CN103320604B - Rolling preheating process for controlling sizes of titanium inclusions in hypereutectoid tire cord steel wire rod - Google Patents

Rolling preheating process for controlling sizes of titanium inclusions in hypereutectoid tire cord steel wire rod Download PDF

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Publication number
CN103320604B
CN103320604B CN201310281262.5A CN201310281262A CN103320604B CN 103320604 B CN103320604 B CN 103320604B CN 201310281262 A CN201310281262 A CN 201310281262A CN 103320604 B CN103320604 B CN 103320604B
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hypereutectoid
steel
rolling
titanium
cord steel
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CN201310281262.5A
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Chinese (zh)
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CN103320604A (en
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张京
熊锐
邹峰
雷家柳
蒋跃东
薛正良
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武汉科技大学
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Abstract

The invention relates to a rolling preheating process for controlling the sizes of titanium inclusions in a hypereutectoid tire cord steel wire rod. The technical scheme of the rolling preheating process is characterized by comprising the following steps of: heating a hypereutectoid tire cord steel continuous casting blank to 1150-1250 DEG C in a steel rolling heating furnace, wherein the heating time is 2-6 hours, the titanium inclusion (TiN or Ti(C,N)) in the casting blank is decomposed (namely solid dissolving) in the heating process, small inclusions disappear, and the sizes of the larger-size titanium inclusions are reduced; cooling the high-temperature-heated hypereutectoid tire cord steel continuous casting blank to the normal rolling temperature of hypereutectoid tire cord steel in a water mist cooling or air mist cooling manner; and carrying out rolling by utilizing a high-speed rolling mill. According to the rolling preheating process for controlling the sizes of the titanium inclusions in the hypereutectoid tire cord steel wire rod, the titanium inclusions in the super-strength hypereutectoid tire cord steel wire rod are diffused and distributed, and the number and the sizes of the titanium inclusions in casting blank are effectively controlled. The rolling preheating process has the characteristics that the titanium inclusions are small in number and sizes and are diffused and distributed, and the process is reliable; and according to the rolling preheating process, the penalty point rate of the titanium inclusions of the hypereutectoid tire cord steel wire rod can be effectively reduced.

Description

In control hypereutectoid Wire Rod Steel for Curtain String Purpose, titanium is mingled with the front heating process of rolling of size

Technical field

The invention belongs to the front heating process technical field of cord steel rolling.Be specifically related to a kind of heating process before the rolling that titanium in hypereutectoid Wire Rod Steel for Curtain String Purpose is mingled with size of controlling.

Background technology

Cord steel is a kind of high-tech product, is mainly used in and produces tire meridian, is commonly called as steel cord.Steel cord strengthens skeleton for tire, has that intensity is high, the feature of good toughness.The process of producing steel cord is the Wire Rod Steel for Curtain String Purpose of φ 5.5mm to be drawn into the filament of φ 0.15 ~ φ 0.38, this process makes length of wires increase by 1000 ~ 1400 times, reduced cross-sectional, to original 0.08%, approached the limit of high carbon steel drawing process, and has required drawing 100km fracture of wire to be no more than 1 time.

Along with automotive light weight technology and from improving car security, the intensity rank of tyres for passenger cars wire of steel wire tire cord is improving constantly; Before nineteen nineties, the main flow of tyre wire product is SWRH62A and the SWRH67A trade mark of 1750MPa regular tenacity, and after nineteen nineties, tyre wire product main flow is the high-intensity SWRH72A of 1870 MPa.Entering 21st century tyre wire product main flow is that hypereutectoid steel SWRH82A and the carbon content of superstrength level reaches the more trade mark of high intensity levels of 0.92 ~ 0.95 wt%.

Produce statistics and show, the brittle inclusion existing in steel be cause major reason that fracture occurs in steel wire drawing process (Y. Yamada, S. Shimazu etc. high strength steel cord wire rod. international metal wire magazine, 986(4): 53 ~ 65; Y. Shinsho, T. Nozaki etc. secondary refining is the impact with the non-metallic inclusion in high carbon steel on cord, international metal wire magazine, 1988.9:145 ~ 153).Experience shows, when the size of brittle inclusion be greater than processed steel wire diameter 2% time, will cause steel wire in cold-drawn and in twisting with the fingers burst process, occur brittle rupture (Wang Jianxin. affect several factors of steel steel for tyre cord silk. metal products, 1993.5:33 ~ 34).Even close by steel wire drawing and sth. made by twisting strand, also can in the dynamic fatigue property test of finished product cord or the practical application at tire, cause early fracture (Zhang Qingzhen. affect steel cord dynamic fatigue property Discussion on Main Factors. metal products, 1993,19 (2): 18).Therefore, cord steel has high requirement to the size of Molten Steel Cleanliness, brittle inclusion, form, is one of steel grade that in wire rod, specification of quality is the highest, production difficulty is maximum.

