Preparation method of low-temperature-resistant alloy steel forged circle

Abstract

The invention discloses a preparation method of a low-temperature-resistant alloy steel forged circle, and relates to the technical field of alloy steel forged circles, and the preparation method comprises the following steps: step S1, preheating treatment of a steel ingot; s2, forging and forming; and S3, heat treatment. The low-temperature-resistant alloy steel forged circle is good in fatigue resistance, good in mechanical property, excellent in low-temperature impact resistance and long in service life.

Description

Technical Field

[0001] The invention relates to the technical field of alloy steel forging round manufacturing, and in particular to a method for preparing low-temperature resistant alloy steel forging round. Background Art

[0002] In the process of industrialization in my country, the most important pillar industry is the steel industry, which has made a huge contribution to the development of my country's national economy. As one of the most common materials in the steel industry, alloy steel forgings are widely used in large port cranes, large offshore floating cranes, climbing gears of offshore oil drilling platforms, mud valve blocks for oil extraction equipment, various heavy-duty transmission shafts, etc. due to their good comprehensive mechanical properties. However, traditional alloy steel forgings are usually manufactured using existing forging and heat treatment methods, and it is difficult for the various performance indicators achieved to meet the use requirements at the same time. Therefore, it is imperative to develop alloy steel forgings with good comprehensive performance and simple preparation process.

[0003] Alloy steel forgings have different performance requirements depending on the application scenario, such as low temperature impact resistance, heat resistance, corrosion resistance, and high strength. Among them, low temperature impact resistance is a necessary condition to ensure the use of alloy steel forgings in low temperature environments, and it has become an important indicator for evaluating the quality of alloy steel forgings. However, the alloy steel forgings on the market still have more or less technical defects such as insufficient fatigue resistance, poor mechanical properties, insufficient low temperature impact resistance, and service life needs to be further extended.

[0004] In order to solve the above problems, the Chinese invention patent with the authorization announcement number CN109536691B discloses a method for preparing a low-temperature impact-resistant CrMo alloy steel forging round, which relates to the technical field of CrMo alloy steel forging processing. The preparation objects include alloy steels with grades of AISI 4130, 4130 and 30CrMo. The process route adopted includes heating the steel ingot to 1180℃~1230℃ in multiple stages, keeping it warm for 3 hours to 6.5 hours, and then forging and forming it at 1200℃~800℃, and air cooling it; then normalizing it at 900±10℃, quenching it in water at 880±10℃, and high-temperature tempering it at 670±10℃, so that the tempered troostite structure with good comprehensive performance is obtained inside the forging round, which effectively solves the technical requirement that the impact toughness Akv in a low temperature environment of -60℃ should reach more than 30J. However, its fatigue resistance still needs to be further improved. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for preparing a low-temperature resistant alloy steel forging circle with good fatigue resistance, good mechanical properties, excellent low-temperature impact resistance and long service life.

[0006] To achieve the above object, the technical solution adopted by the present invention is: a method for preparing a low temperature resistant alloy steel forging circle, comprising the following steps:

[0007] Step S1, preheating of the steel ingot: subjecting the steel ingot to programmed temperature preheating treatment; the steel ingot comprises the following components in weight percentage: C 0.1-0.2%, Si 0.13-0.33%, Cr 1.1-1.8%, Cu 0.1-0.3%, Zr0.03-0.06%, Nb 0.01-0.03%, rare earth elements 0.01-0.03%, Mn 0.65-0.85%, Ni 0.7-1%, B0.001-0.005%, Co 0.08-0.12%, and the balance is Fe and unavoidable impurities;

[0008] Step S2, forging: hoisting the preheated steel ingot to the forging machine to start forging;

[0009] Step S3, heat treatment: heat treatment is performed on the rough forged round product after forging and pressing, and then polishing treatment is performed to obtain a low temperature resistant alloy steel forged round product.

[0010] Preferably, the rare earth elements in step S1 are Sc, Y, and Pr mixed in a mass ratio of (1-3):1:(1-2).

