CN110026708B

CN110026708B - Welding method of dual-phase steel

Info

Publication number: CN110026708B
Application number: CN201910405173.4A
Authority: CN
Inventors: 赵瑾玥; 郭永环; 范希营; 陆伟豪; 王赛博
Original assignee: Jiangsu Normal University
Current assignee: Jiangsu Normal University
Priority date: 2019-05-16
Filing date: 2019-05-16
Publication date: 2021-06-11
Anticipated expiration: 2039-05-16
Also published as: CN110026708A

Abstract

A welding method of dual-phase steel, nano CeO₂Nb is dissolved in the activator, and the nano CeO is welded₂Niobium Nb into deposited metal, welding wire components andnano CeO₂The weight ratio of Nb is: welding wires: 0.06-0.08% of C, 0.03-0.3% of Si, less than or equal to 2.00% of S, 0.03-0.045% of P, 18.00-20.00% of Cr18, 8.00-11.00% of Nis and the balance of Fe; CeO (CeO)₂: 0.467-0.480; nb: 0.096-0.098. When the DP780 dual-phase steel is welded by the welding method, the lower yield strength of deposited metal of a test piece is 360.4-366.5 MPa, the tensile strength is 624.8-631.3 MPa, and the elongation after fracture is 20.38-20.63%. Less adding CeO₂Compared with Nb welding wires, the yield strength of deposited metal is improved by 1.46-1.48 times, the tensile strength is improved by 2.25-2.27 times, and the elongation after fracture is improved by 12.81-12.97 times. The welding wire does not need to be preheated before welding and slowly cooled after welding, so the welding wire has high cost performance and good industrialization prospect.

Description

Welding method of dual-phase steel

Technical Field

The invention relates to the technical field of welding materials, in particular to a welding method of dual-phase steel.

Background

The dual-phase (DP) steel is composed of a ferrite matrix and islands on ferrite grain boundaries, is obtained after a heat treatment process of a critical zone of low-carbon steel or low-carbon alloy steel, becomes the most widely used steel type due to high tensile strength, low yield strength, high work hardening rate and high forming performance, and can effectively reduce the weight of a vehicle body on the premise of not reducing various performance indexes such as the strength, the rigidity and the like of the vehicle body. However, the higher the strength of the dual-phase steel for vehicles, especially the higher the Si and Mn content of the dual-phase steel with a tensile strength of 590MPa or more, the greater the brittleness of the steel after welding, and the need of preheating before welding, slow cooling after welding and other technological measures in production, which is complex in process and high in production cost. Aiming at the problem, the welding wire containing the nano cerium oxide and the nano niobium can be welded without preheating before welding and slow cooling after welding.

Disclosure of Invention

The invention aims to provide a welding method of dual-phase steel, which aims to solve the problems that the dual-phase high-strength steel is not preheated before welding and is not slowly cooled after welding, and the plasticity and the toughness are lower.

In order to achieve the above purpose, the technical scheme of the invention is as follows:

nano CeO-containing₂Nb-containing welding wire comprising the following components in parts by weightThe components are as follows: 0.06 to 0.08 percent of C, 0.03 to 0.3 percent of Si, less than or equal to 2.00 percent of S, 0.03 to 0.045 percent of P, 18.00 to 20.00 percent of CrC, 8.00 to 11.00 percent of NiO, and CeO₂0.467-0.480, Nb0.096-0.098, and the balance Fe.

As a preferable embodiment, the CeO₂The size is 20-25 nm, the purity is 99.0-99.9%, and the size of Nb is 1nm, and the purity is 99.0-99.9%.

As a preferred technical scheme, the welding wire comprises the following components in percentage by weight: c0.08, Si0.03, S2.00, P0.045, Cr19.0, Ni9.0, CeO₂0.473, nb0.097, balance Fe.

The invention also provides a use method of the welding wire, which comprises the step of mixing the nanometer CeO₂Nb is dissolved in the activator, and the nano CeO is welded₂And niobium Nb is added to the deposited metal.

Preferably, the active agent is formed by mixing stearic acid and palm oil.

