JPH01178384A - Stainless clad screw and its manufacture - Google Patents

Abstract

PURPOSE:To obtain a stainless clad screw at the drawing stage by inclined rolling by joining the outer layer stock of a stainless steel by fitting it to the peripheral face of the core stock of a carbon steel or low alloy steel. CONSTITUTION:After hot rolling a carbon steel or low alloy steel as a core bar 11 it is formed in the columnar or bar shape of circular section having specified length and diameter by executing grinding. Then, it is subjected to degreasing and cleaning and plating is executed or N foil is rolled on the peripheral face. As an outer layer stock 12, the welding pipe with a stainless steel as the material or seamless pipe is subjected to cold working after subjecting to hot extrusion or hot rolling and formed in the cylindrical body of circular section having specified length, outer diameter and thickness and the peripheral face is degreased and cleaned. The outer layer stock 12 is then outer-fitted to the core bar 11 and made a clad blank stock 10 by sealing the boundary part 13 at both end parts by welding. The clad blank stock 10 is then heated and rolled as well by drawing by the inclined rolling mill having three or four cone type rolling rolls having plural grooves in the peripheral direction and the stainless clad screw having spiral fins on the outer peripheral face is obtd.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a screw used in a screw feeder, etc., and a method for manufacturing the same. The present invention relates to a stainless steel clad screw having improved corrosion resistance and wear resistance by fitting and joining an outer layer material made of steel, and a method for manufacturing the same.

[Conventional technology]

Screw feeders are used as extrusion screws in extrusion molding machines, injection molding machines, etc., but they are generally manufactured by machining a solid round bar into an integrated shaft material and screw thread. A method of cutting out is used.

By the way, when a screw feeder is used in, for example, an injection molding machine, a food processing machine, a powder mixer, a conveyance machine, etc., it is susceptible to corrosion and wear as it comes into contact with the material. Corrosion resistance is particularly desired since it comes into contact with food, and corrosion resistance is also desired for use in chemical plants where it is mixed with various liquids other than food.

For this reason, stainless steel screws are manufactured by machining corrosion-resistant stainless steel round bars (SUS304゜5US316, etc.), and since stainless steel lacks strength in injection molding machines, which are used under particularly severe conditions, they are manufactured by cutting special steel. However, cutting stainless steel and special steel requires time, resulting in high costs.

Therefore, methods have been taken in which general structural steel, such as 545C, is machined into a screw shape and then thermally sprayed with powdered metal such as Stellite, which has excellent corrosion and wear resistance. Generally, the film tends to peel off due to insufficient adhesive strength of the film itself, and has not been commercialized.

In addition, the surface layer of the screw shaft is nitrided or Tt
Although a method of surface treatment such as N or TiCt chrome plating has been proposed, such a method results in a hardening depth of about 20 to 30 microns at most, which is not sufficient in terms of service life.

[Problem to be solved by the invention 3 Stainless steel is used for food screw feeders, but stainless steel is generally not easy to cut (and takes time to process. Also, since it is cut from a round bar, it takes a long time to cut.) The yield rate is low, and the cost of materials is high, so it has to be expensive. Also, for products that require a high conveyance amount, the height of the screw blades must be increased to increase the capacity, but the blades are high. This makes cutting even more difficult and yields lower, leading to an exponential increase in manufacturing costs.Furthermore, screw feeders for injection molding machines are used under harsh conditions, and stainless steel alone lacks strength. The use of steel and various surface treatments have been considered, but there have been problems in terms of cost and longevity.

An object of the present invention is to provide a stainless steel clad screw that is excellent in corrosion resistance and has sufficient strength, and an inexpensive and easy manufacturing method for the screw.

[Means for solving problems]

The stainless steel clad screw according to the present invention has an outer layer material made of stainless steel fitted onto the peripheral surface of a core material made of carbon steel or low alloy steel. In addition, the manufacturing method involves degreasing and cleaning the outer circumferential surface of the core material and the inner circumferential surface of the outer layer material, respectively, inserting the core material into the outer layer material, and sealing the boundaries between the core material and the outer layer material on both end surfaces by welding. to form a cladding material5. After heating this clad material, three to four cone-shaped rolls are formed on the outer circumferential surface of which a plurality of annular grooves are formed in the circumferential direction to form screws at intervals that gradually become wider from the entry side to the exit side. Stretch and roll using an inclined rolling mill with

[Effect]