By a large amount of theoretical investigationes, the oxide inclusion composition and the morphology Control that have progressively formed in cord steel production process are theoretical, and be applied to production practice, realize the plastification of oxide inclusion during cord steel is produced, solved the drawing fracture of wire problem that hypoeutectoid cord steel (SWRH62A, SWRH67A and SWRH72A) causes because brittle oxide is mingled with.In cord steel molten steel casting process, the titanium of separating out in solid-liquid two-phase region is mingled with (TiN or Ti (C, N)) size much smaller than the size of oxide inclusion, and it is on the impact of the relatively low hypoeutectoid cord steel of intensity not obvious.But other improves along with cord strength level, more and more responsive to the size of brittle inclusion.As found in production practice, to other hypereutectoid cord steel of superstrength level, because being mingled with the drawing fracture of wire phenomenon that reason causes, titanium obviously increases (Liu Hongyu; Zheng Jianqiang; Li Yuhua etc. Ti inclusion research in cord steel. University of Science & Technology, Beijing's journal, 2010,32 (7): 866 ~ 871; Li Yuhua, Zheng Jianqiang, woods Guoqiang. titanium inclusion in cord steel thing pattern and the calculating of separating out size, Nangang's science and technology and management, 2012 (1): 1 ~ 4).

In order to control separating out of hypereutectoid titanium inclusion in cord steel, factory has implemented harsh steel-making and refinery practice measure, as much as possible impurity element Ti and N in molten steel are removed to limit content.However, under the cord steel Ti that can reach in current STEELMAKING PRODUCTION technology, N contents level, solidified front is separated out titanium and is mingled with and remains unavoidable (Lei Jialiu, Xue Zhengliang, Jiang Yuedong etc. in hypereutectoid steel process of setting, TiN is mingled with and separates out theoretical analysis. and international metallurgical. 2012,17 (9): 10 ~ 15).And along with carbon content of molten steel increases (being also that cord steel intensity rank improves), cord steel solidified front temperature reduces, cause solidified front to separate out titanium and be mingled with required titanium nitrogen activity product reduction, under the initial Ti of same molten steel, N content condition (being also limit Ti, the N content that current steel-making can reach), solidify the titanium of separating out and be mingled with size and will increase.Therefore, solve the drawing fracture of wire problem that other hypereutectoid cord steel of superstrength level causes because titanium is mingled with, must take measures from refining steel and rolled steel simultaneously.

Summary of the invention

The object of this invention is to provide a kind of heating process before the rolling that titanium in hypereutectoid Wire Rod Steel for Curtain String Purpose is mingled with size of controlling, realize effective control that titanium in hypereutectoid Wire Rod Steel for Curtain String Purpose is mingled with, reduce hypereutectoid Wire Rod Steel for Curtain String Purpose titanium and be mingled with point penalty rate.

To achieve these goals, the technical solution adopted in the present invention is: first hypereutectoid cord steel continuously cast bloom is heated to 1150~1250 ℃ in heater for rolling steel, be 2~6h heat-up time, then by water smoke, cooling or aerosol is cooled to the normal start rolling temperature of hypereutectoid cord steel by the hypereutectoid cord steel strand of heat.Then enter high-speed wire mill rolling.

Described hypereutectoid cord steel continuously cast bloom is: in the molten steel before casting, impurity element Ti is 4 ~ 6ppm, and N is 30 ~ 40ppm, and molten steel is cast into 150 * 150 ~ 200 * 200mm through continuous caster 2little square billet.

The normal start rolling temperature of described hypereutectoid cord steel is 990~1020 ℃.

Owing to adopting technique scheme, the soaking temperature by hypereutectoid cord steel strand in heater for rolling steel is brought up to 1150 ~ 1250 ℃ from current 1000~1050 ℃, and extended to 2~6h from 1.5~2h heat-up time.The solubleness that TiN is mixed in austenite increases, and TiN is mingled with the backward matrix around of decomposition and fully dissolves and spread.

