JP2005154857A - Alloyed hot dip galvanized steel sheet, and method for manufacturing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an alloyed hot dip galvanized steel sheet containing Si and Al and capable of ensuring the plating property, and a method for manufacturing the same. <P>SOLUTION: In an alloyed hot dip galvanized steel sheet, the steel sheet is heated by using a heating furnace of the direct fire reduction heating system, and led to a reducing furnace. The surface of the steel sheet is reduced and annealed, and immersed in a hot dip galvanizing bath to perform galvanizing. The composition of the base steel sheet satisfies the expression Si(%) ≤ 2.0 mass%, Al(%) ≤ 3.0mass%, and 0.6Si(%) ≤ Al(%) + 0.3. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an alloyed hot-dip galvanized steel sheet containing Si and Al as alloy elements for increasing the strength of steel and having excellent plating properties and surface properties, and a method for producing the same.

  In recent years, from the viewpoint of preventing global warming, the need for improving the fuel efficiency of automobiles has increased, and the weight reduction of the vehicle body has been actively carried out by reducing the thickness of the steel sheet. On the other hand, since the needs for safety of automobiles are also increasing, it is desired to maintain high vehicle body strength while reducing the weight of the vehicle body. For this reason, the movement which is going to employ | adopt a high strength steel plate with respect to the member for motor vehicles is increasing.

  On the other hand, many automotive members have complicated shapes, and most of them are processed by press forming. However, compared with soft steel plates, high-strength steel plates have a disadvantage that they are inferior in press formability because of low ductility. Therefore, development of high-strength steel sheets having both high strength and high ductility and excellent press formability has been actively conducted.

  For example, Patent Document 1 discloses a cold-rolled steel sheet having an excellent strength-ductility balance by utilizing a processing-induced transformation of retained austenite. This cold-rolled steel sheet is a steel sheet containing C, Si, Mn, etc., annealed in the austenite region or ferrite + austenite two-phase region, and then rapidly cooled to the bainite transformation temperature region so as not to cause ferrite-pearlite transformation. By maintaining the temperature for a certain period of time and advancing the austenite to bainite transformation to some extent, C is concentrated in the remaining austenite and cooled to room temperature in the presence of high C austenite to generate residual austenite. It is a cold-rolled steel sheet obtained by this.

  In addition, one of the characteristics required for steel sheets for automobiles is corrosion resistance, so steel sheets that have undergone electroplating or hot dipping are required. Hot-dip galvanized steel sheets that are particularly thick and can be cost-effective Is often used. However, the steel sheet described above contains a large amount of Si, and Si oxides are generated on the steel sheet surface by selective oxidation during annealing, so that the wettability with the galvanizing bath is inferior and the occurrence of non-plating is satisfactory. There is a disadvantage that it is impossible to obtain a hot dip galvanized steel sheet.

  For this reason, in order to achieve both the plateability and plating adhesion and the balance between strength and ductility, Al is added to the steel sheet, and the content of C, Si, Mn, P, S, Al, and N is optimized. A plated steel sheet is disclosed in Patent Document 2. However, the upper limits of Si <0.5% and Al <1.5% for Si and Al required for increasing strength are described from the viewpoint of plating adhesion, and in order to achieve higher strength, the amount of Si and Al Cannot be increased.

Further, although Si is effective in generating retained austenite, Patent Document 3 discloses an invention that pays attention to Al that can provide the same effect, and further compensates with Al content while reducing Si content. The feature of the present invention is that the pre-oxidation treatment is performed in the range of 550 ° C. to 750 ° C., the amount of iron oxide on the surface is formed to ² to 4 g / m ² , and then the reduction is performed in an N ₂ —H ₂ atmosphere. The feature is that the plating property is secured by increasing the amount of Fe. However, even with this method, if the amount of Si is large, the amount of iron oxide produced during pre-oxidation is not sufficient and the plating property is not improved, so the upper limit is defined as 1.0%.

  On the other hand, in order to ensure plating properties for a steel sheet containing a relatively large amount of Si and Al, a method of containing Mn in the plating bath is disclosed in Patent Document 4, but Mn is contained in the plating bath. Is effective for such difficult-to-plate steel sheets, but for other steel sheets, especially soft steel sheets, it activates the Fe-Zn reaction in the plating bath and generates dross. This causes a problem in performing a series of operations.