However, stainless steel is structural carbon steel and structural low alloy steel (
Mechanical strength is lower than that of S45C, SCM448, etc.)
Therefore, by using the above-mentioned structural steel as the core material to give the shaft material strength, and by fitting and joining the stainless steel outer layer material, we improved the corrosion resistance and wear resistance of the screw shape, which was previously used due to strength problems. The present invention can be applied to stainless steel screw shafts, which previously could not be manufactured, and the wall thickness of the stainless steel can be freely controlled by setting the wall thickness of the stainless steel tube.Furthermore, the thickness of the stainless steel can be freely controlled by setting the wall thickness of the stainless steel tube, and the thickness of the core material and the outer layer material can be sufficiently Achieves high bonding strength.

〔Example〕

The present invention will be specifically explained below based on the drawings.

FIG. 1 is a process diagram showing the main steps of the method for manufacturing a stainless steel clad screw according to the present invention, in which 11 indicates a core material and 12 indicates an outer layer material. The core material 11 is made of carbon steel or low-alloy steel, hot-rolled and then polished to form a circular column or rod with a predetermined length and diameter. After that, the core material is degreased and washed, and then the peripheral surface of the core material is plated or Ni foil is wrapped around it. Examples of the polishing method include shot processing, which removes oxides such as scale after hot rolling, and polishes the material.

On the other hand, the outer layer material 12 is a welded pipe or a seamless pipe made of stainless steel, which is hot extruded or hot rolled and then cold worked to a predetermined length and outer diameter.

It is formed into a thick cylindrical body with a circular cross section, and its inner peripheral surface is degreased and cleaned using acetone or the like in the same manner as the core material.

Although it is desirable to apply Ni plating to the inner peripheral surface of the outer layer material 12, plating may be applied only to either the core material or the outer layer material.

The core material 11 and the outer layer material 12 obtained in this way are obtained by fitting the outer layer material 12 onto the core material 11 as shown in FIG. The clad material 10 is obtained by welding and sealing.

Alternatively, after the outer layer material 12 is fitted around the core material 11, the boundary portion 13 between the core material 11 and the outer layer material 12 at the end after cold drawing may be welded and sealed to obtain the clad material 10.

In addition, when cold drawing is not performed, it is necessary to select the outer diameter of the core material 11 and the inner diameter of the outer layer material 12 so that the clearance between the core material 11 and the outer layer material 2 is small. In order to prevent the formation of an oxide film due to heating before rolling, it is preferable that this clearance is not too large, and is 0.3 to 0.
Approximately 6 vans are suitable. If a larger clearance is required, it is desirable to replace the interior with argon.

The boundary part 13 between the core material 11 and the outer layer material 12 is welded and sealed because a gap is created between the two materials 11 and 12 due to the difference in thermal expansion coefficient between the core material 11 and the outer layer material 12 during the later heating process. This is to prevent air from entering.

Next, after heating this clad material 10 to a predetermined temperature, the cladding material 10 is heated to a predetermined temperature, and as shown in FIGS. A stainless steel clad screw having spiral fins on the outer circumferential surface is obtained by elongation rolling.

The case where the number of rolls is three will be explained in detail below.

Figure 3 is a sectional view taken along line mm in Figure 4 (roll grooves omitted), Figure 4 is a front view taken along line IV-IV in Figure 3, and Figure 5 (roll grooves omitted). 1) is a schematic side view showing the inclined state of the rolling roll with respect to the pass line XX. The inclined rolling mill 4 has three cone-shaped rolling rolls 1, 2.3 facing around the bus line X--X,
Annular grooves are cut in each of the three rolling rolls at positions shifted by 1/3 rotation in phase. Each roll 1. 2.
3 has gorge parts 1a, 2a, and 3a at the exit end of the cladding material 10, and gorge parts xa, 2a, and 3a.
The diameter of the entrance side of the clad material 10 is gradually reduced toward the shaft end, and the diameter of the exit side is expanded to form truncated conical artificial surfaces 1b, 2b, 3b and exit surface 1c + 2c.
+ 3c, exit surfaces 1c, 2c,
3c, the distance to the pass line is made to match the distance between the gorge part and the pass line.

