JPS5931827A - Production of quench hardenable steel plate for ultra deep drawing - Google Patents

Abstract

PURPOSE:To produce a titled steel plate virtually irrespectively of cooling rates by adding Ti and Nb in combination within a specific range to a dead soft steel contg. Si, Mn, P, Al, N and annealing the steel continuously at the recrystallization temp. or above after hot rolling and cold rolling. CONSTITUTION:The steel which consists of <=0.007% C, <=0.8% Si, <=1.0% Mn, <=0.15% P, 0.01-0.1% Al, <=0.01% N and other impurities, and with which the combined addition of Ti and Nb in the following range is an essential requirement is used: Ti is added in (48/14)(N%-0.002%)<Ti%<=(48/14)N% range and Nb is added in the range satisfying (93/12)(C%-0.005)<=Nb%<=(93/12)(C%-0.001) and <=0.020% Nb. The steel is subjected to hot rolling and cold rolling, then to continuous annealing at the ecrystallization temp. or above and the AC3 point or below.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for producing a bake-hardenable steel plate for ultra-deep drawing.

In recent years, demand for high-strength steel sheets has been increasing in the automobile industry in pursuit of improved fuel efficiency and safety through lighter vehicle bodies. On the other hand, as the salability of automobiles is increasingly influenced by the styling of the car body, more emphasis has been placed on the press formability of steel sheets than ever before. Against this background, there is an increasing demand for a steel sheet that exhibits good formability during press forming and has the property of increasing yield strength and tensile strength after baking the paint, that is, has bake hardenability. The present invention relates to a method for manufacturing a bake-hardenable steel sheet for ultra-deep drawing that satisfies such requirements.

Regarding the manufacturing method of ultra-deep drawing steel sheets that do not have bake hardenability, Ti killed steel sheets (% Kosho 44-180
66 Publication) and Nb killed steel plate (Special Publication No. 1984-12)
45) are known. However, in these steel sheets, the CXN in the steel sheets is completely replaced by Ti.
Or, in order to fix it as a precipitate such as Nb,
There are some products that do not cause strain aging phenomenon during the first coating and baking process after pressing, and therefore have no 111 hardening properties.

Next, as a method for producing ultra-deep drawing steel sheet σ with 1 hardenability, Nb-added steel is heated at °C to produce carbon, nitrogen, and a
Add Nb according to the I content meter, Nb (a t%)/
By restricting (solid solute C (at%) 1N (at%)) within a certain range, the amount of solid solute C1 and solid solute N in the steel sheet is controlled, and the cooling rate 18i after annealing is further controlled. There is a method (Japanese Patent Publication Nos. 55-41526 and 55-141.555) characterized by this.

1. Upon careful investigation and consideration, we found that this manufacturing method has the following drawbacks. hot rolling winding temperature,
4) There are limitations on the annealing temperature and cooling rate after annealing.

Nb-added steel is hot-rolled at high temperatures (rolling 1 item tw; 70
0°C). At normal coiling temperatures, the redundant recrystallization temperature is very low/c-), and in the continuous cutting and blunt furnace temperature range (usually about 850'C or less), unrecrystallized parts may remain. Also, the quality of the particles varies greatly depending on the degree of Nb sensitivity.

It has been variously reported that when high-temperature coiling is performed, a steel plate with a high r value is scorched at an annealing temperature of approximately SOO to 850°C, except for the longitudinal ends of the hot-rolled coil. It is. However, when sifting and high-temperature winding is performed, not only does the scale become thick and the pickling efficiency is extremely reduced, but also the cooling rate at the end of the coil is faster than normal winding temperature. The materials are of the same quality, and sufficient profit cannot be obtained (・
Therefore, the decrease in yield is particularly severe in Nb quilted steel.

The second problem is the annealing temperature and the cooling rate after annealing. As in the above-mentioned known technology, when annealing at a high temperature (approximately 900°C or above), Nb(C,N) precipitates during hot rolling.
As AIN redissolves, solute N1 and solid solute C increase and 7
The statute of limitations increases. In addition, as stated in the patent, the cooling rate after annealing is 50°C/sec or less up to 400°C (・ means 50°C/sec or more up to 400°C and 400°C
Unless it is slowly cooled from 10° C. to 200° C. at a rate of 10° C./sec or less, it will not have slow aging properties due to the influence of solid solute N and solid solute C. In the case of Nb-added steel, a particular problem is in-in which is remelted at high temperatures, and it is this N aging that causes a 2:↑ problem in room temperature aging.