The prior art document information is described below.
JP-A-60-43430 Japanese Patent Laid-Open No. 5-247586 Japanese Patent Laid-Open No. 11-236621 JP 2003-55751 A

  As described above, although there is a need to contain a large amount of Si and Al from the viewpoint of increasing the strength, there is an upper limit from the viewpoint of plating properties with hot-dip plated steel sheets, and a plating bath is devised to ease the upper limit. Even so, other steel types currently have problems such as adversely affecting plating properties.

  This invention solves the said problem, and makes it a subject to provide the alloyed hot-dip galvanized steel plate which contains Si and Al, and can also ensure plating property, and its manufacturing method.

In order to solve the above-mentioned problems, the present inventors have worked on the development of a steel sheet containing Si and Al and further ensuring plating properties. As a result, even with steel sheets containing Si and Al, after weak oxidation is performed in advance and an Fe oxide layer is formed on the surface, the Fe oxide layer is reduced in an N ₂ -H ₂ atmosphere, thereby ensuring sufficient plating properties. It has been found that a method of applying rapid heating is effective when performing weak oxidation.

  Furthermore, when steel sheets containing Si and Al are annealed in a reducing atmosphere, the concentration of Si is suppressed by the concentration of Al on the surface, and this Al has little effect on the plating properties. It has been found that if the Al addition amount is optimized according to the amount, sufficient plating properties can be secured.

  The present invention has been made based on the above findings, and the gist thereof is as follows.

  In the first invention, the steel sheet is heated by using a direct-fire reduction heating type heating furnace, further led to the reduction furnace and subjected to reduction and annealing of the steel sheet surface, and then intruded into a hot dip zinc bath and galvanized. In the alloyed hot-dip galvanized steel sheet alloyed with, the components of the base steel sheet are Si (%) ≦ 2.0 mass%, Al (%) ≦ 3.0 mass%, and 0.6 Si (%) ≦ Al (%) + 0.3 An alloyed hot-dip galvanized steel sheet is provided.

The second invention, in the first invention, the zinc coating weight of the galvannealed steel sheet is 30~90g / m ^2, and Fe concentration and the Al concentration in the plating film, respectively from 8 to 14%, 0.1 An alloyed hot-dip galvanized steel sheet characterized by being in the range of ˜0.5% is provided.

  The third invention is a direct heating reduction heating of a steel plate whose steel components satisfy Si (%) ≦ 2.0 mass%, Al (%) ≦ 3.0 mass%, and 0.6 Si (%) ≦ Al (%) + 0.3. An alloyed hot-dip galvanized steel sheet that was heated using a heating furnace of the type, led to a reduction furnace, reduced and annealed on the surface of the steel sheet, penetrated into a hot-dip galvanized bath, and then galvanized and alloyed. In the manufacturing method, the air-fuel ratio in the direct-fire reduction heating type heating furnace is in the range of 0.7 to 1.2, the air-fuel ratio in the front stage of the heating furnace is 1.0 or more, and the air-fuel ratio in the rear stage is less than 1.0. A method for producing an alloyed hot-dip galvanized steel sheet is provided.

  The fourth invention is a direct heating reduction heating of a steel plate whose steel components satisfy Si (%) ≦ 2.0 mass%, Al (%) ≦ 3.0 mass%, and 0.6 Si (%) ≦ Al (%) + 0.3. An alloyed hot-dip galvanized steel sheet that was heated using a heating furnace of the type, led to a reduction furnace, reduced and annealed on the surface of the steel sheet, penetrated into a hot-dip galvanized bath, and then galvanized and alloyed. In the manufacturing method, the Al concentration in the molten zinc bath is 0.05 to 0.20%, the bath temperature is 450 to 480 ° C., and the penetration time of the steel sheet into the molten zinc bath is in the range of 2 to 5 seconds. The manufacturing method of the galvannealed steel plate characterized by these is provided.

