CN108406156B

CN108406156B - Low-heat-input narrow-gap vertical electro-gas welding method

Info

Publication number: CN108406156B
Application number: CN201810318532.8A
Authority: CN
Inventors: 沈若松
Original assignee: Zhangjiakou Nihewan Industry Development Co ltd
Current assignee: ZHANGJIAKOU NIHEWAN INDUSTRY DEVELOPMENT Co.,Ltd.
Priority date: 2018-04-09
Filing date: 2018-04-09
Publication date: 2020-06-19
Anticipated expiration: 2038-04-09
Also published as: CN108406156A

Abstract

The invention discloses a low-heat-input narrow-gap vertical electro-gas welding method, wherein a groove is in an I-shaped groove, the groove gap is 10-14mm, a traditional cylindrical welding gun is designed into an elliptic cylindrical structure to be suitable for welding of the narrow-gap groove, in order to ensure that a certain included angle exists between an electric arc and a side wall, a welding wire is bent through two asymmetric gears, so that the welding wire can swing back and forth in the groove, and a relational expression of the groove gap d (mm), the plate thickness h (mm) and the welding heat input Q (KJ/cm) is fitted through a large number of welding tests: q =0.8h +20 (d-10). The narrow gap welding method and the vertical electro-gas welding method are combined, single-layer single-pass welding with low heat input of the thick plate is realized, and the defects that single-layer multi-pass welding is needed in the narrow gap welding and the heat input is large and the side wall penetration is poor in the traditional vertical electro-gas welding method are overcome.

Description

Low-heat-input narrow-gap vertical electro-gas welding method

Technical Field

The invention belongs to a welding technology, and particularly relates to a low-heat-input narrow-gap vertical electro-gas welding method.

Background

The vertical electrogas welding method is a high-efficiency welding method which is very suitable for welding medium and thick plates, a welding seam is formed at one time, the biggest problem of the vertical electrogas welding method is that the welding heat input is high, the plate thickness of 30mm is generally required, the heat input is required to be more than 150KJ/cm, the heat input of 80mm plate thickness is required to be close to 500KJ/cm, and the crystallization speed of welding seam metal is reduced due to the fact that the heat input is increased along with the increase of the plate thickness during welding, crystal grains are large, the mechanical property of the welding seam is reduced, and the low-temperature impact toughness of the welding seam is seriously influenced. In order to ensure the penetration performance of two side walls, the vertical electro-gas welding generally adopts a V-shaped groove, a certain gap is reserved at the root part, the larger the plate thickness is, the larger the seam cross section is, for the welding of a steel plate with the plate thickness of 100mm, the bottom gap is 15mm, the width of the top end of the groove with the groove angle of 10-15 degrees can reach 40mm, and the large filling area can be produced only by increasing the heat input mode in order to ensure the one-step forming. Although twin wire electrogas welding has been effectively used for thick plates, the filling area is not reduced and the reduction of heat input is very limited. The method is characterized in that when welding is carried out by using an I-shaped groove, because the included angle between an electric arc and a side wall is 0, the penetration of the two side walls cannot be ensured, and the application of the swing welding wire gas welding method is greatly limited due to the problem of welding quality. Patent CN 102423827 a discloses a welding gun swinging device for vertical electro-gas welding, although the welding wire can swing left and right in the groove gap, the welding wire and the I-shaped groove are always in parallel state, i.e. the included angle between the electric arc and the side wall is still 0, and the penetration of the two side walls cannot be guaranteed, therefore, when the device is used for welding, in order to achieve good effect, the groove must be in V shape.

Disclosure of Invention

Aiming at the defects of the prior art, the invention aims to provide a low-heat-input narrow-gap vertical electro-gas welding method, which realizes the low-heat-input single-layer single-channel welding of a thick plate and overcomes the defects of single-layer multi-channel welding, large heat input in the traditional vertical electro-gas welding and poor side wall penetration of a swing welding wire electro-gas welding method in the narrow-gap welding.

In order to achieve the purpose, the invention adopts the following technical scheme:

(1) the method comprises the following steps of (1) increasing the groove gap of the traditional vertical electro-gas welding, which is mostly adopted in the traditional vertical electro-gas welding, to be 10-14mm, wherein the groove gap is increased along with the increase of the plate thickness;

(2) the traditional cylindrical welding gun is designed into an elliptic cylindrical structure to be suitable for welding of a narrow-gap groove, and in order to ensure that a certain included angle is formed between an electric arc and a side wall, the welding wire is bent through two asymmetric gears, so that the welding wire can swing back and forth in the groove;

(3) after a large number of welding tests, the relation of the groove gap d (mm), the plate thickness h (mm) and the welding heat input Q (KJ/cm) is fitted: q ═ 0.8h +20 (d-10).

