WO2021133343A1 - High strength, low alloy steel composition - Google Patents

High strength, low alloy steel composition Download PDF

Info

Publication number
WO2021133343A1
WO2021133343A1 PCT/TR2020/051351 TR2020051351W WO2021133343A1 WO 2021133343 A1 WO2021133343 A1 WO 2021133343A1 TR 2020051351 W TR2020051351 W TR 2020051351W WO 2021133343 A1 WO2021133343 A1 WO 2021133343A1
Authority
WO
WIPO (PCT)
Prior art keywords
ratio
weight
maximum
steel composition
alloy steel
Prior art date
Application number
PCT/TR2020/051351
Other languages
French (fr)
Inventor
Fulya EYÇİN
Osman ÇULHA
Original Assignee
Ti̇rsan Kardan Sanayi̇ Ve Ti̇caret Anoni̇m Şi̇rketi̇
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Ti̇rsan Kardan Sanayi̇ Ve Ti̇caret Anoni̇m Şi̇rketi̇ filed Critical Ti̇rsan Kardan Sanayi̇ Ve Ti̇caret Anoni̇m Şi̇rketi̇
Publication of WO2021133343A1 publication Critical patent/WO2021133343A1/en

Links

Classifications

    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/14—Ferrous alloys, e.g. steel alloys containing titanium or zirconium
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21J—FORGING; HAMMERING; PRESSING METAL; RIVETING; FORGE FURNACES
    • B21J1/00—Preparing metal stock or similar ancillary operations prior, during or post forging, e.g. heating or cooling
    • B21J1/06—Heating or cooling methods or arrangements specially adapted for performing forging or pressing operations
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/005—Modifying the physical properties by deformation combined with, or followed by, heat treatment of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/02—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips
    • C21D8/0247—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of plates or strips characterised by the heat treatment
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D8/00—Modifying the physical properties by deformation combined with, or followed by, heat treatment
    • C21D8/06—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires
    • C21D8/065—Modifying the physical properties by deformation combined with, or followed by, heat treatment during manufacturing of rods or wires of ferrous alloys
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D9/00—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor
    • C21D9/08—Heat treatment, e.g. annealing, hardening, quenching or tempering, adapted for particular articles; Furnaces therefor for tubular bodies or pipes
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/001—Ferrous alloys, e.g. steel alloys containing N
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/002—Ferrous alloys, e.g. steel alloys containing In, Mg, or other elements not provided for in one single group C22C38/001 - C22C38/60
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/02—Ferrous alloys, e.g. steel alloys containing silicon
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/04—Ferrous alloys, e.g. steel alloys containing manganese
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/08—Ferrous alloys, e.g. steel alloys containing nickel
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/12—Ferrous alloys, e.g. steel alloys containing tungsten, tantalum, molybdenum, vanadium, or niobium
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/16—Ferrous alloys, e.g. steel alloys containing copper
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22C—ALLOYS
    • C22C38/00—Ferrous alloys, e.g. steel alloys
    • C22C38/18—Ferrous alloys, e.g. steel alloys containing chromium
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/002—Bainite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/004—Dispersions; Precipitations
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/005—Ferrite
    • C—CHEMISTRY; METALLURGY
    • C21—METALLURGY OF IRON
    • C21D—MODIFYING THE PHYSICAL STRUCTURE OF FERROUS METALS; GENERAL DEVICES FOR HEAT TREATMENT OF FERROUS OR NON-FERROUS METALS OR ALLOYS; MAKING METAL MALLEABLE, e.g. BY DECARBURISATION OR TEMPERING
    • C21D2211/00—Microstructure comprising significant phases
    • C21D2211/009—Pearlite

