ES2381356T3 - Steel sheet resistant to atmospheric corrosion, with high mechanical strength and excellent folding; and method to produce it - Google Patents

Abstract

A sheet of steel of high mechanical resistance, weather resistant and excellent folding, containing, in mass: C: 0, 05 to 0, 15%, Si: 0, 5% or less, Mn: 0, 5 a 2, 0%, P: 0, 02% or less, S: 0, 005% or less, Ni: 0, 2 to 2, 0%, Cu: 0, 2 to 0, 5%, Cr: 0, 2 at 1.0%, Ti: 0.03 to 0.2%, and optionally one or more of Nb: 0.01 to 0.07%, V: 0.01 to 0.07%, and B: 0, 0005 to 0.0050%, the rest being Fe and unavoidable impurities, and having an elastic limit of 700 MPa or greater.

Description

Steel sheet resistant to atmospheric corrosion, with high mechanical strength and excellent folding; and method to produce it.

Detailed description of the invention

The present invention relates to a steel material for use in automobiles and containers for land or sea transport, which is required to have a high mechanical strength, a good ease of work after blasting or the like and a good resistance to outdoor; and to a method to produce this steel material.

So far, for the containers a material having the properties of a low weight, long duration and good weather resistance has been desired, and thus for such applications a material produced using aluminum has been used primarily. However, such a material has the disadvantages of high cost and low mechanical strength, and for this reason a steel material having a high mechanical strength and good weather resistance has been sought. As a conventional, weather-resistant steel material, there is a highly weather-resistant laminated steel material of the 490 MPa (50 kgf / mm2) class of tensile strength, as stipulated in JIS G3125. With respect to steel materials that have a greater strength than that, Japanese Unexamined Patent Publication No. H3-2321 describes a method of producing a weather resistant steel sheet having a tensile strength of 590 MPa ( 60 kgf / mm2) or greater and a good ease of cold work.

Meanwhile, with the increase in the use of sea containers, the environment becomes even more severe and there are increasing cases in which even a painted container undergoes local corrosion and cannot withstand long-term use. To cope with the problem, JP-A-63-72853 reveals that an increase in life can be achieved by adding Nb, Ti, V and B to a steel with a high P content.

However, in recent years the most desired is a container of high mechanical strength and low weight, and we have sought a weather-resistant steel material and an ultra-high mechanical resistance that has an elastic limit of 700 MPa or greater and a good folding. On the other hand, as the folding work is applied after the steel material is subjected to a blasting or the like, in order to improve the ease of application of paint in the painting phase, fatigue properties and hardenability superficial, very high levels of mechanical strength and ease of work are required for the steel material. The reason why the required mechanical strength is not expressed in terms of tensile strength but of the elastic limit is because the maintenance of stiffness must be guaranteed, even when the thickness of the material is reduced, in order to obtain a Ultra high mechanical strength and low weight. For this reason, such specifications are not met by the components and the production method described in Japanese Unexamined Patent Publication No. H3-2321.

In addition, with the types of components such as those proposed in JP-A-63-72853, which is intended to last longer, although the longer duration is guaranteed due to weather resistance, cracking occurs during blasting and blasting. folded in the container manufacturing process and, for this reason, the necessary requirements are not met. For the resolution of the aforementioned problems, the object of the present invention is to provide: a steel material that supports the folding work after a blasting or the like, and that has a good weather resistance, while ensuring a ultra high mechanical strength corresponding to an elastic limit of 700 MPa or greater; and a method to produce this steel material.

JP-A-3-2321 describes a method for manufacturing hot-rolled, weather-resistant and high-strength hot rolled steel, a method comprising the steps of: producing a slab containing

C: 0.02-0.12%, Si: 0.50%, Mn: 0.10-2.00%, P: 0.070-0.150%, S: 0.020%, AI: 0.010-0.050%, Cu: 0.25-0.55%, Cr: 0.30-1.25%, N: 0.0060%, Ti: 0.06-0.20% and 12.1 x Tief (%) / Mn (% ) � 1.0, [where, Tief (%) = Ti (%) - 3.4 xN (%) 1.5 x O (%)], and the rest Fe with the inevitable impurities, by means of, in continuous, melt, heat the slab to 1,180oC or more, laminate the hot slab to the finishing temperature of 880-950oC and wind at 650oC or less, to obtain a sheet of weather-resistant hot rolled steel that has a resistance to the traction of 590 MPa (60 kgf / mm2) or greater and a good ease of cold work.

