CN109175786B

CN109175786B - Wire rod for high-strength weather-resistant gas shielded welding wire

Info

Publication number: CN109175786B
Application number: CN201811289471.3A
Authority: CN
Inventors: 易敏; 陈涛; 马跃; 吕迺冰; 佟倩; 刘珂; 徐士新; 徐兵伟; 唐龙敏; 孙齐松
Original assignee: Shougang Corp
Current assignee: Shougang Corp
Priority date: 2018-10-31
Filing date: 2018-10-31
Publication date: 2021-04-16
Anticipated expiration: 2038-10-31
Also published as: CN109175786A

Abstract

A high-strength weather-resistant wire rod for a gas shielded welding wire belongs to the technical field of welding materials. The chemical elements comprise the following components in percentage by mass: c: 0.06-0.10%, Si: 0.45-0.64%, Mn: 0.60-0.90%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, Ni: 3.0-5.0%, Cr: 1.10-1.50%, Cu: 0.15-0.35%, Ti: 0.06-0.15%, V: 0.01-0.05%, and the balance of iron and inevitable impurities. Has the advantages that: the deposited metal and the welding joint obtained by the welding wire made of the wire rod of the invention obtain the deposited metal metallographic structure which mainly comprises an acicular ferrite structure under the welding state condition, and have good comprehensive mechanical property and good weather resistance, wherein the tensile strength is as follows: more than or equal to 650MPa, elongation: not less than 17%, A at-40 deg.C_kvGreater than 47J.

Description

Wire rod for high-strength weather-resistant gas shielded welding wire

Technical Field

The invention belongs to the technical field of welding materials, and particularly relates to a wire rod for a high-strength weather-resistant gas shielded welding wire.

Background

In order to adapt to the development of large load, light weight and reliability of a railway wagon and further improve the corrosion resistance of a body of the railway wagon, the Bao steel develops novel high-corrosion-resistance weather-resistant steel (S450EW) for a third-generation railway vehicle and a matched welding material thereof, the content of the S450EW alloy belongs to medium alloy, and the main characteristic is that the corrosion resistance is improved by about 30-50% compared with the prior second-generation Q450NQR1 type high-strength weather-resistant steel by properly increasing the content of Cr, and the steel is successfully applied to models such as a C70E type coal-carrying open wagon, a C70C type coke transport vehicle, an 80-ton general open wagon, a box wagon, an 80-ton hopper wagon and the like. Part of the information of the welding material matched with S450EW can be found in the patent and literature, and the chemical compositions of the weather-proof gas-shielded welding wire and the wire rod and the performance requirements of deposited metal in the welding material matched with S450EW are respectively listed in the table 1 and the table 2.

TABLE 1

TABLE 2

Note: relative corrosion rate of 100% × (base material weight loss rate-deposited metal weight loss rate)/base material weight loss rate

As can be seen from the table, the products CN201210553022.1, CN201110104281.1 and CN201610594463.4 are low-carbon Ni-Cr-Mn-Cu-Ti alloy systems, and can realize the optimization of the strength and the low-temperature toughness of the welding seam by means of solid solution strengthening, precipitation strengthening, fine grain strengthening and the like; but also brings the technical difficulty of large alloy amount to the production of the wire rod; in addition, the requirement on carbon content is low, so that the requirements on the tooling condition of a production line for smelting the raw materials of the welding wire and the smelting process are strict, and the production cost is greatly increased. Therefore, the invention utilizes pilot test conditions to carry out the test exploration of component adjustment, and the main aims are to adjust the carbon content to the range which can be realized by a first steel production line, understand the influence of the increased carbon content on the welding seam performance and adjust other elements so as to ensure that the mechanical property and the corrosion resistance of the welding seam meet the requirements.

Disclosure of Invention

The invention aims to provide a wire rod for a high-strength weather-resistant gas shielded welding wire, which solves the problems of high production difficulty and high production cost of the existing product. The product of the invention has the advantages of low cost, excellent mechanical property and weather resistance of the welding line, and is suitable for welding the high corrosion-resistant weather-resistant steel for the third generation railway vehicles. In a welding state, the mechanical property of the welding line meets the requirement of S450EW grade, the tensile strength is more than or equal to 650MPa, and the impact toughness at minus 40 ℃ is more than or equal to 47J. The weather resistance of the welding seam also meets the requirement.

