Search

KR-102962162-B1 - Hydrogen-resistant coated steel

KR102962162B1KR 102962162 B1KR102962162 B1KR 102962162B1KR-102962162-B1

Abstract

A method for manufacturing a coated steel substrate comprising: a step of providing a steel substrate; a step of electroplating the steel substrate with an electroplating solution having a pH of 2 to 6 and containing 100 g /l to 500 g/l of NiSO₄ and 1 g/l to 15 g/l of MoS₂ by applying a current density of 15 A/ dm² to 45 A/dm² for 30 seconds to 300 seconds to produce a Ni- MoS₂ coating layer; and a step of rinsing and drying the steel substrate to obtain a coated steel substrate.

Inventors

  • 복 로레타
  • 샴수조하 엠디

Assignees

  • 아르셀러미탈

Dates

Publication Date
20260508
Application Date
20201217

Claims (12)

  1. A method for manufacturing a coated steel substrate comprising the following steps: Step of providing a steel substrate; A step of electroplating the steel substrate with an electroplating solution having a pH of 2 to 6 and containing 100 g/l to 500 g/l of NiSO₄ and 1 g/l to 15 g/l of MoS₂ by applying a current density of 15 A/dm² to 45 A/ dm² for 30 to 300 seconds to produce a Ni- MoS₂ coating layer; After that, the step of rinsing and drying the steel substrate to obtain a coated steel substrate.
  2. In Article 1, A method for manufacturing a coated steel substrate, wherein the pH of the electroplating solution is 2 to 5.
  3. In Article 1, A method for manufacturing a coated steel substrate, wherein the concentration of NiSO₄ in the above electroplating solution is 100 g/l to 400 g/l.
  4. In Article 1, A method for manufacturing a coated steel substrate, wherein the concentration of MoS₂ in the above electroplating solution is 1 g/l to 15 g/l.
  5. In Article 1, A method for manufacturing a coated steel substrate, wherein the steel substrate submitted to the above electroplating step is a cold-rolled steel sheet obtained through the following steps: Step of providing semi-finished products for the lecture; A step of reheating the above semi-finished product to a temperature of 1000℃ to 1280℃; A step of obtaining a hot-rolled steel sheet by rolling the above semi-finished product in an austenitic range with a hot-rolling finishing temperature exceeding 850℃; A step of cooling the steel plate to a coiling temperature of less than 650℃ at an average cooling rate of more than 30℃/s, and coiling the hot-rolled steel plate; A step of cooling the above hot-rolled steel plate to room temperature; Optionally, a step of performing a scale removal process on the hot-rolled steel plate; Optionally, a step of performing annealing on a hot-rolled steel sheet at a temperature of 400℃ to 750℃; Optionally, a step of performing a scale removal step on the hot-rolled steel plate; A step of cold-rolling the above hot-rolled steel sheet with a reduction rate of 35 to 90% to obtain a cold-rolled steel sheet; Subsequently, a step of performing annealing by heating the cold-rolled steel sheet to a soaking temperature of Ac1 to Ac3+100℃ at a heating rate of more than 2℃/s and maintaining it for 10 seconds to 500 seconds; Subsequently, a step of obtaining a cold-rolled steel substrate by cooling the steel plate to a temperature of less than 550°C at a rate of more than 5°C/s, wherein during the cooling, the cold-rolled steel plate can be selectively maintained in a temperature range of 150°C to 500°C for a time of 10 to 1000 seconds; After that, a step of acid pickling the cold-rolled steel substrate at a temperature range of 30°C to 100°C for 5 to 100 seconds.
  6. A coated steel substrate manufactured according to a method according to any one of claims 1 to 5, A coated steel substrate having a Ni-MoS₂ layer having a thickness of at least 0.1 micron and containing at least 0.3 wt% of MoS₂ particles.
  7. In Article 6, A coated steel substrate having the above Ni-MoS 2 layer having a thickness of at least 0.2 microns.
  8. In Article 6, A coated steel substrate having the above Ni-MoS2 layer containing at least 0.4 wt% of MoS2 particles.
  9. In Article 6, A coated steel substrate having a hydrogen embrittlement ratio of less than 30%.
  10. In Article 6, The above-mentioned coated steel substrate comprises the following elements, expressed in weight percent: 0.05 % ≤ C ≤ 0.5 %; 0.2 % ≤ Mn ≤ 5 %; 0.1% ≤ Si ≤ 2.5 %; 0.01% ≤ Al ≤ 2 %; 0% ≤ S ≤ 0.09%; 0.002% ≤ P ≤ 0.09%; 0% ≤ N ≤ 0.09%; It is a cold-rolled steel sheet containing, and the following optional elements: 0% ≤ Cr ≤ 1 %; 0% ≤ Ni ≤ 1%; 0% ≤ Cu ≤ 1%; 0% ≤ Mo ≤ 0.5%; 0% ≤ Nb ≤ 0.1%; 0% ≤ Ti ≤ 0.1%; 0% ≤ V ≤ 0.1%; 0% ≤ B ≤ 0.003%; 0% ≤Mg≤ 0.010%; 0% ≤ Zr ≤ 0.010%; 0.001% ≤ Ca≤ 0.005%; It may contain one or more of the following, A coated steel substrate in which the remainder composition consists of iron and inevitable impurities resulting from processing.
  11. In Article 6, The above substrate is a coated steel substrate having an ultimate tensile strength of 900 MPa or more and a yield strength of 700 MPa or more.
  12. A coated steel substrate obtainable according to the method of any one of claims 1 to 5, wherein the coated steel substrate is used to manufacture structural parts of a vehicle.