Compared with the prior art, the invention has the beneficial effects that:

when the welding wire is used for welding DP780 dual-phase steel, the lower yield strength of deposited metal of a test piece is 360.4-366.5 MPa, the tensile strength is 624.8-631.3 MPa, and the elongation after fracture is 20.38-20.63%. Less adding CeO₂Compared with Nb welding wires, the yield strength of deposited metal is improved by 1.46-1.48 times, the tensile strength is improved by 2.25-2.27 times, and the elongation after fracture is improved by 12.81-12.97 times. When C is 0.08, Si is 0.03, S is less than or equal to 2.00, P is 0.045, Cr19.0, Ni9.0 and CeO₂0.473, Nb0.097, and the balance Fe, less CeO₂Compared with Nb welding wire, the yield strength of deposited metal is improved by 1.48 times, the tensile strength is improved by 2.27 times, and the elongation after fracture is improved by 12.97 times. The welding wire does not need to be preheated before welding and slowly cooled after welding, so the welding wire has high cost performance and good industrialization prospect.

Drawings

FIG. 1 is a fracture morphology graph of a comparative example;

FIG. 2 is a fracture energy spectrum of the comparative example;

FIG. 3 is a fracture morphology map of example 2 of the present invention;

FIG. 4 is a fracture energy spectrum of example 2 of the present invention.

The specific implementation mode is as follows:

the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Comparative example

A2 mm thick DP780 dual phase steel plate was used as a weldment material (base metal), and the specification of each welded steel plate was 160 mm. times.65 mm. times.2 mm. And combining every two steel plates into a group of I-shaped grooves of the butt joint, and performing positive and negative double-sided welding by adopting Tungsten Inert Gas (TIG). The composition of the wire is shown in Table 1, length 1m, wire diameter 1.6 mm. During welding, the flow rate of argon is 7L/min, the purity of argon is 99.99%, and the welding speed is 2.32 mm/s. Welding power supply type polarity: the direct current is reversely connected, the welding current is 135A, and the welding voltage is 16V; the diameter of the tungsten electrode is 1.6mm, the length is 50mm, the angle of the tip is 45 degrees, the diameter of the tip is 0.8mm, the diameter of the nozzle is 8mm, and the distance between the nozzle and the weldment is 10 mm.

The welding wire composition without adding nano cerium oxide and niobium is taken as a comparative example. The mechanical properties of the test pieces of comparative examples are shown in Table 2.

TABLE 1 comparative example wire compositions

TABLE 2 mechanical Properties of test pieces of comparative examples

In the comparative example, the appearance of the-40 ℃ impact fracture without adding rare earth and niobium is shown in fig. 1, wherein fig. 1a is a macro appearance diagram, fig. 1b is a micro appearance diagram, and fig. 2 is an energy spectrum diagram. As can be seen from fig. 1a, the whole surface of the fracture is smooth and regular, and has crystal flakes and rough radiating edges, the crystal grain cleavage plane and the fracture plane are not in the same direction, and there are many reflective facets under light, typical brittle fracture characteristics, and the fracture has a few uneven fibrous fracture morphology, and still mainly brittle fracture, and the performance exhibited by the material is poor. From fig. 1b, it can be seen that the fracture is mainly brittle fracture, the fracture has many cleavage steps, the cleavage surface steps have many secondary cracks, and a large number of high-density short and curved tearing edge lines, the whole fracture exhibits quasi-dissociation fracture, and the fracture surface has micropores and many granular oxides and inclusions. FIG. 2 is a fracture energy spectrum, and it can be seen from FIG. 2 that the existing elements are mainly C, O, Si, etc., which are the causes of welded joint degradation, the C element has a large component ratio and is liable to cause welded joint toughness degradation, the Si element improves the steel strength and simultaneously causes welded joint plasticity and toughness degradation, and the oxygen element is too much and is liable to cause hot brittleness.

Examples and test results of the invention:

the welding process parameters of the invention are the same as the comparison example, the nano cerium oxide and niobium are selected, dissolved in the activator mixed by stearic acid and palm oil, fully oscillated, brushed at the welding interface of two steel plates with corresponding numbers, and transited to deposited metal by welding wire, so as to improve the structure and mechanical property of the deposited metal and the heat affected zone.

The following examples were prepared by changing CeO with the base composition of the wire formulation in Table 1₂The weight ratio of Nb and other components is not changed,

example 1:

transition CeO with the formula of the welding wire in Table 1 as the basic formula₂0.467 and Nb0.096 (the unit is percentage of deposited metal, the symbol is% and the number can be expanded or reduced by several times according to the production quantity) have greatly improved mechanical properties compared with those of the deposited metal of the comparative example, and the results are shown in Table 3.