The third drawback is the galvanizing properties. Generally, when hot-dip galvanizing is performed, the Si content in the steel is approximately (1.3%).
It is said that if it exceeds this, the plating adhesion will deteriorate. This is said to be because a thin (oxidized) film is formed due to SiK concentrating on the surface of the steel plate, and the reaction between the base iron and molten 11j lead does not proceed well.

For this reason, hot-dip galvanizing steel has been produced by limiting the Si-containing M content in the steel to about 0.3% or less in order to suppress the surface concentration of Si.

However, when manufacturing steel sheets with a tensile strength of 40 Kg/mA or more, the P content is limited due to the problem of secondary stress cracking, and it is necessary to add alloying elements with this ability to increase the strength. Despite the fact that Si and Mn cannot be added from the viewpoint of adhesion to the plating, it is a zinc-plated ultra-deep drawable sinterable material with good performance that has a tensile strength that substantially exceeds 40K97mA. It is very difficult to harden steel sheets.The surface concentration phenomenon of S+ described below is a general phenomenon during slow cooling, and has remained an unsolved problem until now.

As a result of a detailed examination of these defects of conventional Nb-added steel, the present inventors came to the conclusion that the essential causes are the following three points.

(1) A1, which is greatly affected by the temperature history during hot rolling and winding.
Precipitation of H. (2) The amount of solid solution C1 and solid solution N changes depending on the annealing temperature and the cooling rate after annealing.

(3) Concentration of alloying elements at grain boundaries or on the surface depends on the cooling rate after annealing.

(1) In Nb-added steel, Nb actually forms carbides, but the tendency to form nitrides is relatively weak, and nitrogen is
It is precipitated and viewed as IN. AIN is difficult to form at normal coiling temperatures, and does not precipitate in hot-rolled sheets unless the coiling temperature is lower than 700°C, and precipitates as fine precipitates during continuous annealing after cold rolling, resulting in formation of crystal grains. It suppresses growth and causes material deterioration such as increasing yield strength and decreasing elongation.

(jY-') Even when high-temperature winding is performed, AIN precipitates at the center of the hot-rolled coil length. However, as with normal winding, there is no precipitation, and there is no significant decrease in yield strength, elongation, or r value.

In addition, due to slight irregularities in the hot-rolling coiling temperature and differences in the degree of AIN precipitation at the center and ends of the coil, material deterioration at the front and rear ends of the hot-rolled coil and inside the coil may occur. Regarding (2), when high-temperature annealing is performed, precipitates such as Nb (C,,N) and AIN that precipitate during hot-rolling and coiling occur. is the solubility product at that temperature, rlf (6
M' L, solid solution d, and solid solution N increase. In particular, the solid solution N resulting from AIN dissolution has longer room temperature aging properties than solid solution CK, which violates the goal of slow aging properties. N precipitates as Nb (C, N) or AIN during the subsequent cooling process, but the precipitation rate of AIH in particular peaks at about 815°C and decreases as the temperature decreases, so single-child cooling in a high temperature range is necessary. According to the patent, it is necessary to slowly cool down to 400°C or rapidly cool down to 400°C, and slowly cool from 400°C to 200°C, or substantially 400°C.
The precipitation rate in the temperature range from °C to 200 °C is extremely low, which means that slow cooling is required in the high temperature range. In any case, in this manufacturing method, it is still essential to control the annealing temperature and the cooling rate after annealing (・0(
3) has already been mentioned.

Based on the ideas described above, the homogeneity of the material inside the coil is good regardless of the hot-rolling coiling temperature, and the sinter hardenability is determined to be 1.] regardless of the annealing temperature and the cooling rate after annealing. I can do it,
Furthermore, the concept of a method for producing ultra-deep drawing steel sheets that does not have the problem of secondary work brittleness and has good plating adhesion during the production of hot-dip galvanized steel sheets is as follows.

In other words, N is precipitated as TiN by Ti instead of AIN before finishing hot rolling, and during the following hot rolling coiling, cold rolling, and recrystallization annealing, it does not cause any reaction such as re-solid solution or precipitation (...-). In other words, the process after hot rolling is independent of the material with respect to N. In addition, C is mainly precipitated as NbC by Nb, but in order to stably obtain bake hardenability regardless of the hot rolling coiling temperature, annealing temperature, and cooling rate after annealing, the content range of C amount is set as follows. The Excess C amount (defined as the value of C (%) 2 - surface Nb (%)) determined by the relationship only with Nb addition 2111 M is 10 to 50.
The basic idea of the present invention is to control the steel plate within the ppm range.

