CN101464248A - Method for detecting high-strength steel fillet welding joint performance - Google Patents

Abstract

The invention relates to a method for detecting the performance of high-strength steel fillet weld joints, comprising the following steps: 1) butt jointing of test plates for T-shaped fillet welds, and opening a single V-shaped groove at the fillet weld joints; 2) before welding Use mechanical treatment to clean the groove surface; 3) Use Ar+CO ₂ mixed gas shielded welding or CO ₂ gas shielded welding; 4) Use solid wire for multi-layer and multi-pass welding, continuous welding without stopping in the middle; 5) Cutting Bend the sample, machine the side of the sample flat, and bend it at 120°; 6) Macroscopically or microscopically inspect the fillet weld area of the sample after bending. Compared with conventional welded joint detection methods, the present invention can reliably detect the appropriate groove angle, welding wire matching and welded joint crack resistance of high-strength steel fillet welds with a tensile strength of 600-800 MPa, avoiding unnecessary multi-layer and multiple One-way welding, greatly reducing welding costs. The invention has the characteristics of simple and convenient operation and strong applicability, and is convenient for popularization and application and improves production efficiency.

Description

Method for testing the performance of high-strength steel fillet weld joints

technical field

The invention relates to a method for detecting the performance of welded joints, in particular to a method for detecting the anti-crack performance of fillet welded joints of low-alloy high-strength steel with a tensile strength of 600-800 MPa.

Background technique

Low-alloy high-strength steel not only has high strength, but also has good plasticity and toughness. It is not only economical but also can improve the performance of welding products and structures. Therefore, high-strength steel is widely used in welded engineering structures.

In recent years, the progress of metallurgical production technology, especially the application of computer automatic control technology in smelting, rolling and heat treatment, has provided an important technical guarantee for the development of high-strength steel for welding engineering structures. Especially low-alloy high-strength steel with a tensile strength of 600-800MPa has been widely used in important welding structures such as construction machinery, coal mine hydraulic supports, and bridges due to the gradual improvement of production technology and the formation of mass production scale. At the same time, the development and application of high-strength steel put forward higher requirements for welding materials, welding technology and welding quality inspection.

In order to eliminate welding cracks and improve the welding production efficiency of high-strength steel with a tensile strength of 600-800MPa, most of the welding of similar steels at home and abroad adopts mechanized or semi-mechanized welding methods such as CO ₂ gas shielded welding or mixed gas shielded welding (MAG). The strength matching of welded joints has an important impact on crack sensitivity and joint performance, and is an important issue in the design of welded structures and the performance of welded joints. However, how to determine the relationship between strength matching and crack sensitivity of high-strength steel welded joints is still controversial. Especially for the fillet welds of high-strength steel medium and thick plates, the clarification of the relationship between the groove angle, welding wire matching and the number of welds has also attracted people's attention. Because reducing the groove angle of the fillet weld can greatly reduce the number of weld passes and the amount of filler metal, which is directly related to reducing welding costs and improving welding production efficiency. However, there is still no good detection method for the relationship between groove angle, welding wire matching and number of welds.

Therefore, if the detection of the crack resistance of high-strength steel fillet weld joints with a tensile strength of 600-800 MPa can be realized under the existing welding process conditions, and the relationship between the groove angle, welding wire matching and the number of welds can be clarified, it will be beneficial to simplify the welding process. , Improving the performance of the welding zone and reducing production costs are of great significance.

Contents of the invention

The purpose of the present invention is to overcome the shortcomings of the above-mentioned prior art, and provide a method for detecting the performance of high-strength steel fillet weld joints that is easy to operate, strong in applicability, and low in cost.

