CN110468369A - 300 series stainless steel screw fasteners nitridation heat treatment processing procedure - Google Patents

Abstract

A kind of 300 series stainless steel screw fasteners nitridation heat treatment processing procedure includes: forming step is carried out to the disk member of 300 series stainless steel materials, so that the disk member has screw terminal and screw rod；It carries out rolling over tooth step, so that at least one portion of the screw rod becomes screw thread portion, thus forms screw；Nitridation process step is carried out to the screw, to increase the hardness of the screw surface；And surface treatment step is carried out to the screw, to form antirust coat in the screw surface.

Description

Nitriding heat treatment process for 300 series stainless steel screw fasteners

technical field

The invention relates to a heat treatment process for screw fasteners, in particular to a nitriding heat treatment process for 300 series stainless steel screw fasteners.

Background technique

Due to its special design of the drill tail end, the drill tail screw integrates the three functions of "drilling", "tapping" and "locking" at the same time: Drilling - the tail end part of the drill bit shape (referred to as the drill tail), It can directly drill holes on the surface of the lock; tapping—the self-tapping part other than the drill bit, which can be directly tapped in the hole to form an internal thread; lock—the main purpose of the screw can be achieved without pre-drilling and tapping: Lock payment objects.

Drilling screws are available in a variety of materials and processes. For example, carbon steel is used for the material of the drill tail, and stainless steel is used for the screw shaft, and the two are joined by welding. However, the disadvantages of this kind of compound drill end screw are that the process is complicated, the cost is high, and the welding point is easy to break.

Alternatively, 400 series stainless steel can be used to manufacture the drill end screws in one piece. However, although the 400 series stainless steel drill tail screw has enough hardness to penetrate the lock, it has the disadvantage of being easy to rust.

Alternatively, 300 series stainless steel can be used to manufacture the drill end screws in one piece. However, although 300 series stainless steel drill tail screws have good corrosion resistance, they have low hardness because they cannot be subjected to a general heat treatment process, so they cannot penetrate through the relatively high-hardness locking parts. For example, the existing 300 series stainless steel Drilling screws cannot penetrate steel sections with a Rockwell hardness B scale (HRB) of 80±5 and a thickness of 3 mm to 6 mm. So, it is necessary to find a solution.

Contents of the invention

The object of the present invention is to provide a nitriding heat treatment process for 300 series stainless steel screw fasteners.

The 300 series stainless steel screw fastener nitriding heat treatment process of the present invention includes: (a) forming a disc element made of 300 series stainless steel, so that the disc element has a screw head and a screw shaft; (b) performing a tooth rolling step, making at least one portion of the screw shank a screw thread, thereby forming a screw; (c) subjecting the screw to a nitriding treatment step to increase the hardness of the surface of the screw; and (d) subjecting the screw to a surface A treatment step to form an anti-rust layer on the surface of said screw.

The 300 series stainless steel screw fastener nitriding heat treatment process of the present invention also includes the (e) step between the (b) step and the (c) step, which is to clean the surface of the screw with an acid agent and polish it. To improve the brightness of the screw surface.

In the 300 series stainless steel screw fastener nitriding heat treatment process of the present invention, in the step (c), the screw is placed in a vacuum box furnace for nitriding treatment.

In the nitriding heat treatment process of the 300 series stainless steel screw fasteners of the present invention, in the (c) step, the nitriding treatment step is carried out at a temperature of 700°C ± 50°C for 90 minutes to 120 minutes, and then cooled to normal temperature, so that the nitriding The nitrogen depth reaches 3 microns to 4 microns.

The 300 series stainless steel screw fastener nitriding heat treatment process of the present invention, in the (c) step, first place the screw in a vacuum box furnace, and carry out the nitriding treatment step at a temperature of 700°C ± 50°C. 90 minutes to 120 minutes, and then cooled to normal temperature, so that the nitriding depth reaches 3 microns to 4 microns.

In the nitriding heat treatment process of the 300 series stainless steel screw fasteners of the present invention, in the step (d), the anti-rust layer needs to be subjected to a salt spray test for more than 1000 hours.

