Mg-deoxidized high-performance 75cr1 steel and production process thereof

Abstract

The application discloses Mg-deoxidized high-performance 75Cr1 steel and a production process thereof, and belongs to the technical field of metallurgy. The 75Cr1 steel comprises the following elements in mass fraction: C: 0.72% to 0.75%, Si: 0.25% to 0.30%, Mn: 0.65% to 0.75%, Cr: 0.45% to 0.60%, P: less than or equal to 0.035%, S: less than or equal to 0.035%, Mg: 0.001% to 0.003%, and Al: 0.01% to 0.03%. After the magnesium is used to treat inclusions in the steel, the influence of the inclusions on the fatigue performance of the material as fatigue crack sources is obviously reduced, and the fatigue life is increased by 15% under the same fatigue load condition. The magnesium-aluminum alloy core-spun thread is added in a mode, so that the problems of molten steel spattering and low yield caused by the too active magnesium element can be effectively avoided.

Description

Technical Field

[0001] This invention belongs to the field of metallurgical technology, specifically a Mg-deoxidized high-performance 75Cr1 steel and its production process. Background Technology

[0002] 75Cr1 steel is widely used in various blades and saw blades due to its excellent hardness, hardenability, wear resistance, and toughness that meets various application requirements. Because 75Cr1 steel must be able to operate stably at high speeds, high requirements are placed on its mechanical and fatigue properties. It is generally believed that the fatigue performance of a material is closely related to its internal inclusions; large inclusions can act as fatigue crack initiation sites under cyclic loading, which is a significant factor. Therefore, controlling the morphology, size, and distribution of inclusions in the steel is expected to further improve its fatigue resistance. Furthermore, the good wear resistance and strength of 75Cr1 steel also depend on its internal pearlite lamellar spacing and the original austenite grain size. Summary of the Invention

[0003] The purpose of this invention is to provide a Mg-deoxidized high-performance 75Cr1 steel to solve the problems mentioned in the prior art.

[0004] The present invention also provides a production process for the above-mentioned Mg-deoxidized high-performance 75Cr1 steel.

[0005] Specifically, the first aspect of this invention provides a Mg-deoxidized high-performance 75Cr1 steel:

[0006] It is composed of the following elements in weight fractions: C: 0.72%–0.75%, Si: 0.25%–0.30%, Mn: 0.65%–0.75%, Cr: 0.45%–0.60%, P≤0.035%, S≤0.035%, Mg: 0.001%–0.003%, Al: 0.01%–0.03%, with the balance being Fe and unavoidable impurities.

[0007] Magnesium (Mg) is a strong deoxidizing element that can be used for deoxidation and desulfurization to improve the cleanliness of steel. Adding trace amounts of magnesium can improve the type of inclusions, making them finer and more dispersed, and thus increasing the purity of the steel. The microalloying effect of magnesium can refine the grain structure and improve mechanical properties. Therefore, the Mg content in this invention should be controlled between 0.001% and 0.003%.

[0008] Al (Al) acts as an effective deoxidizer, helping to remove oxygen from steel. This helps reduce oxide formation, improves steel quality, and reduces the formation of bubbles and inclusions, thus increasing steel purity. Aluminum also functions as a grain refiner in steelmaking. It helps control grain size and shape, resulting in more uniform and finer grains in the steel. This improves the strength and toughness of the steel. Therefore, the Al content in this invention should be controlled between 0.01% and 0.03%.

[0009] A second aspect of this invention provides a production process for Mg-deoxidized high-performance 75Cr1 steel, comprising the following steps:

[0010] S1, BOF furnace smelting;

[0011] S2, LF furnace refining, wherein the LF furnace refining process is to make reducing slag refining and carry out alloying operation, the slag binary basicity CaO / SiO2 ratio is 3 to 5, and the TFe in the slag is ≤0.5%;

[0012] After S3 and Ca treatment, Mg treatment is carried out. After refining in the LF furnace, the sulfur content in the steel is controlled at 0.002% to 0.004%, and the oxygen content is controlled at 0.001% to 0.002%. After vacuum degassing in the LF furnace, magnesium-aluminum alloy cored wire is added.

[0013] S4, production and processing of arc-shaped continuous casting machine.

