JP6281284B2 - Abrasion-resistant steel plate with excellent formability and method for producing the same - Google Patents

Description

  The present invention relates to a wear-resistant steel sheet having excellent formability and a method for producing the same.

  Abrasion resistance is one of the important characteristics of steel materials used in industrial machinery and transportation equipment. In order to improve wear resistance, it is effective to increase the hardness. In construction, civil engineering, mining, etc., a large amount of alloy elements such as Cr and Mo are added to power shovels, bulldozers, and buckets to increase the hardness. Materials have been used. Further, in the field of automobile steel plates and the like typified by transmission parts having a tooth shape, a material whose surface is made hard by heat treatment such as carburizing and nitriding has been used.

  However, a material obtained by adding a large amount of alloy elements such as Cr and Mo to increase the hardness extremely increases the manufacturing cost, and further, the formability when the steel sheet is processed into a member by bending or the like is insufficient. . On the other hand, a material whose surface is made hard by heat treatment such as carburizing and nitriding has a high heat treatment cost, and there may be a problem of dimensional change due to heat treatment or softening due to heat treatment other than the surface layer portion.

  Patent Document 1 discloses a TS829-922 MPa high-strength steel sheet to which a large amount of alloying elements such as Nb, V, Cu, Ni, Cr, Mo, and W are added as a wear-resistant hot-rolled steel sheet having excellent workability. However, it has a problem of increasing the cost of alloying elements, and from the viewpoint of workability, it is difficult to press-mold in the TS829 to 922 MPa class, and the part shape is limited.

  Patent Document 2 discloses a TS516 to 585 MPa high-strength steel sheet to which Cr or the like is added as a wear-resistant hot-rolled steel sheet having excellent stretch flangeability, which is one form of formability. Compared to Patent Document 1, the alloy addition amount is reduced and the formability is improved, but in terms of wear resistance, it relies on surface hardening by heat treatment after forming, heat treatment cost, dimensional change by heat treatment, etc. From the point of view, the problem is not solved.

JP 2008-214736 A JP 9-49065 A

  Therefore, the present invention can be formed into a complicated part shape without increasing the cost represented by the increase in alloy cost or the addition of heat treatment cost, and is excellent in wear resistance without being subjected to heat treatment after forming. It is an object to provide a rolled steel sheet and a manufacturing method thereof. In addition, as an index for determining whether or not it can be formed into a complicated part shape, uniform elongation and hole expansion ratio by a test method described later were used. Uniform elongation is an indicator of stretchability (for example, the performance when a flat plate is formed into a cylindrical shape or a spherical head shape), and the hole expansion ratio is the stretch flangeability (for example, when the peripheral length of a punched end face is enlarged and molded. Performance). In particular, in the field of steel plates for automobiles such as transmission parts, it is anxious to achieve uniform elongation ≧ 12% (preferably 14%, more preferably 16%) and hole expansion ratio ≧ 1.25. From the upper limit of the press machine capacity, it is desired that the tensile strength is 810 MPa or less, preferably 690 MPa class, more preferably 590 MPa class.

  As a result of conducting detailed studies on the above problems, the present inventors can control the additive elements, structure, and the like of the hot-rolled steel sheet, and can be molded into a complicated part shape without increasing costs, and As a result, they have come to know a technology that exhibits excellent wear resistance as it is (without heat treatment).

