阅读说明：本技术 经冷轧和涂覆的钢板及其制造方法 (Cold rolled and coated steel sheet and method for manufacturing the same ) 是由 全现助 纳拉扬·波托雷 范东伟 陈翔(弗兰克) 奥列格·雅库鲍夫斯基 于 2020-05-12 设计创作，主要内容包括：一种经冷轧和涂覆的钢板,以重量百分比表示,其组成包含以下元素：0.140％≤碳≤0.2％、1.5％≤锰≤2.15％、0.5％≤硅≤0.8％、0.4％≤铝≤0.8％、0％≤磷≤0.09％、0％≤硫≤0.09％、0％≤氮≤0.09％、0.01％≤铌≤0.1％、0.01％≤钛≤0.1％,并且可以包含以下任选元素中的一者或更多者：0％≤铬≤0.1％、0％≤镍≤3％、0％≤钙≤0.005％、0％≤铜≤2％、0％≤钼≤0.5％、0％≤钒≤0.1％、0％≤硼≤0.003％、0％≤铈≤0.1％、0％≤镁≦0.010％、0％≤锆≦0.010％,剩余部分组成由铁和因加工产生的不可避免的杂质构成,所述钢板的显微组织以面积分数计包含：40％至60％临界区铁素体、25％至45％转变铁素体、8％至20％和5％至20％新鲜马氏体、0％至10％贝氏体,其中临界区铁素体和转变铁素体的累积量为75％至85％。(A cold rolled and coated steel sheet, the composition of which comprises, in weight percent: 0.140% to less than or equal to 0.2% carbon, 1.5% to less than or equal to 2.15% manganese, 0.5% to less than or equal to 0.8% silicon, 0.4% to less than or equal to 0.8% aluminum, 0% to less than or equal to 0.09% phosphorus, 0% to less than or equal to 0.09% sulfur, 0% to less than or equal to 0.09% nitrogen, 0.01% to less than or equal to 0.1% niobium, 0.01% to less than or equal to 0.1% titanium, and may include one or more of the following optional elements: chromium is more than or equal to 0 percent and less than or equal to 0.1 percent, nickel is more than or equal to 0 percent and less than or equal to 3 percent, calcium is more than or equal to 0 percent and less than or equal to 0.005 percent, copper is more than or equal to 0 percent and less than or equal to 2 percent, molybdenum is more than or equal to 0 percent and less than or equal to 0.5 percent, vanadium is more than or equal to 0 percent and less than or equal to 0.1 percent, boron is more than or equal to 0 percent and less than or equal to 0.003 percent, cerium is more than or equal to 0 percent and less than or equal to 0.1 percent, magnesium is more than or equal to 0 percent and less than or equal to 0.010 percent, zirconium is more than or equal to 0.010 percent and the rest part consists of iron and inevitable impurities generated by processing, and the microstructure of the steel plate comprises by area fraction: 40% to 60% intercritical ferrite, 25% to 45% transformed ferrite, 8% to 20% and 5% to 20% fresh martensite, 0% to 10% bainite, wherein the cumulative amount of intercritical ferrite and transformed ferrite is 75% to 85%.)

1. A cold rolled and coated steel sheet, the composition of which comprises, in weight percent:

carbon is between 0.140 and 0.2 percent

Manganese is more than or equal to 1.5 percent and less than or equal to 2.15 percent

Silicon is more than or equal to 0.5 percent and less than or equal to 0.8 percent

Aluminum is between 0.4 and 0.8 percent

Phosphorus is between 0 and 0.09 percent

Sulfur is between 0 and 0.09 percent

Nitrogen is between 0 and 0.09 percent

Niobium is more than or equal to 0.01 percent and less than or equal to 0.1 percent

Titanium is more than or equal to 0.01 percent and less than or equal to 0.1 percent

And optionally can contain one or more of the following optional elements:

chromium is between 0 and 0.1 percent

Nickel is more than or equal to 0 percent and less than or equal to 3 percent

Calcium is between 0 and 0.005 percent

Copper is more than or equal to 0 percent and less than or equal to 2 percent

Molybdenum is more than or equal to 0 percent and less than or equal to 0.5 percent