[0011] Preferably, the preheating treatment in step S1 is specifically as follows: heating from room temperature to 550-680°C at a heating rate of 3-5°C / min, keeping warm for 1-2h, then heating to 760-830°C at a heating rate of 5-8°C / min, keeping warm for 1.5-2.5h, then heating to 880-1000°C at a heating rate of 6-9°C / min, keeping warm for 0.6-1.5h, and finally heating to 1200-1250°C at a rate of 8-10°C / min, keeping warm for 4-7h.

[0012] Preferably, the total forging ratio of the forging in step S2 is (2-5):1; the start forging temperature during the forging process is 1190-1260°C, and the final forging temperature is 750-850°C.

[0013] Preferably, the heat treatment in step S3 includes normalizing treatment, quenching treatment and tempering treatment performed sequentially.

[0014] Preferably, the normalizing treatment temperature is 920-960°C, the time is 1-2h, and then cooled in air; the quenching treatment temperature is 700-800°C, and after keeping warm for 1-3h, it is cooled with quenching oil; the tempering treatment is a two-stage tempering treatment, the first stage tempering treatment temperature is 630-700°C, the holding time is 1-2h, and the second stage tempering treatment temperature is 190-230°C, and the holding time is 1-3h. DETAILED DESCRIPTION

[0015] The preferred embodiments of the present invention will be described in detail below.

[0016] A method for preparing a low temperature resistant alloy steel forging circle comprises the following steps:

[0017] Step S1, preheating of the steel ingot: subjecting the steel ingot to programmed temperature preheating treatment; the steel ingot comprises the following components in weight percentage: C 0.1-0.2%, Si 0.13-0.33%, Cr 1.1-1.8%, Cu 0.1-0.3%, Zr0.03-0.06%, Nb 0.01-0.03%, rare earth elements 0.01-0.03%, Mn 0.65-0.85%, Ni 0.7-1%, B0.001-0.005%, Co 0.08-0.12%, and the balance is Fe and unavoidable impurities;

[0018] Step S2, forging: hoisting the preheated steel ingot to the forging machine to start forging;

[0019] Step S3, heat treatment: heat treatment is performed on the rough forged round product after forging and pressing, and then polishing treatment is performed to obtain a low temperature resistant alloy steel forged round product.

[0020] Preferably, the rare earth elements in step S1 are Sc, Y, and Pr mixed in a mass ratio of (1-3):1:(1-2).

[0021] Preferably, the preheating treatment in step S1 is specifically as follows: heating from room temperature to 550-680°C at a heating rate of 3-5°C / min, keeping warm for 1-2h, then heating to 760-830°C at a heating rate of 5-8°C / min, keeping warm for 1.5-2.5h, then heating to 880-1000°C at a heating rate of 6-9°C / min, keeping warm for 0.6-1.5h, and finally heating to 1200-1250°C at a rate of 8-10°C / min, keeping warm for 4-7h.

[0022] Preferably, the total forging ratio of the forging in step S2 is (2-5):1; the start forging temperature during the forging process is 1190-1260°C, and the final forging temperature is 750-850°C.

[0023] Preferably, the heat treatment in step S3 includes normalizing treatment, quenching treatment and tempering treatment performed sequentially.

[0024] Preferably, the normalizing treatment temperature is 920-960°C, the time is 1-2h, and then cooled in air; the quenching treatment temperature is 700-800°C, and after keeping warm for 1-3h, it is cooled with quenching oil; the tempering treatment is a two-stage tempering treatment, the first stage tempering treatment temperature is 630-700°C, the holding time is 1-2h, and the second stage tempering treatment temperature is 190-230°C, and the holding time is 1-3h.

[0025] Due to the application of the above technical solution, the patent of the present invention has the following advantages compared with the prior art: the present invention gives the product the advantages of good fatigue resistance, good mechanical properties, excellent low-temperature impact resistance and long service life through the reasonable design of alloy steel forging round component formula, preheating temperature gradient, forging process and heat treatment process. The preparation method adopted is simple in process, convenient in operation and control, high in preparation efficiency and finished product qualification rate, low in equipment requirements, low in energy consumption and capital investment, and suitable for mass production.