The reason why the present invention, Medium 4, has significantly superior material properties compared to conventional Nb-added steel is due to the composite addition of Ti and Nb. In other words, N in the steel has already precipitated as 'I'iN in the hot rolling furnace due to 1'i.
・Ru. As is well known, N is a nitrogen atom and becomes a stable precipitate at extremely high temperatures, so it does not change during each production process of hot rolling, cold rolling, and recrystallization annealing, and therefore However, the quality of the material is not affected in any way by the effects of Gakaro manufacturing. In steel sheets to which Nb is added alone, the amount of N precipitated as AIN varies significantly depending on the hot rolling and coiling temperature. The yield strength of finely precipitated AIN at ℃ is high due to the influence of NbN (,
The elongation and r value are low and the target material properties cannot be obtained. Furthermore, even in the case of high-temperature winding, the cooling rate at the front and rear ends in the longitudinal direction of the coil during winding is fast, so as described above, the material is equivalent to that for normal winding.

The steel of the present invention has already been precipitated in the hot-rolling furnace as N-TiN in the steel, and since TiN is a stable precipitate even at extremely high temperatures, the amount of precipitation can be adjusted depending on the hot-rolling temperature as described above. It's not something that changes. Furthermore, as is well known, TiN is a large-sized precipitate, so it does not hinder the growth of crystal grains during gate crystal annealing and does not deteriorate the material quality.

As described above, the steel of the present invention can be manufactured by adding 1゛i to produce a good material even when it is normally rolled, regardless of the hot-rolling and winding temperature. Further, even when high-temperature winding is performed, the material inside the coil becomes extremely homogeneous, and there is no need to consider a decrease in manufacturing yield at all.

Next, although the annealing temperature and cooling rate have an influence, the steel of the present invention fixes N as TiN, and as a result, precipitates are stable even in a temperature range that is much higher than the annealing temperature. Therefore, even during high-temperature annealing, there is no re-dissolution, and there is almost no effect on the amount of solute N. Therefore, the bake hardenability is determined only by the amount of solid solute C. For this reason, there is no need to consider the cooling rate, and any cooling rate may be used.Furthermore, even if it is rapidly cooled to room temperature, it will not affect the room temperature aging property in any way.

If high-temperature annealing was performed, the N that had precipitated during hot rolling and winding.
If a part of bCσ is re-dissolved (2), even if the solid solution 0 loss changes slightly, by rapid cooling, the segregation of elements such as C to the grain boundaries is 41i, Since it becomes lower at the edge, the yield point elongation does not appear after aging due to the effect of the grain boundaries being highly pure, as described in papers and the like.

By controlling only the amount of C1N1) in the steel without depending on the annealing temperature and cooling rate as described above, the present invention S with the combined addition of T1 can achieve ultra-deep drawing baking that is virtually non-aging. Hardenable steel sheets can be manufactured.

Furthermore, in the steel of the present invention, as mentioned above, due to the composite addition of Ti,
Since it can be manufactured without depending on the cooling rate after annealing, St
When producing hot-dip galvanized steel sheets with tensile strength exceeding 40 Kf/mA at high temperatures by adding XMn, etc., it is possible to produce steel sheets with extremely good plating adhesion, which are unprecedented in quality.

As mentioned above, the plating adhesion of hot-dip galvanized steel sheets deteriorates mainly due to the influence of alloying elements such as Si that concentrate on the steel sheet surface during annealing and cooling, so the Si content is approximately 0.
For this reason, the tensile strength is particularly limited to 4 or less.
It can be said that virtually no galvanized steel sheet for ultra-deep drawing with good performance of 0 K9/- or higher has been manufactured to date.

This drawback can also be overcome by the composite addition of Ti in the steel of the present invention, which makes the material almost completely independent of the cooling rate, allowing for rapid cooling of up to 6 J, and significantly reducing alloying elements such as Si that concentrate on the surface. As mentioned above, the steel of the present invention has a high Si-containing strength (ultra-deep drawable, sinter-hardening, high-strength steel sheet). It is a completely new steel plate with various material properties and is extremely advantageous.

Next, we will discuss the component range. As mentioned above, the amount of Ti added is determined by the relationship with N. The reason for adding Ti is to add N to AIN.
Alternatively, if NbN is to be precipitated, the precipitation rate is greatly affected by the coiling temperature, and the solid solution NJit in the steel sheet is ultimately affected by the annealing temperature and cooling rate after annealing ((, coil longitudinal direction The material at the end may deteriorate, the quality of the coil inside the coil may vary greatly, and furthermore, depending on the winding temperature, annealing temperature IW, and cooling rate of the material,
This is to prevent large changes due to i.

