JPS63128168A - Production of alloyed and zinc plated steel sheet having excellent deep drawability - Google Patents

Abstract

PURPOSE:To improve powdering resistance by maintaining a base plate temp. as low as possible and limiting an alloying temp. and time to a specific range at the time of subjecting a low-carbon Ti killed steel having a specific compsn. to zinc plating by vapor deposition. CONSTITUTION:The low-carbon Ti killed steel contg., by weight %, <=0.010 C, <0.15 Si, 0.15-0.85 Mn, 0.05-0.30 Ti and contg., as impurities, <= 0.020 P, <=0.20 S, and <=0.050 solAl is subjected to Zn-plating by vapor deposition. The temp. of the steel sheet just before the plating is set at 180-280 deg.C at this time. The adhesiveness of the plating layer is defective if the steel sheet temp. is to low and, therefore, said temp. is kept at >=180 deg.C. Said temp. is kept at <=280 deg.C in order to minimize the diffusion from the steel into the plating layer. The steel sheet is then heated for 1-50hr at 220-320 deg.C in a nonoxidative atmosphere in a batch annealing furnace. The alloyed and zinc-plated steel sheet having the alloyed plating layer contg. 8.0-12.0% iron concn. and the excellent deep drawability and powdering resistance is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for producing an alloyed vapor-deposited galvanized steel sheet having excellent deep drawability and powdering resistance.

[Prior art] Generally, A-shaped guild steel and Ti steel are used as steel sheets for deep drawing.
Killed steel is known. By the way, when an alloyed vapor deposited galvanized steel sheet based on Ti killed steel is alloyed under the same conditions as AfL killed steel, there is a problem in that the plated layer tends to flake during processing. The reason for this is thought to be that iron in the Ti-killed steel diffuses into the plating layer more easily than in the AM guild steel, and the average iron concentration in the plating layer becomes excessive. An example of the iron concentration gradient in the galvanized layer is shown in Figure 1 when vapor deposited galvanizing is applied to Ti killed steel and An killed steel, and then alloyed to the surface of the plated layer. In this case, the iron concentration is about 5-6.5% from the plating surface to the deep part of the plating layer, and the iron concentration gradient increases rapidly from the deep part of the plating layer to the interface with the steel plate. On the other hand, in Ti-killed steel, the iron concentration near the first surface layer is A9. It's the same 5~6z as Guild Steel.

The iron concentration from the middle to the deep part of the plating layer is higher than that of AI guild steel. It can thus be seen that the Ti-guild steel has an alloyed plating layer with a higher iron concentration than the A-cross-killed steel. For this reason, the evaporated galvanized Ti
If killed steel is alloyed under the same conditions as killed steel, alloying will proceed excessively and the average iron concentration in the plating layer will be A.
The iron concentration is 1.5 to 2.0% higher than that of n-killed steel, resulting in an excessive average iron concentration, resulting in a problem that the powdering resistance decreases and the plating layer is easily damaged by peeling during processing.

[Knowledge for solving the problem] The present inventors found that when alloying vapor deposited galvanizing is applied to Ti-killed steel as described in 1. above, alloying progresses excessively when the alloying treatment is performed under the same conditions as A-stand killed steel. However, we discovered that there was a problem of reduced powdering resistance, and as a way to solve this problem, we tried to maintain the substrate temperature as low as possible immediately before vapor deposition plating for low carbon Ti killed steel, and to maintain the temperature of the substrate as low as possible just before the vapor deposition plating, and to reduce the alloying temperature. By limiting the time to a predetermined range.

We have found that by controlling the average Fe concentration in the alloy layer to 8.0 to 12.0% by weight, it is possible to obtain alloyed galvanized Ti killed steel with good powdering resistance.