Such cone-shaped rolling rolls 1, 2.3 are all in a state in which their inlet surfaces 1b, 2b, 3b are located on the upstream side in the moving direction of the clad material 10, and the axis Y-Y,
Intersection points 0 (hereinafter referred to as the rolling roll setting center) with the plane including the gorge portions 1a+2a+3a are arranged at approximately equal intervals around the bus line X-X on the same plane orthogonal to the pass line x-xNIA of the cladding material 10. It is set up. The axis Y-Y of each rolling roll 1, 2.3 is the pass line X-X of the clad material 10 around the rolling roll setting center 0.
&'i, the intersection angle γ is adjusted so that the front shaft end approaches the pass line
As shown in FIGS. 4 and 5, the front shaft ends are inclined toward the same side in the circumferential direction of the cladding material 10 by an inclination angle β.

The rolling rolls 1, 2.3 are each connected to a drive source (not shown), and are driven to rotate in the same direction as indicated by arrows in FIG.

Note that it is desirable that the rolling roll shaft holding mechanism be of a double-supported type. The reason why the rolling roll shaft is of a double-sided type is that in the case of a double-sided type, the outer diameter dimensional accuracy of the rolled material is ±0.2%, whereas in the case of a cantilever type, the mill rigidity is low. At the same time, the outer diameter dimensional accuracy of the clad material 10 deteriorates to ±0.7% due to the influence of slippage at the interface between both metals of the clad material 10.

A plurality of annular grooves, e.g. Seven to seven strips are cut in the circumferential direction at appropriate distances apart in the axial direction. The position, spacing, width, and depth of the grooves are different for each rolling roll 1゜2.3, and the spacing for each rolling roll 1゜2.3 also varies depending on the amount of stretching and twisting in the axial direction. The grooves are gradually widened accordingly, and the groove spacing is kept constant on the gluing surface on the exit side of the gorge.

Note that the groove width and groove depth at approximately the same position between the rolling rolls 1' and 2.3 are equal to the distance between the lanes.

Further, the groove depth in each of the rolling rolls 1 and 2.3 is appropriately varied from the entry side to the exit side so as to obtain a desired thread height at the exit end.

The position and distance of the grooves are determined according to the height and distance of the threads to be formed, and the number of rows of the grooves, and the corresponding rolling roll.
2.3 cone half angle α, inclination angle β.

The crossing angle γ etc. are determined.

As a result, the threads emerging from the grooves of one rolling roll are guided into the grooves of the next rolling rolls 1, 2.3 and formed in sequence.

FIG. 6 is an explanatory drawing showing the rolling process step by step, and the arrows in the drawing indicate the direction of the load applied to the cladding material 10. When the clad material 10 (see Fig. 6 ■) starts rolling in the inclined rolling mill, the kraft material 10 is sequentially bitten by the rolling rolls 1 and 2.3 and then rolled by them at three locations in the circumferential direction. (See Fig. 6 (■)), it advances to the rolling roll exit side by so-called spiral movement, which progresses while rotating around the axis.

Then, sequential rolling with three rolling rolls (Fig. 6 ■
, (see ■), the inside of the rolled part is stretched in the axial direction and the thread spacing is widened.

The roll is designed so that the grooves that contribute to the next rolling are located in the thread parts where the interval has widened, so it goes without saying that the threads will not be crushed during rolling, but also allows the threads to be taller, thicker, and with wider intervals. It can be formed by Furthermore, the wall thickness of the stainless steel is as shown in Figure 7 (a) and (b).
It can be set arbitrarily by selecting the wall thickness.

Note that the setting range of the crossing angle γ and the inclination angle β is 0° and γ<1
56 In the case of 3" x β <20"5'< γ + β < 30°, even if there are defects inside the cladding material 10, the stretch rolling of the present invention can prevent Mannesmann fracture, which is a fracture peculiar to inclined rolling. High-quality stainless steel clad screws can be manufactured without causing any problems.

The reason why a cross-type inclined rolling mill equipped with three or four rolling rolls is used is that the above-mentioned Mannesmann fracture (rotary forging effect) becomes noticeable with two rolling rolls.
In addition, if the number of rolling rolls is increased to 5 or more, the structure of the rolling mill becomes complicated due to too many rolling rolls, and the rolling rolls interfere with each other, making it impossible to reduce the set diameter. This is because the roll has to be made thinner than the material diameter, resulting in weak rolling roll rigidity and reduced dimensional accuracy.

[Numerical example]

Next, the method of the present invention will be explained using specific numerical values.

The outer layer material is S [15304], and the core material is carbon steel with a carbon content of 0.06%. After degreasing and cleaning the outer peripheral surface of the carbon steel core material, which has gone through the polishing process, An outer layer material made of stainless steel whose inner circumferential surface was similarly degreased and cleaned was inserted, and cold drawn to an outer diameter of 57 m so that the circumferential surface of the core material and the inner circumferential surface of the outer layer material were in close contact.

