Preparation method of in-situ regenerated titanium nitride steel-based roller

[0034] Example 1:

[0035] like figure 1 As shown, it is an alloy cast steel BD roll manufactured by the static integral top casting method provided by the present invention, which is suitable for single-stand BD or double-stand BD1, in-situ regenerated titanium nitride steel-based roll preparation. The preparation steps are:

[0036] (1) Modeling: According to the product specifications and processes produced, shape the bottom box for the neck of the lower roll, the cold mold for the roll body, the upper box and the riser for the upper roll neck; bake and dry; and The bottom box, the cold box, the upper box and the riser box are connected in sequence and then assembled (the box is combined);

[0037] (2) Smelting: add each raw material to the intermediate frequency furnace for smelting, slag removal, and then roughly adjust the chemical composition of the original steel-based alloy melt according to the middle and lower limits of the following ranges: C0.6-0.75%, Si0.4-0.8 %, Mn0.5-1.2%, Cr0.8-1.5%, Ni0.2-1.2%, Mo0.2-0.8%, V0.01-0.2%, Al0.02-0.03% and the balance Fe and inevitable (P≤0.03%, S≤0.025%, deoxidized [O]≤0.0015%), adding titanium-containing and nitrogen-containing alloys to Ti and [N] content adjusted to Ti0.02-0.03%, [N]0.02 -0.03%, and then kept at 1580℃ for more than 40 minutes with the electromagnetic stirring of the intermediate frequency furnace, so that the elemental Ti and the [N] in the molten steel fully react with each other to form TiN particles with an equivalent weight of Φ5-20nm;

[0038] (3) Refining: the alloy suspension obtained in step (2) is sent out for refining in an LF refining steel furnace with a bottom blowing nitrogen device, and each chemical component is finely adjusted to the mid-process limit, and adjusted to Ti0.02-0.05 %, while blowing industrial nitrogen from the bottom of the package to make [N] in the molten steel ≥ 0.03-0.04%, and keep blowing nitrogen at 1650 ° C for more than 40 minutes. During the process of liquid mixing and stirring, complete the reaction of elemental Ti and N in the alloy suspension to fully transform to TiN (conversion rate above 90%); form a high melting point (2950℃) dispersed in the superalloy suspension above 1500℃ , high microhardness (1800-2100HV), extremely stable, high wear-resistant phase TiN (titanium nitride) suspended particles with an equivalent diameter of Φ5-20um (while the elemental Ti in the alloy suspension reaches a trace amount); for the above-mentioned particles containing TiN The alloy suspension is subjected to conventional inoculation and metamorphic treatment to obtain an alloy mixed suspension;

[0039] (4) pouring: the pouring temperature is controlled to be about 5°C lower than the traditional superheat value, and the alloy mixed suspension obtained in step (3) is poured by using the static integral top casting method, specifically: in step (3) obtained When the temperature of the alloy mixed suspension is TL liquidus temperature + (35~40) ℃, the alloy mixed suspension is injected from the upper mouth of the riser box along the central axis into the closed roll cavity (the bottom of the lower roll neck box). box + roll body box body cold box + upper roll neck box body upper box + riser box). The pouring speed is controlled by fast pouring on the lower roll neck and roll body, and slow pouring on the upper roll neck and riser to improve the feeding effect. At the same time, the riser is covered with exothermic agent and thermal insulation agent for heat preservation;

[0040] During the solidification process of the roll, the in-situ regenerated TiN tiny particles suspended in the alloy mixed suspension act as the initial nucleation core of the primary austenite phase. The function of uniform structure and refinement of original grain size of castings creates conditions for subsequent heat treatment and improvement of material mechanical properties;

[0041] (5) (diffusion annealing and normalizing + tempering) heat treatment of alloy steel BD rolls: when the temperature of the roll body of the solidified blank roll obtained in step (4) is cooled to 700-800 ° C, hot unpacking (that is, removing the After dropping the bottom box, the cold box, the upper box and the riser box), the hot state enters the high temperature heat treatment furnace, conducts the overall diffusion at 1000-1050 °C, and then air-cools to 600 °C. The furnace is cooled to room temperature, and after the diffusion annealing heat treatment is completed, the rough opening type is processed (leave the allowance required for subsequent heat treatment decarburization, deformation and post-heat roughing), and then normalized at 920-950 ℃ +560-590 ℃ tempering heat treatment, the furnace is cooled to room temperature to enter the rough turning and finishing process after the subsequent heating;