[0026] The present invention will be further described below in conjunction with specific embodiments, but the protection scope of the present invention is not limited thereto:

[0027] Example 1

[0028] This example provides a method for preparing a low temperature resistant alloy steel forging circle, comprising the following steps:

[0029] Step S1, preheating of the steel ingot: subjecting the steel ingot to programmed temperature preheating treatment; the steel ingot comprises the following components in weight percentage: C 0.1%, Si 0.13%, Cr 1.1%, Cu 0.1%, Zr 0.03%, Nb 0.01%, rare earth elements 0.01%, Mn 0.65%, Ni 0.7%, B 0.001%, Co 0.08%, and the balance is Fe and unavoidable impurities;

[0030] Step S2, forging: hoisting the preheated steel ingot to the forging machine to start forging;

[0031] Step S3, heat treatment: heat treatment is performed on the rough forged round product after forging and pressing, and then polishing treatment is performed to obtain a low temperature resistant alloy steel forged round product.

[0032] The rare earth elements in step S1 are Sc, Y, and Pr mixed in a mass ratio of 1:1:1.

[0033] The preheating treatment in step S1 is specifically as follows: heating from room temperature to 550°C at a heating rate of 3°C / min, keeping warm for 1 hour, then heating to 760°C at a heating rate of 5°C / min, keeping warm for 1.5 hours, then heating to 880°C at a heating rate of 6°C / min, keeping warm for 0.6 hours, and finally heating to 1200°C at a rate of 8°C / min, keeping warm for 4 hours.

[0034] The total forging ratio of the forging in step S2 is 2:1; the start forging temperature in the forging process is 1190°C, and the final forging temperature is 750°C; the heat treatment in step S3 includes normalizing, quenching and tempering in sequence; the normalizing temperature is 920°C, the time is 1h, and then cooled in air; the quenching temperature is 700°C, and after keeping warm for 1h, it is cooled with quenching oil; the tempering treatment is a two-stage tempering treatment, the first stage tempering temperature is 630°C, the holding time is 1h, and the second stage tempering temperature is 190°C, and the holding time is 1h.

[0035] Example 2

[0036] This example provides a low temperature resistant alloy steel forging round, which is basically the same as Example 1, except that the steel ingot comprises the following components in weight percentage: C 0.12%, Si 0.16%, Cr 1.3%, Cu 0.15%, Zr 0.04%, Nb 0.015%, rare earth elements 0.015%, Mn 0.7%, Ni 0.8%, B 0.002%, Co 0.09%, the balance being Fe and unavoidable impurities; the rare earth elements in step S1 are Sc, Y, and Pr mixed in a mass ratio of 1.5:1:1.3; the preheating treatment in step S1 is specifically as follows: heating from room temperature to 580°C at a heating rate of 3.5°C / min, keeping warm for 1.2h, then heating to 790°C at a heating rate of 6°C / min, keeping warm for 1.9h, then heating to 920°C at a heating rate of 7°C / min, keeping warm for 0.8h, and finally heating at a rate of 8.5°C / min to 1220°C, and keep warm for 5h; the total forging ratio of the forging in step S2 is 3:1; the start forging temperature in the forging process is 1210°C, and the final forging temperature is 770°C; the temperature of the normalizing treatment is 930°C, and the time is 1.2h; the temperature of the quenching treatment is 730°C, and after keeping warm for 1.5h, it is cooled with quenching oil; the tempering treatment is a two-stage tempering treatment, the temperature of the first stage tempering treatment is 660°C, the holding time is 1.2h, and the temperature of the second stage tempering treatment is 200°C, and the holding time is 1.5h.

[0037] Example 3

[0038] This example provides a low temperature resistant alloy steel forging round, which is basically the same as Example 1, except that the steel ingot comprises the following components in weight percentage: C 0.15%, Si 0.23%, Cr 1.5%, Cu 0.2%, Zr 0.045%, Nb 0.02%, rare earth elements 0.02%, Mn 0.75%, Ni 0.85%, B 0.003%, Co 0.1%, the balance being Fe and unavoidable impurities; the rare earth elements in step S1 are Sc, Y, and Pr mixed in a mass ratio of 2:1:1.5; the preheating treatment in step S1 is specifically as follows: heating from room temperature to 630°C at a heating rate of 4°C / min, keeping warm for 1.5h, then heating to 810°C at a heating rate of 6.5°C / min, keeping warm for 2h, then heating to 940°C at a heating rate of 7.5°C / min, keeping warm for 1.2h, and finally heating to 1 230℃, keep warm for 5.5h; the total forging ratio of the forging in step S2 is 3.5:1; the start forging temperature in the forging process is 1230℃, and the final forging temperature is 800℃; the temperature of the normalizing treatment is 940℃, and the time is 1.5h; the temperature of the quenching treatment is 750℃, and after keeping warm for 2h, it is cooled with quenching oil; the tempering treatment is a two-stage tempering treatment, the temperature of the first stage tempering treatment is 660℃, the holding time is 1.5h, and the temperature of the second stage tempering treatment is 210℃, and the holding time is 2h.

