JPH04191323A - Manufacture of steel tube for cylinder excellent in machinability - Google Patents

Abstract

PURPOSE:To manufacture a steel tube for a cylinder excellent in machinability by subjecting a resistance welded tube constituted of specified ratios of Fe, C, Si, Mn, P and S to quench-and-temper to form its structure into a bainitic one and thereafter executing cold drawing and stress relieving annealing. CONSTITUTION:A resistance welded tube contg., by weight, 0.15 to 0.30% C, 0.05 to 0.50% Si, 0.30 to 1.00% Mn, <=0.040% P, <=0.010% S and the balance Fe with inevitable impurities is used as stock, which is held at about 870 to 930 deg.C for about 10 to 30min and is thereafter subjected to water quenching. Next, the resistance welded tube is subjected to tempering of holding at about 650 to 710 deg.C for about 10 to 30min and thereafter executing air-cooling to form its structure into a bainitic one, and cold drawing and stress relieving annealing are executed. In this way, the steel tube for a cylinder excellent in machinability is manufactured, and in its grooving in the inner face, the chipping of a bite or the like ca be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application This invention relates to a method for producing a steel pipe for cylinders that has excellent machinability without impairing dimensional accuracy and surface roughness using an electric resistance welded pipe as a raw material.

Conventional steel pipes for cylinders are JIS G 3473 STC38-60, J
IS G 3445 STK 13 types are used as general purpose materials.

Among the manufacturing methods for such steel pipes for cylinders, when using electric resistance welded pipes as the material, - cold drawing is carried out in the state of ferrite/pearlite structure to ensure dimensional accuracy and surface roughness; Stress relief annealing is carried out to remove processing distortion due to

Steel tubes for cylinders obtained by cold drawing and stress relief annealing of ERW tubes with ferrite/pearlite structure induce tool breakage during cutting of cylinder inner seal grooves, resulting in extremely short tool life. This is causing trouble in groove cutting.

This is thought to be because the metal structure has a greater influence on tool life in groove cutting than in normal cutting.

Furthermore, as a method for improving machinability, it is effective to add S, which is a known free-machinability imparting element. Furthermore, in order to ensure dimensional accuracy and surface roughness as a steel pipe for cylinders, electric resistance welded pipes are considered to be the most suitable material for cold drawing. However, in the electric resistance welded pipe to which S is added, many A-based inclusions such as MnS that have been viscously deformed due to rolling exist along the weld metal flow, which adversely affects the quality of the electric resistance welded joint.

Furthermore, as an electric resistance welded pipe with excellent cutting workability, C:0.
15% or less, Si: 0.35% or less, Mn: 1.50%
Hereinafter, the hardness of a welded part made of steel containing P: 0.040% or less, 3: 0.040% or less, further containing Nb: 0.010 to 0.050%, and the remainder substantially consisting of Fe. Proposals have also been made, such as an electric resistance welded pipe (Japanese Patent Application Laid-Open No. 163716/1983) in which the Hv (10 kgf) is suppressed to 350 or less.

Problems to be Solved by the Invention Methods for solving the above-mentioned drawbacks of the prior art include increasing the hardness with the conventional metal structure of ferrite/pearlite, or performing quenching and tempering treatment before cold drawing to create bainite. It is conceivable to make it an organization. It is also conceivable to perform quenching and tempering treatment after cold drawing, but dimensional accuracy and surface roughness deteriorate due to thermal distortion and scale formation on the surface.

Furthermore, the electric resistance welded pipe of JP-A-54-163716 is N
It is necessary to use steel of a predetermined composition with addition of b.

The purpose of this invention is to use an electric resistance welded tube that does not contain Nb as a material,
An object of the present invention is to provide a method for producing a steel pipe for a cylinder that has excellent machinability without impairing dimensional accuracy or surface roughness.

Means for Solving the Problems The inventors of the present invention have conducted extensive research and testing to achieve the above object. As a result, water quenching and tempering is performed before cold drawing to create a bainite structure, followed by cold drawing and stress relief annealing, resulting in excellent machinability without sacrificing dimensional accuracy or surface roughness. The inventors discovered that it is possible to manufacture steel pipes for cylinders, and achieved this invention.

That is, in this invention, the component composition is expressed in weight percent, and C: 0.
15-0.30%, Si: 0.05-0.50
m, Mn: 0.30-1.00L P: 0
．． 0407: Hereinafter, S: including 0.010Z or less,
The material is an electric resistance welded tube with the remainder consisting of Fe and unavoidable impurities, and after quenching and tempering it to a bainite structure,
Cold drawing and stress relief annealing are performed.

