JP3456459B2 - Surface-treated steel sheet with excellent drawability and ironability after drawing - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface-treated steel sheet excellent in drawability and workability in high surface pressure working such as ironing and rolling after drawing. [0002] Conventionally, parts such as gears have been manufactured by processes such as casting and machining, but in recent years, in order to reduce manufacturing costs, these parts have been formed by pressing a thin steel plate. It has come to be manufactured by rolling or ironing. For this reason, it is necessary for materials for such uses to have excellent deep drawability at the time of press forming and to prevent galling or cracking at the time of rolling or ironing after drawing. Hitherto, in order to improve the workability at the time of press molding, a method of performing a zinc phosphate treatment before molding or a method of applying a high-viscosity press oil to perform molding has been adopted. On the other hand, from the viewpoint of production efficiency and work environment,
As disclosed in JP-A-151206, a steel sheet having improved galling resistance by adjusting the surface roughness,
As described in No. 2, a steel sheet having an improved galling resistance by applying an organic film has been proposed. [0004] However, the zinc phosphate treatment requires a high temperature and a long time treatment, so that the productivity is reduced and the working environment is deteriorated by the treatment liquid. . In addition, the method using high-viscosity press oil does not provide a sufficient effect. Especially, in the processing such as rolling and ironing, where the material and the tool come into contact with very high surface pressure, "galling" and cracking often occur. Such a problem occurs. Further, in this method, there are problems that the oiling work is complicated and workability is poor, that degreasing after processing is troublesome, and that the working environment is deteriorated. [0005] In the method of improving galling resistance by adjusting the surface roughness of a steel sheet, in the above-mentioned materials, flattening rapidly proceeds by contact with a tool at the time of processing, and a sufficient effect is obtained. Absent. Also, in the method of improving the galling resistance by applying an organic film, since the organic film has a low film strength, the material for the above-mentioned applications is not sufficiently peeled off at the time of rolling or ironing. No effect is obtained, and the peeled film is deposited on the mold, so that the mold needs to be cleaned frequently. To solve such a problem, Japanese Patent Application Laid-Open No. H11-189
No. 827 proposes a steel sheet which has been subjected to zinc phosphate treatment after galvanizing the surface of the steel sheet. However, even with such a treated steel sheet, problems such as cracking during press forming, cracking and galling during rolling and ironing, and deposition of a film on a mold may occur. Therefore, an object of the present invention is to solve the problems of the prior art described above, and to have excellent workability in high surface pressure working such as drawing workability, ironing work after drawing work, and rolling, and furthermore, in the forming process by the user. An object of the present invention is to provide a surface-treated steel sheet that can be simplified, omit tool care, and improve a working environment. [0007] In order to solve the above-mentioned problems, the present inventors have developed materials and tools such as drawing forming and subsequent ironing, rolling, etc. The form of the surface treatment film most suitable for the processing that makes contact with high contact pressure was studied. As a result, a pure zinc plating film was formed on the steel sheet surface with a predetermined adhesion amount and the plating surface roughness adjusted to a predetermined level, and the upper surface thereof was adjusted to a predetermined adhesion amount in relation to the plating surface roughness. It was found that by forming a zinc phosphate film, excellent workability (drawing workability, workability in high surface pressure working after drawing) was obtained. [0008] The present invention has been made based on such knowledge, and the plating amount on one side or both sides of the steel sheet is 2.0 to 2.0.