[0039] Example 4

[0040] This example provides a low temperature resistant alloy steel forging round, which is basically the same as Example 1, except that the steel ingot comprises the following components in weight percentage: C 0.18%, Si 0.32%, Cr 1.7%, Cu 0.25%, Zr 0.055%, Nb 0.025%, rare earth elements 0.025%, Mn 0.82%, Ni 0.95%, B 0.004%, Co 0.11%, the balance being Fe and unavoidable impurities; the rare earth elements in step S1 are Sc, Y, and Pr mixed in a mass ratio of 2.5:1:1.8; the preheating treatment in step S1 is specifically as follows: heating from room temperature to 660°C at a heating rate of 4.5°C / min, keeping the temperature for 1.8h, then heating to 820°C at a heating rate of 7.5°C / min, keeping the temperature for 2.3h, then heating to 990°C at a heating rate of 8.5°C / min, keeping the temperature for 1.4h, and finally heating to 990°C at a heating rate of 9.5°C / min. The temperature is raised to 1240°C and kept at this temperature for 6.5 hours; the total forging ratio of the forging in step S2 is 4.5:1; the starting forging temperature during the forging process is 125°C and the final forging temperature is 840°C; the temperature of the normalizing treatment is 950°C and the time is 1.8 hours; the temperature of the quenching treatment is 790°C, kept at this temperature for 2.5 hours and then cooled with quenching oil; the tempering treatment is a two-stage tempering treatment, the temperature of the first stage tempering treatment is 690°C and the holding time is 1.8 hours, and the temperature of the second stage tempering treatment is 220°C and the holding time is 2.5 hours.

[0041] Example 5

[0042] This example provides a low temperature resistant alloy steel forging round, which is basically the same as Example 1, except that the steel ingot comprises the following components in weight percentage: C 0.2%, Si 0.33%, Cr 1.8%, Cu 0.3%, Zr 0.06%, Nb 0.03%, rare earth elements 0.03%, Mn 0.85%, Ni 1%, B 0.005%, Co 0.12%, the balance being Fe and unavoidable impurities; the rare earth elements in step S1 are Sc, Y, and Pr mixed in a mass ratio of 3:1:2; the preheating treatment in step S1 is specifically as follows: heating from room temperature to 680°C at a heating rate of 5°C / min, keeping warm for 2h, then heating to 830°C at a heating rate of 8°C / min, keeping warm for 2.5h, then heating to 1000°C at a heating rate of 9°C / min, keeping warm for 1.5h, and finally heating at a rate of 10°C / min to 1250°C, and keep warm for 7h; the total forging ratio of the forging in step S2 is 5:1; the starting forging temperature in the forging process is 1260°C, and the final forging temperature is 850°C; the temperature of the normalizing treatment is 960°C, and the time is 2h; the temperature of the quenching treatment is 800°C, and after keeping warm for 3h, it is cooled with quenching oil; the tempering treatment is a two-stage tempering treatment, the temperature of the first stage tempering treatment is 700°C, the holding time is 2h, and the temperature of the second stage tempering treatment is 230°C, and the holding time is 3h.

[0043] Comparative Example 1

[0044] This example provides a method for preparing a low-temperature resistant alloy steel forging circle, which is basically the same as Example 1, except that Nb and rare earth elements are not added, and the preheating treatment is specifically to keep the temperature at 1200°C for 4 hours.

[0045] Comparative Example 2

[0046] This example provides a method for preparing a low-temperature resistant alloy steel forging, which is basically the same as Example 1, except that Co and Cu are not added, and there is no tempering treatment during the heat treatment process.