In order to achieve the above object, the present invention adopts the following technical solutions: a method for detecting the performance of high-strength steel fillet weld joints, comprising the following steps:

1) The test plate butt joint form of the T-shaped fillet weld is: weld a vertical plate on the three test plates respectively to form a T-shaped structure, fillet welds on both sides, the vertical plate must not be deflected; Single V-shaped bevel, three bevel angles are 25°, 35°, 45° respectively;

2) Before welding, use mechanical treatment to clean the groove surface to remove oil and rust;

3) Ar+CO ₂ mixed gas shielded welding or CO ₂ gas shielded welding; welding process parameters: welding voltage 26V ~ 30V, welding current 160A ~ 310A, welding speed 0.4cm/s ~ 0.6cm/s, welding heat input Controlled at 10kJ/cm～20kJ/cm, protective gas flow rate 10L/min～20L/min;

4) For high-strength steels with a tensile strength of 600MPa, 700MPa and 800MPa, respectively use a solid core wire with a nominal strength of 600MPa or 700MPa for multi-layer and multi-pass welding, and weld continuously without stopping in the middle;

5) Cut at least 3 bending samples along the vertical direction of the weld, machine the sides of the samples flat, and bend them at 120°;

6) Macroscopic or microscopic inspection of the bending results of the sample: macroscopic inspection is to use a 5-10 times magnifying glass to directly observe the fillet weld area with the naked eye; microscopic inspection is to use a metallographic microscope to inspect the fillet weld area of the bent sample.

The mechanical treatment in the step 2) is to use a wire brush to remove the rust on the surface of the groove to expose the metallic luster.

The volume percentage of Ar and _CO2 used in the Ar+ _CO2 mixed gas shielded welding in the step 3) is 80%:20%.

The diameter of the 600MPa and 700MPa solid welding wires in the step 4) is 1.2mm.

The 600MPa solid core welding wire in the step 4) contains the following chemical components in weight percentage: C<0.11%, Si0.5%～0.80%, Mn 1.5%～1.9%, Mo 0.3%～0.5%; 600MPa solid core The mechanical properties of the deposited metal of the welding wire are: tensile strength σ _b >670MPa, yield strength σ _s >545MPa, elongation δ>25%, and impact absorption energy A _KV >85J at -40°C.

The 700MPa solid welding wire in step 4) contains the following chemical components in weight percentage: C<0.10%, Si0.4%-0.8%, Mn 1.25%-1.80%, Mo 0.3%-0.6%, Ni 0.5% ~1.0%; 700MPa solid wire deposited metal mechanical properties are: tensile strength σ _b >750MPa, yield strength σ _s >700MPa, elongation δ>21%, -40℃ impact absorption energy A _KV >100J.

In the multi-layer multi-pass welding in the step 4), except for the bottom layer welding bead, the interlayer temperature of the other layers of the weld bead is controlled at 60-150° C. during welding.

Both macro detection and micro detection in the present invention are prior art, and will not be repeated here.

The present invention adopts Ar+CO ₂ mixed gas shielded welding, welding wires of different strength levels are matched with appropriate groove angles, and the method proposed by the present invention is used for detection to determine the appropriate fillet weld groove angle, so that the weld metal has a relatively high High plasticity and toughness reserves, good toughness at the root of the weld, which can prevent the generation and expansion of micro-cracks in the fusion zone and the root of the weld, and has good crack resistance; even under the conditions of no preheating and post-weld heat treatment, it can Effectively avoid welding cracks.

Compared with conventional welded joint detection methods, the detection method of the present invention aimed at the performance of high-strength steel fillet weld joints with a tensile strength of 600-800MPa can reliably detect suitable groove angles, welding wire matching and welded joints Crack resistance, avoiding unnecessary multi-layer and multi-pass welding, can also greatly reduce welding costs and improve production efficiency. Therefore, the method for detecting the performance of fillet weld joints in the present invention has the characteristics of simple operation and strong applicability, which is convenient for popularization and application and reduces production costs.

Description of drawings

Fig. 1 is a fillet weld structure schematic diagram of the present invention;

Fig. 2 is a schematic diagram of the finished structure of the foot weld of the present invention;

Fig. 3 is a schematic diagram of the cutting position of the fillet weld sample of the present invention;

Among them 1. Test plate, 2. Vertical plate, 3. Groove.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Example 1:

Base material: As shown in Figure 1, Q550 low-alloy quenched and tempered high-strength steel with a thickness of 20mm is welded on three test panels 1 with a height of 45mm to form a T-shaped structure. A single V-shaped groove 3 is made at the corner joint between the vertical plate 2 and the test plate 1, and the angles of the three grooves 3 are 25°, 35°, and 45° respectively.