JP-A-2000-63981 describes a weather-resistant steel that shows a blackish color tone from the initial oxidation stage and excellent exterior appearance and color tone stability, and also describes a steel comprising, in Weight, C: 0.01-0.15%, Si: 0.01-1.0%, Mn: 0.8-3.0%, Cu: 0.05-1.0%, Ni: 0, 25-5.0%, Al: more than 0.1% to 0.2%, the rest consisting of Fe and unavoidable impurities, which satisfies that Mn + Ni� 1.8, and which optionally also includes one or more of Cr: 25-5.0%; Mo: 0.25-1.0%, P: 0.03-1.0%, Nb: 0.01-0.05%, V: 0.01-0.1%, Ti: 0.005-0, 05%, Zr: 0.01-0.1%.

The means to achieve the above object according to the present invention are:

(one)

 A sheet of steel of high mechanical resistance, weather resistant and excellent folding, which contains, in mass:

C: 0.05 to 0.15%, If: 0.5% or less, Mn: 0.5 to 2.0%,

P: 0.02% or less,

S: 0.005% or less, Ni: 0.2 to 2.0%, Cu: 0.2 to 0.5%, Cr: 0.2 to 1.0%, Ti: 0.03 to 0.2%, and optionally one or more of Nb: 0.01 to 0.07%,

V: 0.01 to 0.07%, and

B: 0.0005 to 0.0050%, the rest being unavoidable Faith and impurities, and with an elastic limit of 700 MPa or greater; and the method of Production of it is:

(2)

 a method for producing a steel sheet of high mechanical resistance, weather resistant and excellent folding, which has an elastic limit of 700 MPa or greater, the method comprising the steps of:

heating a steel material containing, in bulk, at a temperature of 1,200 ° C or greater

C: 0.05 to 0.1%, If: 0.5% or less, Mn: 0.5 to 2.0%,

P: 0.02% or less,

S: 0.005% or less, Ni: 0.2 to 2.0%, Cu: 0.2 to 0.5%, Cr: 0.2 to 1.0%, Ti: 0.03 to 0.2%, and optionally one or more of Nb: 0.01 to 0.07%,

V: 0.01 to 0.07%, and

B: 0.0005 to 0.0050%, the rest being unavoidable Faith and impurities;

after that, finish the steel material in the temperature range of 850 to 950 ° C; Y

Wind the rolled steel material in the temperature range of 500 to 650oC.

The reasons for defining a steel sheet and a production method according to the present invention are explained in detail below, together with the drawings, in which:

Figure 1 is a graph showing the effects of the amount of Ni and the amount of P on corrosion loss,

Figure 2 is a schematic drawing showing the sketch of a compression folding test, and

Figure 3 is a graph showing the influence of the amount of P on corrosion loss and the folding R (radius).

In order to solve the aforementioned problems, methods for producing steel sheets comprising various kinds of steels were investigated and studied for the present invention, and the present invention was thus established. In the following, the present invention is explained in detail.

In general, the same kind of oxide appears in a weather-resistant steel material as in ordinary steel during the initial stage of exposure to the atmosphere. However, after that, it is said that some of the rust of the weather-resistant steel material forms a dense oxide very adhered to the base material, an oxide that plays the role of a protective film and, therefore, prevents the development of rust caused by the environment. In order to create such an oxide, it is also said that it is effective to contain Cu, Cr and P.

In the case of a conventional material that has a tensile strength of 490 to 590 MPa (50 to 60 kgf / mm2), containing such types of components, the material has been applicable to containers as a steel material resistant to outdoor. In recent years, associated with global environmental issues, weight reduction in cars aimed at improving fuel efficiency has been reported, and there is also a marked need for container weight reduction used for land or sea transport. In order to achieve a reduction in weight greater than ever the desired thickness in steel materials has become less, and in order to guarantee stiffness an elastic limit of 700 MPa or greater is required. Meanwhile, a certain roughness is applied to the surface of the steel sheets in the production of containers by means of blasting, in which pellets, sand, shot or the like are blown over the steel sheets in order to improve the performance of the peeling and ease of paint application. The process makes the surface of the same hard and, for this reason, cracking tends to occur with the folding in the subsequent folding conformation. In particular, in the case of a steel material that has an elastic limit that exceeds 700 MPa, a marked propensity for cracking appears and the selection of the additive elements has a great influence.