[0014] According to one technical solution of the production process technology of Mg-deoxidized high-performance 75Cr1 steel of the present invention, it has at least the following beneficial effects:

[0015] Due to the high vapor pressure of magnesium in high-temperature steel, the yield of magnesium added to steel is extremely low. Using magnesium-aluminum alloy cored wire can effectively improve the magnesium yield. This invention improves the nucleation rate of magnesium oxides by treating the magnesium alloy in an LF furnace before adding it to the molten steel. The strong deoxidizing ability of magnesium treatment can reduce the total oxygen content in the molten steel from 0.002% to below 0.001%.

[0016] The inclusions in molten steel treated with Mg according to this invention are transformed from large-sized alumina into magnesium aluminum spinel, with CaS coating the surface to form a core-shell structure. The inclusion refinement effect is significant, and the distribution is more dispersed. Inclusions larger than 10 μm account for <12%.

[0017] During the pearlite phase transition, the presence of small inclusions effectively hinders the long-range diffusion of carbon atoms, causing the carbon elements to undergo the pearlite transformation before they have time to diffuse, thereby reducing the interlamellar spacing of the pearlite.

[0018] By incorporating magnesium-aluminum alloy cored wire, problems such as steel splashing and low yield caused by the high reactivity of magnesium can be effectively avoided. The addition of aluminum, a relatively less reactive alloying element with a certain deoxidizing ability, can suppress the vaporization reaction rate of metallic magnesium and increase its solubility. Furthermore, the large oxides formed by aluminum can float to the surface under the action of magnesium alloy bubbles, thus not harming the quality of the steel.

[0019] According to some embodiments of the present invention, the binary basicity of the slag, CaO / SiO2 ratio, is 5.

[0020] The control of binary basicity affects the adsorption and separation effect of slag on inclusions and oxides. Appropriate binary basicity helps to effectively adsorb and remove impurities and improve the quality of steel.

[0021] According to some embodiments of the present invention: the magnesium-aluminum alloy cored wire is a combination of Al, Mg and Fe, wherein the weight percentages are: Al: 45% to 65%, Mg: 15% to 30%, and the balance is Fe.

[0022] Magnesium and aluminum act as deoxidizers, removing oxygen and sulfur from molten steel. Controlling the appropriate ratio of magnesium to aluminum content can improve deoxidation and desulfurization effects, thereby enhancing the purity of the steel.

[0023] On the other hand, the alloying of magnesium and aluminum helps to refine the grains and improve the grain uniformity of steel. An appropriate content ratio can promote grain formation, thereby improving the mechanical properties of steel.

[0024] According to some embodiments of the present invention: the magnesium-aluminum alloy cored wire is added to the molten steel by a wire feeding method, the core weight of the magnesium-aluminum alloy cored wire is 190 g / m to 240 g / m, the feeding amount of the magnesium-aluminum alloy cored wire is 1.8 m / ton of steel to 2 m / ton of steel, and the wire feeding speed is controlled at 1.5 m / s to 2.5 m / s.

[0025] Controlling the amount, method, and timing of magnesium-aluminum alloy cored wire addition can achieve better steel cleanliness, improved steel toughness, and enhanced product performance.

[0026] According to some embodiments of the present invention, the tapping temperature of the BOF furnace is 1650℃~1665℃.

[0027] According to some embodiments of the present invention, the tapping temperature of the BOF furnace is 1650℃~1655℃.

[0028] According to some embodiments of the present invention, the tapping temperature of the BOF furnace is 1655℃~1665℃.

[0029] Appropriate tapping temperature helps ensure the uniformity of the chemical composition of steel, prevents compositional deviations due to premature solidification, and helps ensure that various elements can dissolve in the steel at appropriate levels, avoiding the formation of unnecessary solid phases at low temperatures.

[0030] According to some embodiments of the present invention, the carbon content of the steel produced by the BOF furnace smelting is 0.65% to 0.75%.

[0031] According to some embodiments of the present invention, the carbon content of the steel produced by the BOF furnace smelting is 0.65% to 0.70%.

[0032] According to some embodiments of the present invention, the carbon content of the steel produced by the BOF furnace smelting is 0.70% to 0.75%.