  The fifth aspect of the present invention is a direct heating reduction heating of a steel sheet whose steel components satisfy Si (%) ≦ 2.0 mass%, Al (%) ≦ 3.0 mass%, and 0.6 Si (%) ≦ Al (%) + 0.3. An alloyed hot-dip galvanized steel sheet that was heated using a heating furnace of the type, led to a reduction furnace, reduced and annealed on the surface of the steel sheet, penetrated into a hot-dip galvanized bath, and then galvanized and alloyed. In the manufacturing method, the air-fuel ratio in the direct-fire reduction heating type heating furnace is in the range of 0.7 to 1.2, the air-fuel ratio in the front stage of the heating furnace is 1.0 or more and the air-fuel ratio in the rear stage is less than 1.0, and in the molten zinc bath Alloying hot dip galvanizing characterized in that the Al concentration of the steel is 0.05 to 0.20%, the bath temperature is 450 to 480 ° C., and the penetration time of the steel sheet into the hot dip zinc bath is in the range of 2 to 5 seconds A method for producing a steel sheet is provided.

  In addition, in this specification,% which shows the component of steel is mass%.

  According to the present invention, even if Si and Al are contained as alloy elements, an alloyed hot-dip galvanized steel sheet having excellent plating properties and surface properties can be stably obtained.

  Hereinafter, the present invention will be specifically described.

  In the present invention, the steel sheet is heated using a direct-fire reduction heating furnace, and further led to the reduction furnace to reduce and anneal the steel sheet surface, and then penetrated into a molten zinc bath and galvanized, and then alloyed. It is premised on an alloyed hot-dip galvanized steel sheet.

  The direct-fire reduction heating furnace can rapidly heat the steel sheet by directly colliding the flame with the steel sheet. At this time, by adjusting the air-fuel ratio, the ratio of the reducing flame to the oxidizing flame can be adjusted. It can be controlled arbitrarily, and is characterized in that the oxidation state and reduction state of the steel sheet can be easily controlled.

  Here, when annealing is performed only in a commonly used radiant tube type reducing furnace without rapidly heating the steel sheet in a direct flame reduction heating type heating furnace, heating proceeds at a relatively low speed, and Since the reduction of the natural oxide film on the surface of the steel sheet is completed in a relatively short period of time, selective oxidation of Si in the steel sheet occurs. Will occur.

  On the other hand, when a steel sheet is rapidly heated in a direct flame reduction heating furnace, impurity components such as rolling oil remaining on the steel sheet surface burn, and at the same time, a phenomenon occurs in which the steel sheet surface is slightly oxidized. Further, since the surface of the steel sheet is rapidly heated, formation of Si-based oxides that are harmful during plating does not occur. Thereafter, when guided to a reduction furnace, a reduction reaction of the slightly oxidized steel sheet surface occurs, and the steel sheet has clean Fe formed on the surface. The oxide layer slightly formed in the direct-fire reduction heating furnace is thicker than the natural oxide film, and it takes time for the reduction reaction in the reduction furnace, and at the same time, selective oxidation of Si is suppressed. Moreover, a hot-dip galvanized steel sheet that does not cause non-plating can be obtained even for a steel sheet containing a relatively large amount of Si. However, if the Si content is increased due to demands such as strength and elongation of the steel sheet, even if it is weakly oxidized in a direct-fire reduction heating furnace, selective oxidation of Si cannot be suppressed, and non-plating is likely to occur. . Here, in the steel sheet containing Al at the same time as Si, when annealing in a reduction furnace, Al is concentrated on the surface and an Al-based oxide is formed, but the surface concentration of Si does not occur. is there. The reason why the surface concentration of Al occurs in this way and the surface concentration of Si is suppressed is thought to be because the affinity for oxygen is higher in Al than in Si.

  Further, even when Al is concentrated on the surface and an Al-based oxide is formed, no wettability failure such as non-plating occurs when immersed in a hot dip galvanizing bath. Although this mechanism is not clear, it can be considered as follows. In general, a small amount of Al is added to the hot dip galvanizing bath in order to suppress an excessive Fe—Zn reaction with the steel sheet. Al in this bath reacts preferentially with Fe over Zn, and an Fe-Al alloy layer is formed on the surface of the steel sheet, but Al-based oxides present on the surface of the steel sheet also contribute to the formation of the Fe-Al alloy layer. It is considered that it does not cause wettability deterioration with molten zinc.

