CN112553405A

CN112553405A - Control method for improving flaw detection qualification rate of steel for automobile motor claw pole

Info

Publication number: CN112553405A
Application number: CN202011363249.0A
Authority: CN
Inventors: 沙鹏飞; 徐乐钱; 庞卓纯; 李大明; 沈艳; 林俊; 万文华; 叶玉奎
Original assignee: Zenith Steel Group Co Ltd; Changzhou Zenith Special Steel Co Ltd
Current assignee: Zhongtian Iron And Steel Group Huai'an New Materials Co ltd; Zenith Steel Group Co Ltd; Changzhou Zenith Special Steel Co Ltd
Priority date: 2020-11-27
Filing date: 2020-11-27
Publication date: 2021-03-26
Anticipated expiration: 2040-11-27
Also published as: CN112553405B

Abstract

The invention relates to the technical field of steel for an automobile claw pole, in particular to a control method for improving the flaw detection qualification rate of the steel for the automobile claw pole. The method enhances desulfurization, improves Mn/S, reduces the crack sensitivity of the casting blank, and reduces the probability of generating axial center crystal tip cracks; by optimizing the continuous casting parameter specific water quantity, the drawing speed and the proportion of secondary cooling water, and by trying under electric stirring, final stirring and light pressing and matching with sampling to carry out low power analysis, the steel rolling heating, initial rolling and final rolling temperatures are adjusted, so that the low power center defects are greatly improved, the defect rating is reduced, the defect rate of failure of internal damage during flaw detection is obviously reduced, part of furnace flaw detection is completely qualified, the failure loss is effectively reduced, the on-site production efficiency is improved, the on-site management difficulty is reduced, and the good cost reduction and efficiency improvement effects are achieved.

Description

Control method for improving flaw detection qualification rate of steel for automobile motor claw pole

Technical Field

The invention relates to the technical field of steel for an automobile claw pole, in particular to a control method for improving the flaw detection qualification rate of the steel for the automobile claw pole.

Background

Along with the vigorous development of the automobile industry, the requirements of a host factory on an automobile generator are higher and higher, and the requirements are mainly reflected in two aspects: on one hand, the power and the generated energy of the automobile generator are required to be continuously improved due to the power consumption requirements of various electronic equipment in the automobile; on the other hand, the automobile generator is required to continuously reduce the weight of each part due to the requirements of reducing oil consumption, saving energy and reducing emission of the automobile. The claw machine is a key part of an automobile engine, the shape and the electromagnetic performance of the claw machine directly influence the waveform of induced alternating current electromotive force and the power generation capacity of an alternating current generator, the claw pole is mainly produced by a forging method at home and abroad at present, the forming methods mainly comprise hot forging reverse extrusion, hot forging forward extrusion, hot forging and cold forging combined technology and the like, and the systematic research on the internal quality control of raw materials before forging is carried out by a fresh enterprise.

The processing requirement of a subsequent user on raw materials is very high, the internal quality of the round steel is very important for subsequent processing, and if the center of the round steel has an axis intercrystalline crack, the client cracks in the processes of shearing, blanking and forging forming, so that the product is scrapped. In order to enhance quality control and reduce product scrap, raw material manufacturers are required to perform flaw detection on round steel, how to improve the flaw detection qualification rate of the raw materials is a production problem which must be solved by each steel enterprise, unqualified flaw detection can directly influence finishing efficiency, the delivery period is prolonged, meanwhile, the raw materials can be judged or scrapped, quality dissatisfaction payment is generated, and great influence is brought to the sales and benefits of companies.

Disclosure of Invention

The invention provides a control method for improving the flaw detection qualification rate of steel for an automobile claw pole, and aims to improve the low-power quality of a continuous casting billet and the flaw detection qualification rate of round steel, so that the judgment rate, the scrappage and the abnormal claim payment are reduced, the company benefit is increased, and the product competitiveness is improved.

The steel for the automobile claw pole is low-carbon steel, and comprises the following chemical components in percentage by weight: [C] less than or equal to 0.08 percent, 0.15 to 0.35 percent of [ Si ], 0.30 to 0.60 percent of [ Mn ], less than or equal to 0.035 percent of [ P ], less than or equal to 0.035 percent of [ S ], less than or equal to 0.10 percent of [ Cr ], lessthan or equal to 0.10 percent of [ Ni ], and less than or equal to 0.20 percent of [ Cu ].

