KR20010015587A - Hot rolling high-strength steel structural members - Google Patents

Abstract

High strength steel structural members by providing a high strength steel material having a specific chemical composition and preferably a tensile strength of at least about 120,000 psi and a yield strength of at least about 90,000 psi, and hot rolling the steel material to obtain a structural member of the desired geometry. And methods for their preparation are described.

Description

Hot rolling high-strength steel structural members

Related Applications

This application is a partial consecutive application of US Patent Application No. 08 / 275,841, filed July 15, 1994, which is a partial continuous application of Patent Application No. 08 / 091,640, filed July 14, 1993, Is a partial consecutive application of Patent Application No. 07 / 827,740, filed January 29, 1992, which is filed on October 24, 1990, filed with US Patent Application No. 07 / 602,675 filed March 10, 1992; Patent No. 5,094,698], which is a parent application of Patent Application No. 07 / 848,646, filed March 9, 1992, issued US Patent No. 5,236,520, issued August 17, 1993. , The patent application is the parent application of Patent Application No. 08 / 992,123 (US Patent No. 5,330,594), filed December 17, 1992, the patent application is the patent application No. 08 / 276,217, filed July 15, 1994 It is a source of appeal. Each of which is incorporated herein by reference.

High strength steel parts and structural members have been molded using cold forging techniques known in the art. Cold formed parts and structural members have disadvantages. Because the structural members or parts are molded at about room temperature, the reshaping and forming steps require substantially high forces. This frequently requires a series of cold forming steps in which the material is molded sequentially into the desired shape. This increases the die wear and noise involved in this process. In addition, as the material is processed, the strength of the member or part increases. When processed to substantial grades, the increase in strength obtained requires annealing to lower the strength added to the time and cost of this process.

To avoid the above drawbacks, hot forging may be used to form structural members and parts from the material at intermediate temperatures that are high enough to reduce the strength of the material to promote molding, but still recrystallization, scaling and decarburization It is only used below the hot forging temperature at which it occurs. Examples of patents describing processes for rolling or forming members to obtain specific shapes and desired mechanical properties include US Pat. Nos. 5,287,715, 5,203,193, 5,121,622, 4,982,591, 4,966,026, 4,685,319 And 4,378,687.

The documents cited above do not clearly indicate prior art or assert that these documents are the most representative documents. These patents describe a complex and associated process that includes various example repeated molding and cooling steps for forming a structural member that may be expensive and require an associative step to obtain a final member having the desired mechanical properties.

To date, the blanks are molded into the desired shape by including a hot forging or rolling step, and the mechanical properties of the structural members can be kept substantially the same or greater than originally contained in the blanks, further to impart mechanical strength properties. There was no method for producing a high strength steel structural member from a blank of steel having a specific composition and containing the desired high strength properties, in which the member could be produced without the step of strengthening the process.

Summary of the Invention

The method of the present invention is useful for producing various high strength steel structural members from high strength steel blanks. In particular, the present invention relates to a method of forming an elongated high strength steel structural member having a uniform cross-sectional shape at least in part of and at substantially all of its entire length. For example, structural members and other members having O, L, C, Z, T, I, W, U, V shapes are easy for molding by the hot forging or rolling process described herein.

The structural member of the present invention is a workpiece and has one or more flanges included in its cross-sectional shape. The flange is a member that has a thickness of less than the overall external dimension of the cross-sectional shape to provide increased support to the structural member.

The present invention provides a method of making a high strength steel structural member from a high strength steel material having a tensile strength of at least about 120,000 psi and a yield strength of at least about 90,000 psi. In one aspect, the present invention provides a high strength steel in which the steel material has a desired geometric shape by hot forging or rolling and provides a structural member whose mechanical properties of the tensile and yield strengths of the member are substantially equal to or greater than that of the steel material. Provided is a method of making a high strength steel structural member from a material. The molded structural member is then cooled or quenched, preferably at a controlled rate, without a change in shape due to deformations that may occur from cooling.

The present invention also provides that the mechanical properties of the tensile and yield strength of the member are formed by hot forging, rolling or other methods to be substantially the same as or greater than the material used to form the member, and the tensile strength and yield A method of making a high strength steel structural member is provided in which members having the desired mechanical properties of strength are produced without further reinforcing process steps.

The principles, objects and advantages of the present invention will be further understood by reference to the following detailed description.

The present invention relates to a method for producing a high strength steel structural member, and more particularly to a method of hot rolling or forging a blank of high strength steel into a structural member having a desired geometric cross-sectional shape while maintaining the high strength properties of the steel blank. .