When adjusted and examined, this effect of more N was found to be due to the presence of M:
201) The lower limit of Ti addition cannot be fixed with Ti because it is not large below pITI (・N N, or 20 pp
m or less. That is, 48/M(N(%)-
0,002% (20 ppm))<Ti (%). In this case, since N is a (Ti, Al)N precipitate that is stable even at relatively high temperatures, substantially all the N amount is replaced by Ti.
Experiments have confirmed that it has the same effect as when precipitated as N. Also, the upper limit of the amount of Ti added is 1.
If Ti is added in an amount greater than the equivalent amount to N (i.e. 48/14N (%)), it will form sulfides or carbides, deteriorating ductility and secondary workability, and making it difficult to control bake hardenability. Moreover, when P is added, phosphides are formed and the quality of the material is deteriorated, so it is preferable not to add Ti in an amount exceeding the equivalent amount of N. From the above, the Ti weight is 48/14(N(
%)-0,002%)<Ti(%)≦48714N (relationship).

On the other hand, Nb is determined by the relationship with C, and Excess C (
C (%) −] 2/93 Nb (%)) is 10 to 5
It is desirable that the Nb content be within the range of 0 (ppm) and the amount of Nb be 0.02% or less. Therefore, the amount of Beb added is
% (soppm) )riNb (%) S93/I 2
(C(%) -0(1(1% (IO'ppm) 'J
becomes.

The 1· limit of Nb I'f+ is determined from the limit at which it is practically 1-1 non-aging. If the amount of C that introduces a +1 song to Nb is 50 ppm or -1-, there will be too much solid solution C in the steel sheet, and the sintering (-1' lfability will increase or yield after aging. Point elongation is currently the highest, making it unsuitable as a material for exterior panels.N
The limit of bM is determined so that the solid solution C remains appropriate. If the Excess C amount is less than 1 Oppm, the final solid solution C amount will be too small, even in the case of rapid operation.
Cannot provide sufficient sintering hardenability (・.

When the amount of F; (Dimensions shown in Figure 5).

History K Nb addition-state is 0. If it exceeds o2chi, fine Nb
Due to the addition of force to the C output, the recrystallization temperature is extremely high.
, < l The precipitation strengthening element due to NbC is thick and causes a decrease in the upper layer of YP, El, and r values, so it is outside the target particle quality of the steel of the present invention7
．． IO FIGS. 1 and 2 illustrate the Ti and Nb content ranges of the steel according to the present invention in relation to the N and C contents. FIGS. 3 and 4 show the scope of the present invention from the relationship between the amount of 'r'+% Nb and the scale.

In Figure 3, the amount of Nb is fixed at a constant amount (o, oos),
These are material characteristic values when changing the amount of Ti. Other alloy components are C: 0.0035, Si: O, O], Mn:
0.25, P: 0.020, S: 0.010, sol.

Al: 0040, N: 0.0040 (tani-, vt
%) and the remainder consists essentially of Fe,
a.

The center part in the longitudinal direction of the coil, b: The front and rear ends of the coil in the longitudinal direction are shown. The hot rolling coiling temperature is high temperature coiling of 700 °C, the annealing condition is 800 °C x 30 seconds, and the cooling rate is cold shoulder J to room temperature.
The speed is 100°C/sec.

In addition, the skin pass rolling ratio after annealing is 0.8%.
The amount is N to A1. Instead of precipitating as N, TiN and 1
．． If there is insufficient amount to fix it, i.e. 48/14
(N (%) - 0, OO2%) > Ti mino, there is a rise in grain deterioration iYP at the front and rear ends of the coil, a decrease in El and r values, and an excessive BoS (see Figure 7). Kii 1, = 1i/
The 111M section in front of L is t'11 rejected when winding.
I, = me, equivalent to normal winding 1-a), represents the feed quality, and in the region of such 1゛i amount, good 6
/ to ensure the quality of the moon.
K 2J-4 - When adding more than 48 N (%l) (J, front and rear ends of the coil, J... during continuous winding, grain deterioration is small, but TiN is formed. In order to exceed the required skewer and include 2+'l"i,
This results in the formation of sulfides and carbides, deteriorating ductility and r-value.

soil! , :, In this region, T1 forms the precipitate as TiC (
In order to form ((, the same bath c will be less and suitable
E-1-911j conversion property is 1-no change. If the above range is '1゛itf:'
'C3i is determined by Excess(-', i:4,
Annealing 11 hardenability regardless of annealing temperature and cooling rate A:j~
can.

