CN111571062A

CN111571062A - Low alloy steel gas shielded welding wire for 800 MPa-level welding

Info

Publication number: CN111571062A
Application number: CN202010456165.5A
Authority: CN
Inventors: 吕晓春; 徐锴; 孙静涛; 李小宇; 杨昊泉; 姜英龙; 杨子佳
Original assignee: Harbin Research Institute of Welding
Current assignee: Harbin Research Institute of Welding
Priority date: 2020-05-26
Filing date: 2020-05-26
Publication date: 2020-08-25

Abstract

The invention discloses a low alloy steel gas shielded welding wire for 800 MPa-level welding, which consists of the following elements in percentage by mass: c: 0.035-0.065, Si: 0.20 to 0.50, Mn: 1.50 to 1.90, Ni: 2.4-3.0, Cr: 0.10 to 0.30, Mo: 0.30 to 0.80, Ti: 0.020 to 0.10, S: less than or equal to 0.010, P: less than or equal to 0.005, less than or equal to 100ppm of O, less than or equal to 50ppm of N, less than or equal to 1ppm of H, and the balance of Fe and inevitable impurities. Correspondingly, the invention also discloses a welding method by adopting the welding wire.

Description

Low alloy steel gas shielded welding wire for 800 MPa-level welding

Technical Field

The invention relates to the technical field of welding materials, in particular to a low alloy steel gas shielded welding wire for 800 MPa-level welding.

Background

With the implementation of strong manufacturing strategies, green manufacturing and light manufacturing technologies have attracted considerable attention. Low alloy, high strength steel has become one of the most prominent structural materials in large welded structures. The steel grade of the low-alloy high-strength steel thick-wall structural engineering application is gradually improved to the grade Q890. In the aspect of influencing the comprehensive performance of a high-strength steel welded structure, the welding cracks are one of very important influencing factors, and the safety and the like of low-alloy high-strength steel can be influenced. With the increase of the thickness and the strength grade of the steel for the welding structure, the problem of the cold crack of the low-alloy high-strength steel during welding is more obvious.

Meanwhile, with the development of manufacturing of marine engineering and high-end equipment, welded structures in service at low temperature, such as marine equipment, ships, high-end engineering machinery, pipeline engineering and the like, have higher requirements on low-temperature toughness of welding seams. Welding cold cracks, excellent low-temperature toughness and embrittlement and softening of a welding heat affected zone become main problems in welding of low-strength thick-wall, high-strength thin-wall and low-alloy high-strength steel structures.

When traditional high-strength steel is welded, measures such as pre-welding preheating, heat preservation in the welding process, postweld heat treatment and the like are usually adopted to prevent cold cracks, so that the production efficiency of the high-strength steel is reduced, the cost is increased, and the working condition and the environment are also deteriorated.

At present, the types of gas shielded welding wires matched with the low-alloy high-strength steel with the pressure of more than 800MPa in the domestic market are few, and the commercial welding wires cannot realize the non-preheating welding of the low-alloy high-strength steel, and the welding preheating temperature is generally required to be 100-165 ℃. For example, in the chinese patent application No. 201410705126.9, the interlayer temperature is controlled between 100-165 ℃ to make the welded metal have higher strength and higher low temperature toughness.

Under the condition of no preheating, the welding crack rate of the existing 800MPa grade welding wire is as high as 80 percent. The problem to be solved in the prior art is to provide a low alloy steel gas shielded welding wire which simultaneously meets 800 MPa-level strength and has good low-temperature impact toughness and low crack sensitivity.

Disclosure of Invention

In order to solve the problems in the prior art, the invention provides a low alloy steel gas shielded welding wire for 800 MPa-level welding, which is suitable for non-preheating welding or low-temperature preheating welding of 800 MPa-level low alloy steel, and has extremely low crack rate while ensuring that metal at a welding seam has low-temperature impact toughness.

The invention provides a low alloy steel gas shielded welding wire for 800 MPa-level welding, which consists of the following elements in percentage by mass: c: 0.035-0.065, Si: 0.20 to 0.50, Mn: 1.50 to 1.90, Ni: 2.4-3.0, Cr: 0.10 to 0.30, Mo: 0.30 to 0.80, Ti: 0.020 to 0.10, S: less than or equal to 0.010, P: less than or equal to 0.005, less than or equal to 100ppm of O, less than or equal to 50ppm of N, less than or equal to 1ppm of H, and the balance of Fe and inevitable impurities.