As explained above, in order to produce a weather-resistant steel material that has an elastic limit that exceeds 700 MPa and is capable of withstanding the folding work after being subjected to blasting, it is necessary to satisfy simultaneously The following requirements:

one.

Improvement of the mechanical strength of the material,

2.

folding guarantee, and

3.

weather resistance guarantee.

When P is used extensively in the production of such high mechanical strength steel materials that have good weather resistance, several problems arise. First, when a slab of 200 to 300 mm thickness melts in the production process, the P tends to cause a central segregation and is concentrated in the central part of the thickness, which is the part that finally solidifies. The part where the P is concentrated is likely to cause embrittlement cracking. In addition, since the high mechanical strength steel material itself has a high propensity for cracking, the slab cracking is frequently caused and also a very low yield on the high mechanical strength, weather resistant steel sheet and with the addition of P.

On the other hand, even if the steel sheet could be produced, the material would be fragile due to the addition of P and, for this reason, its ease of work would be scarce. Generally speaking, as the mechanical strength of the steel material increases, its elongation decreases. For this reason, the ease of work of a material with the addition of P decreases further and, on the other hand, as the subject material is subjected to a folding work after blasting with pellets or the like, the material is very prone to cracking With the folding. In addition, when such a steel material is used to manufacture a container by welding, welding cracking is likely to occur. As a result of thoroughly investigating the characteristics of Cu, Cr and P, which in conventional steels have been used as weather-resistant elements, it has become clear that P has a very adverse influence on requirement 2 above and does not Can use in high strength steel materials. For the present invention, the relationship between the amount of P and the cracking generation conditions with the folding was investigated in the 90 degree compression folding test shown in Figure 2, while the R (radius) was varied from the tip of the die. At the same time, for the present invention, the relationship between the addition of P and the corrosion loss was investigated, and the results are shown in Figure 3. It is obvious that. although as the amount of P increases, the corrosion loss decreases and weather resistance improves, the increase in the amount of P causes the critical folding R (radius) to increase, below which cracking occurs with folding, and worsen the folding of the steel sheet. For this reason, in order to guarantee folding, it is necessary to study a method to guarantee weather resistance without the use of P. Cu and Cr less adversely influence folding. However, only with the increase in its quantity, weather resistance is hardly guaranteed. On the other hand, the steel material cannot withstand the work of folding after blasting or the like.

In view of this, as a result of the repetition of several tests, for the present invention it has been found that: weather resistance can be guaranteed by the use of Ni instead of P; Folding can be guaranteed by lowering the C content to improve workability, reduce the addition of P as much as possible, and reduce as much as possible the addition of S, to prevent the formation of MnS that adversely affects the folding; and the mechanical resistance adjustment can be achieved using the precipitation effect caused by combining one or more of Ti, Nb, V and B.

Figure 1 shows the effect of the amount of Ni on the corrosion loss, compared to the effect of the amount of P. It has been found that, as the amount of Ni increases, the corrosion loss decreases and an effect is obtained similar to the case of the addition of P.

In addition, unlike P, Ni does not secrete during slab smelting, slab cracking is not relevant, and performance is also good. On the other hand, Ni does not cause problems with ease of work and weldability, and for this reason the work of folding, after blasting with pellets or the like, and cracking in welding are not relevant. Therefore, Ni is a very suitable element for the production of steel sheets of high mechanical resistance, weather resistant and excellent folding. With respect to weather resistance, the effect of Ni is presented through joint use with Cu and Cr.

Experiments were repeated based on the above conditions and the present invention was established. The reasons for defining the additive elements according to the present invention are described in detail below.