Definitions

  • the present invention relates to a high strength, low alloy steel composition developed for use in all areas where hot forging processes can be applied.
  • the invention particularly relates to a micro alloy steel composition
  • a micro alloy steel composition comprising; carbon (C) in a ratio of 0.05 - 0.15 % by weight, boron (B) in a ratio of 0.005 % maximum by weight, nitrogen (N) in a ratio of 0.007 % maximum by weight, silicon (Si)in a ratio of 0.25 % maximum by weight, manganese (Mn) in a ratio of 0.9 % maximum by weight, chromium (Cr) in a ratio of 0.4 % maximum by weight, molybdenum (Mo) in a ratio of 0.1 % maximum by weight, nickel (Ni) in a ratio of 0.2 % maximum by weight, vanadium (V) in a ratio of 0.1 % maximum by weight, titanium (Ti) in a ratio of 0.05 - 2 % by weight, phosphorus (P) in a ratio of 0.3 % maximum by weight, sulphur (S) in a ratio of 0.3 %
  • Micro alloy steels have an important position among steel types by constituting approximately 12 % of the world’s steel production. These steels, which are used in all major steel markets in many parts of the world, play an important role in the automotive, gas and oil pipelines, construction, and transportation industries.
  • micro alloy steels are steels with perlite and without perlite.
  • Features such as formability, thickness, and weldability etc. are significantly increased by substantially reducing the carbon ratio. Said features are generally required in the production of high strength and lightweight parts by forming the same.
  • the carbon ratio is low, the yield limit of these steels can only reach 500 N/mm 2 with controlled rolling with the grain refinement and hardening effects of micro alloy elements as aluminum (Al), niobium (Nb), titanium (Ti), vanadium (V).
  • Carbides, nitrides and carbonitrides formed by micro alloy elements remain insoluble in the austenite phase in case the dissolving temperatures are not exceeded during hot forming processes. These insoluble hard structures provide to obtain both a small - grain steel structure and an increase in the toughness of the material by preventing austenite grain growth.
  • the patent application numbered CA2666677A1 is found in the literature regarding the subject matter.
  • the invention relates to the production process of steel and high strength, segmented machine parts.
  • the inventive chemical composition of the steel contains 0.40 - 0.60 % carbon (C), 0.20 - 1.00 % silicon (Si), 0.50 - 1.50 % manganese (Mn), max. 1 % chromium (Cr), max. 0.5 % nickel (Ni), max. 0.2 % molybdenum (Mo), max. 0.050 % niobium (Nb), max. 0.3 % vanadium (V), max. 0.05 % aluminium (Al), 0.005 - 0.02 % nitrogen (N) by weight, the remainder consists of iron (Fe) in balance with the other elements and impurities.
  • Patent application numbered EP1070153B1 relates to a steel composition containing; 0.6 - 0.65 % carbon (C), max. 0.4 % silicon (Si), 0.6 - 0.9 % manganese (Mn), 0.03 - 0.07 % phosphorus (P), 0.07 - 0.11 % Sulphur (S), max. 0.5 % chromium (Cr), max. 0.1 % molybdenum (Mo), max. 0.5 % nickel (Ni), max. 0.5 % copper (Cu), max. 0.5 % aluminium (Al), max. 0.03 % nitrogen (N) by weight, vanadium and iron.
  • the present invention is related to high strength, low steel alloy steel composition which fulfills the abovementioned requirements, eliminates all disadvantages and brings some additional advantages.
  • the main aim of the invention is to provide a micro alloy steel composition that can be used in hot forging processes as bar product of raw material.
  • the aim of the invention is to provide a high strength, low alloy steel composition.
  • the aim of the invention is to provide a steel composition that has yield strength of 500 - 600 MPa, tensile strength of 700 - 750 MPa and hardness of 210 - 230 HV after a controlled forging.
  • the aim of the invention is to increase the strength by activating the strength increasing mechanism by refining the grain as a consequence of using titanium and vanadium in combination as a carbide maker.
  • the aim of the invention is to provide grain refining elements to reveal their effect by the fact that, in the primary cooling, the heat transfer coefficient is 80 - 120 W/m 2 K for 100 - 130 seconds, in the secondary cooling, the heat transfer coefficient is 40 - 80 W/m 2 K for 1200 - 1500 seconds required for forging temperature and cooling environment after forging.
  • the aim of the invention is to increase hardness with the use of boron element in the steel composition. Boron is placed in the crystal structure as an intermediate atom like carbon, and it creates distortion in the crystal and thus increases the hardness due to its high solubility.
  • An aim of the invention is to develop mechanical features of the steel composition by benefiting from the features of intermediate atoms such as C, N, B and elements such as Mn, Si, Ni, V and Ti are used to make nitride, carbide and carbonitride,