Vanadium is between 0 and 0.1 percent

Boron is between 0 and 0.003 percent

Cerium is more than or equal to 0 percent and less than or equal to 0.1 percent

Magnesium is between 0 and 0.010 percent

Zirconium is between 0 and 0.010 percent

The remainder being composed of iron and unavoidable impurities resulting from processing, the microstructure of the steel sheet comprising, in area fraction: 40% to 60% intercritical ferrite, 25% to 45% transformed ferrite, 8% to 20% residual austenite and 5% to 20% fresh martensite, 0% to 10% bainite, wherein the cumulative amount of intercritical ferrite and transformed ferrite is 75% to 85%.

2. The cold rolled and coated steel sheet according to claim 1, wherein the composition comprises 0.5 to 0.7% silicon.

3. The cold rolled and coated steel sheet according to claim 1 or 2, wherein the composition comprises 0.14 to 0.19% carbon.

4. The cold rolled and coated steel sheet according to any one of claims 1 to 3, wherein the composition comprises 0.4 to 0.7% of aluminium.

5. The cold rolled and coated steel sheet according to any one of claims 1 to 4, wherein the composition comprises 1.7 to 2.15% manganese.

6. The cold rolled and coated steel sheet according to claim 4, wherein the composition comprises 0.4 to 0.6% of aluminium.

7. The cold rolled and coated steel sheet according to claim 5, wherein the composition comprises 1.8 to 2.15% manganese.

8. The cold rolled and coated steel sheet according to claim 3, wherein the composition comprises 0.14 to 0.18% carbon.

9. The cold rolled and coated steel sheet according to any one of claims 1 to 8, wherein the cumulative amount of silicon and aluminum is 0.9 to 1.2%.

10. The cold rolled and coated steel sheet according to any one of claims 1 to 9, wherein the cumulative amount of silicon and aluminum is 1% to 1.2%.

11. The cold rolled and coated steel sheet according to any one of claims 1 to 10, wherein the carbon content of the residual austenite is 0.8 to 1.1%.

12. The cold rolled and coated steel sheet according to claims 1 to 12, wherein the intercritical ferrite is 45 to 55%.

13. The cold rolled and coated steel sheet according to any one of claims 1 to 12, wherein the transformed ferrite is 25 to 40%.

14. The cold rolled and coated steel sheet according to any one of claims 1 to 13, wherein the fresh martensite is 5% to 15%.

15. The cold rolled and coated steel sheet according to any one of claims 1 to 14, wherein the steel sheet has an ultimate tensile strength of 780MPa or more and a total elongation of 18% or more.

16. The cold rolled and coated steel sheet according to claim 15, wherein the steel sheet has a yield strength of 400MPa or more and a hole expansion ratio of 20% or more.

17. A method of producing a cold rolled and coated steel sheet comprising the sequential steps of:

-providing a steel composition according to any one of claims 1 to 10;

-reheating the semi-finished product to a temperature of 1000 ℃ to 1280 ℃;

-rolling the semi-finished product at a temperature ranging from Ac3+100 ℃ to Ac3+200 ℃ to obtain a hot-rolled steel, wherein the hot finishing rolling temperature should be higher than Ac 3;

-cooling the hot rolled steel to a coiling temperature of 475 ℃ to 650 ℃ at a cooling rate of at least 30 ℃/s; and coiling the hot rolled steel;

-cooling the hot rolled steel to room temperature;

-optionally descaling the hot rolled steel sheet;

-optionally annealing the hot rolled steel sheet at 400 ℃ to 750 ℃;

-optionally descaling the hot rolled steel sheet;

-cold rolling the hot rolled steel sheet at a reduction of 35% to 90% to obtain a cold rolled steel sheet;

-heating the cold rolled steel sheet from room temperature to a soaking temperature of Ac1 to Ac3,

then annealing at the soaking temperature for 5 to 500 seconds,

-then cooling the cold rolled steel sheet from the soaking temperature to an overaging temperature of 425 ℃ to 500 ℃ at an average cooling rate of at least 5 ℃/s,

-the cold rolled steel sheet is then overaged at an overaging temperature for 5 to 500 seconds and to a temperature range of 420 to 680 ℃ to facilitate coating,

-then coating the cold rolled sheet,

-thereafter cooling the cold rolled steel sheet to room temperature at a cooling rate of at least 55 ℃/s to obtain a cold rolled coated steel sheet.

