Method for regulating strength and plasticity of high-strength steel by using double-wire CMT additive

Abstract

The application discloses a method for regulating the strength and plasticity of high-strength steel by using double-wire CMT additive manufacturing, and specifically, the method is to use double-wire CMT to alternately feed wires to prepare stainless steel wire and low-alloy high-strength steel wire through a set additive manufacturing process; the volume fraction of the two materials and the layer thickness ratio can be regulated to achieve the regulation of the strength and ductility of the high-strength steel. The high-strength steel prepared by the method belongs to a heterogeneous material, and the strength and plasticity of the high-strength steel can be regulated in the excellent tensile strength of the low-alloy high-strength steel and the good elongation range of the stainless steel; additionally, the high-back stress generated by the uneven deformation of the soft material and the hard material can obtain additional work hardening effect, and the tensile strength of the high-strength steel can be greatly improved. The double-wire CMT alternately cladding two ordinary wire materials can be used to prepare the high-strength steel, and the tensile strength of the high-strength steel is not limited to the strength of the low-alloy high-strength steel wire, and the additional work hardening effect can be obtained simultaneously.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electric arc additive manufacturing, and particularly relates to a method for regulating the strength and plasticity of high-strength steel by using double-wire CMT. BACKGROUND

[0002] Steel is the most widely used material in the industrial field, and has a high demand in various industries. High-strength steel is a kind of steel that is widely used, and has an irreplaceable position in many fields such as bridge construction, transportation, tank armor, etc. When the chemical composition of high-strength steel is determined, the strength and toughness mainly depend on the microstructure of the steel, and different processing and heat treatment processes can significantly affect the microstructure of the steel and thus affect the performance. At present, the performance of the steel is mainly optimized from two aspects: first, the content and shape of non-metallic inclusions are controlled; and second, a reasonable microstructure is obtained through heat treatment.

[0003] Laser additive manufacturing of metal materials mainly includes selective laser melting technology and laser melting deposition technology. Laser additive manufacturing melts the material to be cladded by laser beam energy, and according to the designed model, the required structure is prepared by layer-by-layer deposition. Laser additive manufacturing has high forming precision and energy that is precisely controllable. However, laser additive manufacturing has low efficiency and high cost of equipment and raw materials, and is not suitable for processing large and complex metal structural parts. Electric arc additive manufacturing has high efficiency, low cost and good processing flexibility, and can directly process one or more complex metal structures, and has unique advantages in processing large metal structural parts. Among various electric arc additive manufacturing methods, CMT additive manufacturing has lower heat input, smaller deformation, no spatter and extremely stable arc, which is more beneficial to the forming of high-strength steel.

[0004] The patent 'Heat treatment process for improving comprehensive mechanical properties of low-alloy high-strength steel' (application number 201010159100.0) discloses a heat treatment process for improving the comprehensive mechanical properties of low-alloy high-strength steel. The heat treatment method consists of two parts of cyclic quenching and tempering. This method has a complex process flow, high manufacturing cost, limited improvement of the tensile strength of high-strength steel, and quenching may cause deformation and cracking of the material, which greatly affects the use of high-strength steel. SUMMARY

[0005] In view of the deficiencies of the above prior art, the purpose of the present application is to provide a method for regulating the strength and plasticity of high-strength steel by using double-wire CMT additive manufacturing, which can not only obtain high-strength steel within the strength and plasticity range of two kinds of wire materials, but also obtain additional work hardening effect and tensile strength beyond that of low-alloy high-strength steel wire.

[0006] To achieve the above purpose, the present application provides the following technical solutions:

[0007] The application discloses a method for regulating the strength and plasticity of high-strength steel by using double-wire CMT, wherein the high-strength steel is prepared by alternately cladding stainless steel wire (ER316L) and low-alloy high-strength steel wire (ER120S-G) by using double-wire CMT; during the additive process, the line energy density of the additive stainless steel wire is less than 400 J·mm -1 , and the line energy density of the additive low-alloy high-strength steel wire is less than 650 J·mm -1 ; the volume fraction ratio of the stainless steel wire ER316L and the low-alloy high-strength steel wire ER120S-G is less than 18 / 25.