The target steel grade is easy to generate shear cracking in the blanking process of a user, and the main reason for analyzing the cracking is that the central crack level of the continuous casting blank is too high, the welding is performed to a certain extent after rolling and passes the inspection, but the continuity of metal is reduced because the welding degree is not enough (small holes which are distributed along the longitudinal strip can be still seen at high power), and when the target steel grade is subjected to a larger shearing force, the target steel grade cracks from the defect, and the defect is mainly caused by the defect inheritance of the casting blank, so that the central crack defect of the continuous casting blank is solved as much as possible.

The alloy content of the target steel grade is low, internal defects such as cracks, shrinkage cavities and the like easily occur in the characteristic center of the steel grade, residual molten steel in a liquid cavity at the final stage of solidification is solidified and contracted, surrounding solid blocks the contraction to generate stress, the central molten steel releases latent heat to heat the surrounding solid to expand the solid, and the central crack is caused by the damage of the central area under the combined action of the two. When the secondary cooling condition is not appropriate and the surface temperature of the cast slab at the end of the liquid cavity is raised, the center of the cast slab is further quenched to increase the stress, thereby promoting the formation of a center crack.

In order to improve the internal quality of a casting blank, continuous casting parameters such as water ratio, pulling speed and secondary cooling water ratio are optimized, electric stirring, final stirring and light pressing are tried, sampling is matched for low-power analysis, and the heating, initial rolling and final rolling temperatures of steel rolling are adjusted, so that the low-power central defects are greatly improved, the defect rating is reduced, the failure rate of internal damage during flaw detection is obviously reduced, partial heat flaw detection is completely qualified, the failure loss is effectively reduced, the on-site production efficiency is improved, the on-site management difficulty is reduced, and good cost reduction and efficiency improvement effects are achieved.

The specific production process route of the target steel grade is as follows: molten iron, scrap steel → BOF smelting → LF furnace refining → continuous casting CCM (220mm × 260mm) → cold filling → cold charging → heating furnace heating → high pressure water descaling → rolling (roughing mill train → middle mill train → pre-finishing mill train → KOCKS mill train) → cold bed → cold cutting → cold filling → flaw detection → finishing → inspection → packaging → weighing, marking → warehousing → storage, transportation → delivery.

All steel materials are subjected to ultrasonic flaw detection and are executed according to grade A in GB/T4162 standard quality grades.

The control method provided by the invention comprises LF refining, continuous casting and heating rolling, and specifically comprises the following operations:

(1) the LF enhances the desulfurization operation, and proper amount of slag charge lime and fluorite can be added according to the slag condition and the sulfur content in the argon station; aluminum particles and ferrosilicon powder are used for diffusion deoxidation in refining, and desulfurization is enhanced; ensuring that the refining time is more than or equal to 40 minutes.

The control target of the refining S is less than or equal to 0.002 percent.

Preferably, the refining time is controlled to be 45-60 min, argon blowing operation is carried out after the components and the temperature are properly adjusted, the argon blowing time is 15-25 min, and the proper ladle adjusting temperature is ensured after soft blowing.

And (3) the temperature of the ladle is controlled to be 1623 ℃ according to 1613-.

(2) The continuous casting process adopts a 220mm multiplied by 260mm section for production, the whole process is protected for casting, the low superheat degree and the constant drawing speed are adopted for control, the superheat degree is controlled at 15-30 ℃, the drawing speed is controlled at 0.90m/min, the crystallizer adopts an electromagnetic stirring and non-sinusoidal vibration mode, the secondary cooling adopts a weak cooling water distribution cooling mode, and the electromagnetic stirring and the soft pressing at the tail end are matched.

In the step (2), the electromagnetic stirring parameters of the crystallizer are current (200 +/-10) A and frequency (2.5 +/-0.5) Hz; the electromagnetic stirring parameters at the tail end are current (50 +/-10) A and frequency (6 +/-0.5);

preferably, based on the established solidification heat transfer model, the central solid phase rate distribution of the casting blank at the 1# to 5# rollers under 0.90m/min is calculated according to the cross section of 220mm multiplied by 260mm by considering the current continuous casting process parameters, and the 1# and 2# rollers are selected to carry out soft reduction by considering the proper reduction interval and avoiding the generation of intermediate cracks in the reduction process, wherein the reduction amount is respectively 2mm and 3 mm.