[0047] In order to further illustrate the beneficial technical effects of each product, relevant performance tests were conducted on each product. The test methods refer to the current national standards of my country or conventional methods in this field. The fatigue resistance performance was tested by conducting a constant amplitude fatigue test (maximum load 100MPa, minimum load 20MPa) on the specimens on an Amsler HFP-422 high frequency fatigue testing machine, and the fatigue life was recorded and counted. The test results are shown in Table 1.

[0048] Table 1

[0049] project tensile strength -60℃ impact toughness Fatigue life unit MPa J Ten thousand times Example 1 682 52 14.8 Example 2 687 55 15.1 Example 3 695 60 15.6 Example 4 705 62 15.8 Example 5 712 66 16.2 Comparative Example 1 667 47 12.5 Comparative Example 2 673 44 13.2

[0050] It can be seen from Table 1 that the low-temperature resistant alloy steel forgings produced by the method for preparing low-temperature resistant alloy steel forgings in the embodiment of the present invention have better mechanical properties, low-temperature impact resistance and fatigue resistance, and the combined use of Nb, rare earth elements, Co and Cu, preheating treatment and heat treatment processes are beneficial to improving the above properties.

[0051] The above embodiments are only for illustrating the technical concept and features of the present invention, and their purpose is to enable people familiar with this technology to understand the contents of the present invention and implement them accordingly. They cannot be used to limit the protection scope of the present invention. All equivalent changes or modifications made according to the spirit of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a low temperature resistant alloy steel forging round, characterized in that: The steps include: Step S1, preheating of the steel ingot: subjecting the steel ingot to programmed temperature preheating treatment; the steel ingot comprises the following components in weight percentage: C 0.1-0.2%, Si 0.13-0.33%, Cr 1.1-1.8%, Cu 0.1-0.3%, Zr0.03-0.06%, Nb 0.01-0.03%, rare earth elements 0.01-0.03%, Mn 0.65-0.85%, Ni 0.7-1%, B0.001-0.005%, Co 0.08-0.12%, and the balance is Fe and unavoidable impurities; Step S2, forging: hoisting the preheated steel ingot to the forging machine to start forging; Step S3, heat treatment: heat treatment is performed on the rough forged round product after forging and pressing, and then polishing treatment is performed to obtain a low temperature resistant alloy steel forged round product.

2. The method for preparing low temperature resistant alloy steel forgings according to claim 1, characterized in that: The rare earth elements in step S1 are Sc, Y, and Pr mixed in a mass ratio of (1-3):1:(1-2).

3. The method for preparing low temperature resistant alloy steel forging round according to claim 1, characterized in that: The preheating treatment in step S1 is specifically as follows: heating from room temperature to 550-680°C at a heating rate of 3-5°C / min, keeping warm for 1-2h, then heating to 760-830°C at a heating rate of 5-8°C / min, keeping warm for 1.5-2.5h, then heating to 880-1000°C at a heating rate of 6-9°C / min, keeping warm for 0.6-1.5h, and finally heating to 1200-1250°C at a rate of 8-10°C / min, keeping warm for 4-7h.

4. The method for preparing low temperature resistant alloy steel forging round according to claim 1, characterized in that: The total forging ratio of the forging in step S2 is (2-5):1; the starting forging temperature during the forging process is 1190-1260°C, and the final forging temperature is 750-850°C.

5. The method for preparing low temperature resistant alloy steel forging round according to claim 1, characterized in that: The heat treatment in step S3 includes normalizing treatment, quenching treatment and tempering treatment performed in sequence.

6. The method for preparing low temperature resistant alloy steel forging round according to claim 5, characterized in that: The normalizing treatment is performed at a temperature of 920-960° C. for 1-2 hours, followed by cooling in air.

7. The method for preparing low temperature resistant alloy steel forgings according to claim 5, characterized in that: The quenching treatment temperature is 700-800°C, and after keeping the temperature for 1-3 hours, the quenching oil is used for cooling.

8. The method for preparing low temperature resistant alloy steel forging round according to claim 5, characterized in that: The tempering treatment is a two-stage tempering treatment, the temperature of the first stage tempering treatment is 630-700° C., the insulation time is 1-2 hours, and the temperature of the second stage tempering treatment is 190-230° C., the insulation time is 1-3 hours.