JPH0545653B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is applicable to the production of tin plate or stain-free steel sheet (hereinafter referred to as TFS).
Regarding the manufacturing method of the original plate for surface treatment, in particular, the continuous annealing method is applied to the original plate for surface treatment to the tempering degree of T4 and T5.
This is about how to make them separately. BACKGROUND ART As is well known, tin plate is produced by hot-rolling and cold-rolling a steel material, annealing the cold-rolled steel plate, and then subjecting it to temper rolling if necessary. , usually to obtain the required hardness. The degree of heat treatment of such tin plate is specified as follows by JIS G3303. In other words, the tempering degrees are classified from T1 to T6 in order from the softest, and the target hardness values for each are Rockwell hardness (HR30T), with T1 being 49±3 and T2 being 53±.
3. T3 is 57±3, T4 is 61±3, T5 is 65±
3. T6 is said to be 70±3. Among these tinplate blanks with different degrees of temper, so-called soft plates with degrees of temper T1 to T3 are manufactured by applying the box annealing method to the annealing process, and those with degrees of temper T4 to T6 are manufactured by applying the box annealing method to the annealing process. Hard plates are usually manufactured by applying a continuous annealing method. By the way, how to make different plates for each tempering degree of tin plate obtained by the continuous annealing method with tempering degrees T4 to T6, and in particular, how to make different plates with tempering degree T4 and original plates with tempering degree T5. Conventionally, this was usually done by changing only the chemical composition of the steel material. In other words, the original plate with a heat treatment degree of T4 is made of ordinary bottom carbon steel, while the original plate with a heat treatment degree of T5 is made of copper hardened by adding N and C. In general, inter-rolling conditions, continuous annealing test results, skin pass rolling reduction ratio, etc., were not changed depending on the heat quality degree. The reasons why original plates with heat treatment degrees T4 and T5 were made differently by changing only the chemical composition of the steel material were, first of all, because changing the chemical composition itself was technically easy. The second reason is that it is difficult to change the manufacturing conditions due to the equipment, and the technical basis for doing so has not been established. However, in recent years, the requirements of tin plate base plate users have become even more stringent than before, and they are now required to have hardness that precisely matches the target value. There are cases in which the general methods cannot satisfy the demands of consumers. On the other hand, it is desired to establish a more efficient manufacturing method for the original plate itself, but the production volume of the original plates with the above-mentioned tempering degrees T4 and T5 is large, and Although their uses are similar, in the past they had to be handled separately from the steelmaking stage due to their different chemical compositions, making process control extremely complicated, and improvements are desired. . Therefore, there are several methods that have been proposed in the past to differentiate between T4 and T5 original plates by assuming that the chemical composition of the steel material itself is the same and changing the conditions of the annealing process or adjustment rolling process, which is close to the final process. or has been proposed. For example, JP-A-57-70227 proposes a method of controlling the degree of tempering by changing only the cooling rate during annealing. On the other hand, in JP-A No. 55-114401, a special skin pass rolling mill equipped with work rolls with a diameter of 50 to 300 mm is used to achieve a high rolling reduction of T1 to T6. A method has also been proposed in which plates of all tempering degrees up to 100% are made from the same material. Problems to be Solved by the Invention In order to efficiently produce tinplate blanks with different degrees of tempering, especially blank plates with tempering degrees T4 and T5, the composition of the steel material must be the same, and the final stage of the blank manufacturing process must be the same. It is preferable to control the degree of tempering by controlling the conditions in a process close to the process, and methods for doing so include the method described in JP-A-57-70227, as already mentioned, and the method described in JP-A-55-114401. The method described in the publication is proposed. However, none of these proposed methods is practical, and some new problems may arise. That is, the method described in JP-A-57-70227 is as follows:
By using commonly used bottom carbon Al-killed steel or rimmed steel as a material, and continuously annealing it after hot rolling and cold rolling, the cooling rate after soaking to room temperature is greatly changed. This publication aims to produce plates with a thermal quality of T4 and plates with a thermal quality of T5, and this publication states that in order to obtain a plate with a thermal quality of T4, the cooling rate should be 5 to 20°C/sec, and the temperature should be In order to obtain a plate with quality T5, the cooling rate should be 100 to 300.