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

(1) In mass%,
C: 0.01-0.20%
Si: 2.2 ~5%,
Al: 0.001-2%,
P: 0.1% or less,
S: 0.01% or less,
N: not more than 0.010%, further containing one or more of Mn, Cu, Ni, Cr, Mo so as to satisfy the following formulas (1) to (3), the balance being Fe and inevitable A hot-rolled steel plate made of mechanical impurities, the structure of the hot-rolled steel plate having a ferrite fraction Vf = 0.65 to 0.98, a second phase fraction V2 = 0.02 to 0.35, and a ferrite fraction Vf + Second phase fraction V2 = 1, second phase micro Vickers hardness H2 ≦ 400, and {211} plane, {111} plane parallel to the plate surface at 1/4 thickness part of the hot-rolled steel plate, { A hot-rolled steel sheet for wear resistance excellent in formability, characterized in that the reflection X-ray intensity ratios of the 100} plane and the {110} plane are both less than 1.9.
Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2: 0.3 to 5%
・ ・ ・ Formula (1)
Si + 0.024 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) ≧ 1.48
・ ・ ・ Formula (2)
Si + 0.525 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) ≦ 5.31
・ ・ ・ Formula (3)
The component element shown in the above formula is the mass% of the element contained in the steel, and the element not contained is 0%.

(2) The wear-resistant hot-rolled steel sheet having excellent formability as described in (1) above, further satisfying the following formula (4) by mass%.
Si / (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) ≧ 1.0
Formula (4)
The component element shown in the above formula is the mass% of the element contained in the steel, and the element not contained is 0%.

(3) Furthermore, in mass%,
Nb: 0.001 to 0.3%,
V: 0.001-0.3%
Ti: 0.001 to 0.3%,
B: 0.0001 to 0.005%
The wear-resistant hot-rolled steel sheet having excellent formability as described in (1) or (2) above, comprising one or more of the above.

(4) Furthermore, in mass%,
Ca: 0.0001 to 0.01%,
REM: 0.0003 to 0.03%
Any one or two of the above, (1) to (3), the wear-resistant hot-rolled steel sheet excellent in formability according to any one of the above.

(5) above (1) heating a steel having a component according to any one of to (4), rough rolling, finish rolling, cooling, either performing the winding of (1) to (4) 1 The finish rolling end temperature is set to T1 + 50 ° C. or higher, the average cooling rate of the finish rolling end temperature to T1 is set to 60 ° C./second or more, and the residence time t at T1 to 650 ° C. A method for producing a hot-rolled steel sheet for wear resistance having excellent formability, characterized in that the coiling temperature is T2 and 300 ° C for 5 seconds or more.
Here, T1 (° C.) is the temperature shown in the following formula (5), and T2 (° C.) is the temperature shown in the following formula (6).
T1 (° C.) = 905−320 × C + 30 × (Si + Al) −85 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) −17000 × B Formula (5)
T2 (° C.) = 600−240 × C × t−35 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) Equation (6)
The component element shown in the above formula is the mass% of the element contained in the steel, and the element not contained is 0%.

  According to the present invention, it is possible to manufacture automobile parts with excellent wear resistance without performing heat treatment after molding without increasing the cost, and because it can be molded into a complicated part shape, its application is wide and useful industrially. There is a remarkable effect.

It is a graph which shows the relationship between (2) Formula and the frequency | count of durability by a wear test. It is a graph which shows the relationship between (3) Formula and uniform elongation.

  Hereinafter, the present invention will be specifically described.

  The present inventors have intensively studied a method for improving the wear resistance while maintaining the formability, and that the wear resistance is remarkably improved especially by increasing Si in the additive element, and the second phase component in the microstructure. We found that the wear resistance deteriorates due to an increase in the rate and hardness of the second phase, and in addition to these (added elements, microstructure), excellent formability by controlling the texture to a specific range It was found that can be maintained. The range and reasons for limitation will be described in detail below. The reason why the wear resistance is remarkably improved by the increase of Si is considered to be that Si has a high flow resistance against plastic deformation during wear and does not localize material damage due to plastic deformation. It is presumed that the influence of Si on the slip system and dislocation drag effect is different from other elements. The reason why the wear resistance deteriorates due to the increase in the second phase fraction and the increase in the second phase hardness is presumed to be the effect of promoting the wear of ferrite, that is, the role of abrasive grains.

  First, the reason why the composition of steel is limited to the above range in the present invention will be described. Here, “%” means mass%.