The invention provides a low alloy steel gas shielded welding wire for 800 MPa-level welding, which consists of the following elements in percentage by mass: c: 0.043-0.053, Si: 0.25 to 0.40, Mn: 1.65 to 1.85, Ni: 2.6-2.8, Cr: 0.15 to 0.25, Mo: 0.45-0.60, Ti: 0.045-0.085, S: less than or equal to 0.010, P: less than or equal to 0.005, less than or equal to 100ppm of O, less than or equal to 50ppm of N, less than or equal to 1ppm of H, and the balance of Fe and inevitable impurities.

The content of C in the welding wire is generally controlled within the range of 0.035-0.065 of the treatment content percentage, preferably can be controlled to be lower than 0.06, such as 0.043-0.053; for example 0.043, 0.045, 0.047, 0.049, 0.051 or 0.053.

The content of Si in the welding wire is generally controlled within the range of 0.20-0.50 percent by mass, and the preferable content of Si can be controlled below 0.04, such as between 0.025-0.040, such as 0.025, 0.027, 0.029, 0.031, 0.033, 0.035, 0.037 or 0.040.

The Mn content in the welding wire is generally controlled to be between 1.50 and 1.90 percent by mass, and preferably can be controlled to be lower than 1.65 to 1.85, such as 1.65, 1.75 or 1.85.

The content of the Ni element in the welding wire is generally controlled within the range of 2.4-3.0 percent by mass, and preferably, the content of the Ni element can be controlled within the range of 2.6-2.8, such as 2.6, 2.7 or 2.8.

The content of the Cr element in the welding wire is generally controlled within the range of 0.10-0.30 percent by mass, and preferably, the content of the Cr element can be controlled within the range of 0.15-0.25, such as 0.15, 0.17, 0.19, 0.21, 0.23 or 0.25.

The content of the Mo element in the welding wire is generally controlled within the range of 0.30-0.80 percent by mass, and preferably, the content of the Mo element can be controlled within the range of 0.45-0.60, such as 0.45, 0.47, 0.49, 0.51, 0.53, 0.55, 0.57 or 0.60.

The content of Ti element in the welding wire is controlled within the range of 0.020-0.10 percent by mass, and preferably, the content of Ti element can be controlled between 0.045-0.085, such as 0.055, 0.060, 0.065, 0.070 or 0.080.

The cold cracks of the welded joint often appear in root welding seams and welding seam metals with high restraint degree, and the alloy elements of the welding seam metals are important factors influencing the tissues and the performances of the welding seams. As the composition and content of the alloy elements in the welding wire change, the structure and the performance of the welding seam change correspondingly. Therefore, the alloy elements of the welding wire play an important performance role and have important influence on the strength, impact toughness and crack sensitivity of the welding wire deposited metal. Particularly, the C element can obviously improve the strength of the welding seam and is a strengthening element in the welding wire. However, too high a content of C element increases the cold crack sensitivity and also affects the toughness of the weld metal. The invention reduces the sensitivity of welding seam crack by reducing the content of C element, thereby achieving the effect of reducing the welding preheating temperature.

Si is the most commonly used deoxidizing element in the welding wire, and can also improve the strength of the weld metal. Si and Mn elements have interaction in a weld joint, acicular ferrite in the weld joint increases along with the increase of the content of silicon, the proper proportion of the Si and Mn elements can improve the strength of weld metal and make up for the strength loss caused by the reduction of C elements, but the overhigh Si element can influence the low-temperature impact toughness of the weld metal. The Mn element has similar action to Si, and the Mn contained in the welding wire can inhibit proeutectoid ferrite and promote the formation of acicular ferrite besides the deoxidation action, and the proper Mn content can improve the normal temperature toughness of weld metal. In addition, an appropriate content of Mn element can reduce the cold crack tendency caused by sulfur. However, too high Mn element has a large influence on the toughness parameter of the weld metal.