The above process steps are specifically described as follows:

1) the groove gap is within the range of 10-14mm, the groove gap is increased along with the increase of the plate thickness, the welding heat input and the groove gap have great relation, and the reduction of the groove gap can greatly reduce the welding heat input

2) Compared with the traditional vertical electro-gas welding, the special welding gun design is adopted, so that the welding can be completed in a narrow space.

Compared with the prior art, the invention has at least the following beneficial effects:

(1) the heat input of the traditional process is several times that of the new process, the thicker the plate is, the more the difference is, and on the basis, the low-temperature impact toughness of a welding line and a heat affected zone can be greatly improved;

(2) the electric arc points to the side wall, so that the melting-through effect of the side wall can be ensured;

(3) the filling area of the welding line is reduced, the production cost is reduced, and meanwhile, the production efficiency is improved.

Drawings

FIG. 1 is a view of a welding gun of an elliptical cylinder configuration;

FIG. 2 is a diagram showing the joining of 65mm thick welded plates in example 1;

FIG. 3 is a diagram showing the joining of 65mm thick weld plates in comparative example 1;

FIG. 4 is a splicing view of a 140mm thick weld plate of example 2;

FIG. 5 is a splicing view of a 140mm thick weld plate in comparative example 2;

Detailed Description

The technical solution of the present invention is further described in detail below with reference to the accompanying drawings and several preferred embodiments, but not limited thereto.

Example 1

A welding test plate EH36 is prepared, the label A is marked, the plate thickness is 65mm, the length is 1000mm, the groove does not need to be formed, the root gap is 11mm, the heat input is about 72kJ/cm according to a formula Q which is fitted by a new process and is 0.8h +20 (d-10), and the proper welding current, voltage and welding speed are deduced according to the calculated heat input, which is shown in Table 1.

Table 1 example 1 welding process parameters

Comparative example 1

A welding test piece EH36 was prepared in exactly the same manner as in example 1, designated by the reference numeral B, and had a plate thickness of 65mm, a length of 1000mm, a V-shaped groove, an angle of 20 degrees, a root gap of 8mm, and CO as a shielding gas₂Double-wire electrogas welding is adopted, and the technological parameters are shown in table 2.

Table 2 comparative example 1 welding process parameters

A adopts a new process for welding, greatly saves welding materials, and greatly improves the low-temperature impact toughness because the heat input is obviously reduced, as shown in Table 3

TABLE 3 comparison of the effects of A and B

Example 2

A welding test plate EQ47 is prepared, the label C is marked, the plate thickness is 140mm, the length is 1200mm, the groove does not need to be formed, the root gap is 12mm, the heat input is calculated to be about 152kJ/cm according to a formula Q which is fitted by a new process and is 0.8h +20 (d-10), and the proper welding current, voltage and welding speed are deduced according to the calculated heat input, which is shown in a table 4.

Table 4 example 2 welding process parameters

Comparative example 2

A welding test plate EQ47 was prepared in exactly the same manner as in example 2, designated by the reference numeral D, and had a plate thickness of 140mm, a length of 1200mm, a V-shaped groove, an angle of 30 degrees, a root gap of 10mm, and a shielding gas of CO₂Double-wire electrogas welding is adopted, and the technological parameters are shown in table 5.

Table 5 comparative example 2 welding process parameters

A comparison of the effects of C and D is shown in Table 6, which shows that the welding amount of the new technique is reduced to about one third of that of the conventional technique, and the heat input is reduced to about one fifth of that of the conventional technique, and the low temperature impact value at-40 ℃ is increased to about two times that of the conventional technique, as shown in Table 6.

TABLE 6 comparison of C and D Effect

In addition to the above examples, the present invention may have other embodiments. All technical solutions formed by adopting equivalent substitutions or equivalent transformations fall within the protection scope of the claims of the present invention.

Claims

1. A low heat input narrow gap vertical electro-gas welding method is characterized in that:

(1) the V-shaped groove mostly adopted by the traditional vertical electro-gas welding is changed into an I-shaped groove, the groove gap is 10-14mm, and the groove gap of the traditional vertical electro-gas welding is increased along with the increase of the plate thickness;

(3) after a large number of welding tests, the relation of the groove gap d (mm), the plate thickness h (mm) and the welding heat input Q (KJ/cm) is fitted: q =0.8h +20 (d-10).