(C: 0.01-0.20%)
C is an inexpensive reinforcing component, and 0.01% is contained as the minimum amount for that purpose. However, if the addition amount exceeds 0.20%, the second phase fraction and the second phase hardness increase, which deteriorates wear resistance and formability and deteriorates weldability. Is 0.20%. The upper limit of addition is preferably 0.15%, more preferably 0.10%. Further, in order to avoid an excessive increase in decarburization costs and other alloy costs, and to sufficiently exhibit the grain boundary strengthening function by C and to obtain excellent low temperature toughness, preferably 0.04% is set as the lower limit of addition. .

(Si: 1.4-5%)
Si is an element having a deoxidizing action and a strengthening action, and further has an action of increasing the ferrite fraction. Furthermore, it is an element that has a great effect on wear resistance. In order to exert the effect, 1.4% is necessary as a minimum amount, and preferably 2.0% or more. However, if it exceeds 5%, the above action is saturated and weldability deteriorates, so the upper limit is made 5%.

(Al: 0.001-2%)
Al is an element having a deoxidizing action and a strengthening action, and further has an action of increasing the ferrite fraction. In order to exert the effect, 0.001% is necessary as a minimum amount. However, if it exceeds 2%, the above action is saturated and weldability deteriorates, so the upper limit is made 2%.

Mn, Cu, Ni, Cr, Mo are strengthening components, and in order to exert their effects, the total amount of Mn, Cu, Ni, Cr, Mo depends on the contribution ratio of the action of each element. To satisfy (1), 0.3% is necessary as the minimum amount. However, if the addition amount exceeds 5.0%, the second phase fraction and the second phase hardness increase, which deteriorates the wear resistance and formability and deteriorates the weldability. Is 5.0%. The upper limit of the addition is preferably 3.0%, more preferably 2.5%. The reason why elements other than Mn are halved is because the strengthening ability per unit addition amount is ½ with respect to Mn.
Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2: 0.3 to 5%
・ ・ ・ Formula (1)

Furthermore, as a result of examining in detail the influence of Si, Mn, Cu, Ni, Cr, and Mo on the wear resistance, the effect of improving the wear resistance of Si is remarkably large and 1.48 so as to satisfy the following formula (2). It has been found that practical wear resistance can be expressed by setting it as above (preferably 2.04 or more).
Si + 0.024 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) ≧ 1.48
・ ・ ・ Formula (2)

  FIG. 1 shows the relationship between the mathematical formula (2) and the number of times of durability in the wear test (method and the like will be described later). Practical wear resistance in actual vehicle running can be expressed when the number of endurance is 4 million times or more (preferably 5 million times or more), but the increase in the number of times (2) improves the number of endurance (that is, wear resistance is reduced). Improvement), the number of endurances can be remarkably improved by setting the numerical formula (2) to 1.48 or more, and 4 million times or more can be achieved. Furthermore, by setting the numerical formula (2) to 2.04 or more, the number of durability can be further improved and 5 million times or more can be achieved.

It was also found that the effect of Si on wear resistance was further improved by setting it to 1.0 or more so as to satisfy the following formula (4).
Si / (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) ≧ 1.0
Formula (4)

  As shown in FIG. 1, even if the value of the formula (2) is substantially the same, 4.2 million can be obtained by setting Si / (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) ≧ 1.0 shown in the formula (4). This is an improvement of 44.5 million times for the number of times and 7.83 million times for the number of 6.48 million times. The effect of improving wear resistance by Si is considered to be a function as a solid solution element, but a larger amount of Si is present with respect to Mn, Cu, Ni, Cr, and Mo, which are solid solution elements other than Si. This is presumed to be more effective in some cases.

In addition, even if elements other than Si are added in large quantities, the wear resistance is improved, but the yield strength and tensile strength of the steel are excessively increased, the formability is lowered, cracks during molding of the part, mold In order to achieve both wear resistance and formability, in order to avoid the deterioration of formability while making maximum use of the effect of improving the wear resistance of Si. The inventors have found that it is necessary to satisfy the following formula (3).
Si + 0.525 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) ≦ 5.31
・ ・ ・ Formula (3)
In addition, the component element shown to said Formula (1)-(4) is the mass% of the element contained in steel, Comprising: The element which is not contained shall be 0%.

