Method for improving overall heat treatment effect of steel material section

Abstract

The invention relates to a method for improving the overall heat treatment effect of a steel material section, and belongs to the technical field of steel material section heat treatment. In order to solve the problem that the existing large steel material section heat treatment method cannot truly and accurately reflect the steel heat treatment performance, the invention provides a method for improving the overall heat treatment effect of a steel material section, a steel ring is welded at the center position of the end part of the cross section on one side of a material section to be detected, a wire rod penetrates through the steel ring, and two ends of the wire rod are butted and welded to form a lifting ring; in the process of heat treatment charging, discharging and cooling in a cooling medium, a crown block is used for being matched with a hoisting iron hook to hook a hoisting ring to transfer a material section to be detected. According to the invention, the material section vertically enters the cooling medium, so that the supercooling degree is equal on the outer surface of the steel, the heating rate, the heat treatment effect and the inspection efficiency of the whole heat treatment sample are improved, the quality level of steel heat treatment and mechanical properties is reflected more truly and accurately, and a guiding effect is played on steel production.

Description

Technical Field

[0001] The invention belongs to the technical field of heat treatment of steel material segments, and in particular relates to a method for improving the overall heat treatment effect of steel material segments. Background Art

[0002] For marine crankshafts or other steel products for specific purposes, customers usually require suppliers to provide mechanical performance index data after overall heat treatment. Before the material enters the production process, customers will also conduct a factory re-inspection, which also includes a re-test of the overall heat treatment performance of the material section.

[0003] The general process of overall heat treatment of material segments is to place the material segments securely on a dedicated sample rack, and then place the entire device package of the material segment and the sample rack in a heating furnace for heat treatment. After the heat treatment is completed, they are transferred together to a cooling medium such as water, oil or air for cooling treatment. It is worth noting that the size of the sample rack is usually designed to be slightly larger than the material segment to facilitate the stable placement of the material segment. However, since the sample rack and the material segment are carried out synchronously during the heat treatment and cooling process, the heat released by the sample rack during the cooling process will have an adverse effect on the cooling rate of the material segment, resulting in a decrease in the cooling rate of the material segment. In this case, the final organizational transformation of the material segment cannot reach the ideal state, which makes the measured mechanical properties indicators low and cannot truly and accurately reflect the quality level of the steel. Summary of the invention

[0004] In order to solve the problem that the existing heat treatment method for large steel material segments cannot truly and accurately reflect the heat treatment performance of steel materials, the present invention provides a method for improving the overall heat treatment effect of steel material segments.

[0005] The technical solution of the present invention:

[0006] A method for improving the overall heat treatment effect of a steel material segment, comprising: welding a steel ring at the center position of the end of a cross section of one side of the material segment to be measured, passing a round plate through the steel ring, butting and welding the two ends of the round plate together to form a lifting ring, and during the process of loading and unloading a furnace for heat treatment and cooling in a cooling medium, using a crane in conjunction with a lifting iron hook to hang the lifting ring to transfer the material segment to be measured.

[0007] Furthermore, the size of the material section to be measured is Φ120-400mm and the length is 120-300mm.

[0008] Furthermore, different steel rings are provided according to the size specifications of the material section to be measured, and the steel rings are circular, elliptical or semi-elliptical.

[0009] Furthermore, when the diameter of the material segment to be measured is Φ120-180 mm, an elliptical steel ring is used for welding, and the major axis * thickness * minor axis size of the elliptical steel ring is Φ50*5*40 mm. The elliptical steel ring is placed at the center position of the end of the cross section on one side of the material segment to be measured with the major axis parallel to the cross section of the material segment to be measured for welding.

[0010] Furthermore, when the diameter of the material section to be measured is Φ180-250 mm, a circular steel ring is used for welding, and the diameter*thickness size of the circular steel ring is Φ50*5 mm.

