Production and preparation method for smelting 20Cr on section of 320mm*415mm casting blank

Abstract

The invention discloses a production and preparation method for smelting 20Cr on the section of a 320mm * 415mm casting blank. The production and preparation method comprises the following steps: a steelmaking process: molten iron pretreatment, converter treatment, refining, VD vacuum treatment, continuous casting and slow cooling; the steel rolling technological process comprises the steps of casting blank heating, high-pressure water dephosphorization, rolling through a phi 850 cogging mill, rolling through a 4 continuous rolling unit, saw cutting, slow cooling in a slow cooling pit, checking, coping, bundling, warehousing and delivery, wherein the casting blank heating temperature is controlled to be 1220-1260 DEG C, and the heating time is 3.5-4 hours; the initial rolling temperature is larger than or equal to 1150 DEG C and smaller than or equal to 1180 DEG C, and the compression ratio of a phi 850 cogging mill is larger than 2.0; the finish rolling temperature is greater than or equal to 900 DEG C and less than or equal to The burial pit entering temperature is greater than or equal to 460 DEG C; the slow cooling pit outlet temperature is less than or equal to 80 DEG C; through reasonable setting of steelmaking and continuous casting process parameters, the macroscopic structure defects of the casting blank are effectively reduced, the quality of the casting blank is improved, and a guarantee is provided for subsequent rolling and user use.

Description

Technical Field

[0001] The invention relates to the technical field of material metallurgy, and in particular to a production method for smelting 20Cr with a 320mm×415mm casting section. Background Art

[0002] 20Cr steel is mainly used to manufacture machine tool gearbox gears, gear shafts, cams, piston pins, etc., so it is required to have strong surface wear resistance and impact load resistance. 20Cr is a low-carbon alloy structural steel and belongs to the hypoeutectic range. During the continuous casting process, the volume shrinkage of α ferrite will cause cracks on the surface of the ingot. In addition, the chemical composition of 20Cr contains higher Mn and Cr. As the cooling rate increases, greater internal stress will be generated, resulting in tensile stress in the weak places of the continuous casting ingot shell, and cracks will appear on the surface of the ingot.

[0003] The cross-sectional size of the 320mm×415mm ingot is relatively large. If the pulling speed, superheat and cooling speed are not matched during the continuous casting process, a large amount of porosity and shrinkage holes will occur in the ingot, affecting the quality of the subsequent rolled products and the stability of the quality of the finished products processed by users.

[0004] 20Cr is mainly used to manufacture various parts of machinery, and a large amount of cutting processing is required afterwards, so the cutting performance of the product is also very important. In order to better carry out subsequent cutting processing, a certain amount of S element needs to be added according to user needs. S is a hot brittle element, and adding it to steel will cause micro cracks in the casting. Summary of the invention

[0005] The purpose of the present invention is to provide a production and preparation method for smelting 20Cr with a 320mm×415mm ingot cross section, which can effectively reduce the macroscopic structural defects of the ingot by reasonably setting the steelmaking and continuous casting process parameters, improve the ingot quality and provide guarantee for subsequent rolling and user use.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] The present invention provides a production method for smelting 20Cr with a 320mm×415mm ingot cross section, comprising:

[0008] Steelmaking process: molten iron pretreatment - converter - refining - VD vacuum treatment - continuous casting - slow cooling; among them:

[0009] 1) The molten iron is subjected to desulfurization treatment, and the sulfur content of the molten iron after desulfurization is less than 0.010%;

[0010] 2) After desulfurization, the slag is removed and the surface of the molten iron becomes mirror-like;

[0011] 3) The total loading amount of molten iron and scrap steel is 100±10 tons;

[0012] 4) The converter oxygen lance control adopts low-high-low or high-low-high-low control, and the oxygen flow rate is 17000-32000m 3 / h, gun position 1.3-2.0m;

[0013] 5) Single slag or double slag is used according to the molten iron conditions, and the end point basicity is controlled at 2.7-3.5;

[0014] 6) The control target of converter endpoint: C ≥ 0.06%, molten steel temperature T ≥ 1600 ° C, add 150-200 kg of dolomite thick slag before tapping, and prevent slag from tapping;

[0015] 7) Steel is deoxidized by aluminum, and aluminum iron, ferrosilicon, ferromanganese, high carbon ferrochrome and carburizer are used for deoxidation and alloying;

[0016] 8) After the refining is powered on and heated for 5-10 minutes, temperature measurement and sampling are carried out, and Al is controlled at ≤0.010% to ensure good slag fluidity and white slag color;

[0017] 9) Use ferrosilicon and ferromanganese to adjust and control the composition according to the test results of the samples;

[0018] 10) The refining temperature is controlled between 1630 and 1650°C;

[0019] 11) Refining time ≥45min, white slag time ≥20min;

[0020] 12) VD vacuum degree ≤ 100Pa; argon gas flow rate is controlled at 150-500NL / min, based on the actual argon blowing effect, to prevent molten steel from overflowing; deep vacuum treatment time ≥ 12min;