  In the steel having the main structure as in the present invention (ferrite fraction = 0.65 to 0.98) and the second phase hardness ≦ 400, with respect to the strengthening action per unit addition amount, when Si is 1, Mn is 0.525 times that of Cu, Ni, Cr, and Mo. Further, it is 1/2 of that. In order to effectively strengthen the value, it is necessary to set the value of Equation (3) to 5.31 or less (preferably 4.38 or less, more preferably 3.29 or less). As an example, FIG. 2 shows the relationship between the formula and the uniform elongation. By setting the value of equation (3) to 5.31 or less, it is possible to avoid the uniform elongation from being less than 12%, and by setting the value of equation (3) to 4.38 or less, the uniform elongation is 14% or more. The uniform elongation of 16% or more can be secured by setting the value of the expression (3) to 3.29 or less.

(P: 0.1% or less)
Although P is contained as an impurity and is an inexpensive reinforcing component, it causes embrittlement and weldability deterioration, so its upper limit is made 0.1%. Preferably it is 0.03% or less.

(S: 0.01% or less)
S is contained as an impurity in the same manner as P, and is known to react with Mn in steel to produce stretched inclusions, and is a harmful element that lowers formability (particularly the hole expansion ratio) and fatigue strength. The upper limit is made 0.01%. Preferably it is 0.005% or less.

(N: 0.010% or less)
N is an element that is inevitably mixed, but since it forms nitrides with Al and the like, it may be necessary to add more Al than necessary, and may have a harmful effect on formability, so the upper limit is 0. .010%. Preferably it is 0.005% or less.

  The above is the reason for limiting the basic components of the hot-rolled steel sheet according to the present invention, and the remaining balance of the basic components is composed of Fe and inevitable impurities. Inevitable impurities include O, Zn, Pb, As, Sb, etc. Even if these are included in the range of 0.02% or less, the effects of the present invention are not lost.

  Moreover, the hot-rolled steel sheet according to the present invention may contain one or more of Nb, V, Ti, and B in the following contents as necessary.

(Nb: 0.001-0.3%, V: 0.001-0.3%, Ti: 0.001-0.3%)
Nb, V, and Ti generate carbides and have the effect of refining the microstructure such as ferrite and the effect of precipitation strengthening, and 0.001% or more of each is necessary to exert the effect. . However, if it exceeds 0.3%, the effect becomes saturated and the cost becomes excessive, so the upper limit is made 0.3% respectively. Moreover, it is desirable to add a small amount from the viewpoint of the anisotropy of the mechanical properties of the steel sheet.

(B: 0.0001 to 0.005%)
B is an element that effectively acts for strengthening in a small amount. In order to exert the effect, 0.0001% or more is added. However, if added in a large amount, the second phase fraction and the second phase hardness increase, which deteriorates wear resistance and adversely affects weldability. Therefore, the upper limit is made 0.005%.

  Moreover, the hot-rolled steel sheet according to the present invention may contain one or two of Ca and REM in the following content.

(Ca: 0.0001 to 0.01%)
Ca has an effect of controlling the form of inclusions, and has the effect of reducing the degree of harm by spheroidizing the inclusions that are harmful to the formability (particularly the hole expansion ratio). In order to exert the effect, addition of 0.0001% or more is necessary. However, if it exceeds 0.01%, the effect is saturated, and there is a concern that it may adversely affect, and from the viewpoint of weldability deterioration, 0.01% is made the upper limit of addition.

(REM: 0.0003-0.03%)
REM has an effect of controlling the shape of inclusions, and has the effect of reducing the degree of harm by making the elongated inclusions harmful to formability (particularly the hole expansion ratio) into a fine sphere. In order to exert the effect, 0.0003% or more must be added. However, if it exceeds 0.03%, the effect is saturated and there is a concern that adverse effects may be caused, and 0.03% is made the upper limit of addition from the viewpoint of weldability deterioration.