FIELD OF THE INVENTION The present invention relates to a method of making a structural member that extends into a uniform cross-sectional shape at one or more and typically substantial portions of its length and includes one or more flanges. The flange is a member having a thickness less than or equal to the overall circumferential length or external dimension of the cross-sectional shape (ie, the width, height or outer diameter of the structural member). The flange distinguishes the structural member from the blank in that the flange provides increased support to the member. In other words, when the structural members have the same material composition and properties, the structural members with flanges have an increased bearing force than members without flanges. The load may be applied to the structural member as an axial load as a load on the end, as a lateral load as a lateral load, or as any other type of load. In contrast, the high strength steel material prior to rolling is typically a newly shaped billet of molten or cooled metal, which may be a typical one-piece shape used in some continuous casting processes and the like.

The flange is integrally molded continuously or discontinuously taking into account the remainder of the structural member. Examples of discontinuous flanges are the upper or lower part of the leg of the L-shaped truss taking into account the upper or lower part of the I-shaped beam taking into account the center part or the other leg of the truss. Examples of continuous flanges are all chords or cross-sectional shaped portions of O-shaped structural members. Examples of structural members having one or more flanges are members of the form O, L, C, Z, I, T, U, V and W.

In a preferred embodiment, the method of the present invention for producing high strength steel structural members is a high strength steel having a tensile strength of at least about 120,000 psi, preferably at least about 150,000 psi and a yield strength of at least about 90,000 psi, preferably at least about 130,000 psi. Provision of the material. In one form, the high strength steel materials used are hot smelted and cold drawn to provide billets or blanks having the mechanical properties of the tensile and yield strengths described above. The high strength materials used for forming the structural members can be processed in one form into melted, softened or cured forms, and in other forms can be billets or blanks which are hot rolled according to the invention.

High strength steel material is weight percent

About 0.30 to about 0.65% carbon,

About 0.30 to about 2.5% manganese,

At least one ferrous particle micronized from the group consisting of up to about 0.35% particle micronized effective amount of aluminum, niobium, titanium and vanadium and mixtures thereof, and

It can be exemplified by the composition of the residual amount of iron.

In a further preferred form, the high strength steel material is in weight percent

About 0.40 to about 0.55% carbon,

About 0.30 to about 2.5% manganese,

At least one ferrous particle micronized from the group consisting of up to about 0.20% particle micronized effective amount of aluminum, niobium, titanium and vanadium and mixtures thereof, and

Has a composition of iron residues.

In a further preferred form, the high strength steel material is in weight percent

About 0.50 to about 0.55% carbon,

About 1.20 to about 1.65% manganese,

At least one ferrous particle micronized from the group consisting of aluminum, niobium, titanium and vanadium and mixtures thereof in an effective amount of particle refining from about 0.03 to about 0.20%, and

Has a composition of iron residues.

On the other hand, aluminum, niobium (i.e. cB), titanium and vanadium act as particle refinements, with vanadium being the most preferred particle refiner. In addition, the compositions recorded and claimed herein can include other ingredients that do not affect the practice of the invention.

High strength steel materials having a tensile strength of at least about 120,000 psi and a yield strength of at least about 90,000 psi, used as starting materials in the process of the present invention, are produced according to suitable methods known in the art.

Steel materials having the above described composition and mechanical properties of tensile and yield strengths are formed by hot rolling, forging or other methods at recrystallization temperatures, typically above about 2000 ° F., to provide structural members having the desired geometry. do. The temperature at which the structural member is rolled is associated with the chemical composition of the steel material used. With the chemical composition described above, the hot rolled structural member can have a large amount of martensite content depending on the cooling rate. The rolled structural member has a mechanical property of a given tensile strength and yield strength so that it can be produced without any further strengthening process steps subsequent to its hot forging.

The advantages of the invention are achieved by rolling steel of suitable composition at a suitable temperature. The hot rolled steel is then cooled from the rolling temperature to room temperature, preferably at an increased and adjusted rate. Alternatively, the rolled steel is quenched in oil or water and then tempered if it has a sufficient martensite content to reduce the brittleness in the resulting structural members.

The following examples illustrate the practice of the present invention for producing structural members from high strength steel materials produced according to the methods described above.

High strength AISI 1552 steel stocks have the following composition by weight:

0.52% carbon

Manganese 1.43%

Phosphorus 0.009%

Sulfur 0.017%

Silicon 0.22%

Vanadium 0.075%

Chromium 0.05%

Molybdenum 0.01%

Iron residue

The stock was tested and had a tensile strength of 130,000 psi and a yield strength of 95,120 psi. The stock is then hot rolled under 65,000 lbf into an I-beam structural member having a central portion 0.177 "thick and a top and bottom flange each having a taper thickness in the range of 0.23" to about 0.16 "at a temperature of about 2000 F. I The overall height of the beam is 2.64 ", the overall width is the same as each flange and specifically 1.825". A radius fillet of 0.125 "joins each flange with each face of the center portion. Testing of the I-beam showed a tensile strength of about 133,000 psi and a yield strength of about 89,000 psi.

