JP2020050914A - Lead-free free-cutting phosphor bronze rod wire - Google Patents

Abstract

To provide a lead-free free-cutting phosphor bronze rod wire that is excellent in machinability and cold workability.SOLUTION: The lead-free free-cutting phosphor bronze rod wire contains 3.00 to 7.00 mass% of tin, 1.00 to 5.50 mass% of zinc, 0.35 to 4.50 mass% of nickel, 0.05 to 0.70 mass% of sulfur, and 0.06 to 0.50 mass% of phosphorus, and the remainder of copper and inevitable impurities.SELECTED DRAWING: None

Description

  The present invention relates to a lead-free free-cutting phosphor bronze rod wire excellent in machinability and cold workability.

  Phosphor bronze is a copper (Cu) -tin (Sn) -phosphorus (P) alloy, and various properties are produced depending on the Sn content. Phosphor bronze is tough, has excellent corrosion resistance, wear resistance, and solderability, and is suitable for a wide range of applications.

  Also, this free-cutting phosphor bronze is an alloy in which lead (Pb) is added to phosphor bronze to improve the cutting properties of phosphor bronze, such as small screws, bearings, bushes, bolts, nuts, ballpoint pen parts, and the like. Used for

  Here, in Japanese Industrial Standards JIS H 3270, C5341 is listed as a free-cutting phosphor bronze whose leadability is improved by adding lead. The chemical components of C5341 are as follows: Pb: 0.80 mass% to 1.50 mass%, Sn: 3.50 mass% to 5.80 mass%, P: 0.03 to 0.35 mass%, Cu + Sn + Pb + P: 99. .50% by mass or more.

Japanese Industrial Standards, JIS H 3270, Free-cutting phosphor bronze, 2012

  Here, in recent years, since lead is considered to affect the human body and the environment, its use is being restricted, and there is an increasing demand for a material containing no lead and having improved machinability.

  In addition, in the directive (RoHS Directive) by the European Union regarding the restriction on the use of specific harmful substances in electronic and electrical equipment, electronic and electrical equipment containing Pb exceeding 1000 mass ppm cannot be put on the market in the European Union. However, at present, the use of copper alloy is exempted up to 4% by mass because there is no suitable alternative.

  However, since the above-mentioned exemption may be eliminated in the near future, it is a substitute material having a Pb content not exceeding 1000 mass ppm (0.1 mass%), and a wire material having excellent machinability. Development is eagerly awaited.

  Further, in the above-mentioned C5341, there is a problem that the cold workability is inferior because it contains a large amount of lead.

  Then, this invention is made in view of the above-mentioned problem, and an object of this invention is to provide a lead-free free-cutting phosphor bronze rod wire excellent in machinability and cold workability.

  In order to achieve the above object, the lead-free free-cutting phosphor bronze rod wire according to the present invention has a content of 3.00 to 7.00% by mass of tin, 1.00 to 5.50% by mass of zinc (Zn), and nickel ( Ni) in an amount of 0.35 to 4.50% by mass, sulfur (S) in an amount of 0.05 to 0.70% by mass, and phosphorus in an amount of 0.06 to 0.50% by mass. It is characterized by being an impurity.

  ADVANTAGE OF THE INVENTION According to this invention, the lead-free free-cutting phosphor bronze rod wire excellent in machinability and cold workability can be provided.

  Hereinafter, a lead-free free-cutting phosphor bronze rod wire according to the present embodiment will be described.

  The lead-free free-cutting phosphor bronze rod wire of the present embodiment is a wire rod containing a predetermined amount of nickel, tin, zinc, sulfur, and phosphorus, with the balance being copper and inevitable impurities.

  The lead-free free-cutting phosphor bronze rod wire of the present embodiment needs to contain nickel in an amount of 0.35 to 4.50 mass% from the viewpoint of achieving both excellent machinability and cold workability. If the amount is less than 0.35% by mass, the machinability may decrease. If the amount is more than 4.50% by mass, cracks may occur and the cold workability may decrease. The content of nickel is preferably 0.40 to 4.00% by mass, and particularly preferably 0.50 to 3.50% by mass.