Further, in the weak cold water distribution mode in the step (2), the primary cold water flow is (2000 +/-100) L/min, the water temperature difference is 7.0-9.0, the secondary cold specific water amount is 0.30L/kg, and the water distribution ratio of the foot roller section, the secondary cold first section and the secondary cold second section is 45/40/15.

The continuous casting process is protected, the ladle is protected by argon sealing, the integral stopper rod tundish is adopted as the tundish, the diameter of the water gap is more than or equal to 35m, and the service time of the tundish is less than or equal to 12 hours.

(3) And a low-temperature heating process is adopted, the heating time is controlled, and the raw core cracks of the blank are reduced to be oxidized in a heating furnace to form high-temperature oxidation particles. Meanwhile, a low-temperature finish rolling process is adopted, so that the rolling permeability is increased, the welding of the core part of the rolled material can be effectively enhanced, and the formation of internal damage of the rolled material is reduced.

Preferably, the temperature of the preheating section is 800-900 ℃, the temperature of the first heating section is 950-1050 ℃, the temperature of the second heating section is 1100-1150 ℃, the temperature of the soaking section is 1100-1150 ℃, the initial rolling temperature is 1000-1050 ℃ and the final rolling temperature is 800-850 ℃.

The invention has the beneficial effects that:

the invention improves the internal quality of products and improves the flaw detection qualification rate by optimizing parameters such as continuous casting drawing speed, specific water amount, secondary cooling ratio and the like, matching with a tail end electromagnetic stirring and soft reduction technology, combining Mn/S control and assisting in adjusting the initial rolling temperature and the final rolling temperature of steel rolling.

(1) The desulfurization is enhanced, the Mn/S is improved, the crack sensitivity of the casting blank is reduced, and the probability of generating axial center crystal point cracks is reduced.

(2) The optimization of continuous casting parameters and the adjustment of heating and rolling temperature effectively improve the low-power quality of casting blanks and rolled materials and reduce the defect rating.

(3) The internal damage rate of flaw detection is obviously reduced, part of furnace flaw detection is completely qualified, the unqualified loss is effectively reduced, the on-site production efficiency is improved, the on-site management difficulty is reduced, and the good effects of cost reduction and efficiency improvement are achieved.

(4) The shear cracking caused by the axial center crystal point crack is effectively controlled, the number of the furnace to be changed is greatly reduced, and the objections of users are greatly reduced.

Drawings

FIG. 1 is a macroscopic photograph of a continuous casting slab produced by a conventional process;

FIG. 2 is a photomicrograph of a rolled stock produced by a conventional process;

FIG. 3 is a low magnification photograph of a continuous casting slab produced by the process of the invention;

FIG. 4 is a photomicrograph of a rolled stock produced by the inventive process;

FIG. 5 is a comparison of the center crack ratings of continuous casting slabs produced by the conventional process and the inventive process;

FIG. 6 is a comparison of the ratings of the central shrinkage cavity of the continuous casting slab produced by the conventional process and the inventive process;

FIG. 7 is a comparison of center crack ratings for rolled stock produced by the conventional process and the inventive process;

FIG. 8 is a comparison of the center hole ratings of rolled stock produced by the conventional and inventive processes;

FIG. 9 shows the comparison of flaw detection internal damage rates (160 furnaces data) of rolled products produced by two processes.

Detailed Description

Comparing the traditional process with the optimized process of the invention, the method comprises the following specific steps:

conventional process

(1) Adding steelmaking raw materials into a converter for smelting, blowing argon for stirring at the bottom of the whole process, controlling the tapping [ C ] to be 0.01-0.03%, controlling the tapping temperature to be 1630-1660 ℃, adding a deoxidizer, a low-carbon alloy and slag charge into the converter along with steel flow when tapping 1/4, and adopting a sliding plate to block slag during the tapping process for 4-5 min.

(2) Adding 100kg of lime into LF, performing diffusion deoxidation by using aluminum particles during refining, controlling the refining S to be less than or equal to 0.010 percent, carrying out ladle hoisting on a first furnace at 1623-.

(3) The continuous casting process adopts a 220mm multiplied by 260mm section for production, the whole process is protected for casting, the superheat degree is controlled to be 20-40 ℃, the drawing speed is controlled to be 1.00m/min, the electromagnetic stirring parameters of the crystallizer are current (180 +/-10) A and the frequency is (3.0 +/-0.5) Hz; without stirring and pressing lightly.