[0008] The method for regulating the strength and plasticity of high-strength steel by using double-wire CMT comprises the following specific steps:

[0009] 1) presetting process parameters, including setting the process mode, voltage, current, shielding gas and shielding gas flow of the CMT additive according to the wire feeding speed and deposition speed of the two kinds of wires;

[0010] 2) controlling the height of the welding gun from the substrate, selecting an arc starting point on the stainless steel substrate, and after igniting the electric arc, feeding the stainless steel wire (ER316L) to the electric arc to melt and deposit the first layer of the sample according to the preset robot walking track;

[0011] 3) controlling the interlayer temperature, and after the interlayer temperature reaches the preset value, polishing the previously deposited layer by using an angle grinder, and depositing the low-alloy high-strength steel wire (ER120S-G) to the second layer;

[0012] 4) repeating steps 2) and 3) to alternately and reciprocally deposit the stainless steel wire (ER316L) and the low-alloy high-strength steel wire (ER120S-G) until the deposition is stopped after reaching the preset size.

[0013] Further, the layer thickness and layer number ratio of the two kinds of materials are set according to the volume fraction, and the wire feeding speed and deposition speed of the two kinds of wires are preferably set.

[0014] Further, the wire feeding speed of the stainless steel wire ER316L is 8-8.6 M / Min, and the deposition speed is 10.5-12 mm / s; the wire feeding speed of the low-alloy high-strength steel wire ER120S-G is 4.5-5.5 M / Min, and the deposition speed is 4-5 mm / s.

[0015] Further, the process mode of the stainless steel wire ER316L is CMT, the current is 226-243 A, the voltage is 18.6-19.2 V, the shielding gas is Ar+1.5% O2, and the shielding gas flow is 25 L / Min; the process mode of the low-alloy high-strength steel wire ER120S-G is CMT, the current is 158-184 A, the voltage is 16.3-16.9 V, the shielding gas is Ar, and the shielding gas flow is 25 L / Min.

[0016] Further, the distance between the welding gun and the workpiece is controlled to be 15mm.

[0017] Further, the interlayer temperature is controlled, and the interlayer temperature reaches the preset value 100℃.

[0018] Compared with the prior art, the present application has the following advantages: 1. The high-strength steel prepared by the method can control the strength and ductility within a range; 2. The method uses CMT to alternately deposit stainless steel wire and low-alloy high-strength steel wire to manufacture, which can obtain additional work hardening effect by high back stress generated by uneven deformation of soft and hard materials, and greatly improve the tensile strength of high-strength steel; 3. The high-strength steel is prepared by arc melting, which is simpler and has lower equipment cost compared with laser additive manufacturing; 4. The wire arc melting method is used to control the strength and ductility of high-strength steel, making it easier to manufacture complex high-strength steel structural parts. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 The 50 times metallographic structure photo of the high-strength steel deposition sample of Example 1.

[0020] Figure 2 The engineering stress-strain curves of the high-strength steel deposition sample (HSS) of Example 1, pure ER316L and ER120S-G.

[0021] Figure 3 The work hardening curves of the high-strength steel deposition sample (HSS) of Example 1, pure ER316L and ER120S-G. DETAILED DESCRIPTION

[0022] The preferred embodiments of the present application will be described in detail below with reference to the accompanying drawings, so that the advantages and features of the present application can be more easily understood by those skilled in the art, and the protection scope of the present application can be more clearly defined.

[0023] Example 1

[0024] A method for regulating the strength and ductility of high-strength steel by using double-wire CMT, the high-strength steel is prepared by using double-wire CMT to alternately deposit stainless steel wire ER316L and low-alloy high-strength steel wire ER120S-G, wherein the line energy density of the additive stainless steel wire is 388.8J·mm -1 , the line energy density of the additive low-alloy high-strength steel wire is 643.8J·mm -1 , and the volume fraction ratio of the stainless steel wire ER316L and the low-alloy high-strength steel wire ER120S-G is 16 / 25.

[0025] The diameters of the two wires are 1.2mm.