[0033] Controlling the carbon content in steel production can adjust the steel's strength and hardness, helping to balance its toughness and ductility. Excessive carbon content may increase the steel's brittleness, while low carbon content may lead to a decrease in its ductility.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] This invention utilizes magnesium to treat inclusions in steel, which significantly reduces the impact of inclusions as fatigue crack initiation sites on the material's fatigue performance, resulting in a 15% increase in fatigue life under the same fatigue load conditions. Attached Figure Description

[0036] Figure 1 This is a typical inclusion morphology in Example 1;

[0037] Figure 2 The metallographic morphology is shown in Example 1;

[0038] Figure 3 This is a typical inclusion morphology in Example 2;

[0039] Figure 4 The metallographic morphology in Example 2;

[0040] Figure 5 Typical inclusion morphology in Comparative Example 1;

[0041] Figure 6 The metallographic morphology is shown in Comparative Example 1. Detailed Implementation

[0042] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0043] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0044] Example 1

[0045] In this embodiment, the Mg-deoxidized high-performance 75Cr1 steel is composed of the following elements by weight fraction:

[0046] C: 0.72%, Si: 0.25%, Mn: 0.70%, Cr: 0.450%, P≤0.033%, S≤0.033%, Mg: 0.001%, Al: 0.01%, balance Fe and unavoidable impurities.

[0047] The Mg-deoxidized high-performance 75Cr1 steel in this embodiment is produced according to the following steps:

[0048] S1, BOF furnace smelting, the tapping temperature of BOF furnace smelting is 1650℃, and the carbon content of the tapped steel is 0.65%;

[0049] S2 and LF furnaces are used for refining, producing reducing slag and carrying out alloying operations. The slag has a binary basicity of CaO / SiO2 ratio of 5 and TFe ≤ 0.5% in the slag.

[0050] After refining in the S3 and LF furnaces, the sulfur content in the steel is controlled at 0.002% and the oxygen content at 0.001%. Magnesium-aluminum alloy cored wire is added to the molten steel using a wire feeding method. The weight percentage of the magnesium-aluminum alloy cored wire is: Al: 65%, Mg: 15%, with the balance being Fe. The core weight of the magnesium-aluminum alloy cored wire is 240 grams per meter. The feeding rate of the magnesium-aluminum alloy cored wire is 1.8 meters per ton of steel, and the wire feeding speed is controlled at 2.5 meters per second.

[0051] S4 is produced using an arc-shaped continuous casting machine.

[0052] Elemental analysis of inclusions inside the cast billet, such as Figure 1 As shown, the inclusions are relatively small, forming a composite inclusion with CaS encapsulation and Mg-Al-O spinel as the core. Most of the inclusions are spherical, approximately 2 micrometers in size, and are relatively dispersed. Analysis of the metallographic structure of the hot-rolled plate reveals that, as... Figure 2 As shown, the average grain size of the pearlite after magnesium treatment is about 24 micrometers, and the average interlamellar spacing of the cementite within the pearlite is about 0.34 micrometers.

[0053] Example 2

[0054] In this embodiment, the Mg-deoxidized high-performance 75Cr1 steel is composed of the following elements by weight fraction:

[0055] C: 0.75%, Si: 0.28%, Mn: 0.68%, Cr: 0.60%, P≤0.034%, S≤0.034%, Mg: 0.003%, Al: 0.03%, balance Fe and unavoidable impurities.

[0056] The Mg-deoxidized high-performance 75Cr1 steel in this embodiment is produced according to the following steps:

[0057] S1, BOF furnace smelting, the tapping temperature of BOF furnace smelting is 1665℃, and the carbon content of the tapped steel is 0.75%;

[0058] S2 and LF furnaces are used for refining, producing reducing slag and carrying out alloying operations. The slag has a binary basicity of CaO / SiO2 ratio of 5 and TFe ≤ 0.5% in the slag.

[0059] After refining in the S3 and LF furnaces, the sulfur content in the steel is controlled at 0.004% and the oxygen content at 0.002%. Magnesium-aluminum alloy cored wire is added to the molten steel using a wire feeding method. The weight percentage of the magnesium-aluminum alloy cored wire is: Al: 45%, Mg: 30%, with the balance being Fe. The core weight of the magnesium-aluminum alloy cored wire is 190 grams per meter. The feeding rate of the magnesium-aluminum alloy cored wire is 2 meters per ton of steel, and the wire feeding speed is controlled at 1.5 meters per second.

[0060] S4 is produced using an arc-shaped continuous casting machine.

[0061] Elemental analysis of inclusions inside the cast billet, such as Figure 3 As shown, the inclusions are relatively small, forming a composite inclusion with CaS encapsulation and Mg-Al-O spinel as the core. Most of the inclusions are spherical, approximately 2 micrometers in size, and are relatively dispersed. Analysis of the metallographic structure of the hot-rolled plate reveals that, as... Figure 4 As shown, the average grain size of the pearlite after magnesium treatment is approximately 21 micrometers, and the average interlamellar spacing of the cementite within the pearlite is approximately 0.22 micrometers.