The application experimental results show that, when furnace temp is brought up to 1150 ℃, TiN is mingled with can constantly decompose (solid solution is in austenite), the Ti decompositing and N constantly pile up in the austenite of inclusion periphery, and spread in the austenite away from inclusion, when TiN is mingled with decomposition rate and is greater than Ti, N to the speed of austenite depths diffusion, the Ti of inclusion periphery, N concentration constantly increase, until inclusion periphery Ti, N concentration long-pending be greater than equilibrium concentration at this temperature when long-pending TiN be mingled with and stop decomposing.

Slab heating temperature is higher, and the tendency that TiN is mingled with decomposition is larger, and TiN is mixed in austenite size after solid solution diminish gradually (small size inclusion disappears and large-size inclusion diminishes gradually).Strand is longer heat-up time in process furnace, and the TiN of large-size is mingled with size will become less.The time that experiment showed, strand heat in heater for rolling steel is 2 ~ 6h, improve Heating temperature can be corresponding minimizing heat-up time.

Strand after heat is in the process of cooling, and the Ti in austenite, N can recombine separate out TiN and be mingled with, and take undecomposed complete titanium and be mingled with as forming core core and separate out and grow up.The present invention the strand of heat is carried out to water smoke or aerosol cooling, strand temperature is dropped to fast to the start rolling temperature (1000 ℃ of left and right) of hypereutectoid cord steel, make strand in the process of cooling, that has avoided that in austenite, TiN is mingled with grows up again, thereby reaches the object that effective control TiN is mingled with quantity and size.Statistical result showed of the present invention, the small-particle TiN of size < 2 μ m is mingled with quantity significantly to be reduced, and the larger particles TiN of size >=5 μ m is mingled with quantity obviously to be reduced.

The present invention is without existing technique is done to larger change, adopt the front heating process of described rolling, high and the process of feasibility, can effectively control quantity and the size of titanium inclusion in hypereutectoid Wire Rod Steel for Curtain String Purpose, thereby the titanium that has reduced significantly hypereutectoid cord steel is mingled with point penalty rate.

The disperse that the present invention has realized titanium is mingled with in the hypereutectoid Wire Rod Steel for Curtain String Purpose of superstrength distributes, and quantity and size that in strand, titanium is mingled with are effectively controlled.The present invention has that titanium inclusion content is few, size is little, the feature of disperse distribution and process, can effectively reduce hypereutectoid Wire Rod Steel for Curtain String Purpose titanium and be mingled with point penalty rate.

Embodiment

Below in conjunction with embodiment, the invention will be further described, not the restriction to protection domain.

embodiment 1

A kind ofly control heating process before the rolling that titanium in hypereutectoid Wire Rod Steel for Curtain String Purpose is mingled with size.First hypereutectoid cord steel continuously cast bloom is heated to 1150~1200 ℃ in heater for rolling steel, be 4~6h heat-up time, then the hypereutectoid cord steel strand of heat is cooled to the normal start rolling temperature of hypereutectoid cord steel by aerosol.Then enter high-speed wire mill rolling.

Described in the present embodiment, hypereutectoid cord steel is SWRH82A, and its continuously cast bloom is: in the molten steel before casting, impurity element Ti is 4 ~ 6ppm, and N is 35 ~ 40ppm, and molten steel is cast into 150 * 150mm through continuous caster 2little square billet.

Described in the present embodiment, the normal start rolling temperature of hypereutectoid cord steel is 1000~1020 ℃.

embodiment 2

A kind ofly control heating process before the rolling that titanium in hypereutectoid Wire Rod Steel for Curtain String Purpose is mingled with size.First hypereutectoid cord steel continuously cast bloom is heated to 1200~1250 ℃ in heater for rolling steel, be 2~4h heat-up time, then the hypereutectoid cord steel strand of heat is cooled to the normal start rolling temperature of hypereutectoid cord steel by aerosol.Then enter high-speed wire mill rolling.

Described in the present embodiment, hypereutectoid cord steel is SWRH82A, and its continuously cast bloom is: in the molten steel before casting, impurity element Ti is 4 ~ 6ppm, and N is 35 ~ 40ppm, and molten steel is cast into 200 * 200mm through continuous caster 2little square billet.

Described in the present embodiment, the normal start rolling temperature of hypereutectoid cord steel is 1000~1020 ℃.

embodiment 3

A kind ofly control heating process before the rolling that titanium in hypereutectoid Wire Rod Steel for Curtain String Purpose is mingled with size.First hypereutectoid cord steel continuously cast bloom is heated to 1180~1230 ℃ in heater for rolling steel, be 3~5h heat-up time, then the hypereutectoid cord steel strand of heat is cooled to the normal start rolling temperature of hypereutectoid cord steel by water smoke.Then enter high-speed wire mill rolling.