  • the invention is a micro alloy steel composition, characterized by comprising the following; carbon (C) in a ratio of 0.05 - 0.15 % by weight, boron (B) in a ratio of 0.005 % maximum by weight, nitrogen (N) in a ratio of 0.007 % maximum by weight, silicon (Si) in a ratio of 0.25 % maximum by weight, manganese (Mn) in a ratio of 0.9 % maximum by weight, chromium (Cr) in a ratio of 0.4 % maximum by weight, molybdenum (Mo) in a ratio of 0.1 % maximum by weight, nickel (Ni) in a ratio of 0.2 % maximum by weight, vanadium (V) in a ratio of 0.1 % maximum by weight, titanium (Ti) in a ratio of 0.05 - 2 % by weight, phosphorus (P) in a ratio of 0.3 % maximum by weight, Sulphur (S) in a ratio of a ratio of 0.3 % maximum by
  • Micro alloy steel composition production method in order to fulfill the aims of the invention comprising the following process steps,
  • said forging temperature is at 950 - 1150°C
  • the heat coefficient of the primary cooling after forging is 80 - 120 W/m 2 K for 100 - 130 seconds
  • the secondary cooling is 40 - 80 W/m 2 K for 1200 - 1500 seconds under atmospheric conditions.
  • inventive high strength, low alloy steel composition is described only for clarifying the subject matter in a manner such that no limiting effect is created.
  • the present invention is a micro alloy steel composition developed for use in all fields where hot forging processes can be applied, characterized by comprising the following; carbon (C) in a ratio of 0.05 - 0.15 % by weight, boron (B) in a ratio of 0.005 % maximum by weight, nitrogen (N) in a ratio of 0.007 % maximum by weight, silicon (Si) in a ratio of 0.25 % maximum by weight, manganese (Mn) in a ratio of 0.9 % maximum by weight, chromium (Cr) in a ratio of 0.4 % maximum by weight, molybdenum (Mo) in a ratio of 0.1 % maximum by weight, nickel (Ni) in a ratio of 0.2 % maximum by weight, vanadium (V) in a ratio of 0.1 % maximum by weight, titanium (Ti) in a ratio of 0.05 - 2 % by weight, phosphorus (P) in a ratio of 0.3 % maximum by weight, Sulphur (S)
  • the inventive formulation of the micro alloy steel composition First of all the alloy elements are determined so as to obtain the inventive formulation of the micro alloy steel composition.
  • the amount and diversity of alloy elements in the steel composition are important parameters for developing the mechanical features.
  • intermediate atoms such as C, N, B and elements such as Mn, Si, Ni, V and Ti are used so as to make nitride, carbide and carbonitride, in order to make different strength increasing mechanisms to occur in combination.
  • fine grain and multi - phase microstructure is obtained by benefiting from the variable feature of TTT (isothermal conversion diagram) and CCT (continuous cooling conversion diagram) diagrams.
  • hot forging methodology is formed. The temperature and deformation rates in the hot forging process are rearranged with respect to the original alloy.
  • a cooling process is applied. The cooling regime for the target microstructure (ferrite, perlite, bainite) is determined according to the TTT (isothermal conversion diagram) and CCT (continuous cooling conversion diagram) diagrams.
  • Martensite and bainite conversion in the iron - carbon phase diagram has an important position in the hardening mechanism of the alloy, in the iron - carbon phase diagram.
  • cooling rates are significantly higher than balance conditions due to process conditions in industrial steel production.
  • the iron - carbon phase diagram used in determining the phase conversion with the increase of the cooling rate is not used. The most important reason for this is that said diagram is formed under very slow cooling conditions.
  • diagrams which are called TTT and indicate the change of phase conversion due to temperature and time are used at high cooling rates.
  • TTT diagrams are preferred in determining the phase transformations that will occur in the alloy depending on the super cooling conditions as a function of temperature and time.
  • CCT continuous cooling conversion curves
  • Hardness is increased with the use of boron element in the inventive steel composition. Boron is placed in the crystal structure as an intermediate atom like carbon, and it creates distortion in the crystal and thus increases the hardness due to its high solubility.
  • the strength increasing mechanism is activated by refining the grain, and strength is increased with toughness by using titanium and vanadium in combination as a carbide maker.
  • the composition of steel produced by micro - alloying is obtained in the form of billets by continuous casting method by using electric arc furnace, ladle furnace, vacuum furnace and tundish dipping closed ceramic tube respectively,
  • Said forging temperature used in the inventive production method occurs at 950 - 1150°C, the heat coefficient of the primary cooling after forging is 80 - 120 W/m 2 K for 100 - 130 seconds and the secondary cooling occurs 40 - 80 W/m 2 K for 1200 - 1500 seconds under atmospheric conditions.
  • V - Ti - C - N precipitates are formed with 30 - 40 % ferrite, 30 - 45 % perlite and 10 - 15 % bainite phase with the inventive production method.
  • the long product described in a preferred embodiment of the invention covers all steel products such as round, square, square with rounded corners, plate, wide plates etc.