  Next, the reason why the structure of the hot rolled steel sheet is limited in the present invention will be described.

  The ferrite fraction Vf is set to 0.65 to 0.98 (ferrite fraction Vf + second phase fraction V2 = 1, so that the second phase fraction = 0.02 to 0.35). When the ferrite fraction Vf is less than 0.65, the second phase fraction harder than ferrite is increased, and it is estimated that the wear of ferrite is promoted by acting as an abrasive, Since the wear resistance is deteriorated and the formability is also deteriorated due to the decrease in ferrite mainly responsible for the strain at the time of deformation of the steel sheet, the lower limit of the ferrite fraction Vf is 0.65 or more (preferably 0.75 or more, more preferably 0). .85 or more). Further, in order to make the ferrite fraction more than 0.98, the residence time at T1 (temperature defined by Formula 5 described later) to 650 ° C. is increased, which is not preferable from the viewpoint of productivity. Since the ferrite is soft with respect to the second phase, when the ferrite fraction is 0.98 to 1.00, it is necessary to add a larger amount of alloy to compensate for the reduction in strengthening, so the alloy for strengthening the steel Since the cost also increases, the upper limit of the ferrite fraction is set to 0.98.

  The second phase intended in the present invention is bainite, pearlite, and cementite, and excludes hard martensite and retained austenite. Moreover, even if it is bainite, it is necessary to provide an upper limit to the hardness, and the second phase hardness H2 is set to H2 ≦ 400. When H2> 400, it is assumed that it strengthens the role of the second phase abrasive grains and promotes the wear of the ferrite. As a result, the wear resistance deteriorates, and the formability (hole expansion ratio). Therefore, the upper limit of the second phase hardness H2 is set to 400.

  The reflected X-ray intensity ratios of {211} plane, {111} plane, {100} plane, and {110 plane} parallel to the ¼ thick plate surface are all less than 1.9. When the reflection X-ray intensity ratio is 1.9 or more, the anisotropy of mechanical properties increases, and when drawing into a cup shape, the plate thickness fluctuates in the circumferential direction. The surface pressure of the mold increases, galling occurs, and molding becomes difficult, or even if molding can be performed, the dimensional accuracy of the parts deteriorates. 1.8 or less, more preferably 1.6 or less).

  The ferrite fraction and the second phase fraction are obtained by performing a night etching of the hot-rolled steel sheet, and the 1/4 section L-section (cross section perpendicular to the width direction of the hot-rolled steel sheet) is 400 times with a scanning electron microscope. The second phase hardness H2 was determined by observation through a micro Vickers test. The reflected X-ray intensity ratio of {211} plane, {111} plane, {100} plane, {110 plane} parallel to the ¼ thick section plane is determined by the ratio of the hot-rolled steel sheet to the random sample using an X-ray diffractometer. As sought. The reason why the ¼ thickness part is selected is that it is an optimal part for determining the formability.

  Next, the manufacturing conditions of the present invention will be described. The present invention is a method for producing a hot-rolled steel sheet in which steel having the above-described components is heated and subjected to rough rolling, finish rolling, cooling, and winding.

  The heating and rough rolling conditions may be a commonly used method and have no particular characteristics.

  In finish rolling, the finish rolling end temperature is set to T1 + 50 ° C. or higher. Below T1 + 50 ° C., the reflected X-ray intensity ratio of {211} plane, {111} plane, {100} plane, {110 plane} parallel to the ¼ thick plate surface is 1.9 or more, as described above. In addition to problems occurring during molding, the ductility of ferrite deteriorates and elongation decreases, so T1 + 50 ° C. is set as the lower limit. Also, if the finish rolling finish temperature exceeds 1000 ° C, the thickness of the scale formed on the surface of the hot-rolled steel sheet becomes extremely thick, and adverse effects such as generation of scale wrinkles and deterioration of pickling properties are likely to occur. Therefore, the upper limit of the finish rolling finish temperature is preferably 1000 ° C., more preferably 950 ° C.