It is stated that it is appropriate to set the temperature to ℃/second. Regarding temper rolling after continuous annealing, the rolling reduction rate is the same at 1% for both temper degrees T4 and T5.
is applied. Attempts to change the hardness solely by controlling the cooling rate after annealing have been proposed not only in the above-mentioned publication but also in the past. In order to make different types of annealing, it is necessary to significantly widen the variation range of the cooling rate, which increases the length of continuous annealing equipment and increases operating costs, making it difficult to apply in reality. On the other hand, in the method described in JP-A-55-114401 in which the degree of tempering is controlled by changing the rolling reduction in skin-pass rolling after continuous annealing, according to an example in the same publication, the degree of tempering T4 is In order to make different plates and T5 plates, the temper rolling reduction ratio must be changed significantly. In particular, in order to manufacture a plate with a heat treatment degree of T5, the rolling reduction must be extremely high at 2.7 to 2.8%. In order to obtain such a high rolling reduction, a special work roll with a small diameter is required, as explained in detail in the same publication, and therefore it is impossible to apply a normal skin pass rolling mill. It cannot be manufactured on existing lines. Furthermore, in order to significantly change the skin pass rolling reduction ratio as described above, it is also necessary to change the finished cold rolled plate thickness, resulting in the problem of a significant drop in production efficiency. Furthermore, when the steel is under a high pressure of as much as 2.7 to 2.8%, problems arise such as poor workability and cracking at welds and the like. As mentioned above, in the conventionally proposed methods,
By applying it to reality, we can achieve high production efficiency and heat quality T.
It was not suitable for making different original plates for T4 and T5. This invention was made against the background of the above-mentioned circumstances, and it is possible to surface-treat tin plate or TFS plate with a heat treatment level of T4 from steel materials containing the same chemical composition without incurring the various problems mentioned above. It is an object of the present invention to provide a method for efficiently producing an original plate for surface treatment and an original plate for surface treatment with a heat treatment degree of T5. Means for Solving the Problems As a result of various experiments and studies in order to achieve the above-mentioned purpose, the present inventors used steel with a specific chemical composition as a material, and determined the chemical composition conditions, hot rolling conditions, By appropriately combining the continuous annealing conditions and skin pass rolling reduction ratio, it is possible to efficiently and accurately achieve the heat pass degree T4 without having to change the conditions as much as in the conventionally proposed methods. Surface treatment original plate and heat treatment degree T
They discovered that it is possible to make different types of original plates for surface treatment, as described in No. 5, and came up with this invention. That is, the method of this invention can reduce C 0.02 to 006%.
(weight%, same below), N 0.004-0.01%, Mn
0.1 to 0.4%, Al 0.01 to 0.04%, and the ratio N (%) / Al (%) of N amount to Al amount is 0.15 or more, and the balance is Fe and unavoidable impurities. The hot-rolled sheet is hot-rolled to a coiling temperature of 600℃ or less, then cold-rolled, and then soaked and cooled by continuous annealing to a temperature above the recrystallization temperature and below the Al transformation point, and then tempered. When rolling is performed to produce a surface treatment original plate with a tempering degree of T4 or T5, an average cooling rate between 500 and 400°C in the cooling process after soaking in the continuous annealing,
By setting the rolling reduction rate in skin pass rolling to one of the following conditions (a) and (b) depending on the final temper degree T4 or T5 to be obtained, This method is characterized by separately producing a T4 surface treatment original plate and a T5 surface treatment original plate. (b) For temper degree T4: Average cooling rate 55℃/sec or less, temper rolling reduction rate 1.0 to 2.0% (B) For temper degree T5: Average cooling rate 65℃/sec or higher, temper rolling Rolling reduction rate 1.5-2.5%. Detailed Description of the Invention First, the experimental results that formed the basis of this invention will be explained. As shown in Table 1, low carbon Al killed steels having two different chemical components were hot rolled and cold rolled in a normal process to obtain a cold rolled plate with a thickness of 0.25 mm. Each cold-rolled sheet is subjected to annealing heat treatment using two types of heat cycles shown in Fig. 1, A and B, and then temper-rolled at a rolling rate of about 0.1 to 3.5% in a small rolling mill. was applied. Then, after performing a treatment equivalent to molten tin at 250°C for 3 seconds, the Rockwell hardness (HR30T) was measured. The results are shown in FIG. The experimental results revealed that not only the hardness of each steel differs due to changes in steel composition and heat cycle pattern (change in cooling rate), but also that the dependence of hardness on temper rolling rate changes significantly. That is, for example, in the case of Steel 1, the change in hardness due to a change in heat cycle pattern (change in cooling rate) is relatively small, and the change in hardness due to a change in temper rolling rate is also relatively small. Therefore, in the case of Steel 1, in order to obtain the hardness of temper degree T5, the temper rolling rate should be 3.0.