The Ni element can improve the strength and toughness of the welding seam. Particularly, Ni can improve the low-temperature impact toughness of the weld metal, however, Ni is a relatively expensive metal, and the influence of Ni on the production cost needs to be considered when adding Ni. An increase in the Cu content results in an increase in the carbon equivalent and a corresponding increase in the thermal cracking susceptibility. The method avoids the adoption of a Cu element, and can obviously improve the low-temperature toughness of the weld metal by controlling the Mn element and the Ni element within the proper proportion range defined by the method.

Cr element plays an important role in hardenability of weld metal, thereby also improving the strength thereof. A certain content of Cr promotes the formation of acicular ferrite tissues and improves the strength of a welding seam, but the excessive content of Cr reduces the toughness of the welding seam, so that the cold crack sensitivity of the welding seam metal is increased.

The Mo element has the functions of solid solution strengthening and precipitation strengthening, and the strength and toughness of the weld metal are improved by adding a proper amount of the Mo element. However, the content of Mo is too high, so that more quenched structures are generated in the weld joint structure, and the cold crack sensitivity of weld joint metal is increased.

Ti is a strong deoxidizing element, is used as a microalloying element, is favorable for promoting the formation of acicular ferrite tissues, and has beneficial effects on the strength and toughness of a welding seam.

The P element can increase the strength of the steel, reduce the toughness and plasticity of the steel, easily generate cracks during welding and increase the crack sensitivity. The S element significantly reduces the toughness of the steel, and as impurities, the contents of the P element and the S element should be strictly controlled.

Compared with the prior art, the method does not add Cu element and some common rare earth elements, but controls the contents of Mn, Mo and Cr elements, and improves the strength of the welding seam; the content of the added Ni and Ti elements is controlled to improve the strength and the low-temperature toughness of the welding seam; the content ratio of the Si and Mn content is controlled to improve the welding wire process performance; the content of harmful impurity elements such as S, P and the like is strictly controlled, and the toughness and plasticity of the welding seam are improved. Through the welding wire design, the welding seam metal has a proper alloy system, and the welding seam has excellent strength and toughness.

In another embodiment, the invention provides a low alloy steel gas shielded welding wire, and the deposited metal of the welding wire has the tensile strength of 830-890 MP and the impact energy of 55-100J at the temperature of-60 ℃ in a welding state.

The low alloy steel gas shielded welding wire has the following characteristics:

the welding rod is matched with the low alloy high strength and rigidity above 800MPa, and non-preheating or low-temperature preheating welding can be realized; the alloy system adopts a few kinds of alloy elements, the optimal content range of low-carbon Mn-Ni-Cr is taken as a core, and Si and Ti in proper proportion are added; the noble metal element content is relatively low (e.g., Ni is less than 3.0 mass percent); the design of the alloy system ensures that the low-temperature impact toughness and the crack resistance of the weld metal structure are good.

According to the method for welding by adopting the low alloy steel gas shielded welding wire, the low alloy steel gas shielded welding wire is subjected to mixed gas shielded welding, the shielding atmosphere is mixed gas of inert gas and other gases, and preferably, the volume ratio of the inert gas is more than 80%. Preferably, the other gas is CO₂Or O₂。

The method for welding by using the low alloy steel gas shielded welding wire is adopted, and the welding wire is not preheated before welding.

The method for welding by using the low alloy steel gas shielded welding wire is characterized in that the welding wire is preheated at a preheating temperature of 50-100 ℃ before welding.

The invention adopts the method for welding by using the low alloy steel gas shielded welding wire, and the welding process conditions are as follows: the welding current is 260-290A, the welding voltage is 27-32V, the welding speed is 25-27 cm/min, the gas flow is 15-20L/min, and the welding line energy is 16-20 KJ/cm.

In one embodiment, the welding wire is used for gas shielded arc welding of low-alloy high-strength steel with the tensile strength grade of more than 800MPa, and can be widely applied to welding of low-alloy high-strength steel in important fields such as infrastructure construction, engineering machinery, marine structures, coal machines, bridge building structures, military mechanical equipment manufacturing and the like.

The method has the beneficial effects that:

the invention fully considers the crack resistance, the strength and the toughness of weld metal, designs the alloy content of a proper system, reduces the alloy cost, can not be preheated or preheated only at low temperature, and does not need heat treatment after welding. Meanwhile, the low cold crack sensitivity of the high-strength steel welding is ensured. The welding process is simple, and the performance of the welding joint is improved.