  Thus, by simultaneously containing Si and Al in the steel sheet, concentration of the Si-based oxide on the steel sheet surface during heat annealing in the reduction furnace is suppressed, and good plating properties are obtained. The Al concentration balance needs to be 0.6 Si (%) ≦ Al (%) + 0.3. This is because if steel sheets with components that do not satisfy this concentration balance are annealed, the Al present in the steel sheet is not sufficient to suppress the surface concentration of the Si-based oxides, which may lead to deterioration of the plating properties. It is. On the other hand, as the content of Si increases, even if Al is contained at the same time, the surface concentration of the Si-based oxide increases, which may lead to deterioration of the plating property. Thereafter, the alloying treatment speed changes, and if a large amount of Si is contained, the alloying treatment temperature rises and the treatment time is lengthened, so the content needs to be 2.0 mass% or less. Moreover, since Al is expensive and contains a large amount, it causes deterioration of ductility due to increase of inclusions and deterioration of flash butt welding, so the content needs to be 3.0 mass% or less.

  In the steel sheet targeted by the present invention, the total amount of Si and Al is preferably 0.2 mass% or more from the viewpoint of ensuring a balance between strength and ductility. Furthermore, when ensuring high ductility such as TRIP steel, And the total amount of Al is more preferably 0.4 mass% or more.

  In the present invention, the amount of Si and Al in the steel sheet only needs to be within the scope of the present invention, and other components are not particularly limited. In addition to Fe and unavoidable impurities, C, Mn, S, Mg, Cr , Ni, Cu, Ta or the like may be contained. Further, Nb and Ti may be added for the IF steel base, and several ppm of B may be added for preventing secondary work resistance embrittlement.

  As described above, in the present invention, it is assumed that rapid heating is performed by a direct-fire reduction heating type heating furnace before reduction annealing in the reduction furnace. It is necessary to adjust in the range of 0.7-1.2. In addition, the purpose of this direct-fire reduction heating furnace is rapid heating of the steel sheet, and simultaneously burns and removes impurities such as rolling oil remaining on the surface of the steel sheet and oxidizes the surface of the steel sheet in a small amount. Therefore, it is necessary to set the front stage of the heating furnace to an air-fuel ratio of 1.0 or more in a weakly oxidizing atmosphere. In addition, if the entire direct heating reduction heating furnace is made into a weakly oxidizing atmosphere, the steel sheet surface is excessively oxidized and is not sufficiently reduced in the subsequent reduction annealing in the reducing furnace, and unreduced Fe remains on the steel sheet surface. However, since the plating property is deteriorated, the air-fuel ratio in the subsequent stage needs to be less than 1.0 in the reducing atmosphere. There are no particular restrictions on the lengths of these air-fuel ratio control areas, and it may be adjusted based on the relationship between the length of the direct-fire reduction heating furnace and the line speed. Each of them is preferably within 20 seconds in terms of the passage time because it causes the inhibition of sex.

The atmosphere during reduction annealing can be the commonly used H ₂ -N ₂ atmosphere or CO-CO ₂ atmosphere, but it is plated with a small amount of oxide on the surface of the steel sheet formed during direct fire heating It is sufficient that the atmosphere can be reduced immediately before, and the effect of the present invention is not impaired by the atmospheric gas used.

The steel plate of the component specified in the present invention is characterized in that good plating properties can be obtained even if it contains a large amount of Si useful as an additive component in a high-strength steel plate. Many are expected. In addition, since it is intended for alloyed hot-dip galvanized steel sheets that have been subjected to alloying treatment after hot dipping and have been formed with an Fe-Zn alloy plating layer, the amount of zinc deposited should be 30-90 g / m ² desirable. This is because if the amount of zinc deposited is less than 30 g / m ² , sufficient corrosion resistance cannot be obtained even after coating, and conversely if it exceeds 90 g / m ² , This is because a brittle Γ phase is formed at the steel plate-plating interface, resulting in poor powdering.

  In addition, in order to suppress excessive Fe-Zn reaction at the time of immersing the steel sheet in the hot dip galvanizing bath or during the subsequent alloying treatment, by adding a small amount of Al to the plating bath, It is necessary to form an Fe-Al alloy layer at the plating-steel interface. From this point of view, the Al concentration in the plating film is desirably in the range of 0.1 to 0.5%. This is because if the Al concentration in the plating film is less than 0.1%, the effect of suppressing the Fe-Zn reaction is not sufficient, while if it exceeds 0.5%, the Fe-Zn alloying reaction is suppressed. This is because the subsequent alloying process speed is delayed. In order to satisfy the slidability and powdering resistance of the galvannealed steel sheet, it is desirable that the Fe concentration in the film is in the range of 8 to 14%. This is because if the Fe concentration in the film is less than 8%, there is a risk of press cracking due to adhesion between the plating surface and the mold, and if it exceeds 14%, there is less concern about press cracking. However, this is because a fragile Γ phase is formed at the steel plate-plating interface, which may cause poor powdering.

