Plated steel sheet and method for manufacturing the same
Patent Information
- Authority / Receiving Office
- JP · JP
- Patent Type
- Patents
- Current Assignee / Owner
- JFE STEEL CORP
- Filing Date
- 2025-06-19
- Publication Date
- 2026-06-23
AI Technical Summary
【0021】 本発明によると、めっき性に優れ、引張強さ980MPa以上、TS×Elバランスが10000MPa%以上であり、材質安定性に優れためっき鋼板及びその製造方法を提供することができる。
Smart Images
Figure 0007878600000001 
Figure 0007878600000002 
Figure 0007878600000003
Abstract
Claims
1. It comprises a base steel plate and a plating layer formed on the surface of the base steel plate, The aforementioned base steel plate is, by mass %, C: 0.020% or more and 0.500% or less, Si: Over 0.01% and under 2.50% Mn: 1.00% or more and 5.00% or less, P: 0.100% or less, S: 0.0200% or less, Al: 0.100% or less, N: 0.0100% or less, O: 0.0100% or less, One or more elements selected from group A consisting of Nb, Ti, and V: total amount of 0.001% or more and 0.075% or less, One or more elements selected from group B, consisting of Cu, Ni, Sn, and Sb: total amount of 0.005% to 0.200% It contains and the total content of elements in group A is X Ａ Let X be the total content of elements in group B. Ｂ X Ａ ≤ 5X Ｂ The composition satisfies the following conditions, with the remainder consisting of Fe and unavoidable impurities. At the position where the thickness of the base steel plate is 1 / 4, The area ratio of ferrite is 5.0% or more and 60.0% or less. The area percentage of unrecrystallized ferrite is 10.0% or less. The area percentage of bainite is 40.0% or less. The total area ratio of tempered martensite and fresh martensite is 30.0% or more and 70.0% or less. The average particle size of tempered martensite and fresh martensite is 5.0 μm or less. It has a steel structure, The proportion of the elements of group A present in the base steel sheet as solid solution elements and precipitates with a major axis of 20 nm or less is equal to the total content of the elements of group A in the base steel sheet X Ａ It is more than 15% of that, A plated steel sheet characterized in that the rate of change of the total area ratio of tempered martensite and fresh martensite within the base steel sheet is 15.0% or less.
2. The aforementioned component composition is further expressed in mass%, Ta: 0.10% or less, W: 0.10% or less, B: 0.0100% or less, Cr: 1.00% or less, Mo: 1.00% or less Co: 1.00% or less, Ca: 0.0100% or less, Mg: 0.0100% or less, Zr: 0.100% or less, Te: 0.100% or less, Hf: 0.10% or less, Bi: 0.200% or less, REM: 0.0100% or less The plated steel sheet according to claim 1, comprising at least one element selected from the group consisting of the following.
3. The plated steel sheet according to claim 1 or 2, wherein the plated layer is an alloyed hot-dip galvanized layer.
4. A slab heating step comprising heating a slab having the component composition described in claim 1 or 2 at a heating temperature of 1250°C or higher for 1.0 hour or more, Next, under conditions where the finishing rolling temperature is 850°C or higher, the slab is hot-rolled to form a hot-rolled steel sheet in a hot-rolling process. Next, The rapid cooling start temperature T is between 500°C and 700°C. The cooling rate V from the finish rolling temperature to the rapid cooling start temperature T of the hot-rolled steel sheet surface temperature １ The temperature is between 10°C / s and 60°C / s. The cooling rate V from the start temperature T of rapid cooling to (T-30)°C of the hot-rolled steel sheet until the surface temperature reaches (T-30)°C ２ The temperature is between 40°C / s and 500°C / s. V １ <V ２ satisfies Under these conditions, a cooling step is performed to cool the hot-rolled steel sheet, Next, a winding process is performed in which the hot-rolled steel sheet is wound at a winding temperature of 400°C or more and 600°C or less. Next, under conditions where the reduction ratio is 20.0% or more and 80.0% or less, the hot-rolled steel sheet is cold-rolled to produce a cold-rolled steel sheet in a cold-rolling process. Next, the cold-rolled steel sheet is heated to a soaking temperature of 720°C to 870°C, held at the soaking temperature for 5 s to 600 s, and then cooled at an average cooling rate of 3.0°C / s or more until the surface temperature of the cold-rolled steel sheet reaches 500°C in an annealing process. Next, a plating process is performed on the cold-rolled steel sheet, A method for manufacturing a plated steel sheet, characterized by having the characteristics described in claim 1 or 2.
5. The hot rolling process is as follows: The total pressure reduction rate of the final stand and the stand immediately before the final stand is 90.0% or less. The plate temperature drop rate at the final stand is 10,000°C / s or more. The steel plate temperature was below 1000°C when passing the stand just before the final stand. The method for manufacturing a plated steel sheet according to claim 4.
6. The method for manufacturing a plated steel sheet according to claim 4, wherein in the annealing step, the dew point in the temperature range where the surface temperature of the cold-rolled steel sheet is 600°C or higher is -40°C or lower.
7. The method for manufacturing a plated steel sheet according to claim 5, wherein in the annealing step, the dew point in the temperature range where the surface temperature of the cold-rolled steel sheet is 600°C or higher is -40°C or lower.
8. The method for manufacturing a plated steel sheet according to claim 4, wherein the plating treatment is an alloying hot-dip galvanizing treatment.
9. The method for manufacturing a plated steel sheet according to claim 5, wherein the plating treatment is an alloying hot-dip galvanizing treatment.
10. The method for manufacturing a plated steel sheet according to claim 6, wherein the plating treatment is an alloying hot-dip galvanizing treatment.
11. The method for manufacturing a plated steel sheet according to claim 7, wherein the plating treatment is an alloying hot-dip galvanizing treatment.