% or more, and it is found that rolling with a normal temper rolling mill is extremely difficult. On the other hand, Steel 2 has a high sensitivity to heat cycles, and especially when slowly cooled, not only is the hardness small, but the dependence on the skin pass rolling rate is relatively small, and the hardness increases as the skin pass rolling rate increases. While the upward trend is not so great, when the steel is rapidly cooled, the dependence on the skin pass rolling rate becomes significantly large, and the hardness increases rapidly as the skin pass rolling rate increases. Therefore, from these experimental results, if the steel composition is appropriately set, the heat cycle (cooling rate) can be reduced.
The tempering degree T4 and the tempering degree T5 that accurately match the target hardness by appropriately combining the temper rolling rate and the temper rolling rate.
It is expected that it will be possible to efficiently make different plates.
In order to achieve this, it is essential to find a combination of an appropriate component system and an appropriate heat cycle, and it is also essential to find the optimum temper rolling conditions. Therefore, in order to clarify these conditions, more detailed experiments were carried out, and as a result, it was found that the conditions of this invention as already described are necessary, and this invention was completed. Next, each condition in this invention will be explained based on experimental results. First, regarding the cooling rate after soaking and holding at the annealing temperature in the continuous annealing process, the cooling rate is between 500 and 400°C, and when obtaining a tempering degree of T4, the cooling rate is 55°C/sec or less,
In order to obtain a thermal quality of T5, it is necessary to set the temperature to 65°C/sec or higher. In this way, the range for controlling the cooling rate is
The reason why the temperature was defined as between 500 and 400°C was based on the following experimental results. In other words, a cold-rolled plate of Steel 2 in Table 1 with a thickness of 0.25 mm after hot rolling and cold rolling was soaked at 680°C for 5 seconds as shown in Figure 3, and immediately continued to a temperature of 100°C or less. We conducted experiments in which the cooling rate was 25°C/sec, and the cooling rate was 70°C/sec from various temperatures T in the middle of the cooling process at the 25°C/sec cooling rate. The difference in the solid solution amount of C in the steel was investigated when the steel was slowly cooled at 35°C/sec from each temperature T to when it was rapidly cooled at 70°C/sec. The results are shown in FIG. From the results shown in Figure 4, the difference in the amount of C solid solution when changing the cooling rate from slow cooling of 35°C/sec to rapid cooling of 70°C/sec is large because the cooling rate change temperature T is 400°C or higher. and 400
Even if you change the cooling rate after the temperature reaches below ℃,
It can be seen that the amount of solid solution hardly changes. It is the temper rolling process that determines the hardness after temper rolling, and the final hardness is adjusted in this temper rolling to obtain the target hardness of the desired degree of temper rolling.
Since work hardening contributes to hardness adjustment during temper rolling, the change in hardness during temper rolling is largely related to solid solute elements in the steel, particularly solute C and solid solute N. . Therefore, if there is a large difference in the amount of solid solute C during skin pass rolling, even if there is not a very large difference in the rolling ratio during skin pass rolling, a large change in hardness can be reliably imparted and different degrees of heat rolling can be reliably produced. It can be divided. Here, as mentioned above, when changing from slow cooling to rapid cooling in the cooling process after continuous annealing, the change in the amount of C solid solution is large when the cooling rate change temperature T is 400°C or higher. Even if the cooling is changed from slow cooling to rapid cooling at a temperature lower than ℃, the change in the amount of C solid solution becomes extremely small. Therefore, in order to reliably change the hardness after skin pass rolling and to reliably change the amount of C solid solution, it is necessary to change the cooling rate in the temperature range of 400°C or higher in the cooling process of the continuous annealing process. It can be seen that the cooling rate in a lower temperature range has essentially no effect. On the other hand, as understood from Figure 4, even if the cooling rate change temperature is higher than 500℃,
The amount of change in the amount of C solid solution is determined by the cooling rate change temperature of 500 to 400.
