CN112111695A

CN112111695A - Wire rod with excellent low-temperature toughness for 60 kg-grade welding wire and manufacturing method thereof

Info

Publication number: CN112111695A
Application number: CN202010929365.8A
Authority: CN
Inventors: 张宏亮; 任玉辉; 朱莹光; 安同邦; 李建龙; 杨辉; 刘祥; 杜林�; 冯丹竹; 侯家平; 车安; 李凯
Original assignee: Angang Steel Co Ltd
Current assignee: Angang Steel Co Ltd
Priority date: 2020-09-07
Filing date: 2020-09-07
Publication date: 2020-12-22

Abstract

The invention discloses a wire rod for a 60kg grade welding wire with excellent low-temperature toughness and a manufacturing method thereof, wherein the wire rod comprises the following steps: 0.01% -0.06%, Si: 0.50-0.80%, Mn: 1.35% -1.70%, Ni: 2.0% -2.40%, Mo: 0.2-0.4%, Ti: 0.04% -0.09%, P: less than or equal to 0.010 percent, S: less than or equal to 0.005 percent, Al: 0.01 to 0.03 percent, O: less than or equal to 20ppm, N: less than or equal to 60ppm, H: less than or equal to 2ppm, and the balance of Fe and impurities. The yield strength Rp0.2 of the wire rod is more than or equal to 600MPa, the tensile strength Rm is more than or equal to 730MPa, and the elongation A is more than or equal to 21 percent.

Description

Wire rod with excellent low-temperature toughness for 60 kg-grade welding wire and manufacturing method thereof

Technical Field

The invention relates to a hot-rolled wire rod, in particular to a wire rod for a 60 kg-grade welding wire with excellent low-temperature toughness and a manufacturing method thereof.

Background

The exploitation amount of energy sources such as marine oil and natural gas is increasing day by day, and the exploitation area is gradually expanded from the past shallow-sea warm area to the deep-sea cold area, and a large amount of 60 kg-grade low-temperature steel which can meet the use in a low-temperature environment below-50 ℃ is needed. In order to ensure the use safety and long-term service of the low-temperature steel, a large amount of high-quality welding materials with stable performance and wire rods for the welding materials are needed, and the high-strength welding material not only can meet the high-strength requirement of welding, but also has enough excellent low-temperature toughness below 40 ℃ below zero.

However, due to the limitations of smelting, rolling equipment and process technology, high-strength and high-grade welding materials for domestic engineering have low weld line impact performance and poor welding manufacturability, and even though domestic welding materials can meet the requirements of engineering welding, the aspects of welding process performance, welding stability and the like have great difference compared with foreign welding wires of the same kind, so that engineering application is often difficult to realize.

Before the application of the invention, CN 101984121A discloses a steel wire rod for a 600 MPa-grade high-strength welding wire and a production process thereof, wherein the steel wire rod comprises the following chemical components in percentage by weight: 0.05-0.12%, Mn: 1.40-1.90%, Si: 0.50-0.80%, Cr: 0.2-0.6%, Ti: 0.04-0.08%, S is less than or equal to 0.020%, P is less than or equal to 0.020%, and Ca is less than or equal to 0.0015%, the steel wire rod refers to ER55-D2, the low-temperature toughness experiment temperature is-30 ℃, and the requirements of low-temperature environments of-50 ℃ and below on low-temperature toughness of cladding metal and welding joints are difficult to meet. Similarly, CN 104561786a discloses a 600MPa grade high strength hot rolled wire rod for welding and a production method thereof, wherein the chemical composition range is C: 0.05% -0.09%, Si: 0.40-0.80%, Mn: 1.40-1.70%, P is less than or equal to 0.025%, S is less than or equal to 0.025%, V: 0.03-0.06%, Ti: 0.05-0.10 percent, the balance of Fe and inevitable impurities, and elements such as V, Ti and the like are added to only prepare a 600 MPa-grade wire rod, but the application low temperature of the wire rod for preparing the welding wire is not introduced, Ni elements capable of improving the low-temperature toughness of the welding material are not added to the chemical components of the wire rod, and the welding material cannot meet the application requirement of the low-temperature environment below 50 ℃. CN 109706391A discloses a 60 kg-level high-strength hot-rolled wire rod for welding wires and a production method thereof, wherein the chemical component range is as follows: 0.06-0.12%, Si: 0.40-0.80%, Mn: 1.50-2.00%, P is less than or equal to 0.020%, S is less than or equal to 0.020%, V: 0.040 to 0.060%, Ti: 0.050-0.090%, Cr: 0.20-0.45%, the content of C element in the patent is higher, V, Ti element is added, Ni element capable of improving low-temperature toughness of welding material is not added, low-temperature impact toughness of cladding metal is not improved, and the application of low-temperature of welding wire is not described, so that the engineering application requirement of low-temperature environment of-40 ℃ and below can not be met.