Welding material: 600MPa gas shielded welding solid wire with a diameter of 1.2mm.

Welding method: Ar+CO ₂ mixed gas shielded welding, where the volume percentage of Ar and CO ₂ is 80%:20%.

Welding process parameters: welding voltage 28V～29V, welding current 240V～270A, welding speed 0.4cm/s～0.5cm/s, welding heat input 13.4kJ/cm～19.6kJ/cm, shielding gas flow 15～20L/min; Number of welding layers: 3 layers, using multi-layer multi-pass welding; Number of welding passes: 8 passes when the groove angle is 25°, 16 passes when the groove angle is 35°, and 28 passes when the groove angle is 45°.

Key points of welding technology: Welding is carried out under the condition of no preheating at a room temperature of 24°C. Before welding, mechanical treatment is used to clean the surface of the groove to remove oil and rust; in addition to the bottom layer of welding bead, the second layer of welding bead should be kept The interlayer temperature of 60 ~ 120 ℃ makes the first welding pass play a preheating role (it is also conducive to the diffusion and escape of hydrogen). Continuous welding without stopping in the middle. After welding, slow cooling measures are taken to cover the welded joint area with aluminum silicate plate. After welding, the joint is intact, without weld surface cracks and root cracks. as shown in picture 2.

As shown in Figure 3, three bending samples were cut along the vertical direction of the weld, and the sides of the samples were machined and flattened to bend at 120°. Detect the bending results of the sample: the macroscopic inspection is to use a 5-10 times magnifying glass to directly observe with the naked eye; the microscopic inspection is to inspect the bending sample with the help of a metallographic microscope.

The test results show that the crack resistance of the obtained fillet weld joint is the best when the groove angle is 35°, and the number of welding passes is reduced by 12 compared with the groove angle of 45°.

Example 2:

Base material: as shown in Figure 1, HQ80 low-alloy high-strength steel with a thickness of 30mm, the vertical plates 2 of the three T-shaped joints are respectively opened with 25°, 35°, and 45° single V-shaped grooves 3, and the size of the test plate 1 is 300mm×300mm, the size of the vertical plate 2 is 300mm×60mm.

Welding material: 800MPa gas shielded welding solid wire with a diameter of 1.2mm.

Welding method: Ar+CO ₂ mixed gas shielded welding, where the volume percentage of Ar and CO ₂ is 80%:20%.

Welding process parameters: welding voltage 27V～28V, welding current 230A～260A, welding speed 0.5cm/s, welding heat input 12.4kJ/cm～14.6kJ/cm, shielding gas flow 16～18L/min, number of welding layers: 3 Layer, using multi-layer multi-pass welding. Number of weld passes: 10 passes when the groove angle is 25°, 21 passes when the groove angle is 35°, and 35 passes when the groove angle is 45°.

Key points of welding technology: Welding is carried out at a room temperature of 24°C without preheating. Before welding, mechanical treatment is used to clean the groove surface to remove oil and rust. The interlayer temperature of 80 ~ 150 ℃ makes the previous welding pass play a preheating role (it is also conducive to the diffusion and escape of hydrogen). Continuous welding without stopping in the middle.

After welding, the joint is intact and there is no crack on the surface of the weld, as shown in Figure 2.

As shown in Figure 3, three bending samples were cut along the vertical direction of the weld, and the sides of the samples were machined and flattened for 120° bending. Detect the bending results of the sample: the macroscopic inspection is to use a 5-10 times magnifying glass to directly observe with the naked eye; the microscopic inspection is to inspect the bending sample with the help of a metallographic microscope.

The test results show that the crack resistance of the obtained fillet welded joint is the best when the groove angle is 35°, and the number of welding passes is reduced by 14 compared with the groove angle of 45°.

In the above-mentioned embodiment: the mechanical treatment is to use a wire brush or a manual grinding wheel to polish the rust on the surface of the groove, so that it reveals a metallic luster.