This is almost the same as in the case around 500°C, and this shows that if cooling rate control in the temperature range of 500 to 400°C is performed reliably, cooling rate control in higher temperature ranges becomes unnecessary. In the end, 500-400
By controlling the cooling rate only between 0.degree. Such knowledge is extremely important for this invention. In other words, conventionally, in order to control the degree of tempering by changing the cooling rate immediately after continuous annealing, it was necessary to control the cooling rate over the entire range from the annealing soaking temperature to around room temperature. . Therefore, when changing the cooling rate conventionally, there is a problem of a decrease in cooling efficiency in the low-temperature part when cooling rapidly, while when cooling slowly, the efficiency significantly increases due to the increase in the time required to cool from high temperature to low temperature. The decline was becoming a problem. However, this invention greatly overturns the conventional wisdom, and instead of covering the entire range from high to low temperatures,
They found that it is sufficient to control the cooling rate only in the intermediate temperature range of ~400°C. As a result of a detailed study of the influence of the cooling rate after soaking in the continuous annealing process described above on the hardness after temper rolling, it was found that in order to reliably obtain the hardness of temper degree T4, 55 cooling rate between ~400℃
℃/sec or less, preferably 25℃/sec or less. On the other hand, in order to reliably obtain the hardness of heat treatment degree T5, the cooling rate between 500 and 400℃ should be 65℃/sec or less.
It has been found that the temperature can be set to sec or more, preferably 70°C/sec or more. Therefore, these conditions are defined in this invention. Note that when performing continuous annealing, in addition to controlling the cooling rate as described above, it is also necessary to limit the soaking conditions. That is, the annealing soaking temperature needs to be equal to or higher than the recrystallization temperature, but if it is too high, the crystal grains will become coarse, so the upper limit is set at point _A1 . Regarding the soaking time, if the soaking time is too long, the precipitation of AlN may progress and the amount of solid solution N may be insufficient, so it is preferable that the soaking time is as short as possible.
It is desirable to do this within seconds. Furthermore, in the method of the present invention, it is extremely important to control the components of the steel material, and the reasons for limiting each component will be explained below. C: As mentioned above, the amount of solid solute C during skin pass rolling has a large effect on the degree of increase in hardness due to work hardening, and as mentioned above, the amount of solid solute C has a large effect on the cooling rate of the continuous annealing process. greatly affected. The effect of the cooling rate on the change in the amount of solid solute C is that the total C in the steel is
It has been found through the following experiments by the inventors that the carbon content greatly depends on the carbon content, and therefore, appropriate control of the carbon content is important in this invention. In other words, steels with various C contents were used, and heat for temper degree T4 was set at a cooling rate of 25 °C/sec between 500 and 400 °C as shown in pattern C in Fig. 5 for each steel with a different C content. Cyclic heat treatment and cooling rate between 500 and 400℃ as shown in pattern D in Figure 5.
A heat treatment was performed using a heat cycle for a thermal quality T5 at 100°C/sec, and the difference in the amount of solid solute C due to the heat cycle of pattern C and the amount of solid solute C due to the heat cycle of pattern D was investigated. As a result, as shown in Figure 6, the difference in the amount of solid solute C due to the difference in cooling rate largely depends on the amount of C in the steel material, and
It has been found that the difference in the amount of solid solute C is large when the amount is 0.02 to 0.06%, and the difference in the amount of solute C becomes significantly small when the amount is outside of this range. Therefore, in order to noticeably change the amount of solid solute C by changing the cooling rate in the continuous annealing process and reliably bring about a change in hardness after temper rolling, it is necessary to increase the amount of C in the material.
It must be within the range of 0.02 to 0.06%. N and Al: N remains in the steel as solid solution N,
Al is an element necessary to bring about a large change in hardness during temper rolling under low pressure, and Al also has the harmful effect of reducing solid solution N by combining with N. Therefore, controlling the amount of N and the amount of Al as well as controlling the amount of C is extremely important in this invention.