Landscapes

  • Chemical & Material Sciences (AREA)
  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Materials Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Physics & Mathematics (AREA)
  • Thermal Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Heat Treatment Of Steel (AREA)
  • Heat Treatment Of Sheet Steel (AREA)
  • Laminated Bodies (AREA)

Abstract

High strength, low alloy steel composition The invention particularly relates to a micro alloy steel composition comprising; carbon (C) in a ratio of 0.05 - 0.15 % by weight, boron (B) in a ratio of 0.005 % maximum by weight, nitrogen (N) in a ratio of 0.007 % maximum by weight, silicon (Si) in a ratio of 0.25 % maximum by weight, manganese (Mn) in a ratio of 0.9 % maximum by weight, chromium (Cr) in a ratio of 0.4 % maximum by weight, molybdenum (Mo) in a ratio of 0.1 % maximum by weight, nickel (Ni) in a ratio of 0.2 % maximum by weight, vanadium (V) in a ratio of 0.1 % maximum by weight, titanium (Ti) in a ratio of 0.05 - 2 % by weight, phosphorus (P) in a ratio of 0.3 % maximum by weight, Sulphur (S) in a ratio of 0.3 % maximum by weight and copper (Cu) in a ratio of 0.25 % maximum by weight with yield strength of 500 - 600 MPa, tensile strength of 700 - 750 MPa.