According to the present invention, low carbon titanium killed steel (C≦o, ot
o WeightWig, S i <0.15i4%, M
n: 0.15-0.85 ffi$, Ti
: 0.05 to 0.30 weight i% and unavoidable impurities P≦0.020 weight $, S≦0.020 weight J1
%, 5oIAl≦0.050weight iB), the steel plate temperature immediately before plating is set at 180 to 280℃.
and then heated in a non-oxidizing atmosphere in a batch annealing furnace at 220-320°C for 1-50 hours.
A method is provided, characterized in that it produces an alloyed galvanized steel sheet having an alloyed plated layer with an iron concentration of 8.0 to 12.0% by weight.

In the present invention, a low carbon Ti killed steel having the following composition (% by weight) is used.

Ti-killed steel used as a steel plate for deep drawing is an extremely low carbon steel, and usually has C≦o and oio weight %. Moreover, Si is preferably Si<0.15% by weight,
When Si is more than 0.15, plating adhesion decreases. In order to improve this adhesion, it is necessary to raise the substrate temperature, but in the case of Ti-killed steel, Fe diffuses quickly and when the substrate temperature is raised, a weak alloy layer is generated at the interface between the plating layer and the steel plate. occurs. Therefore, the Si content of the Ti-killed steel is preferably 0.15 wt$ or less, and Mn is a component that mainly increases strength, and is preferably 0.15 to 0.85 wt%.

If the Mn content is less than 0.15 wt%, sufficient strength cannot be maintained; on the other hand, if it exceeds 0.85 wt%, no problems with plating adhesion or other quality will occur; Even if it is contained, no further increase in strength can be expected.

Ti is 0.05 to 0.30% by weight. This content is comparable to that of ordinary Ti killed steel for deep drawing.

Generally, in steel sheets for deep drawing, the content of Ti is required to be about four times the amount of normal C in order to fix C in the steel.Furthermore, taking into account the amount of nitrogen as an impurity in the steel, the above content is set. It will be done.

In addition, P≦0.020% by weight as unavoidable impurities
, S≦0.020% by weight, and 5olAI≦0.050% by weight. These are the same impurity levels as ordinary steel.

Regarding the above Ti-killed steel, the temperature of the steel plate immediately before plating was set to 1
Vapor-deposited galvanizing is performed at a temperature of 80 to 280°C. Generally, in vapor-deposited galvanizing, if the substrate temperature during plating is too low, the adhesion of the galvanized layer will be poor, so the substrate temperature is usually kept at 180°C or higher. do. On the other hand, in vapor deposition plating, zinc vapor condenses on the surface of the steel sheet to form a plating layer, so the temperature of the base increases due to the heat of condensation of the zinc.

In addition, heat transfer from the winding rolls in the deposition chamber is also a factor that increases the substrate temperature. Therefore, if the substrate temperature immediately before plating is higher than necessary, the substrate temperature will rise further due to the above-mentioned condensation heat and heat transfer, and this will cause a fragile alloy layer to develop near the interface between the plating layer and the steel plate. This causes a problem of impairing the adhesion of the layer. - In the example, the steel strip temperature after 2-ki is 3
When the temperature reaches around 60°C, an alloy layer of 0.1 to 1.0 liters develops after about 35 seconds, and when the copper strip temperature reaches 410°C or higher, an alloy layer of 0.1 to 1.0 l develops.
An alloy layer of the above thickness develops in seconds or less. Therefore, in order to prevent the development of the alloy layer, the substrate temperature of the steel strip immediately before plating should be adjusted to 18.
The temperature is adjusted to θ to 280°C, and 180 to 300°C in the case of a thin basis weight. In the present invention, since Ti-killed steel is easier to alloy than Ai-killed steel, the temperature of the substrate is lower than the normal substrate temperature, adjusted to 180-260℃ for thick coatings and 180-280℃ for thin coatings. Minimize diffusion of iron from the plated layer to the plated layer.

After the vapor deposition plating described above, alloying treatment is performed.

Generally, batch annealing is performed in a non-oxidizing atmosphere to prevent oxidation of the steel plate.