Figure 1 shows the case where a constant amount of I″i is added to fix N, and Nl) is changed. 1, which is 1, other alloy components +, 1.
30, Si: 0.0 +
, IVIn: 0.2 5, P: 0.
020, S: 0.010.5olAl: 0.04
0.

N: 0.0040 (for each wt) and the remainder is a sample consisting essentially of F'e (a) the center in the longitudinal direction of the coil, b: the front and rear ends of the coil in the longitudinal direction.

Other manufacturing conditions are the same as in the case of FIG.

The amount of Nb is significantly lower than that used in conventional Nb-added steel (93/12 (C (%) - 0,00
5%J, Nb (%)≦93/I 2 CC (%[-
0,001%) is Nb<.

If you add it so that it does not satisfy the 002 ratio, it will be suitable for baking and c-grilling (=
It shows that it can be done by asking the J hardness ratio.

Appropriate sintering hardenability here is 13H = 3-5 Kg
/mA. , If the Nb content exceeds the above range, fine 1'J
Due to the influence of bC, the precipitation strengthening factor due to NbC becomes large,
The material deteriorates due to the increase in YP, the deterioration of E, ], r value, etc.7, and the recrystallization temperature also increases significantly. , furthermore, it becomes impossible to impart sufficient sinter hardenability, which deviates from the spirit of the present invention.3 In Fig. 5, P;
This figure shows the relationship between 12/93 Nb (%)) and sintering and 1 hardening properties. After annealing, the bed speed was kept constant at 100'c/sec until the room temperature was reached.

What percentage of Excess C'$ is the final (
(Solid R: Regardless of whether it remains as Cg or not, solid solute CFA
' remains in proportion to the amount of Excess C. Therefore, solid solution CM and it lli hardening a CmaEx
This corresponds to the amount of cess C.

Figure 6 shows the cooling cycle in continuous annealing, where (i) is the cycle for cold-rolled steel sheets and hot-dip galvanized blades (no alloying treatment), and (II) is the cycle for continuous annealing.
1. The cooling rate after 3゜'' annealing, which is the cycle for lead-plated steel sheets, can be any rate up to room temperature in the steel of the present invention with composite addition of TI, as described above. The hot-dip galvanizing properties are 173, ! or V), and the rapid cooling (270°C/sec) is desired.

Next, the range of alloy 1 other than L'i and Nb is C:n
, (, + (17% or more 1'-1Si: 0.8%lR lower, 84n: 1.0%121t, P: 0. +
5% or more, AI: 0(1] to 01%, N: (10
Less than 1% [- and unavoidable impurities of the song, the remainder essentially consists of Fe.

If there are many C4, the Nb capital to fix C will inevitably be,
! Since the production cost increases, and the amount of N1) produced increases, the precipitation strengthening factor increases, inhibiting the growth of crystal grains, resulting in a low r value of 1; This leads to a decrease in elongation and elongation. Therefore, from the viewpoint of manufacturing ultra-deep drawable steel sheets, C is set to be 0.007 or less.

When manufacturing hot-dip galvanized steel sheets, Sl does not cure the tendency to reduce the adhesion of the plating layer film (4), or in the present invention, the effect of surface concentration is suppressed by rapid cooling to room temperature. Because it is possible, it should be 0.8% or less.

The steel of the present invention is a steel plate with a low i"i addition amount and residual solid solution C, and furthermore, the amount of uneven grain boundary ino can be significantly reduced by rapid cooling. Difficult(・
However, if a large amount of P is used, grain boundary segregation 1 increases, which embrittles the grain boundaries and promotes secondary work cracking.
) is set to O, + 5%.

Is AI 1? +, add molten steel deoxidizer before adding Nb,
If the amount is too small (if possible, deoxidation by AI is sufficient)
T? Because Ti and Nb act as deoxidizers, the i'i, Nb f7) decrease becomes significant.
It also becomes difficult to control the firing rate fd1. On the other hand, if a large amount is added, A]203 inclusions will increase, which is not desirable. For the above reasons, At is set in the range of 0.01 to 01.

J is fixed to Ti as ``I''iN, but if the N content is too high, the required amount of 1゛I will increase l to preferably 7℃.
.

, 2, so N is less than or equal to (1, (l　l factor).