[0026] The specific steps are as follows:

[0027] 1) Preset process parameters: including setting the process mode of CMT additive, voltage, current, shielding gas and shielding gas flow rate according to the wire feed speed and deposition speed of two kinds of wires;

[0028] 2) Control the height of the welding gun from the substrate, select the arc starting point on the stainless steel substrate, after igniting the arc, send the stainless steel wire (ER316L) to the arc to melt and deposit the first layer of the sample according to the preset robot walking trajectory;

[0029] 3) Control the interlayer temperature, use an angle grinder to polish the previously deposited layer when the interlayer temperature reaches the preset value, and deposit the low alloy high strength steel wire (ER120S-G) to the second layer;

[0030] 4) Repeat steps 2) and 3) to alternately and reciprocally deposit stainless steel wire (ER316L) and low alloy high strength steel wire (ER120S-G) until the preset size of 120mm x 60mm x 80mm is reached.

[0031] The specific values are as follows:

[0032] The wire feed speed and deposition speed of the two kinds of wires are set according to the volume fraction. The wire feed speed of the stainless steel wire ER316L is 8.6M / Min, and the deposition speed is 12mm / s; the wire feed speed of the low alloy high strength steel wire ER120S-G is 4.5M / Min, and the deposition speed is 4mm / s.

[0033] The process mode of the stainless steel wire ER316L is CMT, the current is 243A, the voltage is 19.2V, the shielding gas is Ar+1.5%O2, and the shielding gas flow rate is 25L / Min; the process mode of the low alloy high strength steel wire ER120S-G is CMT, the current is 158A, the voltage is 16.3V, the shielding gas is Ar, and the shielding gas flow rate is 25L / Min.

[0034] The height of the welding gun from the workpiece is controlled to be 15mm.

[0035] The interlayer temperature is controlled, and the interlayer temperature reaches the preset value of 100℃.

[0036] The high strength steel deposition sample has no obvious defects and forms well. For example Figure 1 The 50 times metallographic structure photo of the high strength steel deposition sample shows that the sample has a heterogeneous interface, there is no obvious defect at the interface, the upper region is low alloy high strength steel ER120S-G, and the lower region is stainless steel ER316L region. XRD shows that the main organization of the high strength steel is austenite and martensite. EDS line scanning shows that there is element mixing caused by remelting in the low alloy high strength steel and stainless steel regions. For example Figure TwoThe engineering stress strain curves of high strength steel deposition sample (HSS), pure ER316L and ER120S-G show that the tensile strength of high strength steel deposition sample deposited by two kinds of wire alternately reaches 1211Mpa, which is higher than the strength of 981Mpa of pure low alloy high strength steel, and the elongation after fracture decreases. Figure Three The work hardening curves of high strength steel deposition sample (HSS), pure ER316L and ER120S-G show that after the elastic stage, the work hardening rate of high strength steel deposition sample is higher than that of the other two pure materials, and the work hardening rate of ER316L stainless steel sample remains low. The work hardening rate of high strength steel deposition sample (HSS) decreases slower than that of ER120S-G low alloy high strength steel sample, which shows that the heterostructure material prepared by the above method has better work hardening effect.

[0037] Example 2

[0038] The high strength steel was prepared by using double-wire CMT to alternately deposit stainless steel wire ER316L and low alloy high strength steel wire ER120S-G, wherein the line energy density of the additive stainless steel wire was 565J·mm -1 , the line energy density of the additive low alloy high strength steel wire was 643.8J·mm -1 , and the volume fraction ratio of the stainless steel wire ER316L and the low alloy high strength steel wire ER120S-G was 8 / 9.

[0039] The diameters of the two wires were 1.2mm.