The nitriding heat treatment process of the 300 series stainless steel screw fasteners of the present invention also includes the (f) step between the (a) step and the (b) step, performing the tail clamping step so that the screw rod is far away from the screw The end of the head becomes the drill tail, and the step (b) makes the rest of the screw shaft except the drill tail become the screw thread.

According to the nitriding heat treatment process of the 300 series stainless steel screw fasteners of the present invention, the surface hardness of the finished product of the screws is above 600 Vickers hardness, and can penetrate the section steel with a Rockwell hardness B scale of 80±5 and a thickness of 3 mm to 6 mm.

The beneficial effect of the present invention is that the hardness of the surface of the screw can be greatly improved due to the use of the "nitriding treatment" step to break through the limitation that the existing 300 series stainless steel screw fasteners cannot be heat-treated.

Description of drawings

Fig. 1 is a flow chart, illustrates the embodiment of the nitriding heat treatment process of 300 series stainless steel screw fasteners of the present invention;

Fig. 2 is a side view, illustrating that in this embodiment, after the forming step is performed on the disc unit made of 300 series stainless steel, the disc unit has a screw head and a screw shaft;

Fig. 3 is a side view, illustrating the step of clamping the tail of the screw rod in this embodiment, so that the end of the screw rod away from the screw head becomes the tail of the drill; and

Fig. 4 is a side view illustrating the thread rolling step in this embodiment, so that the rest of the screw shaft except the tail of the drill becomes the thread portion.

Detailed ways

The present invention will be described in detail below in conjunction with the accompanying drawings and embodiments.

Referring to Figures 1 to 4, the nitriding heat treatment process for 300 series stainless steel (i.e. SUS300) screw fasteners of the present invention is suitable for carrying out the nitriding heat treatment process for 300 series stainless steel disk elements to form 300 series stainless steel screws with higher surface hardness fasteners.

As shown in step 21 of FIG. 1 and FIG. 2 , in this embodiment, the disc unit made of 300 series stainless steel is formed first, so that the disc unit has a screw head 11 and a screw rod 12 . At this moment, because the thread rolling step has not been carried out, there is no thread on the screw rod 12 yet.

Next, as shown in step 22 of FIG. 1 and FIG. 3 , the end of the screw rod 12 away from the screw head 11 is clamped so that the end of the screw rod 12 away from the screw head 11 becomes a drill tail 121 . For example, in this embodiment, the die can be used for forging to forge the No. 3 drill tail.

Next, as shown in FIG. 1 step 23 and FIG. 4 , the thread rolling step is carried out so that the rest of the screw rod 12 other than the drill tail portion 121 becomes the screw thread portion 122 (coarse thread or fine thread), thus forming the screw 1 .

Since this embodiment needs to use oxalic acid and other oils during the aforementioned steps of molding, tail clamping, and tooth rolling, after the tooth rolling step in step 23 is completed, it is necessary to clean the screw 1 with an acid agent as shown in step 24. The surface is polished to improve the brightness of the screw 1 surface.

Next, as shown in step 25 of FIG. 1 , a nitriding treatment step is performed on the screw 1 to increase the hardness of the surface of the screw 1 . In this embodiment, when carrying out the nitriding treatment step, the screw 1 is first placed in a vacuum box furnace, and the nitriding treatment is carried out at a temperature of 700 ° C ± 50 ° C for 90 minutes to 120 minutes, and then cooled to room temperature , so that the nitriding depth can reach 3 microns to 4 microns. Therefore, the present invention breaks through the limitation that the existing 300 series stainless steel screw fasteners cannot be heat-treated by using the "nitriding treatment" step, thus greatly improving the hardness of the surface of the screw 1 .

Then, as shown in step 26 , a surface treatment step is performed on the screw 1 to form an antirust layer on the surface of the screw 1 , thus producing a finished product of the 300 series stainless steel screw 1 undergoing nitriding heat treatment. In this embodiment, the anti-rust layer is formed by coating, and the anti-rust layer needs to be subjected to a salt spray test for more than 1000 hours.