Description

High strength, low alloy steel composition
Field of the Invention
The present invention, relates to a high strength, low alloy steel composition developed for use in all areas where hot forging processes can be applied.
The invention particularly relates to a micro alloy steel composition comprising; carbon (C) in a ratio of 0.05 - 0.15 % by weight, boron (B) in a ratio of 0.005 % maximum by weight, nitrogen (N) in a ratio of 0.007 % maximum by weight, silicon (Si)in a ratio of 0.25 % maximum by weight, manganese (Mn) in a ratio of 0.9 % maximum by weight, chromium (Cr) in a ratio of 0.4 % maximum by weight, molybdenum (Mo) in a ratio of 0.1 % maximum by weight, nickel (Ni) in a ratio of 0.2 % maximum by weight, vanadium (V) in a ratio of 0.1 % maximum by weight, titanium (Ti) in a ratio of 0.05 - 2 % by weight, phosphorus (P) in a ratio of 0.3 % maximum by weight, sulphur (S) in a ratio of 0.3 % maximum by weight and copper (Cu) in a ratio of 0.25 % maximum by weight with yield strength of 500 - 600 MPa and tensile strength of 700 - 750 MPa.
State of the Art
Micro alloy steels have an important position among steel types by constituting approximately 12 % of the world’s steel production. These steels, which are used in all major steel markets in many parts of the world, play an important role in the automotive, gas and oil pipelines, construction, and transportation industries.
Specific development characteristics of micro alloy steels are steels with perlite and without perlite. Features such as formability, thickness, and weldability etc. are significantly increased by substantially reducing the carbon ratio. Said features are generally required in the production of high strength and lightweight parts by forming the same. Although the carbon ratio is low, the yield limit of these steels can only reach 500 N/mm2 with controlled rolling with the grain refinement and hardening effects of micro alloy elements as aluminum (Al), niobium (Nb), titanium (Ti), vanadium (V).
Niobium (Nb), titanium (Ti), vanadium (V) and aluminium (Al), which are used as alloy elements in micro alloy steels, have a direct effect on the mechanical properties of the material and form carbide, nitride or carbonitride. Carbides, nitrides and carbonitrides formed by micro alloy elements remain insoluble in the austenite phase in case the dissolving temperatures are not exceeded during hot forming processes. These insoluble hard structures provide to obtain both a small - grain steel structure and an increase in the toughness of the material by preventing austenite grain growth.
In the state of the art, feature of increasing the amount of carbon in the alloy and grain refinement of the micro alloy elements are used so as to obtain high strength. The high carbon steel alloy is exposed to heat treatment after hot forging and a secondary treatment is required so as to increase strength. On the other hand, in the state of the art, micro alloy steels cannot increase the strength of the forged material as much as the heat treated high carbon alloy. While the yield strength of the steel alloy in the high carbon C45E standard is 500 MPa and the tensile strength is 750 - 850 MPa, the yield strength is 435 MPa and the tensile strength is between 580 - 780 MPa in the micro alloy steel. As mentioned before, the increase in strength of high carbon steel as a result of a high cost application with secondary process and low yield strength in micro alloy steel shows that there is a need for developing a new steel alloy.
The patent application numbered CA2666677A1 is found in the literature regarding the subject matter. The invention relates to the production process of steel and high strength, segmented machine parts. The inventive chemical composition of the steel contains 0.40 - 0.60 % carbon (C), 0.20 - 1.00 % silicon (Si), 0.50 - 1.50 % manganese (Mn), max. 1 % chromium (Cr), max. 0.5 % nickel (Ni), max. 0.2 % molybdenum (Mo), max. 0.050 % niobium (Nb), max. 0.3 % vanadium (V), max. 0.05 % aluminium (Al), 0.005 - 0.02 % nitrogen (N) by weight, the remainder consists of iron (Fe) in balance with the other elements and impurities.
Patent application numbered EP1070153B1 relates to a steel composition containing; 0.6 - 0.65 % carbon (C), max. 0.4 % silicon (Si), 0.6 - 0.9 % manganese (Mn), 0.03 - 0.07 % phosphorus (P), 0.07 - 0.11 % Sulphur (S), max. 0.5 % chromium (Cr), max. 0.1 % molybdenum (Mo), max. 0.5 % nickel (Ni), max. 0.5 % copper (Cu), max. 0.5 % aluminium (Al), max. 0.03 % nitrogen (N) by weight, vanadium and iron.
As can be seen in said applications, there are many steel compositions in the state of the art. However, the requirement of micro alloy steel alloys with high strength and high yield strength is increasing day by day.
As a result, due to the abovementioned disadvantages, deficiencies, there is a requirement to make an innovation in the relevant technical field. Aim of the Invention
The present invention is related to high strength, low steel alloy steel composition which fulfills the abovementioned requirements, eliminates all disadvantages and brings some additional advantages.
The main aim of the invention is to provide a micro alloy steel composition that can be used in hot forging processes as bar product of raw material.
The aim of the invention is to provide a high strength, low alloy steel composition.
The aim of the invention is to provide a steel composition that has yield strength of 500 - 600 MPa, tensile strength of 700 - 750 MPa and hardness of 210 - 230 HV after a controlled forging.
The aim of the invention is to increase the strength by activating the strength increasing mechanism by refining the grain as a consequence of using titanium and vanadium in combination as a carbide maker.
The aim of the invention is to provide grain refining elements to reveal their effect by the fact that, in the primary cooling, the heat transfer coefficient is 80 - 120 W/m2K for 100 - 130 seconds, in the secondary cooling, the heat transfer coefficient is 40 - 80 W/m2K for 1200 - 1500 seconds required for forging temperature and cooling environment after forging.
The aim of the invention is to increase hardness with the use of boron element in the steel composition. Boron is placed in the crystal structure as an intermediate atom like carbon, and it creates distortion in the crystal and thus increases the hardness due to its high solubility.
An aim of the invention is to develop mechanical features of the steel composition by benefiting from the features of intermediate atoms such as C, N, B and elements such as Mn, Si, Ni, V and Ti are used to make nitride, carbide and carbonitride,
In order to fulfill the aims described above, the invention is a micro alloy steel composition, characterized by comprising the following; carbon (C) in a ratio of 0.05 - 0.15 % by weight, boron (B) in a ratio of 0.005 % maximum by weight, nitrogen (N) in a ratio of 0.007 % maximum by weight, silicon (Si) in a ratio of 0.25 % maximum by weight, manganese (Mn) in a ratio of 0.9 % maximum by weight, chromium (Cr) in a ratio of 0.4 % maximum by weight, molybdenum (Mo) in a ratio of 0.1 % maximum by weight, nickel (Ni) in a ratio of 0.2 % maximum by weight, vanadium (V) in a ratio of 0.1 % maximum by weight, titanium (Ti) in a ratio of 0.05 - 2 % by weight, phosphorus (P) in a ratio of 0.3 % maximum by weight, Sulphur (S) in a ratio of 0.3 % maximum by weight and copper (Cu) in a ratio of 0.25 % maximum by weight.