[0021] 13) Soft blowing time ≥ 15min, the molten steel surface does not boil;

[0022] 14) After VD treatment, feed calcium wire, break vacuum to measure temperature and take samples, feed sulfur wire for 100 meters, blow argon for 10 minutes to feed silicon calcium wire;

[0023] 15) VD off-site temperature is controlled between 1545-1560℃;

[0024] 16) Continuous casting adopts protective pouring, and the superheat is ≤30℃;

[0025] 17) The crystallizer cooling water flow rate is controlled at 150m3 / h and the flow rate is controlled at 9-12m / s;

[0026] 18) The secondary cooling water is controlled by intercooling;

[0027] 19) The pulling speed is controlled between 0.55-0.60m / min;

[0028] 20) Slow cooling time ≥ 48 hours;

[0029] Steel rolling process: billet heating - high-pressure water dephosphorization - Ф850 billet opening machine - Ф700mm×3+Ф550mm×4 continuous rolling mill - sawing - slow cooling in cooling pit - inspection - grinding - bundling - storage - delivery; including:

[0030] The heating temperature of the casting is controlled between 1220-1260℃ and the heating time is between 3.5-4 hours;

[0031] 1150℃≤rolling temperature≤1180℃, compression ratio of Ф850 billet mill is greater than 2.0;

[0032] 900℃≤final rolling temperature≤940℃;

[0033] The temperature of the slow cooling pit is ≥460℃;

[0034] The temperature out of the slow cooling pit is ≤80℃.

[0035] Furthermore, the chemical composition mass percentage is: C: 0.19% to 0.21%, Si: 0.25% to 0.30%, Mn: 0.70% to 0.75%, P≤0.020%, S: 0.017 to 0.030%, Cr: 0.80% to 0.90%, and the rest is Fe and other trace impurity elements.

[0036] Furthermore, samples were taken from the slow cooling pit for low-magnification hot acid testing, and the center porosity was ≤0.5, the center shrinkage cavity was ≤0.5, and the center crack was ≤0.5.

[0037] Furthermore, the chemical composition mass percentage is: C: 0.20%, Si: 0.27%, Mn: 0.74%, P0.014%, S: 0.024%, Cr: 0.85%, and the rest is Fe and other trace impurity elements.

[0038] Furthermore, its chemical composition by mass percentage is: C: 0.19%, Si: 0.27%, Mn: 0.71%, P0.015%, S: 0.025%, Cr: 0.84%, and the rest is Fe and other trace impurity elements.

[0039] Furthermore, its chemical composition by mass percentage is: C: 0.19%, Si: 0.26%, Mn: 0.73%, P0.013%, S: 0.028%, Cr: 0.86%, and the rest is Fe and other trace impurity elements.

[0040] Furthermore, the sulfur-containing 20Cr square steel produced with a 320mm×415mm ingot section has a good internal structure.

[0041] Compared with the prior art, the beneficial technical effects of the present invention are:

[0042] Take samples from the slow cooling pit for low-power hot acid inspection, and the results are as follows: center looseness ≤ 0.5 level, center shrinkage ≤ 0.5 level, center crack ≤ 0.5 level. In practice, the center looseness is 0 level, the center shrinkage is 0 level, and the center crack is 0 level. DETAILED DESCRIPTION

[0043] The present invention is further described below by means of specific examples. The examples are only for the purpose of explanation, and the protection scope of the present invention is not limited to these examples.

[0044] The present invention will be further described below:

[0045] Table 1 is a list of chemical compositions and weight percentages of various embodiments of the present invention.

[0046] Table 2 shows the converter process parameter control of the steelmaking process in various embodiments of the present invention.

[0047] Table 3 shows the refining process parameter control of the steelmaking process of various embodiments of the present invention.

[0048] Table 4 shows the continuous casting process parameter control of the steelmaking process of various embodiments of the present invention.

[0049] Table 5 shows the rolling process control parameters of various embodiments of the present invention.

[0050] Table 6 shows the low-power test results of hot acid in various embodiments of the present invention.

[0051] Table 1 is a list of chemical compositions and weight percentages of various embodiments of the present invention.

[0052]

[0053]

[0054] Table 2 shows the converter process parameters of the steelmaking process of various embodiments of the present invention.

[0055]

[0056] Table 3 shows the refining process parameters of the steelmaking process of various embodiments of the present invention.

[0057]

[0058] Table 4 shows the continuous casting process parameters of the steelmaking process of various embodiments of the present invention.

[0059]

[0060] Table 5 shows the rolling process control parameters of various embodiments of the present invention.

[0061]

[0062] Table 6 shows the low-power test results of hot acid in various embodiments of the present invention.

[0063]

[0064] From the above table, we can know that the sulfur-containing 20Cr square steel produced with 320mm×415mm ingot section has a good internal structure.