Function In this invention, the reason why the component composition of the electric resistance welded tube as a material is limited as described above is as follows. In addition,
The percentages in the following steel compositions are by weight unless otherwise specified.

C is an element that stably increases the strength of steel, but at 0.30
If it exceeds %, quenching cracks are likely to occur during water quenching, and if it is less than 0.15%, it becomes difficult to obtain a bainite structure. Therefore, the C content was set to 0.15 to 0.30%.

Si is a necessary element for deoxidation, but if it exceeds 0.5%, it will be viscous deformed during processing and will exist along the weld metal flow, adversely affecting welding quality. Inclusions increase, and if it is less than 0.05%, a sufficient deoxidizing effect cannot be obtained. Therefore, the Si content is 0.05~
It was set to 0.50%.

Like C, Mn is an element that increases the strength of steel, but 1.
If it exceeds 0.00%, A-based inclusions such as MnS cannot be kept low, and if it is less than 0.30%, M n (Z) / S i (Z) to ensure the integrity of the welded part cannot be suppressed. It cannot be higher than 4. Therefore, the Mn content is 0.
The content was set at 30% to 1.00%.

Since P is an element that tends to segregate, it was set to 0.040% or less in order to substantially prevent any harm caused by segregation.

Since S affects the quality of the weld as an A-based nonmetallic inclusion such as MnS, the content was set to 0.0% or less.

The conditions for quenching and tempering before cold drawing in this invention are as follows:
After being held at 870-930°C for 10-30 minutes and water quenched, it is held at 650-710°C for 10-30 minutes and then air-cooled.

Water quenching is performed at 40℃/
A cooling rate of sec or more is preferred. In addition, tempering is performed at 650 to 710°C for 10 to 30°C to ensure that the bainite structure does not disappear at the transformation point and to soften it for cold drawing.
After holding for several minutes, it was cooled in air.

In this invention, by quenching and tempering an electric resistance welded tube with a limited composition as described above to form a bainite structure before cold drawing, it provides significantly superior machinability compared to conventional methods. This makes it possible to suppress tool breakage and the like during cutting of the cylinder inner seal groove.

Examples Example 1 Each electric resistance welded tube having the composition shown in Table 1 was used as a raw material, and the conventional Pope and H were subjected to cold drawing and stress relief annealing under the conditions shown in Table 2 to produce an electric resistance welded tube for a cylinder. Manufactured.

In addition, in the method of the present invention, an electric resistance welded tube having the composition shown in Table 1 was used as a material, water quenched after holding at a quenching temperature of 900°C for 20 minutes, then holding at a tempering temperature of 700°C for 15 minutes, and then air cooling. . Then, cold drawing and stress relief annealing were performed under the conditions shown in Table 2 to produce cylinder steel pipes having the mechanical properties shown in Table 2. For each of the three types of cylinder steel pipes obtained, the rotation speed was 85 to 1.
Internal groove cutting was performed using a carbide tip under cutting conditions of 25 rpm and depth of cut 0.01 mm/Rev. The results are shown in Table 3.

Table 1 (Unit: w 7%) Margin below Table 2 (Note) Unit of mechanical properties: kgf/mo+” Margin below Table 3 The first and second O marks in Table 3 are 50 Even after grooving was carried out in more than one place, there was no improvement, and as for the X mark, breakage of the cutting tool or chipping of the cutting edge of the cutting tool was observed at about 15 to 25 places.The third time was a visual inspection of the rough cut shape.

As shown in Table 2, the steel pipes for cylinders manufactured by the method of the present invention comply with JIS G 3445 class 13 and JIS G
It has the mechanical properties specified in 3473. Also, the third
As shown in the table, the tool life and rough cut shape of the method of the present invention are significantly improved compared to the conventional methods of HOPE and H, and cutting workability is greatly improved.

Effects of the Invention As described above, according to the method of the invention, the electric resistance welded tube material is quenched and tempered before cold drawing to change the metal structure from a ferrite/pearlite structure to a bainite structure, thereby producing a steel pipe for cylinders. As a result, the machinability of the inner seal groove can be significantly improved without compromising dimensional accuracy or surface roughness.

Applicant: Sumitomo Metal Industries, Ltd.

Claims (1)

[Claims] 1 Component composition in weight%: C: 0.15-0.30%, Si: 0.05-0.50
%, Mn: 0.30 to 1.00%, P: 0.040% or less, S: 0.010% or less, and the remainder is Fe and unavoidable impurities. A method for manufacturing cylinder steel pipes with excellent machinability, which is characterized by forming them into a bainite structure, followed by cold drawing and stress relief annealing.