Micro alloy steel composition production method in order to fulfill the aims of the invention comprising the following process steps,
• obtaining the steel composition produced by micro alloying in the form of billets by continuous casting method,
• converting the produced billets into cylindrical semi - finished products in the round long group by hot rolling,
• forming precipitation by subjecting the long semi - finished products to the controlled hot forging and cooling phases, characterized in that;
• said forging temperature is at 950 - 1150°C, the heat coefficient of the primary cooling after forging is 80 - 120 W/m2K for 100 - 130 seconds and the secondary cooling is 40 - 80 W/m2K for 1200 - 1500 seconds under atmospheric conditions.
The structural and characteristic features of the present invention will be understood clearly by the following detailed description and therefore the evaluation shall be made by taking the detailed description into consideration.
Detailed Description of the Invention
In this detailed description, the inventive high strength, low alloy steel composition, is described only for clarifying the subject matter in a manner such that no limiting effect is created.
The present invention is a micro alloy steel composition developed for use in all fields where hot forging processes can be applied, characterized by comprising the following; carbon (C) in a ratio of 0.05 - 0.15 % by weight, boron (B) in a ratio of 0.005 % maximum by weight, nitrogen (N) in a ratio of 0.007 % maximum by weight, silicon (Si) in a ratio of 0.25 % maximum by weight, manganese (Mn) in a ratio of 0.9 % maximum by weight, chromium (Cr) in a ratio of 0.4 % maximum by weight, molybdenum (Mo) in a ratio of 0.1 % maximum by weight, nickel (Ni) in a ratio of 0.2 % maximum by weight, vanadium (V) in a ratio of 0.1 % maximum by weight, titanium (Ti) in a ratio of 0.05 - 2 % by weight, phosphorus (P) in a ratio of 0.3 % maximum by weight, Sulphur (S) in a ratio of 0.3 % maximum by weight and copper (Cu) in a ratio of 0.25 % maximum by weight.
The inventive formulation of the micro alloy steel composition;
Figure imgf000006_0001
First of all the alloy elements are determined so as to obtain the inventive formulation of the micro alloy steel composition. The amount and diversity of alloy elements in the steel composition are important parameters for developing the mechanical features.
The features of intermediate atoms such as C, N, B and elements such as Mn, Si, Ni, V and Ti are used so as to make nitride, carbide and carbonitride, in order to make different strength increasing mechanisms to occur in combination. On the other hand, fine grain and multi - phase microstructure is obtained by benefiting from the variable feature of TTT (isothermal conversion diagram) and CCT (continuous cooling conversion diagram) diagrams. Secondly, hot forging methodology is formed. The temperature and deformation rates in the hot forging process are rearranged with respect to the original alloy. Finally, a cooling process is applied. The cooling regime for the target microstructure (ferrite, perlite, bainite) is determined according to the TTT (isothermal conversion diagram) and CCT (continuous cooling conversion diagram) diagrams.
Martensite and bainite conversion in the iron - carbon phase diagram, has an important position in the hardening mechanism of the alloy, in the iron - carbon phase diagram. However, cooling rates are significantly higher than balance conditions due to process conditions in industrial steel production. The iron - carbon phase diagram used in determining the phase conversion with the increase of the cooling rate is not used. The most important reason for this is that said diagram is formed under very slow cooling conditions. Thus, diagrams which are called TTT and indicate the change of phase conversion due to temperature and time are used at high cooling rates. In fast - cooled steels, the aspects as when the austenite will begin conversion, how long the conversion will be completed and what products will be formed as a result are determined by means of the isothermal transformation diagrams. Thus, TTT diagrams are preferred in determining the phase transformations that will occur in the alloy depending on the super cooling conditions as a function of temperature and time.
It is required to change the conversion curve so as to see the time and temperature effects separately in the conversion reaction. The curves showing this situation are called continuous cooling conversion curves (CCT). CCT diagrams can be used for all heat treatments that also include continuous cooling. The main aim of CCT diagrams is to foresee which structure elements will be obtained and thus which hardness can be obtained by using the cooling curve. These diagrams ensure determining the phase or phases contained in the final microstructures to be obtained after both isothermal heat treatments where the temperature is kept constant and the conversion in continuous cooling.
Hardness is increased with the use of boron element in the inventive steel composition. Boron is placed in the crystal structure as an intermediate atom like carbon, and it creates distortion in the crystal and thus increases the hardness due to its high solubility. The strength increasing mechanism is activated by refining the grain, and strength is increased with toughness by using titanium and vanadium in combination as a carbide maker.
Production method of the inventive micro alloy steel composition; • The composition of steel produced by micro - alloying is obtained in the form of billets by continuous casting method by using electric arc furnace, ladle furnace, vacuum furnace and tundish dipping closed ceramic tube respectively,
• Converting the produced billets into cylindrical semi - finished products in the round long group by hot rolling,
• Exposing long semi - finished products to controlled hot forging and cooling phases,
• Obtaining a steel alloy with desired mechanical values with the precipitate hardening mechanism,
Said forging temperature used in the inventive production method occurs at 950 - 1150°C, the heat coefficient of the primary cooling after forging is 80 - 120 W/m2K for 100 - 130 seconds and the secondary cooling occurs 40 - 80 W/m2K for 1200 - 1500 seconds under atmospheric conditions.
V - Ti - C - N precipitates are formed with 30 - 40 % ferrite, 30 - 45 % perlite and 10 - 15 % bainite phase with the inventive production method.
Mechanical features of the inventive micro alloy steel composition;
• Yield strength 500 - 600 MPa,
• Tensile strength 700 - 750 MPa,
• Hardness 210 - 230 HV,
• Equivalent carbon value is 0,43 - 0,45 Ceq.
The long product described in a preferred embodiment of the invention covers all steel products such as round, square, square with rounded corners, plate, wide plates etc.

