CN1260018C - Hot-rolling perforation-cold-rolling forming method for hollow rock-drill steel - Google Patents

Abstract

The invention provides a hot rolling piercing-cold rolling forming method of hollow drill steel. It is characterized in that: the hot-rolled piercing-cold-rolled forming method is used to produce B and D-type hollow drill steels, and the hot-rolled piercing Φ50 two-roll cross-rolling piercing machine rolls the round solid tube blank of Φ50～Φ65mm in a hot state. Φ50～Φ65mm, hollow capillary tube with wall thickness of 6～17mm, after cooling, it is rolled and formed on a cold rolling mill. The invention starts from the geometric characteristics of the hollow steel and realizes a specific deformation process through tool design. Compared with the existing production method, the main advantages of the present invention are: few working procedures, short flow process, good quality of inner hole, high precision of shape and size.

Description

Hot-rolled perforation-cold-rolled forming method of hollow drill steel

technical field

The invention belongs to the technical field of metal material processing, and in particular provides a hot-rolled piercing-cold-rolled forming method for hollow drill tool steel.

Background technique

Hollow drill steel is the main tool used for rock drilling and drilling in mining. Commonly used specifications include hexagonal B19~B45 (the number indicates the distance between opposite sides in mm) and circular D32~D51 (the number indicates the diameter in mm). The cross section is shown in Figure 1. The water injection hole in the center is used for water and dust removal and cool.

The geometric characteristics of hollow drill steel are: wall thickness (the ratio of wall thickness to outer diameter S/D is 1/3.2～1/3.5), small inner hole (minimum is only 5.5mm), long length (up to 6mm ). In view of the above-mentioned geometric characteristics of "like (steel) pipe but not (steel) pipe", this product can neither completely adopt the production process of seamless steel pipe, nor can it completely adopt the method of mechanical processing. Since the quality of the inner hole largely determines the bending fatigue resistance of the product (the main performance used for production), the production method and quality of the inner hole have become the main basis for distinguishing the production method and evaluating its pros and cons .

The existing production methods of hollow drilling tool steel mainly include the following two types:

1. In 1994, Hu Ming and Qin Yan proposed the mechanical drilling-core hot rolling method in the paper "Sweden Hollow Steel Production Line" published in "Rock Drilling Machinery and Pneumatic Tools". Its main process flow is shown in Figure 9.

The main feature of this process is that the inserted high manganese steel mandrel is deformed together with the billet, and the mandrel is pulled out after cooling. Since the mandrel plays the role of processing the inner hole of the hollow steel, there are no defects such as cracks on the surface of the inner hole. The main disadvantages of this process are: many procedures, long process, out-of-round inner hole and large mandrel consumption (one mandrel can only roll one hollow drill steel). This process is adopted by the world's most famous Swedish company Sandvik.

2. Ye Lingyun and Feng Zhiyong published the paper "Hot piercing-hot rolling production process of hollow steel for rock drilling rods" published in "Steel" in 1996, and proposed the cross-rolling perforation-cross-rolling forming method. Its main technological process is shown in Figure 10.

The main feature of this process is that thick-walled capillary is obtained by cross-rolling and piercing. On the three-roll cross-rolling extension machine, the capillary is greatly reduced in diameter without mandrel. It has the advantages of short process, less equipment and low production cost. The advantages. The main disadvantage of this process is that due to the absence of the mandrel on the surface of the inner hole and the severe torsion of the pipe during the cross-rolling process, cracks, wrinkles and other defects often appear on the surface of the inner hole, resulting in low service life and instability. China's Xianning Mining Machinery Factory and New Fushun Steel Factory adopt this production process.

Contents of the invention

The quality of hollow drilling tool steel depends on the following three links: the selection of steel type and metallurgical quality, forming method, and heat treatment system. The purpose of the invention is to propose a forming method for producing high-quality B and D-shaped hollow steels aimed at the forming method.

The invention adopts a hot-rolling piercing-cold rolling forming method to produce B and D-type hollow drill steels. Hot-rolled piercing (Φ50 two-roll cross-rolling piercing machine) The round solid tube blank of Φ50~Φ65mm is rolled into a hollow capillary tube of Φ50~Φ65mm and wall thickness 6~17mm in a hot state, and rolled on a cold rolling mill after cooling forming.

Conventional two-roll and three-roll cold rolling mills are special equipment used to produce high-precision thin-walled steel pipes (S/D=1/60～1/250). The utility model utilizes the action principle of the cold rolling mill, starts from the geometric characteristics (S/D=1/3.2～1/3.5) of the hollow steel, and realizes the specific deformation process through the tool design, and produces B on the three-roll cold rolling mill. , D-type products, D-type products are produced on a two-roll cold rolling mill.