In this invention, in order to bring about the maximum change in hardness through low-reduction temper rolling, it is necessary to increase the amount of solid solution of N, and in order to fully demonstrate its effect, it is necessary to increase the amount of solid solution in the steel. The total amount of N needs to be 0.004% or more. On the other hand, if the amount of Al increases relative to the amount of N, N will be fixed as AlN and the amount of solid solution N will decrease. When the present inventors investigated the influence of the ratio (%) of the amount of N to the amount of Al/Al (%) on the amount of solid solution N in the plate after continuous annealing, it was found that
The results shown in FIG. 7 were obtained. As is clear from FIG. 7, when the value of N (%)/Al (%) becomes less than 0.15, the amount of solid solution N decreases rapidly. Therefore, the value of N (%)/Al (%) was limited to 0.15 or more. Also, if the amount of N is too large, it will be difficult to obtain a relatively soft base plate with a heat treatment degree of T4, so the upper limit of the amount of N should be set.
It was set as 0.01%. Note that the amount of N is preferably 0.008% or less. On the other hand, Al is preferably contained in a small amount from the viewpoint of ensuring solid solution N, but it is an element necessary for deoxidation in the normal steelmaking process, and for this purpose, it needs to be contained at least 0.01% or more. Furthermore, if there is too much Al, the solid solution N will be reduced as mentioned above, so in addition to limiting the ratio N (%)/Al (%), it is necessary to set the upper limit of the Al amount to 0.04%. There is. Mn: Mn needs to be added in an amount of 0.1% or more to prevent cracking due to S, which is included as an unavoidable impurity. Must be within the range. The remainder for C, N, Al, and Mn as above is
Fe and unavoidable impurities may be used. Hot rolling of the above-mentioned steel materials may be carried out according to a conventional method, but the winding temperature of the hot rolled sheet after hot rolling must be low in order to achieve the purpose of the present invention. It is. Especially when the winding temperature is 600℃
If it exceeds this, not only will N be more likely to be fixed as AlN, but the crystal grain size will become too large and soft, making it difficult to differentiate between the degrees of tempering T4 and T5. Therefore, the hot-rolled sheet winding temperature is 600℃.
Hereinafter, the temperature is preferably 540°C or less. The hot-rolled sheet is pickled if necessary, then cold-rolled to a desired thickness according to a conventional method, and then continuously annealed. The soaking conditions in this continuous annealing process are as described above, and the average cooling rate between 500 and 400°C in the cooling process after soaking changes depending on the final degrees of heat treatment T4 and T5. As already mentioned, it is also possible to The reduction ratio in temper rolling after continuous annealing is 1.0 to 2.0% when obtaining a temper degree T4, and 1.5 to 2.5% when obtaining a temper degree T5. The reason why the skin pass rolling reduction ratio is determined in this manner is that a normal skin pass rolling mill can be applied with this level of reduction ratio, and there is no need to change the base material plate thickness. Here, there is not much difference in the reduction rate between obtaining the tempering degree T4 and T5, but the cooling rate in the continuous annealing process as described above is By creating a difference in the tempering degrees, it is possible to sufficiently create different hardnesses of tempering degrees T4 and T5 by adjusting the rolling reduction ratio in temper rolling to this extent. Of course, in this temper rolling, there is no need to take special measures such as small-diameter work rolls or wet tempering fluid. As described above, in the method of this invention, the chemical composition, hot rolling conditions, annealing heat cycle (especially 500
By appropriately combining the cooling rate (cooling rate between It became possible to make them separately. Here, it is possible to create different degrees of heat treatment T4 and T5 with a relatively small change in cooling rate and a small change in reduction rate in skin pass rolling, by appropriately setting the material components, the amount of solid solute C, This is thought to be due to the fact that we succeeded in changing the amount of solid solution N to the maximum extent possible. Furthermore, the effect of this invention is that tinplate (tinplate)
Moreover, it does not change depending on the surface treatment method such as TFS, and therefore, the method of the present invention can be applied to the production of tin plates, TFS plates, and all other surface treatment plates. Examples Steels with chemical compositions shown in Steels 3 to 7 in Table 2 were hot rolled to a thickness of 2.3 mm according to the conventional method, and coiled at the coiling temperature shown in Table 3. The steel plate was further cold rolled to a thickness of 0.23 mm and continuously annealed using a heat cycle of pattern C or a heat cycle of pattern D in FIG. Then the third
