seam welding toe polishes smooth, and adopts the TIG cladding, with the welding toe remelting, and electric current 90A.

Welding equipment:

(OTC) PCVM 350 and (OTC) IGBT INVERTER ACCUTIG 300P.

Claims (1)

1. composite arc-welding method is characterized in that realizing as follows:

Prepare before the weldering: remove on butt joint groove and near surface thereof before the welding;

The workpiece group is right: group is to gap 2～3mm, and point is solid, will put the Gu Chu polishing smoothly;

Welding process: MAG welding method, ground floor weld seam electric current 260～280A, voltage 28～30V, postwelding, the interlayer cleaning, interlayer temperature is not less than 200 ℃, second layer weld seam electric current 240～250A, voltage 26～28V, postwelding, the interlayer cleaning, interlayer temperature is not less than 200 ℃, the 3rd layer of weld seam electric current 240～250A, voltage 26～28V, postwelding, interlayer cleaning, interlayer temperature is not less than 200 ℃, and the 3rd layer of postwelding cooled off 2～3 hours, until cool to room temperature;

The weld seam welding toe polishes smooth, and adopts the TIG cladding, with the welding toe remelting, and electric current 85～100A.

Images