The primary cooling water flow is (1850 +/-100) L/min, the water temperature difference is 6.5-8.5, the secondary cooling specific water amount is 0.35L/kg, and the water distribution ratio of the foot roller section, the secondary cooling first-stage and the secondary cooling second-stage is 40/35/25.

The continuous casting process is protected, the ladle is protected by argon sealing, the integral stopper rod is adopted in the tundish, the diameter of the nozzle is 35mm, and the tundish is used for 12 hours.

(4) The temperature of the preheating section is 850-950 ℃, the temperature of the first heating section is 1000-1100 ℃, the temperature of the second heating section is 1150-1200 ℃, the temperature of the soaking section is 1120-1200 ℃, the initial rolling temperature is 1050-1100 ℃, and the final rolling temperature is 900-950 ℃.

The invention optimizes the process

(2) LF enhances the desulfurization operation, and 200kg of lime and 50kg of fluorite are added according to slag conditions and the sulfur content in an argon station; aluminum particles and ferrosilicon powder are used for diffusion deoxidation in refining, the refining S is controlled to be less than or equal to 0.002 percent, the ladle is hung in the first furnace according to 1613 and 1623 ℃, and the continuous casting furnace is hung at 1603 ℃ according to 1583 and ensures that the superheat degree of the tundish is 15-30 ℃. And ensuring that the refining time is controlled to be 45-60 min, performing argon blowing operation after the components and the temperature are properly adjusted, wherein the argon blowing time is 15-25 min, and ensuring the proper ladle temperature after soft blowing.

(3) The continuous casting process adopts a 220mm multiplied by 260mm section for production, the whole process is protected for casting, the low superheat degree and the constant drawing speed are adopted for control, the superheat degree is controlled to be 15-30 ℃, the drawing speed is controlled to be 0.90m/min, the electromagnetic stirring parameter of the crystallizer is current (200 +/-10) A, and the frequency is (2.5 +/-0.5) Hz; the electromagnetic stirring parameters at the tail end are current (50 +/-10) A and frequency (6 +/-0.5); the 1# and 2# rollers are selected to perform soft reduction, and the reduction amount is 2mm and 3mm respectively.

The primary cooling water flow is 2000 +/-100L/min, the water temperature difference is 7.0-9.0, the secondary cooling specific water amount is 0.30L/kg, and the water distribution ratio of the foot roller section, the secondary cooling first section and the secondary cooling second section is 45/40/15.

The continuous casting process is protected, the ladle is protected by argon sealing, the integral stopper rod is adopted in the tundish, the diameter of the nozzle is 40mm, and the tundish is used for 8 hours.

(4) And a low-temperature heating process is adopted, the heating time is controlled, and the raw core cracks of the blank are reduced to be oxidized in a heating furnace to form high-temperature oxidation particles. Meanwhile, the low-temperature finish rolling process is adopted, so that the welding of the core part of the rolled material can be effectively enhanced, and the formation of internal damage of the rolled material is reduced.

The temperature of the preheating section is 800-900 ℃, the temperature of the first heating section is 950-1050 ℃, the temperature of the second heating section is 1100-1150 ℃, the temperature of the soaking section is 1100-1150 ℃, the initial rolling temperature is 1000-1050 ℃ and the final rolling temperature is 800-850 ℃.

Comparison of effects

By optimizing parameters such as continuous casting drawing speed, specific water amount, secondary cooling proportion and the like, matching with a tail end electromagnetic stirring and soft reduction technology, combining Mn/S control and simultaneously adjusting heating and rolling processes, the low-power quality of a casting blank and a rolled material is effectively improved, the failure rate of flaw detection is reduced, the finishing efficiency is further improved, and the delivery period is shortened. In addition, the amount of improvement or rejection of raw materials is reduced, the quality objection payment is reduced, huge economic benefits are created for companies, the number of furnaces which are improved due to unqualified internal quality flaw detection is obviously reduced from 65 furnaces in 2018 to 5 furnaces in 2020, the quality objection is reduced from 2.2 yuan/ton in 2018 to 0.02 yuan/ton in 2020, and specific data are shown in tables 1-3.