After the finish rolling is finished, first, cooling is performed such that the average cooling rate from the finish rolling finish temperature to T1 is 60 ° C./second or more, and the stay time t at T1 to 650 ° C. is 5 seconds or more. T1 is a temperature defined below, and corresponds to a temperature at which ferrite starts to be generated. T1 is a temperature defined by the following formula (5).
T1 (° C.) = 905−320 × C + 30 × (Si + Al) −85 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) −17000 × B Formula (5)

  When the average cooling rate of the finish rolling finish temperature to T1 is less than 60 ° C./second, it is estimated that the selectivity of a specific crystal orientation is strengthened during the transformation from γ to α, and as a result, on the 1/4 thick part plate surface The reflected X-ray intensity ratio of the parallel {211} plane, {111} plane, {100} plane, and {110 plane} is 1.9 or more, and as described above, problems occur during molding. The average cooling rate of T1 has a lower limit of 60 ° C./second. On the other hand, if the cooling rate is excessive, the temperature tends to fluctuate in the width direction in the longitudinal direction of the steel sheet. Therefore, the upper limit of the average cooling rate of the finish rolling finish temperature to T1 is preferably 300 ° C / second, more preferably 150 ° C / second. Seconds.

  Further, if the stay time t at T1 to 650 ° C. is less than 5 seconds, the ferrite fraction Vf becomes less than 0.65, and the wear resistance and formability (particularly uniform elongation) deteriorate as described above. The lower limit is 5 seconds. In addition, since the speed | rate of a ferrite transformation will become extremely slow if it is less than 650 degreeC, 650 degreeC was made into the minimum as a temperature range which prescribes | stays residence time. On the other hand, the upper limit of the staying time t at T1 to 650 ° C. is determined by the length of the cooling table. If the staying time t is too long, the thickness of the scale increases, and the occurrence of scale wrinkles and pickling properties Since it leads to deterioration, the upper limit of the stay time t at T1 to 650 ° C. is preferably 20 seconds or less.

After the above cooling, winding is performed at a temperature exceeding T2 and exceeding 300 ° C. T2 is a temperature defined by the following formula (6), and corresponds to a temperature at which a hard second phase that adversely affects wear resistance starts to be generated.
T2 (° C.) = 600−240 × C × t−35 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) Equation (6)
In addition, the component element shown to said Formula (5) and (6) is the mass% of the element contained in steel, and the element which is not contained shall be 0%.

  When the coiling temperature is T2 or less, the second phase becomes hard, and the wear resistance and formability (particularly the hole expansion ratio) deteriorate. In addition, regardless of the additive element and the residence time t, when the temperature is 300 ° C. or lower, the second phase becomes extremely hard, and wear resistance and formability (particularly, hole expansion ratio) deteriorate. For this reason, the coiling temperature is over T2 and over 300 ° C. Preferably, T2 + 100 ° C., more preferably T2 + 150 ° C. is set as the lower limit of the coiling temperature. On the other hand, if the temperature exceeds 650 ° C., the thickness of the scale increases, leading to generation of scale wrinkles and deterioration of pickling properties. Therefore, the upper limit of the coiling temperature is preferably set to 650 ° C. or less.

  Steel slabs having the component compositions shown in Table 1-1 and Table 1-2 were processed under various conditions shown in Table 2 to obtain hot rolled steel sheets having a thickness of 3.40 mm. The results of evaluating the structure, wear resistance, and formability of the obtained hot-rolled steel sheet are shown in Tables 3-1 and 3-2.

  The tissue is evaluated by the method described in paragraphs 0041 to 0044 above.