[0011] Furthermore, when the diameter of the material segment to be measured is Φ250-400mm, a semi-elliptical steel ring is used for welding, and the size of the major axis * thickness * 1 / 2 minor axis of the semi-elliptical steel ring is Φ108*10*40mm. The semi-elliptical steel ring is placed at the center position of the end of the cross section on one side of the material segment to be measured with the major axis parallel to the cross section of the material segment to be measured for welding.

[0012] Furthermore, the diameter of the disc is 6.5 mm, the length is 300-1000 mm, and the length of the butt welding at both ends of the disc is 50 mm.

[0013] Furthermore, the material of the steel ring is No. 20 steel or Q235B steel, and the material of the hanging ring is Q195 steel or Q235 steel.

[0014] Furthermore, the distance between the steel ring and the lifting hook during the lifting and transfer process is 1 to 1.5 times the length of the material section to be measured.

[0015] Furthermore, the cooling medium is water, oil or quenching liquid.

[0016] Beneficial effects of the present invention:

[0017] The present invention solves the problem that the overall heat treatment of large steel material segments using a sample rack transfer heat treatment effect is poor and cannot truly reflect the heat treatment performance of the steel. The present invention welds a steel ring and a lifting ring at the center position of the cross section of one side of the material segment to be tested. During the process of heat treatment loading and unloading from the furnace and cooling in the cooling medium, the material segment to be tested is transferred by hanging the lifting ring with a crane in cooperation with a lifting hook, so that the material segment enters the cooling medium vertically, which can make the supercooling equal on the outer surface of the steel, thereby improving the heating rate and heat treatment effect. The present invention welds steel rings of different sizes according to the specifications of different material segments to be tested. Vertical lifting can also make the gravity of the material segment average without tilting, thereby ensuring the safety of the operation. The material segment transfer method of the present invention significantly improves the inspection efficiency of the overall heat treatment sample, more truly and accurately reflects the quality level of steel heat treatment and mechanical properties, and plays a guiding role in steel production. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1This is a schematic diagram of the welding method of the material section to be tested, the iron ring and the hanging ring in Example 1;

[0019] Figure 2 This is a schematic diagram of the welding method of the material section to be tested, the iron ring and the hanging ring in Example 3;

[0020] Figure 3 This is a microscopic photograph of the metallographic structure at 1 / 2R of the material section to be tested after heat treatment in Example 1;

[0021] Figure 4 This is a microscopic photograph of the metallographic structure at 1 / 2R of the material section to be tested after heat treatment in Comparative Example 1;

[0022] In the figure, 1 is the material section to be tested, 2 is the iron ring, 3 is the lifting ring, and 4 is the butt welding point of the lifting ring. DETAILED DESCRIPTION

[0023] The technical solution of the present invention is further described below in conjunction with the embodiments, but it is not limited thereto. Any modification or equivalent replacement of the technical solution of the present invention without departing from the spirit and scope of the technical solution of the present invention shall be included in the protection scope of the present invention. The process equipment or devices not specifically noted in the following embodiments are all conventional equipment or devices in the art. If not specifically specified, the raw materials used in the embodiments of the present invention can be obtained commercially; if not specifically specified, the technical means used in the embodiments of the present invention are all conventional means well known to those skilled in the art.

[0024] Example 1

[0025] This embodiment provides a method for improving the overall heat treatment effect of a steel material segment.

[0026] The specifications of the material section to be tested in this embodiment are 260mm in diameter and 240mm in length, and the specific steel type is 40CrNiMoA. A steel ring is welded at the center of the end of the cross section on one side of the material section to be tested. The steel ring is a semi-elliptical steel ring, and its major axis * thickness * 1 / 2 minor axis size is Φ108*10*40mm, and the material is No. 20 steel. The semi-elliptical steel ring is placed at the center of the end of the cross section on one side of the material section to be tested in a direction in which the major axis is parallel to the cross section of the material section to be tested, and then welded. A disc with a diameter of 6.5mm and a length of 770mm is passed through the steel ring, and the two ends of the disc are butt-welded to form a hanging ring. The length of the butt welding is 50mm, and the material of the disc is Q195 steel.