C: C is used as an element to increase mechanical strength. It is used not only as a reinforcing element in solid solution but also, when combined with Ti and Nb and forming carbides, as a precipitation reinforcing element. However, when C is used excessively, the ease of work worsens. Since the ease of work decreases as the mechanical strength of the steel material increases, it is desired that the amount of C be low. The reason why the lower limit of the amount of C is set at 0.05% is that when it is less than that amount the elastic limit of 700 MPa or greater is hardly ensured. On the other hand, the reason why the amount of C is limited to 0.15% or less is to avoid cracking caused by folding work.

Yes: The Si is an element that is likely to form fayalite (2FeO · SiO2) on the surface of the steel sheet, make Fe2O3 thin over most of the surface, and generate red encrustations. When red inlays are created on the surface of the steel sheet, it appears crushed and the product is not acceptable to users. In order to avoid this problem, the upper limit of the amount of Si is set at 0.5%.

Mn: Mn is a necessary element to increase the mechanical strength of steel materials. When the amount of Mn is less than 0.5%, a high mechanical strength steel material is hardly produced. On the contrary, when the Mn is added above 2.0%, the ease of work is hardly assured. For these reasons, the amount of Mn is limited to the range of 0.5 to 2.0%.

P: P is an effective element for the increase of mechanical resistance and beneficial for the improvement of weather resistance, and has been used so far in weather-resistant steel materials. However, in the production of ultra-high mechanical strength steel materials that have an elastic limit above 700 MPa, the P causes the slab embrittlement during the production of the steel material and also makes the weldability worse. In addition to that, the P also worsens the folding, and for this reason the amount of P should be as low as possible. Therefore, the upper limit of the amount of P is set at 0.02%.

S: The S when combined with the Mn forms the manganese sulfide MnS. This sulfide is easy to deform, stretches by rolling and is present in steel materials. MnS worsens the folding and ease of work of steel materials. In the particular case of a high mechanical strength steel material, the S should be reduced as much as possible because it increases the propensity for cracking. For this reason, the upper limit of the amount of S is set at 0.005% as a commercially feasible limit.

Neither: Ni is an element that increases mechanical resistance and weather resistance, and is also effective for the prevention of embrittlement. In particular, Ni is effective for weather resistance in a medium environment mainly influenced by salinity. As explained previously, in the steel materials of High mechanical resistance, the P, which is effective for weather resistance, negatively affects the ease of work and therefore can not be used. Ni can be used as a substitute for P and, unlike the P, does not cause slab cracking or worsen the ease of work of the steel material. Ni is due add by 0.2% or more, in order to effectively use its weather resistance feature. For other On the other hand, Ni is an expensive metal and its effect no longer improves when its quantity exceeds 2.0%. For this reason, the upper limit of the amount of Ni is set at 2.0%. To the containers that are used for land transport and maritime affects the salinity from seawater, in the case of maritime transport, and salinity from the salt of the melted snow precipitated in the cold regions, in the case of land transport. By For this reason, Ni is an important element for weather resistance. In an environment other than saline environment, the elements Cu and Cr, which are described below, are effective, and for this reason The combined addition of these elements is also effective.

Cu: Cu is important for improving weather resistance and is an effective element in forming a stable oxide. To guarantee its effect against a corrosive environment, an amount of Cu of 0.2% or more is required. Without However, when the amount of Cu exceeds 0.5%, surface defects are likely to appear. For those reasons, the amount of Cu is limited to the range of 0.2 to 0.5%.

Cr: Cr is also important for improving weather resistance and is an effective element to form an oxide stable. To guarantee its effect against a corrosive environment, an amount of Cr of 0.2% or plus. However, its effect no longer improves if the amount of Cr exceeds 1.0%. For those reasons, the amount of Cr is limited to the range of 0.2 to 1.0%.

When a steel material having an elastic limit of 700 MPa or greater is produced, the use of the precipitation reinforcement. The following four elements, which allow the effect of precipitation, compensate for insufficient mechanical resistance, and this compensation can be achieved using one or more of those elements.

You: Ti when combined with C and N forms a carbide and a nitride, and thus increases the mechanical resistance of the steel material. Its effect appears when Ti is added by 0.03% or more and no longer improves if Ti is add 0.2% or more.

Nb: The Nb when combined with the C and N also forms a carbide and a nitride, and thus increases the resistance Steel material mechanics. Its effect appears when the Nb is added by 0.01% or more, and it no longer improves if the Nb is added in 0.07% or more.