  The wear resistance was evaluated by the wear test described below. An SCr420 carburized material (HRC ≧ 58) is brought into contact with the hot-rolled steel sheet at a contact pressure of 150 MPa (contact area 2 mm × 10 mm), and a so-called ATF (automatic transmission) is formed in the longitudinal direction (10 mm direction) of the contact area with a ± 1 mm stroke. In the fluid: automatic transmission oil), wear was generated by sliding, and the durability was evaluated to the wear number of 0.4 mm. In order to express practical wear resistance in actual vehicle running, the number of durability times by the above method is 4 million times or more, preferably 5 million times or more.

  Formability was evaluated by a JIS-5 tensile test, a punched hole expansion test, and a drawing test taken from a direction (C direction) orthogonal to the hot rolling direction.

  In the JIS-5 tensile test, TS and uniform elongation were used as indices. As described above, the uniform elongation needs to be 12% or more.

  In the punching hole expansion test, the initial hole d0 = 20 mmφ is punched with a clearance of 12.5%, the diameter is expanded with a conical punch with a vertex angle of 30 degrees, and the ratio to the hole diameter d when a crack generated in the end surface penetrates the plate thickness. D / d0 (hole expansion ratio) as an index. As described above, d / d0 (hole expansion ratio) needs to be 1.25 or more.

  In the drawing test, the presence or absence of galling was used as an index when a blank (thickness 3.40 mm, φ238) was drawn out with a clearance of 3.67 mm using a cylindrical punch (cylindrical diameter 146.5 mm) with a shoulder R40 mm. The case where the iron powder peeled off by galling can be visually confirmed was regarded as galling.

Invention examples obtained according to the present invention, and reference examples (A steel, B steel, C steel, D steel-1, E steel-1, F steel, G steel, H steel, I steel, J steel-1, K Steel, Q steel, S steel, T steel, U steel, V steel, W steel, X steel, Y steel, Z steel, AA steel, AB steel, AC steel) have excellent wear resistance (durability times ≧ 4 million) Times) and formability (uniform elongation ≧ 12%, hole expansion ratio ≧ 1.25, no galling in the drawing test).

  On the other hand, the comparative examples (D steel-2, E steel-2, E steel-3, J steel-2, L steel, M steel, N steel, O steel, P steel, R steel) are all of the present invention. Since it is out of the proper range, wear resistance and formability are deteriorated.

  Although D steel-2 satisfies the requirements of the additive element of the present invention, since the residence time t at T1 to 650 ° C. is less than 5 seconds, the ferrite fraction Vf is less than 0.65, and wear resistance and formability ( Both the uniform elongation and the hole expansion ratio) are deteriorated, and the influence is obvious in comparison with D steel-1.

  Although Steel E-2 satisfies the requirements for the additive element of the present invention, since the finish rolling finish temperature is less than T1 + 50 ° C., the {211} plane, {111} plane, {100} plane parallel to the 1/4 thick plate surface , {110 plane} has a reflection X-ray intensity ratio of 1.9 or more, galling occurs at the time of molding, and the formability is deteriorated, and the influence is obvious in comparison with E steel-1.

  Although steel E-3 satisfies the requirements of the additive element of the present invention, the {211} plane parallel to the ¼ thick plate surface because the average cooling rate from the finish rolling finish temperature to T1 is less than 60 ° C./second, { 111} face, {100} face, and {110 face} have a reflection X-ray intensity ratio of 1.9 or more, galling occurs during forming, and formability deteriorates. It is clear.

  Although Steel J-2 satisfies the requirements for the additive element of the present invention, because the coiling temperature is less than T2, the second phase becomes too hard, and wear resistance and formability (hole expansion ratio) are deteriorated. The effect is clear in comparison with J Steel-1.

  L steel is C, Si, P, S, N, Si + 0.024 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2), second phase fraction and second phase hardness do not meet the requirements of the present invention Both wear resistance and formability (uniform elongation, hole expansion ratio) are deteriorated.

  In M steel, since Si, Si + 0.024 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) does not satisfy the requirements of the present invention, the wear resistance is deteriorated.

  In N steel, Si + 0.525 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) does not satisfy the requirements of the present invention, so in the formability, uniform elongation, hole expansion ratio, and squeezing property in the drawing test deteriorate. ing.

