JPH055127A - Production of high strength steel sheet pile - Google Patents

Abstract

PURPOSE:To produce a high strength steel sheet pile having >=800tf/m joint strength and excellent in corrosion resistance, wear resistance, etc. CONSTITUTION:The high strength steel sheet pile can be produced by subjecting a slab of steel, which has a composition consisting of 0.2-0.45% C, 0.15-0.95% Si, 0.50-1.60% Mn, 0.25-1.0% Cu, 0.03-0.09% V, >=100ppm N, <=0.025% Al, and the balance iron with inevitable impurities or further containing one or >=2 kinds among 0.05-1.0% Cr, 0.03-0.08% Nb, and 0.05-1.0% Ni, to heating up to 1050-1280 deg.C, to hot rolling into a state of steel sheet pile, and to cooling.

Description

Detailed Description of the Invention

[0001]

The present invention has a joint fitting strength of 800 tf.
The present invention relates to a method of manufacturing a steel sheet pile having a corrosion resistance, wear resistance and weldability of at least 1 / m.

[0002]

2. Description of the Related Art Steel sheet piles are mainly used as civil engineering materials for retaining earth such as roads, quays, seawalls, and breakwaters.
The types are classified into Larzen type, Telluruge type, Krupp type, etc. according to the sectional shape, and the sheet pile joint shape is also key type, double claw type, double type and other Japanese Patent Publication 64-81.
There are many types and shapes of steel sheet piles, such as those disclosed in Japanese Patent No. 39, which improve the release angle of the joint engagement edge.

Such a steel sheet pile is disclosed in, for example, Japanese Patent Publication No. 1-1.
As described in the description of the prior art of Japanese Patent No. 3921, it is manufactured by a rolling method in which a steel piece or a cast piece is formed into various cross-sectional shapes by a hole-type rolling mill having horizontal rolls engraved. The material of the steel sheet pile is specified by JIS A5528, the steel composition is P: 0.040% or less, S: 0.04.
0% or less, Cu: 0.25% or more, mechanical properties are yield point (σ _y ): 30 kgf / mm ² or more, tensile strength (σ _B ): 5
It was set to 0 kgf / mm ₂ or more and elongation: 17% or more, and due to such mechanical properties, it was used without any problems in ordinary civil engineering construction work.

However, recently, as in the case of deep underground development and cross-gulf roads, civil works tend to become increasingly difficult and difficult, and the joint strength of steel sheet piles used for this (conventional 600 tf / Along with other properties, steel sheet piles with better values have been required.

[0005]

SUMMARY OF THE INVENTION The present invention satisfies the above-mentioned requirements and aims at a joint strength of 800 tf / m, which is evaluated as a sufficient value in future civil engineering construction work, and has corrosion resistance and wear resistance. It is an object of the present invention to provide a method for producing a high-strength steel sheet pile having properties that are equal to or higher than those of conventional steels in weldability and weldability.

[0006]

In order to achieve the above object, the present invention provides C: 0.20 to 0.45% (wt%), S
i: 0.15 to 0.95%, Mn: 0.50 to 1.60
%, Cu: 0.25 to 1.0%, V: 0.03 to 0.0
9%, N: 100 ppm or more, Al: 0.025% or less, and if necessary, Cr: 0.05 to 1.0.
%, Nb: 0.03 to 0.08%, Ni: 0.05 to
A steel slab containing 1.0% of one type or two or more types and the balance of iron and unavoidable impurities was prepared as 1050 to 1280.
A method for producing a high-strength steel sheet pile, which comprises heating to a temperature of ℃, hot rolling into a sheet pile shape, and cooling.

The present invention will be described in detail below. The composition of steel constituting the present invention is as described above, and the reasons for limiting these constituents are as follows. The C component is
Among the mechanical properties required for steel sheet pile, 0.20% or more is contained as the most effective component for improving strength, hardness and wear resistance. However, an excessive C content exceeding 0.45% has a problem of deteriorating the material of the welding heat affected zone. Therefore, the content of C contained in the steel sheet pile is set to 0.20 to 0.45%, and it is preferable to suppress it as much as possible in order to secure a certain weldability. The Si component needs to be 0.15% or more as a component for improving strength and wear resistance. However, if it exceeds 0.95%, there is a problem that a martensite structure is generated in the cooling process of the manufacturing process of the steel sheet pile to deteriorate the toughness, and cracks are likely to occur at the time of welding at the time of civil engineering work or gas cutting work. The Mn component is an effective component that improves strength and toughness and also increases the yield point, and it is necessary to contain 0.50% or more. However, excess M exceeding 1.60%
Similar to the Si component, n has a problem of increasing the susceptibility to cause cracking during welding during civil engineering work or during gas cutting work. Therefore, Mn needs to be suppressed to a content of 0.50 to 1.60%. The Cu component needs to contain 0.25% or more as a component for improving strength and corrosion resistance, but if it exceeds 1.0%, the weldability is deteriorated. V is an effective component that improves strength and toughness, and is 0.03
If the content is less than%, such an effect cannot be obtained,
In addition, if the content exceeds 0.09%, there is a problem that the degree of the effect obtained reaches a saturation phenomenon and the manufacturing cost becomes high. When the content of the N component is 100 ppm or more, a fine VN compound is precipitated by the composite addition of the above V component to make the steel structure finer and the precipitation strengthening of the compound improves the strength and toughness. However, it is preferable that the upper limit of the excessive content of the N component be 450 ppm because of the concern that AlN, NbN, or their composite nitrides may be formed to deteriorate the strength and toughness.

