JP2573630B2 - Manufacturing method of steel pipe rolling guide - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a guide used when manufacturing steel pipes, steel plates, and the like.

[Prior Art] The above-mentioned guides are severely worn due to contact of high-temperature pipes and steel plates.

Currently, there are two types of this guide: cast and hardfacing.

The former casting is a high-Cr, high-Ni cast steel integrated product as disclosed in, for example, JP-A-55-138062.

On the other hand, the latter hardened product is disclosed in, for example, JP-A-57-60060.
In this case, a wear-resistant alloy such as that shown in Japanese Patent Application Laid-Open No. H10-266 is overlay-welded.

Because this guide is not so strict in dimensional accuracy,
Using a casting method such as the V process with relatively high dimensional accuracy,
It can be used as-cast without additional machining.

Accordingly, the cast product can be manufactured relatively inexpensively, but has a drawback of poor wear resistance.

In addition, after welding, it is necessary to correct the dimensions by machining the overlay surface after welding, so the cost is inevitably high, and the carbon content cannot be too high to prevent welding cracks. The usable materials are also limited, and the wear resistance itself is limited.

[Problems to be Solved by the Invention] The present invention has been made in view of such a situation, and its object is to: (1) freely form a cermet layer having high heat resistance and abrasion resistance in its component structure; It is an object of the present invention to provide a new method using HIP sintering that can be selectively coated and (2) does not require machining, and (3) causes less cracks in the cermet layer.

Means for Solving the Problems In order to solve the above problems, the present invention provides a method of coating a surface of a steel pipe rolling guide with a heat- and wear-resistant cermet layer by a HIP sintering method. The steel pipe which covers the inner surface of the canning material at the time of the HIP sintering with a release agent for preventing welding, wherein ρ ₁ > ρ ₂ where ρ ₁ and ρ ₂ are the linear expansion coefficients of the material and the cermet material. This is a method for manufacturing a rolling guide.

[Operation] Since the present invention requires the cermet layer to be coated by HIP sintering as an essential condition, the HIP sintering method will be described with reference to the schematic diagram of FIG.

This schematic diagram shows a case in which a guide for rolling a steel pipe is manufactured, and a base material 1 used in advance is processed into a guide shape.

A canning material 2 processed along the base material 1 is spaced apart from the base material 1 so that a predetermined gap is formed between the base material 1 and the side surface except for the upper surface portion. The gap between the bottom and the bottom is sealed with an iron plate.

A fixed space is formed between the base material 1 and the canning material 2.

Next, a raw material powder mixture of cermet blended into a predetermined composition is filled from a gap on the upper surface, and after degassing, this gap is also sealed.

 This completes the preparation for HIP sintering.

 Next, this is HIP-processed.

Although the treatment temperature varies depending on the composition of the raw material powder, the pressure is generally applied to 1000 kgf / cm ² or more.

As the reaction progresses, the filled powder is pressed onto the surface of the base material 1 via the canning material 2, densified and sintered.

At this time, in the conventional method, the canning material 2 itself is sintered integrally with the powder alloy layer, and it is necessary to mechanically remove the canning material 2 after sintering.

This requires more man-hours as the shape becomes more complicated.

The first feature of the present invention resides in that the inner surface of the canning material 2 is coated with a release agent for preventing welding, thereby preventing the welding of the canning material 2.

Therefore, the canning material 2 after sintering can be easily removed without machining, and the dimensional accuracy of the sintered layer 3 sufficiently satisfies the dimensional accuracy as a guide.

A second feature of the present invention is that, when the linear expansion coefficients of the base material 1 and the sintered layer (cermet) 3 are ρ ₁ and ρ ₂ , respectively, in order to prevent cracking of the sintered layer 3, ρ ₁ > lies in the fact that in ρ _2.

 As is well known, cermet materials are brittle and fragile.

For this reason, it is necessary to minimize the tensile force acting on the sintered layer.

The reason for defining ρ ₁ > ρ ₂ is to prevent a tensile force from acting on the sintered layer 3.

As the material of the base material 1, since the linear expansion coefficient of the cermet material is generally 10 × 10 ⁻⁶ or less, it is necessary to select a material having at least an expansion coefficient higher than this.

Materials satisfying this include ordinary steel materials and austenitic special steels.

Among them, particularly preferred are austenitic special steels, for example, stainless steel or high Ni and high Cr heat resistant steel.

The material of the cermet of the sintered layer 3 is not particularly limited, but carbides, nitrides, borides, and oxides can be appropriately used as the hard particles.

Among them, NbC is particularly excellent in uniform dispersibility and abrasion resistance, and has excellent toughness because there is no unevenness.

The base metal is (Ni, Co) -C
r-based alloys are preferred.

Example Hereinafter, an example of application to a steel pipe rolling guide will be described as an example.

Base material: Two types of SUS 304 and SUS 310 Base material dimensions: 200 × 500 × 75mm Canning material: A 2mm thick mild steel sheet plastically processed into the same shape as the surface of the base material is used. A release agent containing BN as a main component is applied to the inner surface, and a gap of 20mm between the material and the base material The gap between the bottom surface and the side surface was sealed by welding with a mild steel plate.

Filling of raw material powder: The canning material 2 was filled with the raw material powder having the above-mentioned composition from the gap on the upper surface of the base material 1, and after degassing, the above-mentioned void was also sealed.

HIP sintering: HIP sintering was performed at a temperature of 980 ° C and a pressure of 1100 kgf / cm ² .

After sintering, the canning material 2 was peeled off from the surface of the sintered layer 3.

No welding was observed between the canning material 2 and the sintered layer 3, and the film could be easily peeled off.

Dimensional accuracy: The dimensional accuracy of the obtained sintered body sufficiently satisfied the dimensional accuracy required for the steel pipe rolling guide, and could be used as a product without machining.

No defects such as cracks were observed in the sintered layer 3.

Abrasion resistance: Abrasion resistance was tested by actually incorporating.

Although the wear resistance was slightly different depending on the alloy composition, it was confirmed that the wear resistance was 20 to 30 times that of the conventional high chromium cast steel.

[Effects of the Invention] As described above, the present invention has the following effects.

(1) No machining is required to remove the canning material after HIP sintering.

(2) After sintering, it can be used as a product without machining.

(3) The composition of the cermet ρ alloy of the sintered layer can be freely changed.

(4) The sintered layer is less likely to crack.

[Brief description of the drawings]

FIG. 1 is a schematic diagram for explaining the HIP sintering method. 1. Base metal 2. Canning material 3. Sintered layer of cermet powder.

Claims (1)

(57) [Claims] When a heat- and wear-resistant cermet layer is coated on the surface of a steel pipe rolling guide by a HIP sintering method, the linear expansion coefficients of the material of the guide body and the cermet material are ρ ₁ and ρ, respectively. _2. As ρ ₁ > ρ ₂ , the inner surface of the canning material during the HIP sintering is
A method for producing a steel pipe rolling guide, comprising coating a release agent.