Forming process:

When B and D type products are produced on a three-roll cold rolling mill, the deformation tool has three rolls with equal cross-sections (type B is a triangular pass, and type D is an equal-radius arc-shaped pass) rolls, three supporting plates with variable cross-sections and a Cylindrical mandrel. The roll shaft of the roll is close to the slideway of the support plate, and the following deformation process is realized by using the special shape change of the slideway: When the roll moves to the front limit position (positive stroke), the roll moves closer, and the shape of the pass is consistent with the shape of the product ;When the rollers move to the rear limit position (return stroke), the rollers will separate and leave the pipe material, at this time the rotary feeding mechanism will rotate the pipe material at a certain angle (60° for B type, 40°～60° for D type) And feed a section of pipe material, and then the roll moves forward again, so that the fed section of pipe material is deformed between the roll and the mandrel. Such repeated periodic movement until the hollow capillary is rolled into hollow drill steel. The deformation zone and forming principle are shown in Figure 2.

The deformation zone L in the above-mentioned deformation process is composed of the diameter-reducing and wall-increasing section L ₁ , the wall-reducing section L ₂ , the pre-finishing section L ₃ , and the sizing section L ₄ , and the functions of each section are as follows:

L ₁ : Most of the diameter reduction deformation is completed, and the wall thickness increases significantly (about 1-1.2mm) while the diameter is reduced; the corners begin to form.

L ₂ : complete wall reduction deformation, the amount of wall reduction is equal to or slightly greater than the increased wall thickness in L ₁ section; the corners are filled.

L ₃ : The shape and size meet the product requirements.

L ₄ : Precise shape and size, smooth inner and outer surfaces.

When producing D-type products on a two-roll cold rolling mill, the deformation tool has two variable-section rolls and a tapered mandrel. The deformation process and the composition of the deformation zone are basically the same as the three-roll cold rolling mill.

Process parameters:

Relative diameter reduction rate: $\frac{{\mathrm{D.}}_0-d}{{\mathrm{D.}}_0}\×100\%=15~30\%$

Relative wall reduction rate: $\frac{S_0-\mathrm{the\; s}}{S_0}\×100\%=0~10\%$

Elongation coefficient: μ=1.5～2.5

Hollow tube material: $\frac{S_0}{{\mathrm{D.}}_0}=\frac{1}{4.0}~\frac{1}{4.5}$

Finished product: $\frac{\mathrm{the\; s}}{d}=\frac{1}{3.2}~\frac{1}{3.5}$

In the formula:

D ₀ , d-hollow pipe material, finished product outer diameter, mm

S ₀ , s-wall thickness of hollow pipe material and finished product, mm

Deformation zone parameters:

L ₁ =(0.3～0.5)L

L ₂ =(0.4～0.3)L

L ₃ =(0.2～0.1)L

L ₄ =0.1L

The advantages of the present invention are:

1. Less process and short process.

The main process is: heating the round tube billet, hot-rolling and piercing, and then cold-rolling forming (one-time forming on a cold rolling mill). See Figure 11

2. The product quality is good.

Since the mandrel participates in the deformation, the quality of the inner surface of the water hole is guaranteed; the mandrel can be used repeatedly; the inner and outer surfaces are smooth, the shape and size are precise, and negative tolerance rolling can be realized.

3. The application prospect is broad.

There are many steel pipe manufacturers in my country. For example, Ningbo Tianzhu Special Steel Pipe Co., Ltd. has a Φ50mm piercing machine and a cold rolling pipe mill. The existing production line can be slightly improved to produce hollow drill steel.

Description of drawings

Below in conjunction with accompanying drawing, the present invention is further described:

Figure 1 is a schematic diagram of the roll shape of the B-type product of the three-roll rolled tube. D _m is the maximum diameter of the roll, D _p is the diameter of the bottom of the roll, D _g is the diameter of the roll neck; B is the width of the groove of the B-type product roll, and b is the width of the roll ring of the B-type product roll.

Fig. 2 is a roll shape diagram of a three-roll rolled tube D-type product. D _m , D _p , and D _g are the maximum diameter of the roll, the diameter of the bottom of the roll, and the diameter of the roll neck; R, B, and b: respectively, the radius of the roll pass, the width of the groove, and the width of the roll ring.

Figure 3 is a schematic diagram of a three-roll tube support plate. Among them: β ₁ , β ₂ , β ₃ , β ₄ : are the cone angles of each section of the support plate; H ₁ , H ₂ , H ₃ : are the total height of the support plate, the height of the reverse cone section and the height of the idling section; S ₁ S ₂ : respectively the thickness of the idling end plate and the reverse cone end plate; L, B, b, h: respectively the length, width, side wall thickness and descending height of the reverse cone section of the support plate.