The 600MPa solid core welding wire contains the following chemical composition: C 0.07%, Si 0.60%, Mn 1.45%, Mo 0.38%; mechanical properties: deposited metal tensile strength σ _b >670MPa, yield strength σ _s >545MPa, elongation Rate δ>25%, -40 ℃ impact absorption energy A _KV >85J.

The 700MPa solid core welding wire contains the following chemical components: C 0.07%, Si 0.45%, Mn 1.24%, Mo 0.42%, Ni1.51%; the mechanical properties of the deposited metal are: tensile strength σ _b >750MPa, yield strength σ _s >700MPa, elongation δ>21%, -40℃ impact absorption energy A _KV >100J.

Claims (7)

1. A method for detecting high-strength steel fillet weld joint performance, is characterized in that, comprises the following steps: 1) The test plate butt joint form of the T-shaped fillet weld is: weld a vertical plate on the three test plates respectively to form a T-shaped structure, fillet welds on both sides, the vertical plate must not be deflected; Single V-shaped bevel, three bevel angles are 25°, 35°, 45° respectively; 2) Before welding, use mechanical treatment to clean the groove surface to remove oil and rust; 3) Ar + CO ₂ mixed gas shielded welding or CO ₂ gas shielded welding; welding process parameters: welding voltage 26V ~ 30V, welding current 160A ~ 310A, welding speed 0.4cm/s ~ 0.6cm/s, welding heat input Controlled at 10kJ/cm～20kJ/cm, protective gas flow rate 10L/min～20L/min; 4) For high-strength steels with a tensile strength of 600MPa, 700MPa and 800MPa, respectively use a solid core wire with a nominal strength of 600MPa or 700MPa for multi-layer and multi-pass welding, and weld continuously without stopping in the middle; 5) Cut at least 3 bending samples along the vertical direction of the weld, machine the sides of the samples flat, and bend them at 120°; 6) Macroscopic or microscopic detection of the bending results of the sample: macroscopic detection is to use a 5-10 times magnifying glass to directly observe with the naked eye; microscopic detection is to detect the bending sample with the help of a metallographic microscope. 2. The method for detecting the performance of high-strength steel fillet weld joints according to claim 1, characterized in that: the mechanical treatment in the step 2) is to use a wire brush to remove the rust on the surface of the groove, so that it is exposed Metallic luster. 3. the method for detecting high-strength steel fillet weld joint performance according to claim 1, is characterized in that: Ar+ _CO in the described step 3) The Ar that mixed gas shielded welding adopts and _CO The volume percent is 80%: 20%. 4. The method for detecting the performance of high-strength steel fillet weld joints according to claim 1, characterized in that: the diameter of the 600MPa and 700MPa solid welding wires in the step 4) is 1.2mm. 5. The method for detecting the performance of high-strength steel fillet weld joints according to claim 1, characterized in that: the 600MPa solid welding wire in the step 4) contains the following chemical components in weight percentage: C<0.11%, Si 0.5%～0.80%, Mn 1.5%～1.9%, Mo 0.3%～0.5%; the mechanical properties of deposited metal of 600MPa solid wire are: tensile strength σ _b >670MPa, yield strength σ _s >545MPa, elongation Rate δ>25%, -40 ℃ impact absorption energy A _KV >85J. 6. The method for detecting the performance of high-strength steel fillet weld joints according to claim 1, characterized in that: the 700MPa solid welding wire in the step 4) contains the following chemical composition in weight percentage: C<0.10%, Si 0.4%～0.8%, Mn 1.25%～1.80%, Mo 0.3%～0.6%, Ni 0.5%～1.0%; 700MPa solid wire deposited metal mechanical properties: tensile strength σ _b >750MPa, yield strength σ _s >700MPa, elongation δ>21%, -40℃ impact absorption energy A _KV >100J. 7. the method for detecting high-strength steel fillet weld joint performance according to claim 1, is characterized in that: the multi-layer multi-pass welding in described step 4), except laying the bottom welding bead, all the other each layer of welding bead is applied During welding, the interlayer temperature is controlled at 60-150°C.

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