Temper rolling was performed at the rolling reduction ratio shown in the table, followed by tin plating and reflow treatment on a tin plating line to produce a product (tin plate). When the hardness (HR30T) of each tin plate was examined, the results shown in Table 3 were obtained. As is clear from Tables 2 and 3, when steels (steel numbers 3, 5, and 6) within the composition range of this invention were used and processed within the process condition range of this invention (Experiment No. 3- 1, 3-2; 5-1, 5-2; 6-
1 and 6-2), it was possible to accurately produce hardnesses of T4 and T5. On the other hand, when the process conditions are out of range even if steel within the composition range of this invention is used (Experiment No. 3-3, 3-4)
Or, when conducted under the process condition range of this invention using steels (steel numbers 4 and 7) outside the composition range of this invention (Experiment No. 4-1, 4-2; 7-1, 7-2) In both cases, it was difficult to differentiate between the tempering degrees T4 and T5. Effects of the Invention As is clear from the above explanation, according to the method of the present invention, the cooling rate between 500 and 400°C in the cooling process of the continuous annealing process is slightly changed using steel materials with the same composition. In addition, by only slightly changing the rolling reduction ratio of skin pass rolling, it is possible to accurately produce a surface treatment base plate having a heat quality degree of T4 and a surface treatment base plate having a heat quality degree of T5. In the method of this invention, the tempering degrees T4 and T
As mentioned above, the only change in process conditions necessary to create different types of 5 is to change the cooling rate between 500 and 400℃ in the cooling process of the continuous annealing process, and the range of change is small. ,
There is no risk of increasing the length of continuous annealing equipment or reducing processing efficiency, and on the other hand, the skin pass rolling process can be carried out within the normal skin pass rolling reduction range without applying an excessively high reduction. Since it is sufficient to change the temperature, it can be carried out in a normal temper rolling mill without using a special temper rolling mill or adding special operations, and the high rolling pressure does not adversely affect the product. There is no need to change the thickness of the base material. Therefore, according to the method of the present invention, the same material can be extremely efficiently heated to a temperature of T4,
Each type of T5 surface treatment original plate can be made separately.

【table】

【table】

【table】 [Brief explanation of drawings]

Fig. 1 is a diagram showing the annealing heat cycle pattern in the experiment that was the basis for making this invention, Fig. 2 is a diagram showing the influence of the annealing heat cycle pattern and temper rolling reduction rate on hardness, Third
The figure is a diagram showing the heat cycle pattern in the experiment shown in Figure 4, and Figure 4 is a graph showing the influence of the cooling rate change temperature, which is changed from gradual cooling to rapid cooling, on the change in the amount of solid solute C in the cooling process after annealing. Fig. 5 is a diagram showing an example of the heat cycle pattern of the continuous annealing process in the method of the present invention, Fig. 6 is a graph showing the influence of the amount of C in the steel material on the amount of solid solution C, and Fig. 7 is the graph showing the effect of the amount of C in the steel material on the amount of solid solution C. It is a graph showing the influence of the value of N (%)/Al (%) in the solid solution N amount.

Claims (1)

[Claims] 1 C0.02 to 0.06% (weight%, same hereinafter), N0.004
~0.01%, Mn0.1~0.4%, Al0.01~0.04%, and the ratio of N amount to Al amount N (%) / Al (%)
0.15 or higher, with the balance consisting of Fe and unavoidable impurities, the material is hot rolled to a hot rolled sheet coiling temperature of 600℃ or lower, then cold rolled, and then continuously annealed to a temperature higher than the recrystallization temperature. , in the cooling process after soaking in the continuous annealing, when soaking and cooling to a temperature below the A1 transformation point, and then performing temper rolling to produce a surface treatment base plate with a temper degree of T4 or T5. The average cooling rate between 500 and 400°C and the rolling reduction in temper rolling are the final temper degree T4.
Alternatively, set either of the following conditions (a) or (b) depending on T5 to separately produce a surface treatment original plate with a thermal quality of T4 and a surface treatment original plate with a thermal quality of T5. A method for manufacturing original plates for surface treatment using continuous annealing. (a) In the case of temper degree T4: average cooling rate of 55°C/sec or less, temper rolling reduction rate of 1.0 to 2.0%. (b) In the case of temper degree T5: average cooling rate of 65°C/sec or more, temper rolling reduction rate of 1.5 to 2.5%.