[0065] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A production method for smelting 20Cr with a 320mm×415mm ingot cross section, characterized in that: include: Steelmaking process: molten iron pretreatment - converter - refining - VD vacuum treatment - continuous casting - slow cooling; among them: 1) The molten iron is subjected to desulfurization treatment, and the sulfur content of the molten iron after desulfurization is less than 0.010%; 2) After desulfurization, the slag is removed and the surface of the molten iron becomes mirror-like; 3) The total loading amount of molten iron and scrap steel is 100±10 tons; 4) The converter oxygen lance control adopts low-high-low or high-low-high-low control, and the oxygen flow rate is 17000-32000m 3 / h, gun position 1.3-2.0m; 5) Single slag or double slag is used according to the molten iron conditions, and the end point basicity is controlled at 2.7-3.5; 6) The control target of converter endpoint: C ≥ 0.06%, molten steel temperature T ≥ 1600 ° C, add 150-200 kg of dolomite thick slag before tapping, and prevent slag from tapping; 7) Steel is deoxidized by aluminum, and aluminum iron, ferrosilicon, ferromanganese, high carbon ferrochrome and carburizer are used for deoxidation and alloying; 8) After the refining is powered on and heated for 5-10 minutes, temperature measurement and sampling are carried out, and Al is controlled at ≤0.010% to ensure good slag fluidity and white slag color; 9) Use ferrosilicon and ferromanganese to adjust and control the composition according to the test results of the samples; 10) The refining temperature is controlled between 1630 and 1650°C; 11) Refining time ≥45min, white slag time ≥20min; 12) VD vacuum degree ≤ 100Pa; argon gas flow rate is controlled at 150-500NL / min, based on the actual argon blowing effect, to prevent molten steel from overflowing; deep vacuum treatment time ≥ 12min; 13) Soft blowing time ≥ 15min, the molten steel surface does not boil; 14) After VD treatment, feed calcium wire, break vacuum to measure temperature and take samples, feed sulfur wire for 100 meters, blow argon for 10 minutes to feed silicon calcium wire; 15) VD off-site temperature is controlled between 1545-1560℃; 16) Continuous casting adopts protective pouring, and the superheat is ≤30℃; 17) The crystallizer cooling water flow rate is controlled at 150m3 / h and the flow rate is controlled at 9-12m / s; 18) The secondary cooling water is controlled by intercooling; 19) The pulling speed is controlled between 0.55-0.60m / min; 20) Slow cooling time ≥ 48 hours; Steel rolling process: billet heating - high-pressure water dephosphorization - Ф850 billet opening machine - Ф700mm×3+Ф550mm×4 continuous rolling mill - sawing - slow cooling in cooling pit - inspection - grinding - bundling - storage - delivery; including: The heating temperature of the casting is controlled between 1220-1260℃ and the heating time is between 3.5-4 hours; 1150℃≤rolling temperature≤1180℃, compression ratio of Ф850 billet mill is greater than 2.0; 900℃≤final rolling temperature≤940℃; The temperature of the slow cooling pit is ≥460℃; The temperature out of the slow cooling pit is ≤80℃.

2. The method for producing 20Cr with a 320 mm × 415 mm ingot cross section according to claim 1, characterized in that: Its chemical composition by mass percentage is: C: 0.19% ~ 0.21%, Si: 0.25% ~ 0.30%, Mn: 0.70% ~ 0.75%, P ≤ 0.020%, S: 0.017 ~ 0.030%, Cr: 0.80% ~ 0.90%, and the rest is Fe and other trace impurity elements.

3. The method for producing 20Cr with a 320 mm × 415 mm ingot cross section according to claim 1, characterized in that: Take samples from the slow cooling pit for low-power hot acid inspection, and the center porosity is ≤0.5, the center shrinkage cavity is ≤0.5, and the center crack is ≤0.

5.

4. The method for producing 20Cr with a 320 mm x 415 mm ingot cross section according to claim 2, characterized in that: Its chemical composition by mass percentage is: C: 0.20%, Si: 0.27%, Mn: 0.74%, P 0.014%, S: 0.024%, Cr: 0.85%, and the rest is Fe and other trace impurity elements.

5. The method for producing 20Cr with a 320 mm x 415 mm ingot cross section according to claim 2, characterized in that: Its chemical composition by mass percentage is: C: 0.19%, Si: 0.27%, Mn: 0.71%, P 0.015%, S: 0.025%, Cr: 0.84%, and the rest is Fe and other trace impurity elements.

6. The method for producing 20Cr with a 320 mm x 415 mm ingot cross section according to claim 2, characterized in that: Its chemical composition by mass percentage is: C: 0.19%, Si: 0.26%, Mn: 0.73%, P 0.013%, S: 0.028%, Cr: 0.86%, and the rest is Fe and other trace impurity elements.

7. The method for producing 20Cr with a 320 mm x 415 mm ingot cross section according to claim 1, characterized in that: The sulfur-containing 20Cr square steel produced with a 320mm×415mm ingot section has a good internal structure.

Images