A high-strength weather-proof wire rod for a gas shielded welding wire comprises the following chemical elements in percentage by mass: c: 0.06-0.10%, Si: 0.45-0.64%, Mn: 0.60-0.90%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, Ni: 3.0-5.0%, Cr: 1.10-1.50%, Cu: 0.15-0.35%, Ti: 0.06-0.15%, V: 0.01-0.05%, and the balance of iron and inevitable impurities.

In the composition of the wire rod, the preferable range of Ni is as follows: 3.4-4.5%, and the preferred range of V is: 0.03-0.05%.

The production method of the wire rod comprises the following specific steps and parameters:

1. billet production process

Producing steel billets by using an electric furnace or a converter, refining the steel billets outside an LF furnace, and producing casting billets by using a billet caster, wherein the section specification is as follows: 130mm multiplied by 130mm to 160mm multiplied by 160 mm; adding the required Ni alloy together with scrap steel in front of a furnace, adding the required Si, Mn, Cr, Cu and V alloy after tapping, and finely adjusting the alloy content in the LF treatment process to reach the content requirement range of a finished product; adding the needed Ti alloy in the later stage of LF treatment; the cooling strength of the crystallizer in continuous casting is 30-50 ℃/s, the thickness of the blank shell of the crystallizer is 10-20 mm, and the cooling strength of the secondary cooling area is more than 1.8 ℃/s. The secondary cooling zone cooling intensity is measured at the position of the casting slab 1/4.

2. Wire rod rolling process

Rolling the steel wire at a high speed, wherein the initial rolling temperature is 1000-1050 ℃, and the temperature of the steel wire entering a finishing mill is 920-970 ℃; the spinning temperature is 850-900 ℃; the process temperature can be finely adjusted according to the change of the ambient temperature and the physicochemical performance level of the finished product coil; the water tanks at all sections uniformly supply water, and the water tanks are corrected and adjusted at any time according to the rolling speed and the change of the heating condition, so that the temperature is ensured to meet the requirements.

3. Controlled cooling process for wire rod

The stelmor line is adopted for cooling, the heat-insulating cover is adopted for slow cooling in the cooling process, the slow cooling time in the heat-insulating cover is ensured to be more than or equal to 10min by matching with the speed ratio of the roller way, and the cooling speed of the control panel in the heat-insulating cover is controlled to be less than or equal to 0.5 ℃/s.

The deposited metal obtained by the processed gas-shielded welding wire in a welding state has good comprehensive mechanical property, and the tensile strength of a welding line is more than or equal to 650MPa, and the impact energy of a V-shaped notch sample at-40 ℃ is more than or equal to 47J.

In the chemical composition design of the invention:

the C content is increased, the strength is increased, but the plastic deformation capability of the wire rod is deteriorated, and the cold cracking tendency of the welding wire is increased. But the carbon content is too low, which increases the production process cost and the production difficulty. The selection range of the C is determined to be 0.06-0.10% by comprehensively considering the production cost, the production difficulty, the influence of the carbon content on the welding seam performance and the influence of the carbon content on the strength and the plasticity of the wire rod.

Si is dissolved in ferrite and austenite in a solid solution mode, so that the solid solution strengthening effect is strong, the weld strength can be effectively improved, meanwhile, a certain amount of Si can increase the fluidity of weld metal and improve the welding process performance, but the toughness of the weld metal is reduced and the weld crack sensitivity is increased due to too high Si content, so that the Si content is not too high, and the selection range of the Si is determined to be 0.45-0.64%.

Mn is beneficial to increasing the strength and toughness of weld metal by refining weld structures. Meanwhile, Mn has the weld joint deoxidation effect. However, the excessively high Mn content increases the crack sensitivity of the weld joint, and the selection range of the Mn content is determined to be 0.60-0.90% in order to ensure that the weld joint has good strength and toughness and low crack sensitivity.