Disclosure of Invention

Aiming at the defects in the prior art, the invention aims to provide a 60 kg-grade wire rod for welding wires with excellent low-temperature toughness and a manufacturing method thereof, and develops a hot-rolled wire rod for high-strength and high-toughness gas-shielded welding materials, which meets the requirements of excellent welding manufacturability and welding stability in a low-temperature environment of-40 ℃ and below.

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

a60 kg-grade wire rod with excellent low-temperature toughness for welding wires is characterized by comprising the following chemical components in percentage by weight: c: 0.01% -0.06%, Si: 0.50-0.80%, Mn: 1.35% -1.70%, Ni: 2.0% -2.40%, Mo: 0.2-0.4%, Ti: 0.04% -0.09%, P: less than or equal to 0.010 percent, S: less than or equal to 0.005 percent, Al: 0.01 to 0.03 percent, O: less than or equal to 20ppm, N: less than or equal to 60ppm, H: less than or equal to 2ppm, and the balance of Fe and impurities.

The wire rod of the invention has the following chemical component design principle:

c is an indispensable important element for improving the strength of the weld metal and has stronger hardening and solid solution strengthening effects, but the formation of high-carbon martensite is promoted by excessively high C content, so that the hardenability of the weld metal is increased, the plasticity is reduced, and the crack sensitivity of the metal is increased, therefore, the C is controlled to be 0.01-0.06 percent in the invention.

Si is a main deoxidizing element and improves the strength of the weld metal through the solid solution strengthening effect. If the Si content is too low, deoxidation is insufficient, so that the O content in the welding seam is too high, and if the Si content is too high, the ductile-brittle transition temperature can be obviously increased, the low-temperature toughness of the welding seam metal is reduced, and the use in a low-temperature environment is not facilitated, so that the Si content is controlled to be 0.50-0.80%.

Mn can improve the strength of the wire rod and can play a role of composite deoxidation with silicon, but the Mn content is too high, segregation is formed, an M-A island-shaped structure is generated in a segregation zone, so that the low-temperature toughness of weld metal is reduced, the welding process performance is deteriorated, and the slag stripping property is reduced, so that the Mn content is controlled to be 1.35-1.70%.

P, S element has adverse effect on low temperature toughness of weld metal, and should be reduced as much as possible, and the harmful elements P in the wire rod is less than or equal to 0.010% and S is less than or equal to 0.005%.

Ni is not only a main element for stabilizing austenite, but also one of important elements for improving the low-temperature toughness of the welding material in the invention, and the adding of the Ni element can effectively reduce the ductile-brittle transition temperature, and if the content of the Ni element is lower, the effect of improving the low-temperature toughness of the weld metal is not obvious. However, Ni is a relatively expensive alloy element, and excessive Ni increases the cost, so the Ni content is controlled to 2.0% -2.40%.

Mo mainly plays a role in solid solution strengthening and precipitation strengthening, can effectively increase the hardenability and hardenability of steel, and forms uniform and fine bainite structures in welding seams, thereby improving the welding strength and low-temperature toughness of the welding seams. Meanwhile, Mo can reduce the temper brittleness, and the embrittlement of weld metal during multi-layer and multi-pass welding is avoided. However, too high Mo causes a hardened structure in the weld metal, so that the Mo element in the wire rod is controlled to be 0.2-0.4%.