Fig. 4 is a schematic diagram of a three-roll rolling tube mandrel. Among them, φ is the diameter of the three-roll rolling tube mandrel; L is the length of the three-roll rolling tube mandrel.

Fig. 5 is a schematic diagram of a two-roll rolling tube mandrel. Among them: D ₁ D ₂ D ₃ are the diameters of each section of the two-roller mandrel; l ₁ l ₂ l ₃ are the lengths of each section of the two-roller mandrel; β is the cone angle of the two-roller mandrel.

Fig. 6 is a schematic cross-sectional view of class B and class D drill rods. The water hole is used for dust removal and cooling.

Fig. 7 is a schematic diagram of the limit position after the forming process. Among them, roll 1, pipe material 2, mandrel 3,

Figure 8 is a schematic diagram of the front limit position. Among them, the finished product 5.

Figure 9 is a schematic view of the right side view of the support plate.

Figure 10 is a schematic diagram of the forming process. Among them, the support plate 4 .

Fig. 11 is a schematic diagram of rolling B22 type hollow drill steel.

Fig. 12 is a process flow chart of the mechanical drilling-core hot rolling method.

Fig. 13 is a process flow diagram of cross rolling piercing-cross rolling forming method.

Fig. 114 is a short flow chart of the present invention.

Detailed ways

Example 1: Rolling B28 and B32 pipes with a tube billet heating furnace, Φ50 two-roll piercer, and LD-30 three-roll cold rolling mill.

Example 2: Rolling D38 and B32 pipes with tube billet heating furnace, Φ50 two-roll piercer, and LD-30 three-roll cold rolling mill.

Claims (1)

1. A hot-rolled perforation-cold-rolled forming method for hollow drill steel. The hot-rolled perforation-cold-rolled forming method is used to produce B and D-type hollow drill steels. The Φ65mm circular solid tube blank is rolled into a Φ50～Φ65mm hollow capillary tube with a wall thickness of 6～17mm in a hot state. After cooling, it is rolled and formed on a cold rolling mill; the characteristic is that for D-type products, there are three deformation tools Equal cross-section: Type D is an equal-radius arc-shaped pass roll, three supporting plates with variable cross-section and a cylindrical mandrel; the roller shaft is close to the slideway of the support plate, and the special shape of the slideway is used to change , to achieve the following deformation process: when the rolls move to the front limit position, the rolls move closer together, and the shape of the pass is consistent with the shape of the product; when the rolls move to the rear limit position, the rolls separate and leave the pipe material. The pipe material is rotated at a certain angle, D type is 40°~60°, and a section of pipe material is fed, and then the roll moves forward again, so that the fed section of pipe material is deformed between the roll and the mandrel, and so on. until the hollow capillary is rolled into hollow drill steel; the deformation zone L in the deformation process is composed of a diameter-reducing and wall-increasing section L ₁ , a wall-reducing section L ₂ , a pre-finishing section L ₃ , and a sizing section L ₄ , where L _1. Most of the diameter reduction deformation is completed. While reducing the diameter, the wall thickness increases significantly, which is 1-2 mm; the corners begin to form; L ₂ completes the wall reduction deformation, and the wall reduction amount is equal to or slightly greater than that in the L ₁ section Increased wall thickness; corners are filled; L ₃ shape and size meet product requirements; L ₄ shape and size are accurate, inner and outer surfaces are smooth; when producing D-type products on a two-roll cold rolling mill, the deformation tool has two variable-section rolls and A conical mandrel, the deformation process and the composition of the deformation zone are basically the same as the three-roll cold rolling mill, and the process parameters are: Relative diameter reduction rate: $\frac{{\mathrm{D.}}_0-d}{{\mathrm{D.}}_0}\×100\%=15~30\%$ Relative wall reduction rate: $\frac{S_0-\mathrm{the\; s}}{S_0}\×100\%=0~10\%$ Elongation coefficient: μ=1.5～2.5 Hollow tube material: $\frac{S_0}{{\mathrm{D.}}_0}=\frac{1}{4.0}~\frac{1}{4.5}$ Finished product: $\frac{\mathrm{the\; s}}{d}=\frac{1}{3.2}~\frac{1}{3.5}$ In the formula: D ₀ , d are the outer diameter of the hollow tube material and finished product, S ₀ , s are the wall thickness of the hollow tube material and finished product; parameters of the deformation zone: L ₁ =(0.3～0.5)L, L ₂ =(0.4～ 0.3)L, L ₃ =(0.2-0.1)L, L ₄ =0.1L.

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