18. The method of claim 17, wherein the coiling temperature is 475 ℃ to 625 ℃.

19. The method of claim 17 or 18, wherein the finishing temperature is greater than 950 ℃.

20. The method according to any one of claims 17 to 19, wherein the average cooling rate between the soaking temperature and the overaging temperature is greater than 10 ℃/sec.

21. The method of any one of claims 17 to 20, wherein the soaking temperature is Ac1+30 ℃ to Ac3-30 ℃ and is selected to ensure that at least 40% austenite is present at the end of soaking.

22. The method of claim 21, wherein the annealing soaking temperature is Ac1+30 ℃ to Ac3-30 ℃, and the annealing soaking temperature is selected to ensure that at least 50% austenite is present at the end of annealing.

23. The method of any one of claims 17 to 22, wherein the temperature for overaging is 440 ℃ to 480 ℃.

24. The method of any one of claims 17 to 23, wherein the cooling rate after coating is at least 9 ℃/sec.

25. Use of a steel sheet according to any one of claims 1 to 16 or produced according to the method of claims 17 to 24 for the manufacture of a structural or safety component of a vehicle.

26. A vehicle comprising a component obtained according to claim 25.

Examples

The following tests, embodiments, graphical examples and tables presented herein are non-limiting in nature and must be considered for illustrative purposes only and will show advantageous features of the invention.

In table 1, steel sheets made of steels with different compositions are summarized, wherein the steel sheets are produced according to the process parameters as noted in table 2, respectively. Thereafter, table 3 summarizes the microstructures of the steel sheets obtained during the tests, and table 4 summarizes the evaluation results of the obtained characteristics.

TABLE 1

Steel sample	C	Mn	Si	Al	Cr	Nb	S	P	Ca	N	Mo	Cu	Ni	v	B	Ti
																	A	0.144	2.12	0.65	0.52	0.03	0.012	0.002	0.014	0.0003	0.0060	0.005	0.03	0.010	0.002	0.0002	0.03
B	0.141	2.05	0.65	0.52	0.03	0.012	0.002	0.014	0.0003	0.0060	0.005	0.03	0.010	0.002	0.0002	0.03
																	C	0.138	2.02	0.65	0.52	0.03	0.012	0.002	0.014	0.0003	0.0060	0.005	0.03	0.010	0.002	0.0002	0.03
D	0.150	2.20	0.65	0.52	0.03	0.012	0.002	0.014	0.0003	0.0060	0.005	0.03	0.010	0.002	0.0002	0.03

Underlined values: not according to the invention.

TABLE 2

Table 2 summarizes the annealing process parameters performed on the steels of table 1. Steel compositions a to D were used for manufacturing the plate according to the invention. Table 2 also shows a list of Ac1 and Ac 3. These Ac1 and Ac3 definitions for the inventive and reference steels were determined empirically by dilatometry studies:

the following process parameters are the same for all steels of table 1. All the steels of table 1 were heated to a temperature of 1120 ℃ and then hot rolled, and the finish rolling temperature for all the steels was 900 ℃. Thereafter, all the steels of Table 1 were coiled at 620 ℃.

Table 2 is as follows:

TABLE 2

TABLE 3

Table 3 illustrates the results of tests performed according to the standard on different microscopes, such as scanning electron microscopes, used to determine the microstructure of both the inventive steel and the reference steel.

The results are noted herein:

i-according to the invention: r-reference: underlined values: not according to the invention.

TABLE 4

Table 4 illustrates the mechanical properties of both the inventive steel and the reference steel. To determine tensile strength, yield strength and total elongation, tensile tests were performed according to ASTM standards.

The results of various mechanical tests performed according to the standard are summarized.

TABLE 4

I-according to the invention: r-reference; underlined values: not according to the invention.