V: V when combined with C and N also forms a carbide and a nitride. and thus increases the resistance Steel material mechanics. Its effect appears when V is added by 0.01% or more, and it no longer improves if V is added in 0.07% or more.

B: The B an element that forms a carbide and a nitride, and is effective in increasing hardenability and resistance mechanics. Its effect appears when B is added by 0.0005% or more, and its effect no longer improves if it is added 0.0050% or more.

Next, the reasons for defining the production conditions are explained below.

The purpose of limiting the annealing temperature to 1,200 ° C, or more, is to dissolve the carbide and nitride in the slab state, in order to make use of the precipitation effect of Ti, Nb, V and B, and by doing that form fine precipitates during the production of the steel sheet, so that the precipitation effect can be fully utilized.

In order to fractionate the precipitates, it is necessary to maintain the finishing temperature of the lamination at 850oC or more. However, when the finishing temperature of the lamination exceeds 950 ° C, problems arise such as increasing the probability of thickening of the glass beads, the formation of scale defects, etc. For this reason, the finishing temperature of the lamination is limited to the range of 850 to 950 ° C.

The winding temperature affects the size of the precipitates, and the degree of the precipitation effect varies according to said winding temperature. When a roll is wound at a high temperature, too large precipitates develop and the reinforcing effect decreases. On the contrary, when the winding temperature is too low, the development of the precipitates is insufficient and an increase in mechanical resistance is not expected. For these reasons, the winding temperature is limited to the range of 500 to 650 ° C, as an appropriate temperature range in which an increase in mechanical strength is expected.

In the production processes there are no impediments in the use of a high pressure husking device and a bar heater, and in the use of a continuous-continuous hot rolling in which the bar joint materials are continuously laminated after subjecting them to a raw lamination. In other words, with the use of these devices, it is possible to prevent the formation of scale defects and improve the performance, while improving the capacity of the process for temperature control.

Examples

Steels number 1 to 12 were cast, which as shown in Table 1 have several components, and after that steel materials were produced under the rolling conditions shown in Table 2, samples were taken and a blasting treatment with pellets to their surfaces, and subsequently the properties of the samples were evaluated. For the evaluation, tensile tests were applied and the elastic limit, tensile strength and total elongation were measured. In addition, a folding work with a 90 degree folding angle was applied using a die with a tip whose radius (R) was 3 mm, and the existence of cracks in the folded part was examined.

Weldability was assessed by the existence of cracks in the weld after an arc weld was applied. Regarding the weather resistance, a salt water spray treatment was applied and, after that, corrosion acceleration tests were applied, in which the humidity and dryness conditions were repeated alternately, the weight of each sample before the test was applied and after the oxide was removed after the test, and as a result corrosion losses were obtained. As a comparative example, a commercially available Corten steel of class 490 MPa was used, and the data thereof was used as a standard, and then each sample was evaluated as "X" when the corrosion loss of the sample was greater than that of the standard , and as "O" when the corrosion loss thereof was equal to or less than that of the pattern.

In addition, the surface appearance was evaluated by observing the surface of each steel material after rolling. All lamination conditions of tests number 1 to 12 were within the ranges stipulated in the present invention. In the case of test No. 7, the amount of Ni was small and, thus, the weather resistance thereof was low. In the case of test No. 8, although the weather resistance was good, the amount of P was large and for this reason the weldability was low and cracking appeared in the folding work. As in the case of test No. 9 the amount of Si was large, and in the case of test No. 10 the amount of Cu was too large, scabs and crushed appeared on the surface, and thus the surface appearance was bad in both cases. In the case of test No. 11, the amounts of C and Mn were too large and, for this reason, the folding and weldability were low. In the case of test No. 12, the amount of S was large and, for this reason, cracking appeared in the folding test.