[0027] In this embodiment, the cross section is selected for welding the iron ring and the lifting ring because the object of conventional mechanical properties testing is the longitudinal section of the steel. By vertically lifting the material section so that it enters the cooling medium vertically, the degree of supercooling can be equal on the outer surface of the steel. Vertical lifting can also make the gravity of the material section uniform without tilting, thereby ensuring the safety of the operation.

[0028] like Figure 1 The figure shows a schematic diagram of the welding method of the material section to be tested, the iron ring and the hanging ring in this embodiment. The use of a semi-elliptical steel ring can reduce the weight of the sample and ensure the safety of sample transfer. Compared with the transfer of existing sample racks with large weight and volume, the transfer method provided by the present invention can reduce the operation safety risk level from level 4 to level 5.

[0029] During the process of heat treatment loading and unloading from the furnace and cooling in the cooling medium, the overhead crane is used in conjunction with the lifting hook to hang the lifting ring on the material section to transfer the material section to be tested. The heat treatment conditions are quenching temperature 880℃ oil cooling and tempering temperature 570℃ controlled cooling.

[0030] Example 2

[0031] This embodiment provides a method for improving the overall heat treatment effect of a steel material segment.

[0032] In this embodiment, the specification of the material section to be tested is 240mm in diameter and 240mm in length, and the specific steel type is 40CrNiMoA. A steel ring is welded at the center of the cross-section end of one side of the material section to be tested. The steel ring is a circular steel ring with a diameter*thickness size of Φ50*5mm and a material of No. 20 steel. A disc with a diameter of 6.5mm and a length of 770mm is passed through the steel ring, and the two ends of the disc are butt-welded to form a hanging ring. The length of the butt welding is 50mm, and the material of the disc is Q195 steel.

[0033] During the process of heat treatment loading and unloading from the furnace and cooling in the cooling medium, the overhead crane is used in conjunction with the lifting hook to hang the lifting ring on the material section to transfer the material section to be tested. The heat treatment conditions are quenching temperature 880℃ oil cooling and tempering temperature 570℃ controlled cooling.

[0034] Example 3

[0035] This embodiment provides a method for improving the overall heat treatment effect of a steel material segment.

[0036] In this embodiment, the specification of the material section to be tested is 180mm in diameter and 240mm in length, and the specific steel type is 40CrNiMoA. A steel ring is welded at the center of the end of the cross section on one side of the material section to be tested. The steel ring is an elliptical steel ring, and its major axis * thickness * minor axis size is Φ50*5*40mm. The material is No. 20 steel. A disc with a diameter of 6.5mm and a length of 770mm is passed through the steel ring, and the two ends of the disc are butt-welded to form a hanging ring. The length of the butt welding is 50mm, and the material of the disc is Q195 steel. Figure 2 The figure shows the welding method of the material section to be tested, the iron ring and the hanging ring in this embodiment.

[0037] During the process of heat treatment loading and unloading from the furnace and cooling in the cooling medium, the overhead crane is used in conjunction with the lifting hook to hang the lifting ring on the material section to transfer the material section to be tested. The heat treatment conditions are quenching temperature 880℃ oil cooling and tempering temperature 570℃ controlled cooling.

[0038] Example 4

[0039] This embodiment provides a method for improving the overall heat treatment effect of a steel material segment.

[0040] In this embodiment, the specification of the material section to be tested is 190mm in diameter and 240mm in length, and the specific steel type is 40CrNiMoA. A steel ring is welded at the center of the cross-section end of one side of the material section to be tested. The steel ring is a circular steel ring with a diameter*thickness size of Φ50*5mm and a material of No. 20 steel. A disc with a diameter of 6.5mm and a length of 770mm is passed through the steel ring, and the two ends of the disc are butt-welded to form a hanging ring. The length of the butt welding is 50mm, and the material of the disc is Q195 steel.