In the case of a steel sheet to which Ti and Nb are added together, Japanese Patent Publication No. 54-+2883 and Japanese Patent Application Laid-open No. 13153-1983
No. 6 public 'f1. Disclosed in JP-A-56-166331, JP-A-57-35673, etc.
, lrer-) are not based on the basic idea of the invention to add Ti and Nb in combination, but 1゛i, Nb
e) 口', □ ha Zr, V s Cr, etc. simply c,,
N is precipitated and a) addition jL element and 12 are arbitrarily selected and correspond to 4.1°! 1-1. )'1 In this case, 1'1 causes only N to precipitate and C to precipitate as i''i C,
In order to suppress the aging properties due to C and N, the target material quality is obtained based on the relationship between the total addition ratio of Ti and Nb and the C and N%. Furthermore, this patent is based on the basic idea of Himei's non-aging deep-drawn steel plate, which ensures that solid solution C remains in the steel to an appropriate degree, and that the heat hardenability is not compromised.

The steel of the present invention follows the path already mentioned, with a trace amount of 'ri' added to the ultra-low carbon steel.
The fundamental principle is that the addition of Nb is an essential condition, and that high temperature, deep drawability and sintering (=1 hardenability) are achieved.The addition of Ti has a negative effect on and (・1zuN
It is intended to make TiC harmless, and unlike the above invention, it does not generate TiC (.

Furthermore, the addition of Nb has the purpose of reducing the amount of solid solute C within a range that is not harmful to room temperature aging properties [Secondly, the purpose of adding Nb is to impart sinter hardenability due to the residual solid solute C.

Therefore, the basic idea of the steel of the present invention is not to add TI XNb in combination4.
The purpose of the addition is to render the room-temperature aging property harmless and bake hardenability due to C, and the difference in °C.
＠ Adding a trace amount less than the equivalent amount of kc (Ai) Soil,
If the steel of the present invention, which has ultra-low carbon steel as its basic component, is annealed at 3 points IJ and 12, Δc, random crystal grains will be generated, leading to deterioration of the r value, so the annealing temperature should be set at a peak. hAc is 3 points or less below the crystallization temperature.

Furthermore, the cooling rate after annealing may be arbitrary, and production 4'],
70 from the viewpoint of plating strength and 2θζ machining brittleness of steel plate.
'C/sec or higher is desirable, and over-aging treatment is not necessary1.For the following reasons, the steel of the present invention has fundamental principles and advantages. It is essentially different from that patent.

The present invention significantly reduces the Nb content compared to conventional steel sheets, so the recrystallization temperature 1
v is low regardless of hot court appearance conditions (・.Hot pressure evening meal (C
By high-temperature winding for 1J, the precipitates may agglomerate.
J, i(!), and the recrystallization temperature lW further decreases. Therefore, the steel of the present invention can obtain a high (r value) even with low one-item annealing. Steel 4ti
It provides:

Look, below, describe the example.

Example 1 Table 1 shows the (
5. This shows the generated components.

The above test steel was heated at a hot finishing temperature of 910°C and a coiling temperature of 70°C.
Hot rolled plate B' 1-7.0.8 to 4.0 mm with high temperature winding O6 at 0'C and normal winding at 600C
After cold rolling to 17 mm, the annealing cycle shown in Fig. 6(i) was annealed on a continuous annealing line to produce a cold rolled steel sheet. The cooling rate was set at 1.00°C/sec to room temperature.Then, temper rolling was applied at a rolling rate of 1!2.The texture test is shown in Table 2 (1) and (11). Shown below.

From Table 2 (1) and (II), notifications 1 to 5 according to the claimed invention
The wI board has a homogeneous coil self-interest η with extremely large variations -(
It is small and can be equivalent to normal winding regardless of the winding temperature (+1'
;7c, it is clear that the material is J from within. .

In addition, there is no I-23-11 cracking, and the chemical conversion treatment property is also good.Furthermore, it shows the advantage of being able to control firing hardening with high accuracy regardless of changes in components. ℃・ru7, Comparison 4.4 Tsuta6, A7, I'58 have Ti outside the range of the present invention (・ru1, /I66, A8 have too low Ti content, so Nl) and are close to quilt steel. (・The material deteriorates significantly at the end of the coil during normal winding and temperature winding. Also, due to the shadow of solid solution N due to the dissolution of AIN, yield point elongation appears after aging treatment (・Since there are too many '1゛1- in the machine plate 7, it is close to Ti killed steel.・
(It is a 4-quality material, which makes it easy to cause primary cutting cracks, and has poor chemical conversion treatment and bake hardenability. Flat 9 is Nb guild steel or outside the scope of the present invention. A'1, Tsuki 11Jj, which is close to Nb guild steel, Tobu, c 1,111 In the case of normal winding and temperature winding, the material deterioration of the coil end is extremely large, and the chemical conversion treatment is inferior because the amount of Nl) is high at a high temperature. In addition, comparative steel A66-8 has a Ti content, Nl
) Since rice is outside the scope of the present invention, it is not possible to control the bake hardenability to an appropriate value.