Ni: the Ni element enlarges an austenite area, and in the cooling process of a high-temperature welding line, the Ni completely dissolved in the austenite can greatly reduce the transformation temperature from the austenite to the ferrite, so that the formation of pre-eutectoid ferrite and side plate bar ferrite is inhibited, the acicular ferrite is favorably formed, the precipitated acicular ferrite is uniform and fine due to the lower phase transition temperature, and the toughness, particularly the low-temperature impact toughness of the welding line metal is improved. Meanwhile, Ni and elements such as Cr, Mo and the like act together to form a compact passive film, thereby improving the corrosion resistance. However, too high Ni content may reduce the fluidity of weld metal and the Ni element alloy has high cost, so that the Ni is determined to be selected in the range of 3.0-5.0%.

Cu: the Cu element is beneficial to inhibiting hydrogen embrittlement of weld metal, and the Cu is also one of main elements for increasing weather resistance. However, the content is too high to simultaneously improve the strength and low temperature impact toughness of the weld metal and increase the hot brittleness of the weld, and therefore, it is determined that the Cu selection range of the present invention is 0.15-0.35%.

Cr is an element which obviously improves hardenability, improves the needle-shaped ferrite structure in weld metal, and thus improves strength and toughness. And Cr can improve the pitting corrosion resistance of steel and form a Cr-enriched passivation layer, thereby improving the weather resistance of the welding line. However, too high a Cr content increases the cold crack sensitivity of the weld. Therefore, the selection range of Cr of the present invention is determined to be 1.10 to 1.50%.

Ti is a strong deoxidizer, and a proper amount of Ti is mixed with O in a molten pool₂Forming compound TiO2 mass points which are dispersed and distributed, promoting acicular ferrite nucleation, refining weld joint tissues and increasing the toughness of weld joints; in the welding process, the welding manufacturability is improved and the splashing is reduced. However, the high Ti content can cause the molten steel to be viscous, increase the difficulty in the pouring process and simultaneously be not beneficial to the fluidity of the welding line in a molten state, so that the Ti selection range is determined to be 0.06-0.15%.

And V, for the ultrahigh-strength gas-shielded welding wire, the toughness of the weld joint structure can be improved by adding elements such as microalloyed Ti, V and the like. In the technical scheme of the invention, V is adopted for microalloying. V has higher solid solubility in the austenite region compared with other microalloy elements, and the microalloy elements which are dissolved in the austenite in a solid way can increase the stability of the undercooled austenite, reduce the phase transition temperature, promote the phase transition of acicular ferrite and improve the toughness of welding lines. Meanwhile, V forms a large amount of carbides in a ferrite area, so that the high-temperature tempering resistance of a welding seam can be improved, and a structural steel part needing heat treatment after welding can be tempered at a higher temperature, so that a large amount of fine carbides in original austenite crystals can be uniformly dispersed and precipitated, the aims of refining grains, inhibiting diffused hydrogen and improving the toughness of the welding seam are fulfilled, and the strength of the welding seam is not obviously lost. However, too high a V content may reduce the plasticity and toughness of the weld. Thus, it was determined that the V of the present invention was selected in the range of 0.01 to 0.05%.

Compared with the prior art, the V is adopted for microalloying, the addition amount is less, Mo element is not added, and the alloy cost is also reduced.

P, S, the lower the content of impurity elements, the higher the purity of steel, the better the toughness, and the combination with the tool process capability of enterprises, the selection range of P, S is determined to be that P is less than or equal to 0.020% and S is less than or equal to 0.015%.

In the invention, the steel for the high-strength weather-resistant gas shielded welding wire can be produced by converter smelting and refining outside the furnace, and also can be produced by electric furnace smelting and refining outside the furnace, as long as the final chemical components can meet the requirements of the invention contents.

The high-speed wire rod factory adopts temperature control rolling and slow cooling control technology to roll wire rods with the diameter of 6.5mm, the surface of the wire rods is smooth, and the wire rods have no surface defects such as cracks, folding, lugs, scabs, layering, inclusion and the like. The wire rod is processed into the welding wire by the procedures of annealing treatment, acid cleaning, wire drawing, copper plating, coiling and the like in a welding material factory.