[0042] In the process of diffusion and normalizing heat treatment, when the roll temperature passes the recrystallization transition point (720°C), the tiny dispersed TiN particles distributed in the original solidified casting matrix act as non-uniform nucleation cores, which are different from conventional alloys. For steel materials, the recrystallized nuclei are preferentially nucleated and grown on the surface of TiN particles, which plays a beneficial role in refining the grains. In the case of diffusion at a high temperature above 1000 °C for a long time, the TiN particles also play a role in preventing excessive grains. grow up; the in-situ regenerated titanium nitride particles dispersed on the metal matrix as part of the overall material are completely integrated into the matrix structure to form TiN distributed on the matrix with an area percentage of 0.3-0.8% New alloy cast steel BD rolls in the form of (titanium nitride) particles.

[0043] The final chemical composition of the in-situ regenerated TiN alloy cast steel BD roll obtained in this example is: C0.65%, Si0.45%, Mn0.9%, P≤0.025%, S≤0.008%, Cr1.0%, Ni0 .8%, Mo0.4%, V0.015%, Ti0.035%, [N]≥0.035%, Al0.025%, [O]0.0012%, and the balance Fe and inevitable impurities. The addition of the high-hard wear-resistant phase not only improves the hardness and wear resistance of the roll, but also improves the strength and toughness due to its microstructure refinement. The hardness of the working layer of the actual roll body reaches 45HSD; the tensile strength of the material reaches 1100Mpa. In the case of the same steel grade and the same hardness level, the performance indicators such as tensile strength and elongation toughness are improved by more than 30% compared with the traditional process.

[0044] Example 2:

[0045] like figure 1 As shown, it is a graphite semi-steel BD roll manufactured by the static integral top casting method provided by the present invention, which is suitable for the double stand BD2 and prepared from the raw material of the in-situ regenerated titanium nitride steel-based roll. The specific preparation steps are as follows: :

[0046] (1) Modeling: with Embodiment 1;

[0047] (2) Smelting: This embodiment is different from step (2) of Embodiment 1 in that the chemical composition of the original steel-based alloy melt is adjusted to: C1.2-1.4%, Si0.4-1.0 after slag removal %, Mn0.5-1.2%, Cr0.8-1.5%, Ni0.5-1.5%, Mo0.2-0.8%, V0.01-0.2%, Ti0.02-0.05%, Al0.02-0.03% , [N] 0.02-0.04%, the rest are steel-based alloy materials of Fe, and P, S, [O] as harmful elements are usually P≤0.03%, S≤0.025%, deoxidized [O]≤0.0015% (first Roughly adjust the chemical composition of the alloy according to the lower limit of the process in the intermediate frequency furnace, including Ti to Ti0.02-0.03%, [N]≥0.02-0.03%), and use the electromagnetic stirring of the intermediate frequency furnace at 1580 ° C for more than 40 minutes. , so that elemental Ti and [N] in molten steel are initially combined to form TiN;

[0048] (3) Refining: The difference between this example and the step (3) of Example 1 is that nitrogen blowing is maintained at 1600° C. for more than 40 minutes; the Si content in the finished alloy mixed suspension after conventional inoculation and modification treatment reaches 0.6- 1.5%;

[0049] (4) pouring: adopt the top-casting static integral casting method, and the operation steps are the same as the step (4) of Example 1;

[0050] The difference from alloy steel is that in the process of roll solidification, the in-situ regenerated TiN tiny particles suspended in the alloy mixed suspension are not only the initial nucleation core of the primary austenite phase, but also the pseudo-eutectic carbide phase. and the initial nucleation core of the graphite phase;

[0051](5) Heat treatment of graphite semi-steel BD roll (diffusion + spheroidizing annealing and normalizing + tempering): the difference from step (5) in Example 1 is that the body position of the solidified blank roll obtained in step (4) When the temperature is cooled to 700 ~ 800 ℃, take off the bottom box, cold type, upper box and riser for hot unpacking, and then enter the hot state into the high temperature heat treatment furnace for overall 1050-1100 ℃ diffusion air cooling to the recrystallization transition point ( 550-600 ℃) into the furnace, 780-830 ℃ spheroidizing preparatory heat treatment, then the furnace is cooled to room temperature, after the diffusion + spheroidizing annealing heat treatment is completed, the rough opening type processing is performed (leave the subsequent heat treatment for decarburization, deformation and heat treatment). After the allowance required for roughing), carry out 950-980 ℃ normalizing + 550-580 ℃ tempering heat treatment, and the furnace is cooled to room temperature to enter the subsequent roughing and finishing processes after heating;