Claims

1. A micro alloy steel composition, characterized by comprising the following; carbon (C) in a ratio of 0.05 - 0.15 % by weight, boron (B) in a ratio of 0.005 % maximum by weight, nitrogen (N) in a ratio of 0.007 % maximum by weight, silicon (Si) in a ratio of 0.25 % maximum by weight, manganese (Mn) in a ratio of 0.9 % maximum by weight, chromium (Cr) in a ratio of 0.4 % maximum by weight, molybdenum (Mo) in a ratio of 0.1 % maximum by weight, nickel (Ni) in a ratio of 0.2 % maximum by weight, vanadium (V) in a ratio of 0.1 % maximum by weight, titanium (Ti) in a ratio of 0.05 - 2 % by weight, phosphorus (P) in a ratio of 0.3 % maximum by weight, Sulphur (S) in a ratio of 0.3 % maximum by weight and copper (Cu) in a ratio of 0.25 % maximum by weight.
2. A micro alloy steel composition that comprises the following process steps according the claim 1;
• obtaining the steel composition produced by micro alloying in the form of billets by continuous casting method,
• converting the produced billets into cylindrical semi - finished products in the round long group by hot rolling,
• forming precipitation by subjecting the long semi - finished products to the controlled hot forging and cooling phases, characterized in that;
• said forging temperature is at 950 - 1150°C, the heat coefficient of the primary cooling after forging is 80 - 120 W/m2K for 100 - 130 seconds and the secondary cooling is 40 - 80 W/m2K for 1200 - 1500 seconds under atmospheric conditions.
3. Micro alloy steel composition obtained with a method according to claim 2, characterized in that; the precipitate formed consists of V - Ti - C - N, 30 - 40 % ferrite, 30 - 45 % perlite and 10 - 15 % bainite phase.
4. Micro alloy steel composition obtained with a method according to claim 2, characterized in that; it has a yield strength of 500 - 600 MPa.
5. Micro alloy steel composition obtained with a method according to claim 2, characterized in that; it has a tensile strength of 700 - 750 Mpa.
6. Micro alloy steel composition obtained with a method according to claim 2, characterized in that; it has a hardness of 210 - 230 HV.
7. Micro alloy steel composition obtained with a method according to claim 2, characterized in that; it has an equivalent carbon value of 0.43 - 0.45 Ceq.
PCT/TR2020/051351 2019-12-24 2020-12-22 High strength, low alloy steel composition WO2021133343A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
TR2019/21217A TR201921217A2 (en) 2019-12-24 2019-12-24 High strength, low alloy steel composition
TR2019/21217 2019-12-24

Publications (1)

Publication Number Publication Date
WO2021133343A1 true WO2021133343A1 (en) 2021-07-01

Family

ID=74096042

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/TR2020/051351 WO2021133343A1 (en) 2019-12-24 2020-12-22 High strength, low alloy steel composition

Country Status (2)

Country Link
TR (1) TR201921217A2 (en)
WO (1) WO2021133343A1 (en)