Description

Hydrogen-resistant coated steel The present invention relates to a steel substrate having hydrogen embrittlement resistance and a method for manufacturing the same, and in particular to a coated steel substrate having good hydrogen embrittlement resistance. High-strength steels such as DP (dual phase) steel, AHSS (advanced high strength steel), UHSS (ultra high strength steel), or MS (martensitic steel) are characterized by having high tensile strength. Due to these characteristics, the use of such steels in the manufacture of automobiles has increased in response to the demands placed on the automotive industry to reduce vehicle weight without sacrificing passenger safety, particularly for structural components such as pillars, and reinforcing components such as bumpers and impact beams are required to have even greater strength. Furthermore, all of the aforementioned steels to be used in automobiles are also required to be resistant to the occurrence of hydrogen-induced delayed fracture, commonly known as hydrogen embrittlement steel. Hydrogen embrittlement generally refers to brittleness caused by hydrogen generated during processing such as electroplating or electrolytic cleaning, or during the application of the final product in corrosive environments or in high moisture content. This hydrogen diffuses into defects in the steel sheet, such as dislocations, holes, and grain boundaries, embrittles the defects, degrades the ductility and stiffness of the steel sheet, and causes fracture under static or dynamic stress. For the purposes of the present invention, the term “steel substrate” includes hot-rolled steel strips, cold-rolled steel sheets, flat steel products, tailor-welded blanks, and blank substrates containing one or more of C, Al, Si and Mn as alloying elements and having a Ni-MoS2 layer thereon. The present invention improves the problem of hydrogen embrittlement by coating steel with a Ni-MoS2 layer having at least 0.3 weight% of MoS2 particles with a thickness of 0.1 micron or more. Since the Ni-MoS2 layer of the present invention can withstand a welding process, the Ni-MoS2 layer of the present invention can be welded for automobile manufacturing. For the purpose of understanding the present invention, the above method is described in detail herein. According to the present invention, the method can be produced by a method comprising the successive steps mentioned herein: For the demonstration of the present invention, a martensitic steel is taken as a preferred embodiment of steel to be manufactured into a cold-rolled steel sheet, thereby demonstrating the beneficial effects of the present invention. The use of martensitic steel should not be considered a limitation of the present invention, and the method of the present invention can be implemented in any steel having one or more of C, Mn, Al, and Si as alloying elements. A coated steel substrate according to the present invention can be manufactured by any of the following methods. A preferred method consists of providing a casting of a semi-finished steel having the chemical composition according to the present invention. The casting can be performed in the form of an ingot or continuously in the form of thin slabs or thin strips, with a thickness of about 220 mm in the case of slabs and up to several tens of millimeters in the case of thin strips. For example, a slab having the chemical composition of steel is manufactured by continuous casting, and the slab is optionally subjected to direct soft reduction during the continuous casting process to avoid center segregation and to ensure a ratio of local carbon to nominal carbon maintained at less than 1.10. The slab provided by the continuous casting process can be used directly at high temperatures after continuous casting, or it can be cooled to room temperature initially and then reheated for hot rolling. The temperature of the slab undergoing hot rolling is at least 1000°C and at least 1280°C. It is desirable for the slab temperature to be higher than 1150°C, because below this temperature, an excessive load is applied to the rolling mill, and the temperature of the steel may drop to the ferrite transformation temperature during finishing rolling, thereby causing the steel to be rolled with transformed ferrite contained in its structure. Therefore, it is desirable for the slab temperature to be sufficiently high so that hot rolling can be completed within the temperature range of Ac3 to Ac3 + 100°C and the final rolling temperature is maintained above Ac3. Reheating at temperatures above 1280°C should be avoided as it is industrially costly. A final rolling temperature range of Ac3 to Ac3 + 100°C is preferred to have a structure favorable for recrystallization and rolling. The final rolling pass needs to be performed at a temperature higher than Ac3, because below this temperature, the steel sheet exhibits a significant decrease in rolling ability. Then, the steel sheet obtained in th