In addition, a separate cold drawing process is omitted, and the clearance is reduced to 0.
A test piece of 5+n (one side) was produced, both ends were cut so that the end faces of the core material and the outer layer material were aligned, and then the boundary between both end faces was welded and sealed to obtain a cladding material. The dimensions of the outer layer material and core material used are as shown in Table 1.

(The following is a blank space) Table 1 Next, this clad material was heated and inclined rolled at a temperature of 1100° C. using a cross-type inclined rolling mill. The inclined rolling conditions are as follows.

[Incline rolling conditions]

・Cross angle (γ): 3° ・Inclination angle (β): 5° ・Roll roll diameter: 180 Tsuru (gorge part) ・Roll roll material: SCM440 ・Rolling roll rotation speed: 100 rpi ・Screw diameter: Mountain diameter 55 Tsuru φ, root diameter 39nφ, thread height 8 dragons, screw pitch: 14mm Next, ultrasonic flaw detection was performed to examine the bonding status of the two metal interfaces of the stainless steel clad screw formed using sample material 1.2.3.4. The test was conducted.

〔Test conditions〕

・Flaw detector: USIP12 ・Flaw detection format: Water immersion ・Flaw detection sensitivity: 66 dB ・Frequency 710 MH2 ・Probe: LIOK The results show that there are no defect signals in any of the test materials 1 to 4, and the bonding status is good. This was confirmed.

〔effect〕

As described above, according to the method of the present invention, a stainless steel clad screw can be manufactured by a drawing process using inclined rolling.
The present invention has excellent effects such as being able to obtain a screw feeder having corrosion resistance and high strength using an inexpensive method.

[Brief explanation of the drawing]

Figure 1 is a block diagram showing the manufacturing process of the method of the present invention, Figure 2 is a block diagram showing the manufacturing process of the method of the present invention.
Figure (A) is a schematic front view of the clad material used in the method of the present invention, Figure 2 (B) is a schematic side view, and Figure 3 is a schematic side view of the cladding material used in the method of the present invention.
The figure is a sectional view taken along the nr-m line in Figure 4, Figure 4 is a front view taken along the IV-IV line in Figure 3 (grooves are omitted), and Figure 5 is a roll relative to the pass line X-X. FIG. 6 is a detailed explanatory view of the present invention, and FIGS. 7(a) and 7(b) are partially enlarged half-cut views thereof. 1, 2. 3... Rolling roll Ia, 2a, 3a.
... Gorge part lb, 2b, 3b - ... Entrance surface lc, 2
c, 3cm...Exit surface 4...Inclination rolling mill 10...
Clad material 11...Core material 12...Outer layer material Applicant Sumitomo Metal Industries Co., Ltd. Agent Patent attorney Noboru Kono
Other alloy group i [stainless steel pipe] (a) (b)'v3
z Figure 4 Part 5 Figure 6 (A)
(b)'l, 7 Figure

Claims (3)

[Claims] 1. A stainless steel clad screw characterized in that an outer layer material made of stainless steel is fitted and bonded to the circumferential surface of a core material made of carbon steel or low alloy steel. 2. After degreasing and cleaning the outer peripheral surface of the core material and the inner peripheral surface of the outer layer material, the core material is inserted into the outer layer material, and the boundaries between the core material and the outer layer material on both end surfaces are sealed by welding, and the clad material is After forming the clad material and heating the clad material, a plurality of annular grooves are formed in the circumferential direction of the outer circumferential surface to form a screw, and three to four annular grooves are formed at intervals that gradually become wider from the inlet side to the outlet side. A method for manufacturing a stainless steel clad screw, comprising elongation rolling using an inclined rolling mill having cone-shaped rolls. 3. After degreasing and cleaning the outer circumferential surface of the core material and the inner circumferential surface of the outer layer material, the core material is inserted into the outer layer material, and cold drawing is performed to bring the outer layer material and the core material into close contact. The boundary is sealed by welding to form a cladding material, and after this cladding material is heated, a plurality of annular grooves that shape the screw in the circumferential direction of the outer circumferential surface are formed at intervals that gradually widen from the entry side to the exit side. A method for manufacturing a stainless steel clad screw, which comprises elongation rolling using an inclined rolling mill having three to four cone-shaped rolls.