The trace Ti element is added into the wire rod, a nucleation foundation is provided during solid phase transition, the precipitated titanium carbonitride can refine the structure of the weld metal, the strength and the low-temperature toughness of the weld metal are improved, and the welding performance is improved. Meanwhile, the titanium has high affinity with oxygen, so that Ti in the welding seam is dispersed and distributed in the welding seam in the form of tiny oxides (TiO), and the refining of metal grains of the welding seam is promoted. However, too high Ti content will cause the size of oxide and nitride to be uneven, and affect the metal performance of the welding seam, so Ti is controlled to be 0.04-0.09%.

Particularly, the content of O, N, H and other gas elements is controlled, and the content of the gas elements is too high, so that the wire rod and the weld metal are easy to crack, crisp and contain more inclusions, which affect the processing performance and welding manufacturability of the wire rod on one hand and reduce the low-temperature toughness of the weld metal on the other hand, therefore, the invention controls the gas element range to be as follows: o is less than or equal to 20ppm, N is less than or equal to 60ppm, and H is less than or equal to 2 ppm.

Al is a strong oxide forming element, has strong deoxidation and also has the function of refining grains, so the Al content is 0.01-0.03 percent in the invention.

A manufacturing method of a 60 kg-grade wire rod for welding wires with excellent low-temperature toughness comprises the steps of molten iron pretreatment, smelting, square billet continuous casting, wire rod rolling and wire laying; the method is characterized in that: rolling a wire rod: if the strength of the wire rod is too high, the technical difficulty of the drawing process of the wire rod is increased, the wire is easily broken in the drawing process, or in order to reduce the strength of the wire rod, the wire rod is annealed once or for multiple times before drawing, so that the cost of the welding wire is increased, and meanwhile, iron oxide scales are easily generated in the annealing process, which also increases new problems. In order to prevent the strength of the rolled wire rod from being too high, reduce the drawing difficulty of the wire rod and avoid the cost increase caused by annealing before the wire rod is drawn, the cogging temperature of a small square billet is 1000 +/-20 ℃, the finish rolling temperature is 970 +/-15 ℃, the finish rolling temperature of a double module is 950 +/-15 ℃, and the spinning temperature is 940 +/-15 ℃.

The invention has the beneficial effects that: 1. the invention comprehensively considers the welding manufacturability, crack resistance, strong plastic toughness matching and economy of the welding seam metal with excellent 60 kg-grade low-temperature toughness, adopts the design of low main alloy element content components, adopts a relatively simple C-Si-Mn-Ni-Mo-Ti chemical component system, reduces the alloy cost, simultaneously reduces the carbon equivalent and the cold crack sensitivity index, improves the weldability and crack resistance of the welding wire, improves the low-temperature toughness of the welding seam metal by adding a proper amount of Ni element, separates and refines welding seam metal grains by Ti (C, N) second phase particles, plays a role in simultaneously improving the strength and the low-temperature toughness of the welding seam metal, and improves the strength of the welding seam metal by adding a small amount of Mo element, particularly strictly controls the contents of O, N, H and other harmful gases in a wire rod, avoids generating new impurities and brittle phases in the welding remelting process, the low-temperature toughness of the weld metal is ensured. Meanwhile, rare earth, B and other elements are not required to be added, so that the cost is reduced, and the difficulty of the smelting process is also reduced. 2. The wire rod for the 60 kg-grade welding wire with excellent low-temperature toughness, provided by the invention, has the yield strength Rp0.2 of more than or equal to 600MPa, the tensile strength Rm of more than or equal to 730MPa and the elongation A of more than or equal to 21%. 3. After welding is completed, the yield strength Rp0.2 of the cladding metal is more than or equal to 620MPa, the tensile strength Rm is more than or equal to 700MPa, the elongation A is more than or equal to 20%, and the KV at the temperature of minus 50 ℃ is higher than₂The J is more than or equal to 100J. 4. The low-temperature toughness of each position of the welding joint is as follows: the-50 ℃ KV2 of the center of the welding line is more than or equal to 100J, the-50 ℃ KV2 of the fusion line is more than or equal to 150J, and the-50 ℃ KV2 of the outside of the fusion line is more than or equal to 160J. 5. The welding wire prepared by the wire rod provided by the invention is used for welding 60kg low-temperature steel with the thickness of less than 100mm, deposited metal has good basic mechanical properties under the conditions of normal temperature and low temperature, and a welding joint at the welding positions of horizontal welding, vertical welding and transverse welding has good basic mechanical properties, thereby meeting the requirements of engineering application.