The invention has the advantages that:

1. the deposited metal and the welding joint obtained by the welding wire made of the wire rod of the invention obtain a deposited metal metallographic structure mainly comprising an acicular ferrite structure under the welding state condition. And has good comprehensive mechanical properties and good weather resistance, wherein the tensile strength is as follows: more than or equal to 650MPa, elongation: not less than 17%, A at-40 deg.C_kvGreater than 47J. The metallurgical structure of the deposited metal is shown in figure 1.

2. The relative corrosion rate of the deposited metal corrosion performance of the welding wire made of the wire rod and the base metal is less than 10%, and the deposited metal rust layer has a higher content of FeOOH phase, which shows that the welding wire made of the wire rod has good weather resistance and can be used for welding high weather resistant steel.

Drawings

FIG. 1 is a metallographic structure diagram of a deposited metal.

Detailed Description

According to the chemical composition range of the invention, the wire rod with the diameter of 6.5mm is hot rolled in a high-speed wire rod factory by adopting the smelting modes of electric furnace and external refining and converter and external refining.

Examples 1 to 5

The chemical elements of the wire rod for the high-strength weather-resistant gas shielded welding wire are shown in the table 4 in percentage by mass:

TABLE 4

	C，％	Si，％	Mn，％	P，％	S，％	Cr，％	Ni，％	Cu，％	Ti，％	V，％
											Example 1	0.10	0.46	0.7	0.006	0.008	1.13	3.69	0.12	0.07	0.030
Example 2	0.08	0.49	0.85	0.008	0.0028	1.18	3.64	0.16	0.09	0.040
											Example 3	0.06	0.60	0.64	0.011	0.006	1.23	4.7	0.24	0.12	0.050
Example 4	0.09	0.54	0.76	0.009	0.010	1.45	4.2	0.35	0.14	0.020
											Example 5	0.07	0.51	0.81	0.007	0.004	1.38	3.2	0.20	0.10	0.015

1. billet production process

TABLE 5

	Blank form	Cooling strength of crystallizer	Thickness of shell	Strength of secondary cooling zone
					Example 1	130mm×130mm	35℃/s	16mm	1.9℃/s
Example 2	130mm×130mm	42℃/s	18mm	2.0℃/s
					Example 3	150mm×150mm	41℃/s	15mm	2.4℃/s
Example 4	160mm×160mm	49℃/s	14mm	2.3℃/s
					Example 5	150mm×150mm	45℃/s	13mm	2.2℃/s

2. Rolling for wire rod production

TABLE 6

	Initial rolling temperature	Finish rolling temperature	Temperature of spinning
				Example 1	1020℃	930℃	850℃
Example 2	1040℃	940℃	900℃
				Example 3	1000℃	920℃	860℃
Example 4	1030℃	950℃	880℃
				Example 5	1050℃	960℃	890℃

3. And (3) controlling and cooling the wire rod:

TABLE 7

	Time of slow cooling	Cooling speed in cover
			Example 1	10.5min	0.47℃/s
Example 2	11.0min	0.45℃/s
			Example 3	11.5min	0.40℃/s
Example 4	12.5min	0.38℃/s
			Example 5	13.0min	0.35℃/s

The product is produced into phi 6.5mm specification, and then the phi 1.2mm is produced by the processes of rough drawing, annealing, fine drawing and copper plating.

The welding test plate is made of S450EW steel, the plate thickness is 20mm, argon-rich mixed gas (80% Ar + 20% CO2) is used as protective gas in the process, the interlayer temperature is controlled to be lower than 120 ℃, the welding current is controlled to be 220A-260A, the welding voltage is 31V, and the welding speed is 0.33-0.5 cm/S. Welding tests show that the welding wire has good welding process performance, less splashing and good weld joint formability.

After welding, tensile and impact test pieces of deposited metal were cut out from the welded joint and subjected to performance tests, and the results are shown in table 8. The data satisfy tensile strength: more than or equal to 650MPa, elongation: not less than 17%, A at-40 deg.C_kvGreater than 47J mechanical property requirement.