  Since O, Si, Si + 0.024 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) does not satisfy the requirements of the present invention, the wear resistance is deteriorated.

  P steel has deteriorated wear resistance because Si, Si + 0.024 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) does not satisfy the requirements of the present invention.

  As for R steel, Si + 0.525 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) does not satisfy the requirements of the present invention, so in the formability, uniform elongation, hole expansion ratio, and caulking property in the drawing test deteriorate. ing.

  From the above examples, the effect of the present invention (excellent wear resistance and moldability) was confirmed.

  INDUSTRIAL APPLICABILITY The present invention can stably supply hot rolled steel sheets having excellent formability and wear resistance at a low cost, and can be used for manufacturing automobile parts having a complicated part shape with excellent wear resistance without increasing costs.

Claims (5)

% By mass
C: 0.01-0.20%
Si: 2.2 ~5%,
Al: 0.001-2%,
P: 0.1% or less,
S: 0.01% or less,
N: not more than 0.010%, further containing one or more of Mn, Cu, Ni, Cr, Mo so as to satisfy the following formulas (1) to (3), the balance being Fe and inevitable A hot-rolled steel plate made of mechanical impurities, the structure of the hot-rolled steel plate having a ferrite fraction Vf = 0.65 to 0.98, a second phase fraction V2 = 0.02 to 0.35, and a ferrite fraction Vf + Second phase fraction V2 = 1, second phase micro Vickers hardness H2 ≦ 400, and {211} plane, {111} plane parallel to the plate surface at 1/4 thickness part of the hot-rolled steel plate, { A hot-rolled steel sheet for wear resistance excellent in formability, characterized in that the reflection X-ray intensity ratios of the 100} plane and the {110} plane are both less than 1.9.
Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2: 0.3 to 5%
・ ・ ・ Formula (1)
Si + 0.024 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) ≧ 1.48
・ ・ ・ Formula (2)
Si + 0.525 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) ≦ 5.31
・ ・ ・ Formula (3)
The component element shown in the above formula is the mass% of the element contained in the steel, and the element not contained is 0%. Furthermore, the hot-rolled steel sheet for wear resistance having excellent formability according to claim 1, wherein the following formula (4) is satisfied by mass%.
Si / (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) ≧ 1.0
Formula (4)
The component element shown in the above formula is the mass% of the element contained in the steel, and the element not contained is 0%. Furthermore, in mass%,
Nb: 0.001 to 0.3%,
V: 0.001-0.3%
Ti: 0.001 to 0.3%,
B: 0.0001 to 0.005%
The hot-rolled steel sheet for wear resistance having excellent formability according to claim 1, wherein the hot-rolled steel sheet is excellent in formability. Furthermore, in mass%,
Ca: 0.0001 to 0.01%,
REM: 0.0003 to 0.03%
Any one or hot-rolled steel sheet for wear excellent in formability according to any one of claims 1 to 3, characterized in that it contains two. Heating the steel having the component according to any one of claims 1 to 4, rough rolling, finish rolling, cooling, hot-rolled steel sheet according to claim 1 for performing winding In the manufacturing method, the finish rolling end temperature is set to T1 + 50 ° C. or more, the average cooling rate of finish rolling end temperature to T1 is 60 ° C./second or more, the residence time t at T1 to 650 ° C. is 5 seconds or more, and the winding temperature is A method for producing a wear-resistant hot-rolled steel sheet having excellent formability, characterized by being over T2 and over 300 ° C.
Here, T1 (° C.) is the temperature shown in the following formula (5), and T2 (° C.) is the temperature shown in the following formula (6).
T1 (° C.) = 905−320 × C + 30 × (Si + Al) −85 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) −17000 × B Formula (5)
T2 (° C.) = 600−240 × C × t−35 × (Mn + Cu / 2 + Ni / 2 + Cr / 2 + Mo / 2) Equation (6)
The component element shown in the above formula is the mass% of the element contained in the steel, and the element not contained is 0%.

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