The alloy system used by the welding wire is proper, the processes of wire rod smelting, rolling and welding wire drawing are synchronous with the prior art, and the large-scale production is easy to realize.

In one embodiment, the invention provides the use of said low alloy steel gas shielded welding wire as a weld joint between welded metal sheets.

In another embodiment, the present invention provides a welded structure obtained by welding with the gas-shielded welding wire according to the present invention as described above.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and other drawings can be obtained by those skilled in the art without creative efforts.

Fig. 1 is a microstructure of deposited metal of a welding wire obtained in example 1 of the present invention, which is a small amount of pro-eutectoid ferrite + bainite + acicular ferrite structure, at a magnification of 400 ×;

FIG. 2 shows the crack formation in the weld of example 1, determined by an oblique Y-groove restraint crack susceptibility test using a 28mm thick HQ785T1 low alloy steel.

Detailed Description

The technical solutions of the present invention will be further described with reference to the following embodiments, and it should be apparent that the described embodiments are some, but not all, embodiments of the present invention. These examples are not intended to limit the technical scope of the present invention. All other modifications and variations directly derived or suggested from the present disclosure are within the scope of the invention.

Example 1:

and (3) smelting the welding wire steel by using low-grade S, P steel in a vacuum furnace. The chemical composition of the wire steel is shown in table 1-example 1 column. After smelting, the welding wire steel is processed into finished welding wires with the specification of phi 1.2mm by the same processes of rolling, drawing and the like as the common welding wire processing.

Using a mixed gas (98% Ar + 20% CO)₂) And protecting and welding to prepare a welding joint and welding seam metal.

The welding process comprises the following steps: welding current 270A, welding voltage 29V, welding speed 27cm/min, gas flow 20L/min, and welding line energy 17.4 KJ/cm. The resulting welded metal structure of the welding wire is shown in fig. 1.

The thickness of the deposited metal welding plate is 20mm, the bevel angle is 45 degrees, a backing plate with 10mm is arranged, and the root gap is 12 mm.

The mechanical properties of the deposited metal are shown in table 2.

Example 2:

and (3) smelting the welding wire steel by using low-grade S, P steel in a vacuum furnace. The chemical composition of the wire steel is shown in table 1-example 2 column. After smelting, the welding wire steel is processed into finished welding wires with the specification of phi 1.2mm by the same processes of rolling, drawing and the like as the common welding wire processing.

With a mixed gas (98% Ar + 2% O)₂) And protecting and welding to prepare a welding joint and welding seam metal.

The welding process comprises the following steps: welding current 270A, welding voltage 29V, welding speed 27cm/min, gas flow 20L/min, and welding line energy 17.4 KJ/cm.

The mechanical properties of the deposited metal are shown in table 2.

Example 3

And (3) smelting the welding wire steel by using low-grade S, P steel in a vacuum furnace. The chemical composition of the wire steel is shown in table 1-example 3 column. After smelting, the welding wire steel is processed into finished welding wires with the specification of phi 1.2mm by the same processes of rolling, drawing and the like as the common welding wire processing.

The welding wire adopts mixed gas (80% Ar + 20% CO)₂) And protecting and welding to prepare a welding joint and welding seam metal.

The welding process comprises the following steps: the welding current is 280A, the welding voltage is 30V, the welding speed is 27cm/min, the gas flow is 20L/min, and the welding line energy is 18.6 KJ/cm.

The mechanical properties of the deposited metal are shown in table 2.

Example 4

And (3) smelting the welding wire steel by using low-grade S, P steel in a vacuum furnace. The chemical composition of the wire steel is shown in table 1-example 4 column. After smelting, the welding wire steel is processed into finished welding wires with the specification of phi 1.2mm by the same processes of rolling, drawing and the like as the common welding wire processing.

The mechanical properties of the deposited metal are shown in table 2.

Comparative example 1

The comparison was made according to example 1 in patent CN02158129.0 ultra low carbon high strength gas shielded welding wire material.

Comparative example 2

The comparison was made according to example 1 of the high strength and high toughness gas shielded welding wire of patent CN 200810046960.6.