In the case of tests No. 13 to 17, the steel material No. 2 produced within the ranges stipulated in the present invention was used, and the rolling conditions were varied. In the case of test No. 13, the annealing temperature was too low and, for this reason, precipitation reinforcement could not be used and its elastic limit could not exceed the desired value of 700 MPa. In the case of test No. 14, the lamination temperature was high and, for this reason, the surface appearance was defective. In the case of test No. 15, the rolling temperature was low and, for this reason, a reinforcement was not appreciated by the fractionation of the precipitates and the desired mechanical strength could not be obtained. In the case of test No. 16, the winding temperature was high and, for this reason, the steel material softened and the desired mechanical strength could not be obtained. In the case of test No. 17, the winding temperature was too low and, for this reason, although the mechanical strength increased, a hardened layer originated and cracking occurred after the folding work.

In the case of examples No. 1 to 6, which satisfied the intervals of the components and the lamination conditions stipulated in the present invention, all the properties were acceptable and good evaluation results were obtained.

In addition, tests No. 18 to 20 according to the present invention were cases in which a peeling treatment was used, in the hot rolling process, in order to remove the surface inlays of each of the raw bars by means of a high pressure shelling, after a raw rolling and subsequent continuous hot rolling, in which the raw bars were heated with a bar heater and joined together. In all cases, the properties of the material stipulated in the present invention were satisfied and the effects of using the above treatment means were obtained. In the case of test No. 18, a bar heater was used and, as a result, the temperature of the raw bar before finishing lamination was high and uniform; in this way the precipitation was controlled regularly, the deviation of the quality of the material decreased, and the deviation of the elongation was reduced to 3.8%, while normally the deviation of the elongation of a steel of this class is approximately 6%. Test No. 19 was a case in which a high pressure husking apparatus and continuous-continuous hot rolling was applied. By adopting high pressure husking, the surface appearance of the steel material was significantly improved. In addition, by adopting continuous-continuous hot rolling, the roll end configuration was improved and the material yield improved up to 97%, while the material yield is usually about 95%. In addition, test No. 20 was a case in which a bar heater and continuous-continuous hot rolling were used. The elongation deviation decreased to 3.2% and the material yield improved to 98%.

Table 1: Material components (mass%)

Steel No.

C Yes Mn P S To the N Cu Neither Cr You Nb V B

Examples of the invention

one 0.07  0.29 1.41  0.006 0.002  0.033 0.006 0.25  1.80 0.31  0.078  0.031      

2

0.11  0.18 0.88  0.011 0.001  0.025 0.004 0.28  1.00 0.39  0.085  0.037      

3

0.08  0.10 1.22  0.008 0.002  0.011 0.003 0.23  0.50 0.39  0.082  0.024  0.025 0.0012

4

0.09  0.03 1.11  0.006 0.002  0.030 0.004 0.48  0.25 0.81  0.142  0.055      

5

0.14  0.43 0.62  0.016 0.004  0.022 0.003 0.44 0.65  0.30 0,180         

6

0.05  0.04 1.86  0.005 0.003  0.056 0.005 0.31  1.20 0.52  0.052  0.043  0.045   

Comparative examples

7 0.08  0.22 1.33  0.012 0.002  0.032 0.004 0.42 0.18 0.17  0.089  0.033      

8

0.09 0.30 2.10 0.091 0.004  0.017 0.006 0.27  0.35 0.38  0.080  0.040      

9

0.12 0.75 0.95 0.011  0.002  0.043 0.004  0.41 0.65 0.82  0.090  0.033  0.033   

10

0.09  0.25 0.20  0.005  0.001  0.020 0.003 0.55 0.23 0.30  0,120  0.052    0.0036

eleven

0.23 0.48 2.50 0.028  0.004  0.017 0.006 0.48 1.90 0.90       

12

0.08  0.21 1.50  0.007 0.008 0.380  0, 005 0.38  0.85 0.55  0.090  0.041    0.0008

Note: The underlined and italicized figures indicate that they are outside the relevant ranges stipulated in the present invention.

Table 2: Production and evaluation conditions

Observations

Ni: small quantity Q: large quantity Yes: large quantity Cu: large quantity Cr-Mn: large quantities S: large quantity Low annealing temperature High lamination temperature Low lamination temperature High winding temperature Low winding temperature The elongation deviation decreased to 3.8% due to the use of the bar heater The surface appearance can be improved by high pressure peeling. The material yield was improved to 97% by continuous-continuous hot rolling. The elongation deviation decreased to 3.2% due to the simultaneous use of the bar heater and continuous continuous heating lamination.