[0041] During the process of heat treatment loading and unloading from the furnace and cooling in the cooling medium, the overhead crane is used in conjunction with the lifting hook to hang the lifting ring on the material section to transfer the material section to be tested. The heat treatment conditions are quenching temperature 880℃ oil cooling and tempering temperature 570℃ controlled cooling.

[0042] Comparative Example 1

[0043] This comparative example adopts a method of heat treating the existing sample rack and the material section to be tested as a whole.

[0044] The size of the material segment to be tested in this comparative example is the same as that in Example 1, both of which are 260 mm in diameter and 240 mm in length, and the specific steel type is 40CrNiMoA. During the heat treatment process, the material segment to be tested is placed on a test rack, and the test rack and the material segment to be tested are transferred as a whole. The heat treatment conditions are a quenching temperature of 880°C with oil cooling and a tempering temperature of 570°C with controlled cooling.

[0045] Comparative Example 2

[0046] This comparative example adopts a method of heat treating the existing sample rack and the material section to be tested as a whole.

[0047] The size of the material segment to be tested in this comparative example is the same as that in Example 2, both of which are 240 mm in diameter and 240 mm in length, and the specific steel type is 40CrNiMoA. During the heat treatment process, the material segment to be tested is placed on a test rack, and the test rack and the material segment to be tested are transferred as a whole. The heat treatment conditions are a quenching temperature of 880°C with oil cooling and a tempering temperature of 570°C with controlled cooling.

[0048] Comparative Example 3

[0049] This comparative example adopts a method of heat treating the existing sample rack and the material section to be tested as a whole.

[0050] The size of the material segment to be tested in this comparative example is the same as that in Example 3, both of which are 180 mm in diameter and 240 mm in length, and the specific steel type is 40CrNiMoA. During the heat treatment process, the material segment to be tested is placed on a test rack, and the test rack and the material segment to be tested are transferred as a whole. The heat treatment conditions are a quenching temperature of 880°C with oil cooling and a tempering temperature of 570°C with controlled cooling.

[0051] Comparative Example 4

[0052] This comparative example adopts a method of heat treating the existing sample rack and the material section to be tested as a whole.

[0053] The size of the material segment to be tested in this comparative example is the same as that in Example 4, both of which are 190 mm in diameter and 240 mm in length, and the specific steel type is 40CrNiMoA. During the heat treatment process, the material segment to be tested is placed on a test rack, and the test rack and the material segment to be tested are transferred as a whole. The heat treatment conditions are a quenching temperature of 880°C with oil cooling and a tempering temperature of 570°C with controlled cooling.

[0054] The heat treatment performance of the heat-treated material sections of Examples 1-4 and Comparative Examples 1-4 was tested, and the results are shown in Table 1.

[0055] Table 1

[0056]

[0057] From the data in Table 1, we can see that the welding ring and the specimen holder are used to heat treat the material segments with the same composition and specification, and the 1 / 2R samples are taken for mechanical property testing. The yield strength is increased by an average of 77 MPa, the tensile strength is increased by 64 MPa, the impact energy is increased by 20 J at 20 °C, and the impact energy is increased by 30 J at -20 °C. The overall mechanical performance indicators are improved.

[0058] Figure 3 and Figure 4 They are respectively microphotographs of the metallographic structures at 1 / 2R of the material section to be tested after heat treatment in Example 1 and Comparative Example 1; as can be seen from the comparison of the pictures, Figure 3 The metallographic structure at 1 / 2R is 84% ​​tempered troostite + 2% ferrite + 14% tempered bainite. Figure 4The metallographic structure at the 1 / 2R position is 45% tempered troostite + 7% ferrite + 48% tempered bainite. The content of ferrite and bainite tempered structure after heat treatment with the sample rack is high. This is mainly because when the sample rack is used for quenching and cooling, the sample rack enters the quenching medium together with the sample, emitting a large amount of heat, increasing the temperature of the quenching medium, resulting in slow quenching and cooling speed, less martensite transformation, and thus resulting in low content of tempered troostite produced after tempering, thereby reducing the mechanical properties of the material. The present invention solves the problem that the overall heat treatment of large steel material sections using the sample rack transfer heat treatment effect is poor and cannot truly reflect the heat treatment performance of steel.