Thus, although it is necessary to contain Al in the film, when manufacturing such an alloyed hot-dip galvanized steel sheet, the Al concentration in the plating bath is 0.05 to 0.20%, and the bath temperature is 450 to It is necessary to control to the range of 480 ℃. This is because the Al concentration described above cannot be contained in the plating film if it is out of this range. The immersion time in these plating baths is preferably in the range of 2 to 5 seconds. This is because if it is less than 2 seconds, the reaction in the bath is not sufficient, and even if a steel plate having an appropriate component is used, plating failure may occur. This is because the -Zn reaction becomes excessive, and even if Al is added to the plating bath, no further reaction that cannot be expected to suppress the reaction can be expected. What is necessary is just to adjust the adhesion amount of the steel plate after being immersed in a plating bath to 30-180 g / m < ² > by means of conventional methods, such as gas wiping.

  In the alloying treatment step, methods such as a gas heating method, an induction heating method, and a direct current heating method can be adopted, but the effect of the present invention is not changed depending on the difference in the alloying furnace heating method. Moreover, what is necessary is just to adjust process temperature and process time in order for Fe density | concentration in a film to be the range prescribed | regulated by this invention, and there is no restriction | limiting at all.

  As described so far, the alloyed hot-dip galvanized layer of the present invention only needs to contain Zn, Al, and Fe at a minimum. For the purpose of improving corrosion resistance, etc., As, Bi, Cd, Ce , Co, Cr, In, La, Li, Mg, Mn, Ni, O, P, Pb, S, Sb, Sn, Ti, Zr, etc. Even if it contains, the effect of this invention is not impaired.

Steels with the chemical components shown in Table 1 are melted and cast, hot-rolled under conditions of a heating temperature of 1200 ° C, a finishing temperature of 900 ° C, and a winding temperature of 600 ° C to form a 3.2mm thick steel plate, and then pickling A cold rolled steel sheet having a thickness of 1.2 mm was obtained by cold rolling. Thereafter, annealing and plating were performed in a continuous hot dip galvanizing line having a direct-fired heating furnace. In the direct-fired heating furnace, the steel sheet enters the heating furnace and the first 15 seconds is adjusted to an air-fuel ratio of 1.0, then 15 seconds is adjusted to an air-fuel ratio of 0.9, and the subsequent annealing in the reduction furnace is: Performed in N ₂ -10% H ₂ atmosphere. Here, the plate temperature on the outlet side of the direct-fired heating furnace was set to 650 ° C., and the annealing temperature in the reduction furnace was adjusted to be in the range of 700 to 850 ° C. In the plating, a 470 ° C. plating bath containing 0.20% Al was used, and the immersion time was 3 seconds. In addition, the plating adhesion amount was adjusted to be about 45 g / m ² , and the subsequent alloying treatment was performed using an induction heating type alloying furnace so that the Fe concentration in the plating film was about 10%. . As a result of wet analysis, the amount of Al in the plating film was in the range of 0.15 to 0.25%.

  The galvannealed steel sheet produced in this way was evaluated for the presence or absence of non-plating. In the evaluation, visual judgment was made, and a case where no plating was not generated was evaluated as “◯”, and a case where even a slight amount of non-plating was observed was evaluated as “X”. Further, in the subsequent alloying treatment, the case where the alloying was not completely completed and the burning unevenness was recognized was evaluated as x, and the case where the alloying was completed was evaluated as ◯.

  The evaluation results are shown in Table 1.