29.6 g / m ² and plating surface roughness Ra of 0.5
Has a pure zinc plating film ～1.6Myuemu, the upper portion deposition amount M (g / ^{m 2)} is a 0.5~3.5g / ^{m 2,} and the plating surface roughness Ra ([mu] m) A surface-treated steel sheet excellent in drawability and ironability after drawing, characterized by having a zinc phosphate coating satisfying 1.2 ≦ M / Ra in relation to the following. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of the present invention and the reasons for limiting the same will be described below. The surface-treated steel sheet of the present invention has a pure zinc plating film having a predetermined coating weight and a plating surface roughness Ra on one or both surfaces of a base steel sheet, and a phosphoric acid having a predetermined coating amount on the pure zinc plating film. Has a zinc coating. In order to secure the excellent drawability (deep drawability) and the galling resistance at the time of high surface pressure working performed after the drawing, the coating amount and plating of the pure zinc-plated film are aimed at by the present invention. It is necessary to strictly define the surface roughness Ra and the adhesion amount of the zinc phosphate film as described below. [0010] coating weight of pure zinc plating film is required to be a 2.0~ 29.6 g / m ² in order to ensure the galling resistance under high surface pressure processing after deep drawing. If the coating weight is less than 2.0 g / m ² , galling is likely to occur during high surface pressure processing, while if it exceeds 29.6 g / m ² , the coating amount of plating metal on the tool during high surface pressure processing Is unfavorable because it increases. The plating method for obtaining the pure zinc plating film may be either electroplating or hot-dip galvanizing. Further, in order to secure the deep drawability and the galling resistance during high surface pressure working after the deep draw forming, the plating surface roughness Ra of the pure zinc plating film is set to 0.5 to 1.6 μm.
It is necessary to apply a specific amount of zinc phosphate coating on the pure zinc plating film. If the plating surface roughness Ra is less than 0.5 μm, galling is likely to occur during deep drawing or high surface pressure processing, while if the plating surface roughness Ra exceeds 1.6 μm, the frictional force during deep drawing is reduced. It becomes large and cracks easily occur. The adjustment of the plating surface roughness Ra can be performed by adjusting the surface roughness of the base steel sheet, adjusting the surface roughness after plating, or both. In the case of electroplating, since the surface roughness Ra of the material steel sheet becomes almost the same as the plating surface roughness Ra, the surface roughness Ra of the material steel sheet is reduced by, for example, skin pass rolling using a roll having an appropriate surface roughness. By adjusting, a desired plating surface roughness Ra can be obtained. Also, the plating surface roughness Ra
Can also be adjusted by skin pass rolling using a roll having an appropriate surface roughness after plating. The amount of adhesion of the zinc phosphate coating M (g / g / g)
m ² ) is 0.5 to 3.5 g / m ² , and 1.2 ≦ M / R in relation to the plating surface roughness Ra (μm).
a must be satisfied. Amount of zinc phosphate coating M
When (g / m ² ) is less than 0.5 g / m ² or 1.2> M / Ra in relation to the plating surface roughness Ra (μm), the frictional force during deep drawing becomes large and cracks occur. When the zinc phosphate coating amount is less than 0.5 g / m ² , the adhesion amount of the plating metal to the tool at the time of high surface pressure working is undesirably increased. On the other hand, if the adhesion amount of the zinc phosphate film exceeds 3.5 g / m ² , the amount of film peeling during high surface pressure processing increases. [Example 1] In order to investigate the difference in the effect depending on the type of the surface treatment, various surface-treated steel sheets as shown in Table 1 were manufactured, and their draw formability and post-drawing workability were measured. Evaluation of galling resistance in tooth mold processing was performed. The results are shown in Table 1. Each material (surface-treated steel sheet) had a thickness of 1.6 mm for the material steel sheet, and the mechanical properties after the surface treatment were as follows: yield stress: 168 to 172 MPa, tensile strength: 298 to 30
2 MPa, average r value: 1.68 to 1.72, and almost the same material. A punch diameter of 50 mm, a punch shoulder r of 5 mm, and a die diameter of 55 m are applied to these materials in a state where a rust preventive oil is applied to a steel plate.
m, a tool with a die shoulder r of 5 mm, a cylindrical deep drawing into a circular blank of φ110 mm, and a tool tip r on the entire circumference.