Table 1: chemical composition of welding wire of examples 1 to 4 and comparative examples 1 to 2 (% by mass)

TABLE 2 mechanical Properties of deposited metals of examples 1 to 4 and comparative examples 1 to 2

ND represents undetected-60 ℃ impact absorption work; the data of the impact absorption work at-80 ℃ are not shown.

Note that: the deposited metal in the embodiments of the invention performs substantially equally at 50 ℃ preheat and no preheat conditions.

The iron grinding test is carried out according to GB/T32260.2-2015, and the specific method for detecting the fracture cracks is as follows:

sample preparation:

the Gilles test uses HQ785T1 steel of 28mm thickness. Restraint welds were applied to both sides of the test piece.

After the test piece is welded, the welded test piece is placed for 48 hours under natural conditions, and then crack detection and dissection can be carried out.

And (3) crack detection:

after the test piece is welded, knocking off welding slag, cutting the test welding line into 6 pieces with the same width by using a disc milling cutter, visually checking through (1), and calculating the crack rate; or (2) metallographic dissection: and observing cracks of the weld metal and the heat affected zone on the section by using a microscope with the magnification of more than 50 times. The uncracked specimens were confirmed by observation with a microscope of appropriate magnification (at least 200 times).

And (3) detecting the fracture surface crack rate result by a grinding iron test:

the test results of the crack sensitivity of the inclined Y groove welding of the HQ785T1 steel with the thickness of 28mm show that the fracture rate of the welding of the examples 1 to 4 is 0% when the preheating temperature of the welding is 50 ℃. As shown in fig. 2.

Examples 1-4 the fracture surface cracking rate was 0% at room temperature (i.e., without preheating) for the weld preheating temperature.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. The 800 MPa-level low alloy steel gas shielded welding wire for welding is characterized by comprising the following elements in percentage by mass: c: 0.035-0.065, Si: 0.20 to 0.50, Mn: 1.50 to 1.90, Ni: 2.4-3.0, Cr: 0.10 to 0.30, Mo: 0.30 to 0.80, Ti: 0.020 to 0.10, S: less than or equal to 0.010, P: less than or equal to 0.005, less than or equal to 100ppm of O, less than or equal to 50ppm of N, less than or equal to 1ppm of H, and the balance of Fe and inevitable impurities.

2. The low alloy steel gas shielded welding wire of claim 1, wherein the welding wire is composed of the following elements in percentage by mass: c: 0.043-0.053, Si: 0.25 to 0.40, Mn: 1.65 to 1.85, Ni: 2.6-2.8, Cr: 0.15 to 0.25, Mo: 0.45-0.60, Ti: 0.045-0.085, S: less than or equal to 0.010, P: less than or equal to 0.005, less than or equal to 100ppm of O, less than or equal to 50ppm of N, less than or equal to 1ppm of H, and the balance of Fe and inevitable impurities.

3. The low alloy steel gas shielded welding wire according to any one of claims 1 to 2, wherein a tensile strength of a deposited metal of the welding wire in an as-welded state is 830 to 890 MP.

4. The method for welding by using the low alloy steel gas shielded welding wire according to any one of claims 1 to 2, wherein the low alloy steel gas shielded welding wire is subjected to mixed gas shielded welding, and the shielding atmosphere is selected from a mixed gas of an inert gas and other gases, preferably the inert gas is selected from argon.

5. The method according to claim 4, wherein the volume ratio of the inert gas is 80% or more.

6. The method of claim 4, wherein the wire is not preheated prior to welding and is not heat treated after welding.

7. The method of claim 4, wherein the wire is preheated at a preheating temperature of 50 ℃ to 100 ℃ prior to welding.

8. The method according to any of claims 4-7, characterized in that the welding process conditions are: the welding current is 260-290A, the welding voltage is 27-32V, the welding speed is 25-27 cm/min, the gas flow is 15-20L/min, and the welding line energy is 16-20 KJ/cm.

9. Use of the low alloy steel gas shielded welding wire according to any one of claims 1 to 3 as a weld joint between welded metal plates.

10. A welded structure comprising the low alloy steel gas shielded welding wire according to any one of claims 1 to 3.