Hoe shapes 1 to 165 of the present invention are substantially non-aging at room temperature even when the cooling rate is changed, as shown in Table 2, and
It was confirmed that a bake hardenability of 5Ks+/- was obtained.

Example 2 Table 3 shows the composition of the steel according to the invention and for comparison (4).

(The test steel was made by adding alloying elements to the steel in the scope of the present invention and the comparison steel to increase its strength.

A. The steels 1 to 6 were subjected to cold rolling under the same conditions as in Example 1 (Fig. 6 (1)) The cycles shown in K were continuously annealed at a temperature of 10°C to form cold rolled steel sheets. However, the annealing temperature was 800℃, the holding time was 30 seconds, and the cooling rate was 10℃.
°C/sec, 50 °C/sec, 70 °C/sec z+
00°C/required (constant up to room temperature).

Sample 1 Oka Susumu 7 has a hot rolling finishing temperature of 880°C and a winding temperature of Hgl.
It was hot rolled to a plate thickness of 4.0 mm at 5/IO℃ and (1,
After cold rolling to 8 mm, it was subjected to box annealing at an annealing degree of 720°C.

iK I ~ □ 6, cooling rate 100℃ for eye stings
/5ec (constant up to room temperature) is shown in Table 4, and the results of the simultaneous KJ, 't7 and 1'' quality are also shown.

From Table 4, it is clear that the steel of the present invention has r((
K;/J-extremely high and has excellent ductility. Mild steel plate σ
), the coil circle material is homogeneous and has good chemical conversion treatment property θ.
In addition, the summerization properties of Yakizej1 were achieved as per the target values. In addition, the reason why secondary processing cracks are difficult to occur despite the cooling of alloying elements such as P is that the absence of C or r in the same bath is 1~
This is because the grain boundaries are strengthened and the grain boundary segregation P;11 is significantly reduced by rapid cooling to room temperature.

Table 4 (2) (・ζ Shows the limit of occurrence of secondary processing brittleness when the cooling rate is changed -4". The test temperature was -50°C, and the test piece of test 1 was a shear edge, and the cylindrical molding The outer diameter in the case of 1-mm was set constant at 30 mm.

(All trial months were at the longitudinal center of the coil where the coil was wound at a high temperature.) Table 4 (2) *: Minimum drawing ratio at which secondary processing cracks occur: Box annealing A
From the results in Table 4 (2), it is clear that when P is added to produce a high-strength steel sheet, the limit for secondary work cracking is lower than that for a mild steel sheet, but this Even with the combined addition of Tl, the invention steel has almost the same level as Nb-added steel, and is superior to T1 killed steel (A5 material is a material close to J゛1 killed steel), which is prone to secondary work cracking. Also excellent. In order to obtain the same level of secondary stress-E cracking properties as Nb-added steel, the cooling speed IQ is optional.
In steel, it is desirable to cool at a cooling rate of 70°C/pass or higher in order to obtain the critical drawing ratio of stains.
Rapid cooling is also possible by the combined addition of i, and the amount of grain boundary segregation of P can be significantly reduced, resulting in a sharp effect (4'), which shows the superiority of the steel of the present invention. be.

Comparative @ Flat 4 has a large amount of Nb added, so the material deterioration at the end of the coil during normal winding and high-temperature winding is extremely large, and the chemical conversion treatment property is poor. In addition, because there are too many Nb elbows, even in the case of rapid cooling, sintering (= 1 hardenability) cannot be obtained. If it is inferior, it has 5 drawbacks, and it is not easy to bake or 11.

Since the amount of t in flat 6 (the barb is n l'N is not enough to fix N as TiN), the material is close to Nb-added steel, and the material is difficult to maintain during normal winding and high-temperature winding. The deterioration of the quality of the front and rear ends of the coil is extremely large, and there are large variations in bake hardening properties. Since the front and rear ends of the coil and most of the coiled grains were shown, no particular description is given.) Example 3 All of the test steels shown in Tables 1 and 3 were tested in Example 1.
After the process was carried out under the same conditions as in the case of , a hot-dip galvanized steel sheet was manufactured using the annealing cycle shown in Fig. 6 (i) (+D) at 800°C. is 30 seconds, and the cooling rate is constant at 100℃ until room temperature.
It was cooled at a cooling rate of /see.