Surface appearance

OR OR OR OR OR OR OR OR X X OR OR OR X OR OR OR OR OR OR

Resist intemp

OR OR OR OR OR OR X OR OR OR OR OR OR OR OR OR OR OR OR OR

Weldability

OR OR OR OR OR OR OR X OR OR X OR OR OR OR OR OR OR OR OR

Foldability

OR OR OR OR OR OR OR X OR OR X X OR OR X OR X OR OR OR

Alarms (%)

22 22 2. 3 twenty twenty 2. 3 2. 3 19 twenty-one twenty 18 twenty-one 24 2. 3 19 twenty-one 17 2. 3 twenty-one twenty

Resist traction (MPa)

830 857 805 1,009 1,007 814 813 818 892 959 618 886 755 807 805 782 890 862 810 982

Elastic limit (MPa)

740 746 708 878 876 712 707 711 776 834 537 771 680 692 672 690 802 752 705 877

Temp. of .coiling or C

530 520 550 620 590 520 510 630 550 600 530 520 530 520 590 680 450 530 560 600

Lamination Temp. Or C

900 910 870 920 900 900 890 880 910 910 900 900 900 980 820 930 920 870 920 920

Temp. of annealing C

1,220 1,220 1,220 1,250 1,250 1,230 1,230 1,250 1,210 1,210 1,230 1,260 1,150 1,220 1,230 1,220 1,240 1,210 1,220 1,210

Steel No.

one 2 3 4 5 6 7 8 9 10 eleven 12 2 2 2 2 2 2 3 5

Test No.

one 2 3 4 5 6 7 8 9 10 eleven 12 13 14 fifteen 16 17 18 19 twenty

Examples of the invitation

Examples with parativ os Examples of the invention

Folding: Valued for the existence of cracking in the folded part after a 90 degree folding. The folding R (radius) was set at 3 mm, and expressed as "X" when produced cracking and "O" when it did not occur.

Weldability: Expressed by “X” when cracking occurred in welding after arc welding, and by “O” when it did not occur. Weather resistance: Expressed by “X” when the corrosion loss was greater, and by “O” when it was lower, than the standard corrosion loss defined for Corten steel of 490 Conventional MPa

Note: The underlined and italicized figures indicate that they are outside the relevant ranges stipulated in the present invention.

The steel material according to the present invention has, simultaneously, good folding and good weather resistance, while also having a high mechanical strength. With the use of the steel material, a reduction in the weight of the steel material in the containers or the like that requires good weather resistance can be achieved and, due to its weather resistance, a longer life is also achieved. For this reason, the present invention is environmentally friendly, thanks to weight reduction, and provides an economic effect due to the longer service life.

Claims (2)

1.- A sheet of steel of high mechanical resistance, resistant to the weather and excellent folding, which contains, in mass: C: 0.05 to 0.15%, If: 0.5% or less, Mn: 0.5 to 2.0%, P: 0.02% or less, S: 0.005% or less, Ni: 0.2 to 2.0%, Cu: 0.2 to 0.5%, Cr: 0.2 to 1.0%, Ti: 0.03 to 0.2%, and optionally one or more of Nb: 0.01 to 0.07%, V: 0.01 to 0.07%, and B: 0.0005 to 0.0050%, the rest being Fe and impurities inevitable, and having an elastic limit of 700 MPa or greater. 2.- A method to produce a steel sheet of high mechanical resistance, weather resistant and excellent folding, which has an elastic limit of 700 MPa or greater; the method comprising the steps of: heating a steel material containing, in bulk, at a temperature of 1,200 ° C or greater C: 0.05 to 0.15%, If: 0.5% or less, Mn: 0.5 to 2.0%, P: 0.02% or less, S: 0.005% or less, Ni: 0.2 to 2.0%, Cu: 0.2 to 0.5%, Cr: 0.2 to 1.0%, Ti: 0.03 to 0.2%, and optionally one or more of Nb: 0.01 to 0.07%, V: 0.01 to 0.07%, and B: 0.0005 to 0.0050%, the rest being unavoidable Faith and impurities; after that, finish the steel material in the temperature range of 850 to 950 ° C; Y Wind the rolled steel material in the temperature range of 500 to 650oC.