[0040] The specific steps are as follows:

[0041] 1) Pre-set process parameters: including setting the process mode, voltage, current, shielding gas and shielding gas flow of CMT deposition according to the wire feeding speed and deposition speed of the two wires;

[0042] 2) Control the height of the welding gun distance from the substrate, select the arc starting point on the stainless steel substrate, after igniting the arc, send the stainless steel wire (ER316L) to the arc to melt and deposit the first layer of the sample according to the pre-set robot walking track;

[0043] 3) Control the interlayer temperature, and after the interlayer temperature reaches the pre-set value, use an angle grinder to polish the previously deposited layer, and deposit the low alloy high strength steel wire (ER120S-G) to the second layer;

[0044] 4) Repeat steps 2) and 3) to alternately deposit stainless steel wire (ER316L) and low alloy high strength steel wire (ER120S-G) until the pre-set size of 120mm×60mm×80mm is reached.

[0045] The specific values are as follows:

[0046] The wire feed speed and deposition speed of the two wires are set according to the volume fraction. The wire feed speed of the stainless steel wire ER316L is 5.5 M / Min, and the deposition speed is 5.5 mm / s; the wire feed speed of the low-alloy high-strength steel wire ER120S-G is 4.5 M / Min, and the deposition speed is 4 mm / s.

[0047] The process mode of the stainless steel wire ER316L is CMT, the current is 184 A, the voltage is 16.9 V, the shielding gas is Ar+1.5%O2, and the shielding gas flow rate is 25 L / Min; the process mode of the low-alloy high-strength steel wire ER120S-G is CMT, the current is 158 A, the voltage is 16.3 V, the shielding gas is Ar, and the shielding gas flow rate is 25 L / Min.

[0048] The height of the welding gun from the workpiece is controlled to be 15 mm.

[0049] The interlayer temperature is controlled, and the interlayer temperature is allowed to reach the preset value of 100℃.

[0050] This embodiment increases the line energy density of the additive stainless steel wire beyond the given range, and the volume fraction of the two wires also exceeds the given range. Table 1 shows the tensile property test of the high-strength steel sample, and the average elongation after fracture is 31.68%, and the tensile strength is 726.6 Mpa.

[0051] Example 3

[0052] The high-strength steel is prepared by using double-wire CMT to alternately clad stainless steel wire ER316L and martensitic high-strength steel wire 18Ni300, wherein the line energy density of the additive stainless steel wire is 388.8 J·mm -1 , the line energy density of the additive martensitic high-strength steel wire is 555.5 J·mm -1 , and the volume fraction ratio of the stainless steel wire ER316L and the martensitic high-strength steel wire 18Ni300 is 19 / 25.

[0053] The diameters of the two wires are 1.2 mm.

[0054] The specific steps are as follows:

[0055] 1) Pre-set process parameters: including setting the process mode, voltage, current, shielding gas and shielding gas flow rate of CMT additive according to the wire feed speed and deposition speed of the two wires;

[0056] 2) Control the height of the welding gun from the substrate, select the arc starting point on the stainless steel substrate, and after igniting the arc, send the stainless steel wire (ER316L) to the arc to melt and deposit the first layer of the sample according to the preset robot walking trajectory;

[0057] 3) Control the interlayer temperature, when the interlayer temperature reaches the preset value, use the angle grinder to polish the previous deposited layer, and deposit the martensitic high-strength steel wire (18Ni300) to the second layer;

[0058] 4) Repeat steps 2) and 3) to alternately and reciprocally deposit the stainless steel wire (ER316L) and the martensitic high-strength steel wire (18Ni300) until the preset size of 120mm x 60mm x 80mm is reached, and then stop the deposition.

[0059] The specific values are as follows:

[0060] The wire feeding speed and deposition speed of the two kinds of wires are set according to the volume fraction. The wire feeding speed of the stainless steel wire ER316L is 8.6M / Min, and the deposition speed is 12mm / s; the wire feeding speed of the martensitic high-strength steel wire 18Ni300 is 8.3M / Min, and the deposition speed is 9mm / s.

[0061] The process mode of the stainless steel wire ER316L is CMT, the current is 243A, the voltage is 19.2V, the protective gas is Ar+1.5%O2, and the protective gas flow is 25L / Min; the process mode of the martensitic high-strength steel wire 18Ni300 is CMT, the current is 250A, the voltage is 20V, the protective gas is Ar, and the protective gas flow is 25L / Min.