[0059] The present invention welds a steel ring at the center position of the end portion of the cross section of one side of the material section to be measured, passes a round plate through the steel ring, and butt-welds the two ends of the round plate to form a lifting ring. During the process of heat treatment loading and unloading from the furnace and cooling in a cooling medium, a crane is used to hang the lifting ring with a lifting hook to transfer the material section to be measured, so that the material section enters the cooling medium vertically, and the degree of supercooling on the outer surface of the steel is equal, thereby improving the heating rate, heat treatment effect and the inspection efficiency of the overall heat treatment sample, more truly and accurately reflecting the quality level of heat treatment and mechanical properties of steel, and playing a guiding role in steel production.

Claims

1. A method for improving the overall heat treatment effect of a steel material segment, characterized in that: A steel ring is welded at the center of the end of the cross section of one side of the material section to be tested, and a round coil is passed through the steel ring. The two ends of the round coil are butt-welded to form a lifting ring. During the process of loading and unloading the furnace for heat treatment and cooling in the cooling medium, the lifting ring is hung on the lifting hook to transfer the material section to be tested.

2. A method for improving the overall heat treatment effect of a steel material segment according to claim 1, characterized in that: The size of the material section to be measured is Φ120-400mm and the length is 120-300mm.

3. A method for improving the overall heat treatment effect of a steel material segment according to claim 2, characterized in that: Different steel rings are provided according to the size specifications of the material section to be measured, and the steel rings are circular, elliptical or semi-elliptical.

4. A method for improving the overall heat treatment effect of a steel material segment according to claim 3, characterized in that: When the diameter of the material segment to be measured is Φ120-180mm, an elliptical steel ring is used for welding. The major axis*thickness*minor axis size of the elliptical steel ring is Φ50*5*40mm. The elliptical steel ring is placed at the center of the end of the cross section on one side of the material segment to be measured with the major axis parallel to the cross section of the material segment to be measured for welding.

5. A method for improving the overall heat treatment effect of a steel material segment according to claim 3, characterized in that: When the diameter of the material section to be measured is Φ180-250 mm, a circular steel ring is used for welding, and the diameter*thickness size of the circular steel ring is Φ50*5 mm.

6. A method for improving the overall heat treatment effect of a steel material segment according to claim 3, characterized in that: When the diameter of the material section to be measured is Φ250-400mm, a semi-elliptical steel ring is used for welding. The size of the major axis * thickness * 1 / 2 minor axis of the semi-elliptical steel ring is Φ108*10*40mm. The semi-elliptical steel ring is placed at the center of the end of the cross section on one side of the material section to be measured with the major axis parallel to the cross section of the material section to be measured for welding.

7. A method for improving the overall heat treatment effect of a steel material segment according to any one of claims 1 to 6, characterized in that: The diameter of the disc is 6.5 mm, the length is 300-1000 mm, and the length of the butt welding at both ends of the disc is 50 mm.

8. A method for improving the overall heat treatment effect of a steel material segment according to claim 7, characterized in that: The material of the steel ring is No. 20 steel or Q235B steel, and the material of the hanging ring is Q195 steel or Q235 steel.

9. A method for improving the overall heat treatment effect of a steel material segment according to claim 8, characterized in that: The distance between the steel ring and the lifting iron hook during the lifting and transfer process is 1 to 1.5 times the length of the material section to be measured.

10. A method for improving the overall heat treatment effect of a steel material segment according to claim 9, characterized in that: The cooling medium is water, oil or quenching liquid.

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