Figure 6 (1) corresponds to the case where alloying treatment is not performed,
(11) is a case where an alloyed galvanized steel sheet is manufactured by performing alloying treatment. In these cases, the cooling rate is controlled by the cooling rate until the steel plate enters the galvanizing bath,
The cooling rate from leaving the plating bath to reaching room temperature was also controlled.

The above manufacturing results are as follows.

(1) The mechanical test values were almost the same as those shown in Tables 2 and 4, and the galvanizing did not contradict the gist of the present invention. Although the alloy ratio treatment is held at about 530°C for about 10 seconds, there is no difference in sinter hardenability from Example 1.2.This means that most of the C precipitates at 500°C, This is understood to be because it occurs in a higher temperature range. Material property values are not specified due to bending.
0 However, Table 5 shows the plating adhesion when zinc plating was performed.

Table 5 Umbrella: The evaluation method is based on the DuPont test. Good: ○, Partially defective: △, Poor: × **: The evaluation method is the Metal Phase 11111' test (JIS Z
2248) Peeling by K 1Illf minimum; 0. Peeling #1 #j
From the results, the steel of the present invention has extremely good resistance to zinc plating. In particular, the sample in Table 3 is 8;
The reason why the adhesion is good despite the high hn1 content is that the amount of Si concentrated on the surface can be significantly reduced by rapid cooling.

The samples in Table 1 - Bian 7 and Table 3 - Feng 5 contain a large amount of Ti, which accelerates the alloying reaction between the base iron and molten zinc, resulting in overalloying and hard and brittle coating in the plated layer. It is thought that the adhesion deteriorated due to the formation of an alloy layer. The reason why the adhesion of the 1A materials in Table 1 - Flat 9 and Table 3 - Flat 4 is inferior to that of the steel of the present invention is presumed to be due to the large amount of Nb addition.

1 From this point of view as well, the steel of the present invention has the advantage of having a low adhesion of T + % Nb as an alloying element.

Example 4 Test copper metal 1.2.8 shown in Table 1 was hot-rolled at a finishing temperature of 9 t.
(After cold rolling the plate to a thickness of 5.0.2 mm at 1°C and a coiling temperature of 700°C, it was continuously annealed by the annealing cycle shown in Figure 6(i). 1. Annealing FA [5T=650℃, Soaking time 2
0 seconds, and the cooling rate is constant at 0°C/5ec.

Thereafter, temper rolling was applied at a rolling F ratio of 0.8%. The material results are shown in Table 6.

From the above results in Table 6, the steel of the present invention has significantly reduced Ti and Nb additions, so the ladle crystal temperature is extremely low (it is possible to manufacture ultra-thin steel sheets by low-temperature annealing, and it is suitable for two uses). It provides ultra-thin steel sheets. Comparative copper metal 8 is Nl)
It is non-crystallized when the addition amount is high and low temperature annealing is performed.

As shown in the following, it is essential to add Nb in combination, Ti is added within the range that fixes N, and Nb1Excess C amount is 1v'l O~50
By adding ppm, the hot rolling winding temperature,
The novelty of the present invention is demonstrated by the creation of an ultra-deep drawable and hardenable steel sheet that has extremely excellent seeding properties that have never been seen before, regardless of annealing and cooling temperatures. It was done.

[Brief explanation of the drawing]

Figure 3 is a diagram of Ti addition amount and N, Figure 2 is a diagram of Nl) addition amount and C, Figures 3 and 4 are Ti, Ti amount and Nb amount that affect the material of composite addition steel. diagram showing the impact of
Figure 5 shows Excess C amount < C (@1 oak x qb
(Kai) It's a joke. Related Yao r3 Diagrams, Figure 6 is an explanatory diagram showing the annealing cycle, Figure 7 is B
It is an explanatory diagram of i(σ). Fan l area θ θθθ2 θθθ4 046g
θθθδN (wt %J Leather 20 Fan 3 Figure 4 Figure Nb (wt illusion a31 Figure 1) ゛17

Claims (1)

[Claims] c: o, 007 or below, Si: 0.8% or below, Seed 1
0% or more F', P: 0.15% or less, AI: 0.0
1 to 01%, N: 0.01% or less, and other essential impurities, and a steel containing Ti and Nb added within the range of ``compound addition'' is hot-rolled and cold-rolled. A method for producing ultra-deep drawable and sinterable ("I-hardenable) steel sheets, which is characterized by continuous annealing after rolling at a temperature below the recrystallization temperature and below the hAcs point.