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1070153B1 (en) 1998-03-10 2003-12-17 Corus UK Limited Steel composition
JP2005146303A (en) * 2003-11-11 2005-06-09 Sanyo Special Steel Co Ltd Method for manufacturing curburized steel superior in grain-coarsening resistance after high temperature carburizing
CA2666677A1 (en) 2006-09-01 2008-03-13 Georgsmarienhuette Gmbh Steel and processing method for the manufacture of high strength, fracture-splittable machinery components
JP2016032818A (en) * 2014-07-31 2016-03-10 Ｊｆｅスチール株式会社 Forge-welded steel tube excellent in mouth expanding workability, and manufacturing method and manufacturing equipment of the same
EP3375900A1 (en) * 2016-03-22 2018-09-19 Nippon Steel & Sumitomo Metal Corporation Electric resistance welded steel tube for line pipe
EP3428299A1 (en) * 2016-07-06 2019-01-16 Nippon Steel & Sumitomo Metal Corporation Electroseamed steel pipe for line pipe
EP3521475A1 (en) * 2016-10-03 2019-08-07 Nippon Steel & Sumitomo Metal Corporation Electric resistance-welded steel pipe for torsion beam

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP1070153B1 (en) 1998-03-10 2003-12-17 Corus UK Limited Steel composition
JP2005146303A (en) * 2003-11-11 2005-06-09 Sanyo Special Steel Co Ltd Method for manufacturing curburized steel superior in grain-coarsening resistance after high temperature carburizing
CA2666677A1 (en) 2006-09-01 2008-03-13 Georgsmarienhuette Gmbh Steel and processing method for the manufacture of high strength, fracture-splittable machinery components
JP2016032818A (en) * 2014-07-31 2016-03-10 Ｊｆｅスチール株式会社 Forge-welded steel tube excellent in mouth expanding workability, and manufacturing method and manufacturing equipment of the same
EP3375900A1 (en) * 2016-03-22 2018-09-19 Nippon Steel & Sumitomo Metal Corporation Electric resistance welded steel tube for line pipe
EP3428299A1 (en) * 2016-07-06 2019-01-16 Nippon Steel & Sumitomo Metal Corporation Electroseamed steel pipe for line pipe
EP3521475A1 (en) * 2016-10-03 2019-08-07 Nippon Steel & Sumitomo Metal Corporation Electric resistance-welded steel pipe for torsion beam

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
E.J. PAVLINA ET AL: "Correlation of Yield Strength and Tensile Strength with Hardness for Steels", JOURNAL OF MATERIALS ENGINEERING AND PERFORMANCE., vol. 17, no. 6, 1 December 2008 (2008-12-01), US, pages 888 - 893, XP055550915, ISSN: 1059-9495, DOI: 10.1007/s11665-008-9225-5 *

Also Published As

Publication number Publication date
TR201921217A2 (en) 2021-07-26

Similar Documents

Publication Publication Date Title
US11047027B2 (en) 1500 MPA-grade steel with high product of strength and elongation for vehicles and manufacturing methods therefor
WO2021133345A1 (en) Micro-alloy steel composition with improved mechanical properties
RU2701237C2 (en) High-strength hot-rolled steel with high impact strength and yield point of not less than 800 mpa and method for production thereof
JP5833751B2 (en) Ultra-high strength wear-resistant steel sheet and method for producing the same
AU2013344748B2 (en) Method for the production of high-wear-resistance martensitic cast steel and steel with said characteristics
US20220162731A1 (en) Hot-working die steel, heat treatment method thereof and hot-working die
WO2009154235A1 (en) Steel for heat treatment
AU2017353259B2 (en) Medium-manganese steel product for low-temperature use and method for the production thereof
CN101263239A (en) Method of producing high-strength steel plates with excellent ductility and plates thus produced
WO2007016004A1 (en) Corrosion-resistant, cold-formable, machinable, high strength, martensitic stainless steel
TWI650433B (en) Cold work tool steel
JP6217671B2 (en) Thick steel plate with excellent wear resistance in high temperature environments
CN113802064B (en) Method for improving precipitation of second phase of super austenitic stainless steel grain boundary by regulating and controlling grain boundary boron redistribution
JP2014177710A (en) Hardening method for steel
US20130243639A1 (en) Tool steel for extrusion
US20120315181A1 (en) Stainless mold steel with lower delta ferrite content
US7067019B1 (en) Alloy steel and article made therefrom
WO2021133343A1 (en) High strength, low alloy steel composition
JP2023530420A (en) hot work tool steel
CN111742075B (en) Novel duplex stainless steel
TWI760241B (en) Multi-performance medium-entropy lightweight steel and method of fabricating the same
WO2023014330A1 (en) New micro-alloy steel
WO2023101642A2 (en) High-strength, low-alloy steel composition and related production method
WO2023014331A2 (en) Next-generation micro-alloyed steel
JP6838422B2 (en) High-strength steel sheet and its manufacturing method

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 20830013

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 20830013

Country of ref document: EP

Kind code of ref document: A1