Therefore, in this embodiment, since the screw 1 is subjected to nitriding treatment at a temperature of 700°C±50°C for 90 minutes to 120 minutes, and then cooled to normal temperature, the nitriding depth reaches 3 microns to 4 microns, so the The surface hardness of the finished 300 series stainless steel screw 1 can reach Vickers hardness (HV) 600 or more, and the finished product of the 300 series stainless steel screw 1 can penetrate the Rockwell hardness B scale (HRB) 80±5 and the thickness is 3 mm to 6 millimeter steel.

In addition, it should be pointed out that, in the above-mentioned embodiment, the description is made with the screw 1 being a drill screw. However, the present invention is not limited thereto, but other embodiments of the present invention can also omit step 22. The tail clamping step, that is to say, the nitriding heat treatment process of the 300 series stainless steel screw fastener of the present invention is also applicable to the general 300 series stainless steel screw fastener without the drill tail 121 .

To sum up, the nitriding heat treatment process of the 300 series stainless steel screw fasteners of the present invention breaks through the limitation that the existing 300 series stainless steel screw fasteners cannot be heat treated in step 25 of the "nitriding treatment", thus greatly improving the surface hardness of the screw 1. Hardness, so the purpose of the present invention can really be achieved.

Claims (8)

1. a kind of 300 series stainless steel screw fasteners nitridation heat treatment processing procedure, which is characterized in that comprise the steps of

(a) forming step is carried out to the disk member of 300 series stainless steel materials, so that the disk member has screw terminal and screw rod；

(b) it carries out rolling over tooth step, so that at least one portion of the screw rod becomes screw thread portion, thus forms screw；

(c) nitridation process step is carried out to the screw, to increase the hardness of the screw surface；And

(d) surface treatment step is carried out to the screw, to form antirust coat in the screw surface.

2. 300 series stainless steel screw fastener nitridation heat treatment processing procedure according to claim 1, it is characterised in that: also wrap (e) step being contained between described (b) step and (c) step, is the surface for being cleaned the screw with sour agent, is polished, To improve the brightness of the screw surface.

3. 300 series stainless steel screw fastener nitridation heat treatment processing procedure according to claim 1, it is characterised in that: in institute It states in (c) step, is that the screw is placed in vacuum box-type furnace to carry out nitridation process step.

4. 300 series stainless steel screw fastener nitridation heat treatment processing procedure according to claim 1, it is characterised in that: in institute It states in (c) step, is to carry out nitridation process step with 700 DEG C ± 50 DEG C of temperature up to 90 minutes to 120 minutes, is cooled to often Temperature, so that depth of nitration reaches 3 microns to 4 microns.

5. 300 series stainless steel screw fastener nitridation heat treatment processing procedure according to claim 1, it is characterised in that: in institute It states in (c) step, is that first the screw is placed in vacuum box-type furnace, nitrogen treatment step is carried out with 700 DEG C ± 50 DEG C of temperature Suddenly up to 90 minutes to 120 minutes, it is cooled to room temperature, so that depth of nitration reaches 3 microns to 4 microns.

6. 300 series stainless steel screw fastener nitridation heat treatment processing procedure according to claim 1, it is characterised in that: in institute It states in (d) step, the antirust coat need to be performed for more than 1000 hours salt spray tests.

7. 300 series stainless steel screw fastener nitridation heat treatment processing procedure according to claim 1, it is characterised in that: also wrap (f) step being contained between described (a) step and (b) step carries out folder tail step, so that the screw rod is far from the spiral shell The end of silk head becomes drilling tail portion, and (b) step makes remaining screw bar part other than the drilling tail portion become the spiral shell Silk tooth portion.

8. 300 series stainless steel screw fastener nitridation heat treatment processing procedure according to claim 7, it is characterised in that: described The surface hardness of the finished product of screw is 600 or more Vickers hardness, and can be through Rockwell hardness B scale 80 ± 5 and with a thickness of 3 millimeters To 6 millimeters of fashioned iron.