Table 3 comparison of mechanical properties of deposited metal of inventive example 1 and comparative example

Example 2:

transition CeO with the formula of the welding wire in Table 1 as the basic formula₂0.473 and Nb0.097 (the units are percentages of deposited metal, and the symbols are% and can be expanded or reduced by several times according to the production quantity), the mechanical properties are greatly improved as compared with those of the deposited metal of the comparative example, and the results are shown in Table 4.

Table 4 comparison of mechanical properties of deposited metal of example 2 of the present invention and comparative example

The sample is the optimal sample in the embodiment, and the fracture morphology of the impact fracture at the temperature of-40 ℃ is shown in figure 3, wherein a is the macro fracture morphology, b is the micro fracture morphology, and figure 4 is an energy spectrum. It can be seen from fig. 3a that the fiber area, the radiation area and the shear lip area of the whole fracture are darker in color, the cross section is uneven and fibrous, the cracks in the radiation area continuously expand and are connected in a radiation stripe shape, and the fracture is mainly ductile fracture. As can be seen from FIG. 3b, the existence of a large number of parabolic dimples on the fracture is shear dimples, the dimples are small and shallow in size, and the existence of inclusions and second phase particles at the bottom of the dimples indicates incomplete plastic deformation, and the fracture also has a small number of tearing edges and separation steps, indicating that the fracture specimen is ductile-brittle fracture, mainly ductile fracture. It can be seen from the energy spectrum diagram of fig. 4 that the proportion of Fe, Cr and Mn is large, and the Cr element can improve the hardenability and wear resistance of the welded joint, and improve the corrosion resistance and oxidation resistance of the welded joint; mn element can improve the strength and the wear resistance of the welded joint and eliminate the adverse effect caused by S element, and the elements ensure that the welded joint has better performance.

Example 3:

transition CeO with the formula of the welding wire in Table 1 as the basic formula₂0.480 and Nb0.098 (the unit is the percentage of deposited metal, the symbol is% and the production quantity can be expanded or reduced by several times) have a greatly improved mechanical property compared with the mechanical property of the deposited metal of the comparative example, and the results are shown in Table 5 below.

TABLE 5 comparison of mechanical Properties of deposited metals in inventive example 3 and comparative example

According to the embodiment of the invention, the lower yield strength of deposited metal of a test piece is 360.4-366.5 MPa, the tensile strength is 624.8-631.3 MPa, and the elongation after fracture is 20.38-20.63% when the welding wire is used for welding DP780 dual-phase steel. Less adding CeO₂Compared with Nb welding wires, the yield strength of deposited metal is improved by 1.46-1.48 times, the tensile strength is improved by 2.25-2.27 times, and the elongation after fracture is improved by 12.81-12.97 times. When C is 0.08, Si is 0.03, S is less than or equal to 2.00, P is 0.045, Cr19.0, Ni9.0 and CeO₂0.473, Nb0.097, and the balance Fe

Without addition of CeO₂Compared with Nb welding wire, the yield strength of deposited metal is improved by 1.48 times, the tensile strength is improved by 2.27 times, and the elongation after fracture is improved by 12.97 times. The welding wire does not need to be preheated before welding and slowly cooled after welding, so the welding wire has high cost performance and good industrialization prospect.

Claims

1. The welding method of the dual-phase steel is characterized in that nano CeO₂Nb is dissolved in the activator, and the nano CeO is welded₂Niobium Nb is transferred into deposited metal, and welding wire components and nano CeO₂The weight ratio of Nb is:

welding wires: 0.06-0.08% of C, 0.03-0.3% of Si, less than or equal to 2.00% of S, 0.03-0.045% of P, 18.00-20.00% of Cr18, 8.00-11.00% of Nis and the balance of Fe;

CeO₂：0.467～0.480；

Nb：0.096～0.098。

2. the method according to claim 1, wherein the CeO₂The size is 20-25 nm, the purity is 99.0-99.9%, and the size of Nb is 1nm, and the purity is 99.0-99.9%.

3. The method wire as claimed in claim 1, wherein the welding wire comprises the following components in parts by weight: c0.08, Si0.03, S2.00, P0.045, Cr19.0, Ni9.0, and the balance of Fe and CeO₂The weight ratio of (2) is 0.473, and the weight ratio of Nb is 0.097.

4. The method of claim 1, wherein the active agent is formed by mixing stearic acid and palm oil.