The coil shape is tied with lrJ heat treatment! ·coil,
Any shape of open coil may be used, and the processing temperature and time may be changed depending on the amount of plating deposited and the target F e rij rate. Figure 2 shows the heat cycle for alloying treatment, and Figure 3 shows the range of alloying treatment. In the heat cycle in Figure 2, after alloying treatment, the inside of the furnace was cooled to below 100°C in a non-oxidizing atmosphere. In this case, the non-oxidizing atmosphere in the furnace is
It consists of a gas having a composition based on N2 and containing 3 to 75% N2. Moreover, the CO and Co2e degrees in the gas are both 0 to a lot.

FIG. 3 shows the range of alloying treatment conditions including Fe content of 8' to 12%. The dotted line area surrounded by cd indicates the case of Ti-killed steel base.The reason why the alloying treatment time was set to 1hr or more was because the furnace temperature did not decrease with soaking time longer than 1hr in the experiment, and , 50 hours or less was set as
This is because productivity cannot be improved beyond that.

[Example and Comparative Example] T
i Killed steel is galvanized. In addition, in 1 figure, 1 is a steel plate, 2 is a pretreatment furnace, 3a, 3b is a vacuum seal roll chamber,
4a and 4b are vacuum deposition chambers, and 5 is a cooling chamber. The operating conditions are shown in the table below.

In addition, when performing single-sided plating, vacuum evaporation Zn plating may be performed only in either the first vacuum evaporation plating chamber 4a or the second vacuum evaporation plating chamber 4b.

These vacuum-deposited Zn-plated steel sheets were heated and alloyed in a batch annealing furnace to produce alloyed Zn-plated steel sheets.
The alloying treatment conditions are shown in the table below.

Table 1 shows the results of examining the combinations of adhesion amount, substrate temperature, heating temperature, and holding time, as well as the surface appearance and workability (#powdering property) of the manufactured steel sheets.The powdering resistance was 6t,
After 180° bending and unbending, the powdering on the inside was evaluated. For comparison, the substrate temperature during vapor deposition, the heating temperature during alloying, and the holding time were set to the conditions shown in Table 2, and other conditions were set as shown in Table 2. Alloying treatment for zinc plating was carried out in the same manner as in the examples. The results are shown in Table 2.

Table 1 Table 1 Continued Table 2 As is clear from the above results, the alloyed galvanized steel sheets of this example all have good surface appearance and workability, but the comparative example has an alloy layer. Zinc remains inside or the workability is poor.

[Effects of the Invention] According to the manufacturing method of the present invention, when applying alloyed zinc plating to titanium killed steel, it is possible to form an alloyed layer with an optimal iron content ratio, and improve the surface appearance, deep drawability, and powder resistance. An alloyed galvanized steel sheet with excellent ring properties can be obtained.

[Brief explanation of the drawing]

Figure 1 is a graph showing the iron concentration in the alloy layer for titanium killed steel and aluminum guild steel, Figure 2 is a graph showing the heat cycle of alloying treatment, and Figure 3 is a graph showing the relationship between alloying time and treatment temperature. The graph and FIG. 4 are schematic diagrams showing an example of a continuous vacuum evaporation plating apparatus. In the drawings: 1 - Steel plate, 2 - Pretreatment furnace, 3a, 3b - Vacuum sealing chamber, 4a, 4b - Vacuum deposition chamber. 5-Cooling chamber Figure 1 1 "Meng (Knob A) f) Feather - Stone G
Fig. 2 (M Chr) Fig. 3 1 2 5 lO2050 treatment
L guard M (hr)

Claims (1)

[Claims] (1) Low carbon titanium killed steel (C≦0.010% by weight,
Si<0.15% by weight, Mn: 0.15-0.85% by weight, Ti: 0.05-0.30% by weight, and unavoidable impurities such as P≦0.020% by weight, S≦0.020% by weight. %, so |
A method of producing an alloyed galvanized steel sheet having an alloyed plated layer with an iron concentration of 8.0 to 12.0% by weight by heating at 0 to 320°C for 1 to 50 hours.