The mechanical properties of the tensile and yield strengths of the machined I-beam structural members are substantially the same as or greater than those originally contained in the stock, and thus do not require additional reinforcement process steps. The processing member also has the desired mechanical properties of the ductility originally contained in the bar stock or billet, and the need for additional processing steps for improved toughness is generally eliminated.

Compared with the prior art methods using a heat treatment process (ie austenitizing, hardening and quenching by quenching), heat treatment is used, especially after cold forming, to obtain the desired high strength mechanical properties of the member. In this case, the fabricated structural member produced in accordance with the present invention may consistently have mechanical properties in a narrower range. Thus, the present invention can consistently produce a narrower range of high strength steel structural members that are essentially attributable to the composition of the steel material.

The scope of the invention is not limited by the examples provided herein but is defined by the appended claims.

Claims (14)

Having a tensile strength of at least about 120,000 psi and a yield strength of at least about 90,000 psi, as weight percent About 0.30 to about 0.65% carbon, About 0.30 to about 2.5% manganese, At least about 0.35% particle refinement effective amount of at least one particle refinement from the group consisting of aluminum, niobium, titanium and vanadium and mixtures thereof, and Providing a high strength steel material comprising iron residues; And Structural members having hot cross-sections of high-strength steel that have a uniform cross-sectional shape over at least one portion of its length, where the uniform cross-sectional shape is different from the shape of the material and has a thickness less than or equal to the overall perimeter of the cross-sectional shape. And at least one flange to provide increased support to the substrate. The method of claim 1 wherein the mechanical properties of tensile and yield strength of the structural member are produced without additional processing steps to reinforce the structural member. The method of claim 1 wherein the high strength steel material is About 0.40 to about 0.55% carbon, About 0.30 to about 2.50% manganese, At least about 0.20% particle refining effective amount of at least one particle refining from the group consisting of aluminum, niobium, titanium and vanadium and mixtures thereof, and Method containing iron residue. The method of claim 1 wherein the high strength steel material is About 0.50 to about 0.55% carbon, About 1.20 to about 1.65% manganese, At least one particle refinement from the group consisting of aluminum, niobium, titanium and vanadium and mixtures thereof in an amount of particle refinement of about 0.03 to about 0.20%, and Method containing iron residue. The method of claim 1 wherein the hot rolling is performed at a temperature of about 2000 ° F. or greater. The method of claim 1 wherein the uniform cross-sectional shape is selected from the group consisting of 0, L, C, Z, I, T, U, V and W shapes. The method of claim 1, further comprising cooling the structural member at an increased and adjusted cooling rate. The method of claim 1 wherein the particle refinement is vanadium. At least partially martensitic microstructure and tensile strength of at least about 120,000 psi and yield strength of at least about 90,000 psi, About 0.30 to about 0.65% carbon, About 0.30 to about 2.5% manganese, At least about 0.35% particle refinement effective amount of at least one particle refinement from the group consisting of aluminum, niobium, titanium and vanadium and mixtures thereof, and Providing a high strength steel material comprising iron residues; And Hot rolled steel material to provide a structural member having a uniform cross-sectional shape over at least one portion of its length, where the uniform cross-sectional shape has a thickness less than or equal to the overall circumferential dimension of the cross-sectional shape. And at least two flanges). 10. The method of claim 9 wherein the high strength steel material is About 0.50 to about 0.55% carbon, About 1.20 to about 1.65% manganese, At least one particle refinement from the group consisting of aluminum, niobium, titanium and vanadium and mixtures thereof in an amount of particle refinement of about 0.03 to about 0.20%, and Method containing iron residue. The method of claim 9, wherein the uniform cross-sectional shape is selected from the group consisting of O, L, C, Z, I, T, U, V and W shapes. 10. The method of claim 9, further comprising cooling the structural member at an increased and adjusted cooling rate. The method of claim 9, wherein the particle refinement is vanadium. Having a tensile strength of at least about 120,000 psi and a yield strength of at least about 90,000 psi, as weight percent About 0.50 to about 0.55% carbon, About 1.20 to about 1.65% manganese, At least one particle refinement from the group consisting of aluminum, niobium, titanium and vanadium and mixtures thereof in an amount of particle refinement of about 0.03 to about 0.20%, and Providing a high strength steel material comprising iron residues; And A structural member having a uniform cross-sectional shape over at least one portion of its length by hot rolling a steel material at a temperature of about 2000 ° F or more, wherein the uniform cross-sectional shape has a thickness less than or equal to the overall circumferential dimension of the cross-sectional shape. At least one flange providing increased bearing capacity, and selected from the group consisting of O, L, C, Z, I, T, U, V, and W shapes; And A method of making a high strength steel structural member comprising cooling the structural member.