[0052] In the process of diffusion + spheroidization and normalizing heat treatment, when the roll temperature passes the recrystallization transition point (720°C), the tiny dispersed TiN particles distributed in the original solidified casting matrix act as non-uniform nucleation cores, distinguishing For conventional graphite semi-steel materials, the recrystallized nuclei preferentially nucleate and grow on the surface of TiN particles, which plays a beneficial role in refining the grains. When the temperature is above 1000 ℃ for a long time, the TiN particles play a role in the diffusion and long-term heat preservation. Prevent the excessive growth of grains; the in-situ regenerated titanium nitride particles dispersed on the metal matrix as part of the overall material are completely integrated into the matrix structure to form particles distributed on the matrix with an area percentage of 0.3- New graphite semi-steel BD roll in the form of 0.8% TiN (titanium nitride) particles.

[0053] Different from alloy steel materials, in the process of diffusion heat treatment, in addition to eliminating intergranular segregation, another important role is to break the as-cast primary network carbide and optimize the carbide morphology; the normalizing + tempering process is not only to refine the crystal Outside the grains, the alloy dissolved in supersaturated austenite is precipitated in the form of granular secondary carbides, and TiN particles also play a role in promoting and catalyzing the optimization of secondary carbides.

[0054] The final chemical composition of the in-situ regenerated TiN graphite semi-steel BD roll obtained in this example is: C1.25%, Si1.3%, Mn0.95%, P0.028%, S0.004%, Cr1.1%, Ni 1.15%, Mo 0.45%, V 0.015%, Ti 0.03%, [N] 0.03%, Al 0.03%, [O] 0.0015%, and the rest is Fe. The hardness of the actual working layer of the roller body reaches 50-53HSD; the tensile strength of the material reaches 1000Mpa. In the case of the same steel grade and the same hardness level, the performance indicators such as tensile strength and elongation toughness are improved by more than 30% compared with the traditional process.

[0055] Example 3:

[0056] like image 3 As shown, it is a kind of graphite semi-steel billet continuous rolling roll prepared by in-situ regeneration of titanium nitride steel-based roll raw material, which is manufactured by the static integral top casting method provided by the present invention. The specific preparation steps are as follows:

[0057] The difference between this example and Example 2 is that the content of each component of the raw material is: C1.4-1.8%, Si0.4-1.0% before inoculation (0.6-1.5 after inoculation)%, Mn0.5-1.2%, Cr0 .8-1.5%, Ni0.5-1.5%, Mo0.2-0.8%, V0.01-0.2%, Ti0.02-0.05%, Al0.02-0.03%, [N]0.03-0.04%, the rest Fe-based steel-based alloy materials, and P and S as harmful elements are usually P≤0.03, S≤0.025, and [O]≤0.0015% after deoxidation (non-BD roll specifications and weights are relatively small, generally roughened in intermediate frequency furnaces) Tuning + fine-tuning, do not use a refining furnace for smelting, but use a refining bag to blow nitrogen. The difference between a refining furnace and a refining bag is that the furnace has a heating function, and the bag only has the function of blowing air without heating. All refining bags do not adjust the alloy composition. But if one production The number of counts is relatively large, and the refining furnace can also be used for smelting, casting multiple rolls in one package);

[0058] Step (5): The difference between this embodiment and the step (5) of Example 2 is that after the solidification, the rolls are cooled to room temperature, cold unpacking is performed, and after rough-opening processing is performed to leave a heat treatment allowance, diffusion + normalization is performed. Fire + tempering heat treatment; tiny dispersed TiN particles distributed in the original solidified casting matrix, in the process of diffusion and normalizing heat treatment, when passing through the recrystallization temperature, as a non-uniform nucleation core on this basis. It further refines the grains and prevents the grains from growing indefinitely at high temperatures.

[0059] The final chemical composition of the graphite semi-steel billet continuous rolling roll of in-situ regenerated TiN obtained in this example is: C1.6%, Si1.35%, Mn0.95%, P0.03%, S0.01%, Cr0.95 %, Ni1.25%, Mo0.5%, V0.015%, Ti0.035%, [N]0.04%, Al0.03%, [O]0.0015%, and the rest are Fe. The hardness of the working layer of the physical roller body reaches 53-55HSD; the tensile strength of the material reaches 785Mpa. In the case of the same steel grade and the same hardness level, the performance indicators such as tensile strength and elongation toughness are improved by more than 30% compared with the traditional process.