[0062] The distance between the welding gun and the workpiece is controlled to be 15mm.

[0063] The interlayer temperature is controlled, and when the interlayer temperature reaches the preset value of 100℃.

[0064] This embodiment uses the martensitic high-strength steel 18Ni300 wire, and the proportion of the two kinds of wires exceeds the given range, which is different from the given scheme. Table 1 is the tensile property test of the high-strength steel sample, and the average elongation after fracture is 29.2%, and the tensile strength is 642.2Mpa.

[0065] Table 1

[0066] High strength steel tensile data Tensile strength / Mpa Elongation after break % Example 2 Example 3 726.6±59 31.6±2.8 ​ 642.2±25 29.2±2.3

Claims

1. A method for regulating the strength and ductility of high-strength steel by using double-wire CMT, characterized in that, The method is: first, select double wire CMT alternate cladding stainless steel wire ER316L and low alloy high strength steel wire ER120S-G; when adding, control the line energy density of the added stainless steel wire ER316L to be less than 400J·mm -1 , the line energy density of the added low alloy high strength steel wire ER120S-G is less than 650J·mm -1 ; in addition, the volume fraction ratio of the stainless steel wire ER316L and the low alloy high strength steel wire ER120S-G is less than 18 / 25.

2. The method for regulating the strength and ductility of high-strength steel by using double-wire CMT according to claim 1, characterized in that, The line energy density of the additive stainless steel ER316L and high-strength steel ER120S-G is controlled by adjusting the wire feeding speed and deposition speed, and the volume fraction of the two materials is controlled by the number of deposited layers and layer thickness.

3. The method for regulating the strength and ductility of high-strength steel by using double-wire CMT according to claim 1, characterized in that, The specific steps include the following: 1) Pre-set process parameters: including setting the CMT additive process mode, voltage, current, shielding gas and shielding gas flow according to the wire feeding speed and deposition speed of the two wires; 2) Control the height of the welding gun from the substrate, select the arc starting point on the stainless steel substrate, after igniting the arc, send the stainless steel wire ER316L to the arc for melting and deposit the first layer of the sample according to the pre-set robot walking track; 3) Control the interlayer temperature, and use an angle grinder to polish the previously deposited layer when the interlayer temperature reaches the pre-set value, and deposit the low-alloy high-strength steel wire ER120S-G to the second layer; 4) Repeat steps 2) and 3) to alternately and reciprocally deposit the stainless steel wire ER316L and the low-alloy high-strength steel wire ER120S-G until the pre-set size is reached and the deposition is stopped.

4. The method for regulating the strength and ductility of high-strength steel by using double-wire CMT according to claim 3, characterized in that, The single-layer thickness of the two wires is controlled by the wire feeding speed and deposition speed, and the volume ratio of the two materials is controlled by the designed number of additive layers of the two materials.

5. The method for regulating high-strength steel strength and ductility by double-wire CMT according to claim 3, characterized in that, The wire feeding speed of the stainless steel wire ER316L is 8-8.6 M / Min, and the deposition speed is 10.5-12 mm / s; the wire feeding speed of the low-alloy high-strength steel wire ER120S-G is 4.5-5.5 M / Min, and the deposition speed is 4-5 mm / s.

6. The method for regulating high-strength steel strength and ductility by using double-wire CMT according to claim 3, characterized in that, The process mode of the stainless steel wire ER316L is CMT, the current is 226-243 A, the voltage is 18.6-19.2 V, the shielding gas is Ar+1.5% O2, and the shielding gas flow is 25 L / Min; the process mode of the low-alloy high-strength steel wire ER120S-G is CMT, the current is 158-184 A, the voltage is 16.3-16.9 V, the shielding gas is Ar, and the shielding gas flow is 25 L / Min.

7. The method for regulating high-strength steel strength and ductility by double-wire CMT according to claim 3, characterized in that, The height of the welding gun from the workpiece is controlled to be 15 mm.

8. The method for regulating high-strength steel strength and ductility by double-wire CMT according to claim 3, characterized in that, The interlayer temperature is controlled, and the interlayer temperature reaches the pre-set value of 100℃.

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