Al combines with nitrogen to form AlN,
The effective component for preventing the precipitation of VN is 0.025% or less.

In the present invention, P and S are listed as inevitable impurities. P is a harmful component that embrittles the steel material and reduces the strength, and the content of 0.040% or less is preferable, and the smaller the content, the better. The S component is also an effective component for improving the machinability of steel. However, in the present invention, the S component is 0.040% or less as a harmful component that deteriorates strength and toughness, and the smaller the S content, the more preferable.

Further, in the present invention, in order to further improve the strength and toughness of the steel sheet pile composed of the above steel components and contents, one or more of Cr, Nb and Ni are selectively selected. By including it, a steel sheet pile of a material suitable for the purpose of the present invention can be manufactured. The Cr component is 0.05 to 1.0 for the purpose of improving strength and corrosion resistance.
% Can be included. The Nb component is 0.03 by utilizing the effect of refining the steel structure to improve strength and toughness.
˜0.08% can be included. Further, the Ni component does not have such a remarkable effect on the increase in strength, but as a component effective for securing the toughness of the weld heat affected zone,
~ 1.0% can be included. In addition, the content of these steel components is within the range where each effect is obtained,
If the content exceeds the range, there is a problem that the effect is small, or the intermetallic compound is formed to deteriorate the material of the steel sheet pile.

The steel sheet pile having the above steel components is manufactured through the following steps.

That is, a molten steel produced by a melting furnace such as a converter or an electric furnace or an auxiliary refining technique is manufactured into a steel slab or a slab by the ingot agglomeration method or continuous casting method, and then 1050 Heat to a temperature of ~ 1280 ° C. This heating temperature has high commercial value in terms of material and shape by solidifying V nitrides and other nitrides precipitated in the cooling process during the production of billet into an austenite phase or unifying the austenite phase of the fine grain structure. Manufactures steel sheet pile. At a low temperature of less than 1050 ° C, a steel piece or cast piece having a workability and a uniform structure cannot be obtained, and at a high temperature of more than 1280 ° C, an austenite phase is coarsened and a decarburized layer is formed on the steel surface. It is not possible to manufacture steel sheet piles with the above materials.

[0013] Thus, the steel slab or cast slab heated to such a high temperature is formed into a steel sheet pile through a normal hot rolling process and provided as a product. Further, the rolled and formed steel sheet pile is cut into a predetermined use size or, if necessary, subjected to roller straightening and then provided to a product.
The steel sheet pile of the present invention manufactured in this way can provide a high-strength steel sheet pile having a joint strength of 800 tf / m.

[0014]

EXAMPLES Table 1 shows the components of the material of the present invention and the comparative material. All steels with these components are 1230 in the ingot form.
It was heated to ℃ and rolled into a steel sheet pile.

Table 2 shows the results of measuring the mechanical properties and joint tensile strength of each of the steel types shown in Table 1 by cutting a test piece from the rolled sample.

As is clear from Table 2, in all the cases of the present invention, the mechanical properties are about 1.5 times higher at the yield point and about 1.3 times higher at the tensile strength than the comparative materials. Further, the joint tensile strength was evaluated using a test piece with a width of 10 cm, but it was 612 tf / m in the comparative material, whereas it was more than 800 tf / m in the case of the present invention, showing a sufficiently high strength. It is clear that

[0017]

[Table 1]

[0018]

[Table 2]

[0019]

As described above, the yield point and the tensile strength can be increased by adding a trace amount of alloying elements to the appropriate five elements, and in the case of a straight steel sheet pile,
Whereas the comparative material had a steel hand tensile strength of about 600 tf / m, the present invention can provide a high-strength steel sheet pile capable of ensuring a joint tensile strength of 800 tf / m.

Claims (1)

Claims: 1. As weight%, C: 0.20 to 0.45%, Si: 0.15 to 0.95%, Mn: 0.50 to 1.60%, Cu: 0.25 to 1.0%, V: 0.03 to 0.09%, N: 100 ppm or more, Al: 0.025% or less, and the balance is a steel slab consisting of iron and inevitable impurities, 1050 A method for producing a high-strength steel sheet pile, which comprises heating to a temperature of ˜1280 ° C., followed by hot rolling into a steel sheet pile shape and cooling. 2. C .: 0.20 to 0.45%, Si: 0.15 to 0.95%, Mn: 0.50 to 1.60%, Cu: 0.25 to 1. 0%, V: 0.03 to 0.09%, N: 100 ppm or more, Al: 0.025% or less, Cr: 0.05 to 1.0%, Nb: 0.03 to 0. 08%, Ni: 0.05-1.0% of steel slab containing 1 or 2 or more and the balance consisting of iron and unavoidable impurities, after heating to a temperature of 1050 to 1280 ° C. A method for producing a high-strength steel sheet pile characterized by hot rolling and cooling.