Described in the present embodiment, hypereutectoid cord steel is SWRH92A, and its continuously cast bloom is: in the molten steel before casting, impurity element Ti is 4 ~ 6ppm, and N is 30 ~ 35ppm, and molten steel is cast into 200 * 200mm through continuous caster 2little square billet.

Described in the present embodiment, the normal start rolling temperature of hypereutectoid cord steel is 990~1010 ℃.

This embodiment by hypereutectoid cord steel strand the soaking temperature in heater for rolling steel bring up to 1150 ~ 1250 ℃ from current 1000~1050 ℃, extended to 2~6h from 1.5~2h heat-up time.The solubleness that TiN is mixed in austenite increases, and TiN is mingled with the backward matrix around of decomposition and fully dissolves and spread.

The application experimental results show that, when furnace temp is brought up to 1150 ℃, TiN is mingled with can constantly decompose (solid solution is in austenite), the Ti decompositing and N constantly pile up in the austenite of inclusion periphery, and spread in the austenite away from inclusion, when TiN is mingled with decomposition rate and is greater than Ti, N to the speed of austenite depths diffusion, the Ti of inclusion periphery, N concentration constantly increase, until inclusion periphery Ti, N concentration long-pending be greater than equilibrium concentration at this temperature when long-pending TiN be mingled with and stop decomposing.

Slab heating temperature is higher, and the tendency that TiN is mingled with decomposition is larger, and TiN is mixed in austenite size after solid solution diminish gradually (small size inclusion disappears and large-size inclusion diminishes gradually).Strand is longer heat-up time in process furnace, and the TiN of large-size is mingled with size will become less.The time that experiment showed, strand heat in heater for rolling steel is 2 ~ 6h, improve Heating temperature can be corresponding minimizing heat-up time.

Strand after heat is in the process of cooling, and the Ti in austenite, N can recombine separate out TiN and be mingled with, and take undecomposed complete titanium and be mingled with as forming core core and separate out and grow up.The present invention the strand of heat is carried out to water smoke or aerosol cooling, strand temperature is dropped to fast to the start rolling temperature (1000 ℃ of left and right) of hypereutectoid cord steel, make strand in the process of cooling, that has avoided that in austenite, TiN is mingled with grows up again, thereby reaches the object that effective control TiN is mingled with quantity and size.Statistical result showed of the present invention, the small-particle TiN of size < 2 μ m is mingled with quantity significantly to be reduced, and the larger particles TiN of size >=5 μ m is mingled with quantity obviously to be reduced.

This embodiment is without existing technique is done to larger change, adopt the front heating process of described rolling, high and the process of feasibility, can effectively control quantity and the size of titanium inclusion in hypereutectoid Wire Rod Steel for Curtain String Purpose, thereby the titanium that has reduced significantly hypereutectoid cord steel is mingled with point penalty rate.

Therefore, the disperse that this embodiment has realized titanium is mingled with in the hypereutectoid Wire Rod Steel for Curtain String Purpose of superstrength distributes, and quantity and size that in strand, titanium is mingled with are effectively controlled; Have that titanium inclusion content is few, size is little, the feature of disperse distribution and process, can effectively reduce hypereutectoid Wire Rod Steel for Curtain String Purpose titanium and be mingled with point penalty rate.

Claims (1)

1. control heating process before the rolling that titanium in hypereutectoid Wire Rod Steel for Curtain String Purpose is mingled with size for one kind, it is characterized in that: first hypereutectoid cord steel continuously cast bloom is heated to 1150~1250 ℃ in heater for rolling steel, be 2~6h heat-up time, then by water smoke, cooling or aerosol is cooled to the normal start rolling temperature of hypereutectoid cord steel by the hypereutectoid cord steel strand of heat; Then enter high-speed wire mill rolling;
Described hypereutectoid cord steel continuously cast bloom is: in the molten steel before casting, impurity element Ti is 4~6ppm, and N is 30~40ppm, and molten steel is cast into 150 * 150~200 * 200mm through continuous caster 2little square billet; The normal start rolling temperature of described hypereutectoid cord steel is 990~1020 ℃.
CN201310281262.5A 2013-07-05 2013-07-05 Rolling preheating process for controlling sizes of titanium inclusions in hypereutectoid tire cord steel wire rod CN103320604B (en)

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