The examples of the invention were subjected to the circumferential immersion test of the welding wire deposited metal according to TB/T2375 periodic immersion test method of weathering steel for railways, the corrosive solution was 0.01mol/LNaHSO3 solution, and the circumferential immersion time was 72 h. The experimental temperature was 45 ℃ and the humidity was 70%. The corrosion test results are shown in Table 9. The corrosion performance of deposited metal of the welding wire and the relative corrosion rate of SW450 are 3.4-9.4% and less than 10%. The welding wire can be used for welding high weather-resistant and weathering-resistant steel.

Further, for the deposited metal and the SW450 steel comparative sample in which the immersion test was completed, the phase composition of the rust layer on the surface of the sample was quantitatively measured by a D8advance X-ray diffractometer (XRD). The results of the test specimens are shown in Table 10. The components of the inner rust layer in the atmospheric environment mainly comprise alpha-FeOOH and Fe3O4, the dendritic crystal size of the alpha-FeOOH crystal is fine, the rust layer containing more alpha-FeOOH phases is denser, and the rust layer has a protection effect on a matrix, so that the rust layer has better corrosion resistance. The corrosion rust layer of the deposited metal of the welding wire contains a higher content of FeOOH phase, which shows that the deposited metal of the welding wire has excellent corrosion resistance.

The weather-resistant gas-shielded welding wire is suitable for gas-shielded welding of high-strength weather-resistant steel with the tensile strength grade of more than 650 MPa. The method is suitable for the fields of railway vehicles, bridges and the like.

TABLE 8

TABLE 9

	Corrosion rate W (g/m)²·h)	Relative corrosion rate%
			Example 1	1.923	9.4
Example 2	1.845	5.0
			Example 3	1.801	2.5
Example 4	1.881	7.0
			Example 5	1.817	3.4
SW450	1.757	/

Watch 10

Claims

1. A high-strength wire rod for a weather-resistant gas shielded welding wire is characterized by comprising the following chemical elements in percentage by mass: c: 0.06-0.10%, Si: 0.45-0.64%, Mn: 0.60-0.90%, P is less than or equal to 0.020%, S is less than or equal to 0.015%, Ni: 3.0-5.0%, Cr: 1.10-1.50%, Cu: 0.15-0.35%, Ti: 0.06-0.15%, V: 0.01-0.05%, and the balance of iron and inevitable impurities;

the welding method is suitable for welding the high-corrosion-resistance weathering steel S450EW for the third-generation railway vehicle; in a welding state, the mechanical property of the welding line meets the requirement of S450EW grade, the tensile strength is more than or equal to 650MPa, and the impact toughness at minus 40 ℃ is more than or equal to 47J.

2. The wire rod according to claim 1, wherein said Ni: 3.4 to 4.5 percent.

3. The wire rod of claim 1 wherein said V: 0.03-0.05%.

4. The wire rod of claim 1, wherein the method for producing the wire rod comprises the following steps and parameters:

1) billet production process

Producing steel billets by using an electric furnace or a converter, refining the steel billets outside an LF furnace, and producing casting billets by using a billet caster, wherein the section specification is as follows: 130mm multiplied by 130mm to 160mm multiplied by 160 mm; adding the required Ni alloy together with scrap steel in front of a furnace, adding the required Si, Mn, Cr, Cu and V alloy after tapping, and finely adjusting the alloy content in the LF treatment process to reach the content requirement range of a finished product; adding the needed Ti alloy in the later stage of LF treatment; the cooling strength of the crystallizer in continuous casting is 30-50 ℃/s, the thickness of the blank shell of the crystallizer is 10-20 mm, and the cooling strength of the secondary cooling area is more than 1.8 ℃/s;

2) wire rod rolling process

Rolling the steel wire at a high speed, wherein the initial rolling temperature is 1000-1050 ℃, and the temperature of the steel wire entering a finishing mill is 920-970 ℃; the spinning temperature is 850-900 ℃; the process temperature is finely adjusted according to the change of the ambient temperature and the physicochemical performance level of the finished product coil; water is uniformly supplied to each section of water tank, and the water tanks are corrected and adjusted at any time according to the rolling speed and the change of the heating condition, so that the temperature is ensured to meet the requirement;

3) controlled cooling process for wire rod

5. The wire rod according to claim 4, wherein the secondary cooling zone cooling intensity in step 1) is measured at the position of a cast strand 1/4.