  As shown in Table 1, when the content of Si and Al in the steel is within the range of the present invention, no plating is not generated, and in the subsequent alloying process, no burning unevenness is generated, which is good. Compared to a comparative example (No. 12, 18, 24) in which Al is not added despite the fact that it contains a large amount of Si, Al is contained even if Al is added. In the comparative examples (No. 13, 19, 25, 26) in which the amount was less than the amount specified in the present invention with respect to the Si content, non-plating occurred. Further, in Comparative Examples (No. 30 to 33) in which the Si content exceeds 2.0% specified in the present invention and the Al content is not sufficient with respect to the Si content, non-plating occurs, and in addition, alloying occurs. Unsatisfactory and burn unevenness occurred. Furthermore, in the comparative examples (No. 34 to 36) in which the Si content exceeds 2.0% specified in the present invention and the Al content is sufficient with respect to the Si content, the occurrence of non-plating is not observed. Unevenness occurred, and a good surface appearance could not be obtained.

  The method for producing an alloyed hot-dip galvanized steel sheet according to the present invention is used for producing an alloyed hot-dip galvanized steel sheet that contains Si and Al as alloying elements in order to increase the strength of the steel, and further has excellent plating properties and surface properties. Available.

  The alloyed hot-dip galvanized steel sheet of the present invention can be used for automobile members that require high strength and high ductility.

Claims (5)

The steel sheet was heated using a direct-fire reduction heating furnace, and then led to the reduction furnace. After the steel sheet surface was reduced and annealed, it was infiltrated into a molten zinc bath and galvanized and alloyed. In the alloyed hot-dip galvanized steel sheet, the base steel sheet must satisfy Si (%) ≦ 2.0 mass%, Al (%) ≦ 3.0 mass%, and 0.6 Si (%) ≦ Al (%) + 0.3. An alloyed hot-dip galvanized steel sheet. The alloyed hot-dip galvanized steel sheet has a zinc adhesion amount of 30 to 90 g / m ² and the Fe concentration and Al concentration in the plating film are in the range of 8 to 14% and 0.1 to 0.5%, respectively. The alloyed hot-dip galvanized steel sheet according to claim 1. A steel plate with steel components satisfying Si (%) ≤ 2.0 mass%, Al (%) ≤ 3.0 mass%, and 0.6 Si (%) ≤ Al (%) + 0.3 In the method of producing an alloyed hot-dip galvanized steel sheet that has been subjected to alloying treatment after intrusion into a hot dip galvanizing bath after being introduced into a hot dip galvanizing bath after reducing and annealing the steel sheet surface by using and heating. Alloyed molten zinc characterized in that the air-fuel ratio in a direct-fire reduction heating furnace is in the range of 0.7 to 1.2, the air-fuel ratio in the front stage of the heating furnace is 1.0 or more and the air-fuel ratio in the rear stage is less than 1.0 Manufacturing method of plated steel sheet. A steel plate with steel components satisfying Si (%) ≤ 2.0 mass%, Al (%) ≤ 3.0 mass%, and 0.6 Si (%) ≤ Al (%) + 0.3 In the method of producing an alloyed hot-dip galvanized steel sheet that has been subjected to alloying treatment after intrusion into a hot dip galvanizing bath after being introduced into a hot dip galvanizing bath after reducing and annealing the steel sheet surface by using and heating. An alloy characterized in that the Al concentration in the molten zinc bath is 0.05 to 0.20%, the bath temperature is 450 to 480 ° C, and the penetration time of the steel sheet into the molten zinc bath is in the range of 2 to 5 seconds. Method for producing a galvannealed steel sheet. A steel plate with steel components satisfying Si (%) ≤ 2.0 mass%, Al (%) ≤ 3.0 mass%, and 0.6 Si (%) ≤ Al (%) + 0.3 In the method of producing an alloyed hot-dip galvanized steel sheet that has been subjected to alloying treatment after intrusion into a hot dip galvanizing bath after being introduced into a hot dip galvanizing bath after reducing and annealing the steel sheet surface by using and heating. The air-fuel ratio in a direct-fire reduction heating furnace is in the range of 0.7 to 1.2, the air-fuel ratio in the front stage of the heating furnace is 1.0 or more and the air-fuel ratio in the rear stage is less than 1.0, and the Al concentration in the molten zinc bath is 0.05. A method for producing an alloyed hot-dip galvanized steel sheet, characterized in that the bath temperature is ˜0.20%, the bath temperature is 450-480 ° C., and the penetration time of the steel sheet into the molten zinc bath is in the range of 2-5 seconds.