TABLE 1 continuous casting billet Low Power rating

TABLE 2 Low fold rating of rolled stock

TABLE 3 statistics of flaw detection internal damage rate

	Maximum value	Mean value of
			Conventional process	33.10％	8.25％
Invention process	4.5％	0.99％

Claims

1. A control method for improving the flaw detection qualification rate of steel for an automobile claw pole comprises the following steps: molten iron, scrap steel → BOF smelting → LF furnace refining → continuous casting CCM → cold batch → cold charge → heating furnace heating → high pressure water descaling → rolling → cold bed → cold shear → cold batch → flaw detection → finishing → inspection → packing, characterized in that the control method comprises the following steps:

(1) in the LF process, slag materials, namely lime and fluorite, are added according to slag conditions and the sulfur content in an argon station; aluminum particles and ferrosilicon powder are used for diffusion deoxidation in refining, and the temperature of a ladle is controlled;

(2) the continuous casting process adopts the production of a 220mm multiplied by 260mm section, the whole process is protected and cast, the control of low superheat degree and constant drawing speed is adopted, the crystallizer adopts an electromagnetic stirring and non-sinusoidal vibration mode, the secondary cooling adopts a weak cold water distribution mode, and the electromagnetic stirring and the soft pressing at the tail end are matched;

(3) the low-temperature heating process is adopted, the heating time is controlled, the high-temperature oxidation particles formed by the oxidation of the cracks of the original core part of the blank in a heating furnace are reduced, meanwhile, the low-temperature finish rolling process is adopted, the rolling permeability is increased, the welding of the core part of the rolled material can be effectively enhanced, and the formation of internal damage of the rolled material is reduced.

2. The control method for improving the flaw detection qualification rate of the steel for the automobile claw pole according to claim 1, characterized by comprising the following steps: in the step (1), the control target of the refining S is less than or equal to 0.002%.

3. The control method for improving the flaw detection qualification rate of the steel for the automobile claw pole according to claim 1, characterized by comprising the following steps: in the step (1), the temperature of the ladle is controlled, the ladle is hoisted at 1613-.

4. The control method for improving the flaw detection qualification rate of the steel for the automobile claw pole according to claim 1, characterized by comprising the following steps: in the step (2), the superheat degree is controlled to be 15-30 ℃, the pulling speed is controlled to be 0.90m/min, and the electromagnetic stirring parameters of the crystallizer are as follows: the current (200 +/-10) A and the frequency are (2.5 +/-0.5) Hz; the electromagnetic stirring parameters at the tail end are current (50 +/-10) A and frequency (6 +/-0.5).

5. The control method for improving the flaw detection qualification rate of the steel for the automobile claw pole according to claim 1, characterized by comprising the following steps: in the step (2), in the weak cooling water distribution mode, the primary cooling water flow is (2000 +/-100) L/min, the water temperature difference is 7.0-9.0, the secondary cooling specific water amount is 0.30L/kg, the water distribution ratio of the full roller section, the secondary cooling primary section and the secondary cooling secondary section is 45/40/15, the 1# roller and the 2# roller are selected for soft pressing, and the pressing amount is 2mm and 3mm respectively.

6. The control method for improving the flaw detection qualification rate of the steel for the automobile claw pole according to claim 1, characterized by comprising the following steps: in the step (2), the continuous casting is protected and the ladle is protected by argon sealing, the integral stopper rod tundish is adopted as the tundish, the diameter of the water gap is more than or equal to 35m, and the service time of the tundish is less than or equal to 12 hours.

7. The control method for improving the flaw detection qualification rate of the steel for the automobile claw pole according to claim 1, characterized by comprising the following steps: in the step (3), the temperature of the preheating section is 800-900 ℃, the temperature of the heating section is 950-1050 ℃, the temperature of the heating section is 1100-1150 ℃, the temperature of the soaking section is 1100-1150 ℃, the initial rolling temperature is 1000-1050 ℃ and the final rolling temperature is 800-850 ℃.

8. The steel for an automobile claw pole according to claim 1, characterized in that: the steel for the automobile claw pole is low-carbon steel, and comprises the following chemical components in percentage by weight: [C] less than or equal to 0.08 percent, 0.15 to 0.35 percent of [ Si ], 0.30 to 0.60 percent of [ Mn ], less than or equal to 0.035 percent of [ P ], less than or equal to 0.035 percent of [ S ], less than or equal to 0.10 percent of [ Cr ], lessthan or equal to 0.10 percent of [ Ni ], and less than or equal to 0.20 percent of [ Cu ].