Triangular tooth processing with a depth of 3 mm was performed under the condition of 0.5 mm. As shown in Table 1, among the materials of the present invention and the comparative examples, the materials other than the material in which the zinc phosphate film was formed on the alloyed hot-dip galvanized steel sheet and the material in which the organic film was formed on the cold-rolled steel sheet were as follows. However, cracks occurred during the deep drawing of the cylinder, and subsequent tooth shaping could not be performed. Among the comparative examples, the materials with a zinc phosphate film formed on an alloyed hot-dip galvanized steel sheet and the materials with an organic film formed on a cold-rolled steel sheet were able to perform deep-drawing on a cylinder, but cracking and galling during tooth shaping. There has occurred. [Table 1] Example 2 For a surface-treated steel sheet having a zinc phosphate film on top of a pure zinc-plated film, the effect of drawing surface roughness Ra and plating on drawing formability and ironing workability in tooth forming after drawing. In order to investigate the effects of the adhesion amount and the zinc phosphate film adhesion amount, surface-treated steel sheets having the configurations shown in Tables 2 and 3 were manufactured, and their drawing formability and ironing in the drawing tooth forming process were performed. The sex was evaluated. The results are shown in Tables 2 and 3. Each material (surface treated steel sheet) has a thickness of 2.3 mm, and the mechanical properties after the surface treatment are as follows: yield stress: 402 to 426 MPa, tensile strength: 596 to 61
2 MPa, average r value: 0.96 to 1.03, and almost the same material. When these materials are coated with steel plate rust preventive oil, the punch diameter is 48 mm, the punch shoulder r is 5 mm, and the die diameter is 5 mm.
Under a tool condition of 5 mm and a die shoulder r of 5 mm, cylindrical deep drawing is performed on a circular blank of φ95 mm.
Triangular tooth processing with a depth of 3 mm was performed under the condition of 0.5 mm. According to Tables 2 and 3, N, which is an example of the present invention,
o. 8 to No. In No. 20, there is no problem in workability in both cylindrical deep drawing and tooth mold processing, and the amount of peeling of the plating film and the zinc phosphate film is small. On the other hand, no. 21
-No. In Comparative Example No. 23, since the plating surface roughness Ra was too rough, cracks occurred during cylindrical deep drawing. Also,
No. 24-No. In Comparative Example No. 26, the zinc phosphate coating amount was too small or the zinc phosphate coating amount M and the plating surface roughness Ra did not satisfy 1.2 ≦ M / Ra. are doing. No. 27-N
o. In the comparative example of No. 29, galling has occurred at the time of the tooth mold processing because the plating adhesion amount is too small. No. 30 and No. 3
In Comparative Example 1, the amount of zinc phosphate film peeled was large because the amount of zinc phosphate film adhered was too large. No. 32 and no. Comparative Example No. 33 has a large amount of plating peeling because the amount of plating adhesion is too large. [Table 2] [Table 3] As described above, the surface-treated steel sheet of the present invention has excellent drawability and workability in high surface pressure working such as ironing and rolling after drawing. Deep drawing and subsequent high surface pressure processing can be performed appropriately without using a viscous press oil, and the amount of peeling of the film at that time is small. Maintenance can be omitted and the working environment can be improved.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification code FI C25D 5/26 C25D 5/26 C 5/48 5/48 (56) References JP-A-11-343581 (JP, A) Kaihei 8-325796 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 22/00-22/86 C23C 2/06 B21D 22/20 C23C 2/26 C23C 28/00 C25D 5/26 C25D 5/48

Claims (1)

(57) [Claims 1] A steel plate having a coating weight of 2.0 to 29.6 g / m ² on one or both surfaces and a plating surface roughness Ra
There has pure zinc plating film 0.5～1.6Myuemu, deposition amount M (g / ^{m 2)} is 0.5~3.5g / ^{m 2} thereon
Characterized by having a zinc phosphate film satisfying 1.2 ≦ M / Ra in relation to the plating surface roughness Ra (μm), and ironing workability after drawing. Surface treated steel sheet with excellent properties.