[0062] Comparative Example 1

[0063] In this embodiment, the Mg-deoxidized high-performance 75Cr1 steel is composed of the following elements by weight fraction:

[0064] C: 0.75%, Si: 0.29%, Mn: 0.68%, Cr: 0.60%, P≤0.033%, S≤0.033%, Mg: 0.0026%, Al: 0.03%, balance Fe and unavoidable impurities.

[0065] The Mg-deoxidized high-performance 75Cr1 steel in this embodiment is produced according to the following steps:

[0066] S1, BOF furnace smelting, the tapping temperature of BOF furnace smelting is 1655℃, and the carbon content of the tapped steel is 0.70%;

[0067] S2 and LF furnaces are used for refining, producing reducing slag and carrying out alloying operations. The slag has a binary basicity of CaO / SiO2 ratio of 5 and TFe ≤ 0.5% in the slag.

[0068] After refining in the S3 and LF furnaces, the sulfur content in the steel is controlled at 0.005% and the oxygen content at 0.002%. Magnesium-aluminum alloy cored wire is added to the molten steel using a wire feeding method. The weight percentage of the magnesium-aluminum alloy cored wire is: Al: 45%, Mg: 30%, with the balance being Fe. The core weight of the magnesium-aluminum alloy cored wire is 190 grams per meter. The feeding rate of the magnesium-aluminum alloy cored wire is 3 meters per ton of steel, and the wire feeding speed is controlled at 2 meters per second.

[0069] S4 is produced using an arc-shaped continuous casting machine.

[0070] Elemental analysis of inclusions inside the cast billet, such as Figure 5 As shown, the inclusions are relatively small, forming a composite inclusion with a thick MnS core and Mg-Al-O spinel as the main body. The inclusions are irregular in shape, approximately 3.5 micrometers in size, and relatively diffusely distributed. Analysis of the metallographic structure of the hot-rolled plate reveals that... Figure 6 As shown, the average grain size of the pearlite after magnesium treatment is about 33 micrometers, and the average interlamellar spacing of the cementite within the pearlite is about 0.60 micrometers.

[0071] The above description is merely an example and illustration of the structure of the present invention. Those skilled in the art can make various modifications or additions to the specific embodiments described, or use similar methods to replace them, as long as they do not deviate from the structure of the invention or exceed the scope defined in the claims, all of which should fall within the protection scope of the present invention.

Claims

1. A production process for Mg-deoxidized high-performance 75Cr1 steel, characterized in that, It consists of elements with the following weight fractions: C: 0.72%~0.75%, Si: 0.25%~0.30%, Mn: 0.65%~0.75%, Cr: 0.45%~0.60%, P≤0.035%, S≤0.035%, Mg: 0.001%~0.003%, Al: 0.01%~0.03%, balance being Fe and unavoidable impurities; The process includes BOF furnace smelting, LF furnace refining, and arc continuous casting machine production. The LF furnace refining process involves creating reducing slag and performing alloying operations. The slag has a binary basicity of CaO / SiO2 ratio of 3 to 5, and TFe in the slag is ≤0.5%. After Ca treatment, Mg treatment is performed. After LF furnace refining, the sulfur content in the steel is controlled at 0.002% to 0.004%, and the oxygen content is controlled at 0.001% to 0.002%. After vacuum degassing in the LF furnace, magnesium-aluminum alloy cored wire is added. The magnesium-aluminum alloy cored wire is a combination of Al, Mg and Fe, wherein the weight percentage is: Al: 45%~65%, Mg: 15%~30%, and the balance is Fe; The magnesium-aluminum alloy cored wire is added to the molten steel using a wire feeding method. The core weight of the magnesium-aluminum alloy cored wire is 190 g / m to 240 g / m, the feeding amount of the magnesium-aluminum alloy cored wire is 1.8 m / ton of steel to 2 m / ton of steel, and the wire feeding speed is controlled at 1.5 m / s to 2.5 m / s.

2. The production process of Mg-deoxidized high-performance 75Cr1 steel according to claim 1, characterized in that, The tapping temperature of the BOF furnace is 1650℃~1665℃.

3. The production process of Mg-deoxidized high-performance 75Cr1 steel according to claim 1, characterized in that, The carbon content of the steel produced by the BOF furnace is 0.65% to 0.75%.

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