Drawings

FIG. 1 is a wire rod organization chart of example 1.

Detailed Description

The following description is given with reference to specific examples:

FIG. 1 is a photograph (500 times) of the microstructure of a wire rod made according to the protocol of example 1, corroded with 4% nital, under an optical microscope, the microstructure of the wire rod being ferrite + a small amount of bainite.

The wire rod can be used for preparing 60 kg-grade steel matched gas shielded welding wires with excellent low-temperature toughness, the converter smelting and continuous casting are adopted according to the chemical component range of the wire rod, then the continuous casting square billet is rolled into the wire rod with the diameter of 5.5mm, the surface quality of the wire rod is qualified, the surface of the wire rod is smooth, and the wire rod has no defects of cracks, folding, scabbing, lugs and the like which are harmful to drawing, and the specific embodiment is as follows:

TABLE 1 chemical composition (wt%)

TABLE 2 gas element content (ppm)

	O	N	H
				Example 1	18.7	45	1.24
Example 2	7.8	18	0.82
				Example 3	9.8	20	0.32
Example 4	11.2	32	1.64
				Example 5	2.5	12	1.8
Example 6	11.6	32	0.63
				Example 7	6.3	15	0.58
Example 8	5.2	23	0.44
				Example 9	4.9	17	1.95

TABLE 3 Rolling Process parameters of wire rods

TABLE 4 tensile Properties of the wire rod

	R_p0.2/MPa	Rm/MPa	A/％
				Example 1	630	745	24
Example 2	636	739	23.8
				Example 3	629	762	22.1
Example 4	618	752	21.7
				Example 5	626	748	23.6
Example 6	622	746	24.1
				Example 7	635	759	23.9
Example 8	628	758	23.4
				Example 9	640	772	21.6

Drawing the wire rod into a steel plate with the diameter of phi 1.2mm, selecting steel plates with the diameters of 30mm and 14mm, welding the welding wire at three typical positions of vertical welding, horizontal welding and transverse welding, and testing the mechanical properties of welding joints at the three welding positions after welding.

TABLE 5 mechanical Properties of deposited metals

TABLE 6 Low temperature toughness of welded joints

Claims

1. A60 kg-grade wire rod with excellent low-temperature toughness for welding wires is characterized by comprising the following chemical components in percentage by weight: c: 0.01% -0.06%, Si: 0.50-0.80%, Mn: 1.35% -1.70%, Ni: 2.0% -2.40%, Mo: 0.2-0.4%, Ti: 0.04% -0.09%, P: less than or equal to 0.010 percent, S: less than or equal to 0.005 percent, Al: 0.01 to 0.03 percent, O: less than or equal to 20ppm, N: less than or equal to 60ppm, H: less than or equal to 2ppm, and the balance of Fe and impurities.

2. The wire rod for a grade 60kg welding wire excellent in low-temperature toughness according to claim 1, wherein: the yield strength Rp0.2 of the wire rod is more than or equal to 600 MPa.

3. The wire rod for a grade 60kg welding wire excellent in low-temperature toughness according to claim 1, wherein: the tensile strength Rm of the wire rod is more than or equal to 730 MPa.

4. The wire rod for a grade 60kg welding wire excellent in low-temperature toughness according to claim 1, wherein: the elongation A of the wire rod is more than or equal to 21 percent.

5. A method for manufacturing a wire rod for a grade 60kg welding wire excellent in low-temperature toughness according to any one of claims 1 to 4, comprising molten iron pretreatment, smelting, billet continuous casting, wire rod rolling and wire laying; the method is characterized in that: the rolling of the wire rod is as follows: the initial rolling temperature is 1000 +/-20 ℃, the finish rolling temperature is 970 +/-15 ℃, the finish rolling temperature of the double modules is 950 +/-15 ℃, and the spinning temperature is 940 +/-15 ℃.