  Thus, in the lead-free free-cutting phosphor bronze rod wire of the present embodiment, by including a predetermined amount of nickel, the cold workability is improved, and the crystal grains are refined by repeated cold work, Since the cutting chips are small, good cutting properties can be obtained.

  In the lead-free free-cutting phosphor bronze rod wire of the present embodiment, it is necessary to contain 1.00 to 5.50% by mass of zinc. If the amount is less than 1.00% by mass, the cutting chips may be discolored by heat, and if the amount is more than 5.50% by mass, the machinability may decrease.

  As described above, in the lead-free free-cutting phosphor bronze rod wire of the present embodiment, by including a predetermined amount of zinc, it is possible to suppress a decrease in machinability and to suppress thermal discoloration of cutting chips.

  Moreover, in the lead-free free-cutting phosphor bronze rod wire of the present embodiment, it is necessary to contain 3.00 to 7.00% by mass of tin. If the amount is less than 3.00% by mass, the strength may be reduced. If the amount is more than 7.00% by mass, cracks may occur and the cold workability may be reduced.

  Further, by including a predetermined amount of sulfur instead of the lead in the above-mentioned 5341, the machinability can be improved. Sulfur reacts with copper, iron (Fe) and the like to form sulfide. And, due to this sulfide, in the lead-free free-cutting phosphor bronze rod wire of the present embodiment, since the chips become short chips that are cut at the time of cutting, they may be wrapped around the blade used for cutting. As a result, the machinability can be improved.

  The lead-free free-cutting phosphor bronze rod wire of the present embodiment needs to contain 0.05 to 0.70 mass% of sulfur. If the amount of sulfur is less than 0.05% by mass, the above-described effect of the machinability may not be sufficiently obtained. On the other hand, if it exceeds 0.70% by mass, cracks may occur, and cold working may be difficult.

  That is, since the lead-free free-cutting phosphor bronze rod wire of the present embodiment contains 0.05 to 0.70 mass% of sulfur, the dispersed sulfide acts as a chip breaker at the time of cutting. As a result, the machinability can be improved without lowering the cold workability.

  The lead-free free-cutting phosphor bronze rod wire of the present embodiment needs to contain 0.06 to 0.50% by mass of phosphorus. If the phosphorus content is less than 0.06% by mass, the deoxidizing effect at the time of dissolution may be insufficient, and if the phosphorus content exceeds 0.50% by mass, cold working may be performed. This is because the property is reduced. The phosphorus content is preferably 0.35% by mass or less, because more stable cold workability can be obtained.

  Elements contained as impurities in the lead-free free-cutting phosphor bronze rod wire of the present embodiment include iron, silver, carbon, zirconium, manganese, bismuth, indium, selenium, aluminum, oxygen, boron, tungsten, antimony, silicon, and lead. And the like. In addition, the content of each of them is preferably less than 0.05% by mass, and more preferably less than the detection limit.

  In addition, as a method of manufacturing the lead-free free-cutting phosphor bronze rod wire of the present embodiment, cold working is performed.

  Examples of the cold working include cold rolling, cold forging, and cold drawing. The number of times of cold working is not particularly limited, but is preferably four or more times from the viewpoint of obtaining a uniform composition in a lead-free free-cut phosphor bronze rod. After the cold working, it is preferable to perform annealing.

  Hereinafter, the lead-free free-cutting phosphor bronze rod wire of the present invention will be described with reference to specific examples, but the present invention is not limited to these examples.

(Preparation of test pieces)
First, the compounding amount of tin, the compounding amount of zinc, the compounding amount of nickel, the compounding amount of sulfur, and the compounding amount of phosphorus are appropriately changed, and the rest is compounded as copper and unavoidable impurities. After producing an ingot by a mold casting method, samples of Examples 1 and 2 and Comparative Examples 1 to 3 were produced, and the components were analyzed. The above results are shown in Tables 1 and 2.

  Next, for each of the above ingots, cold rolling at a working ratio of about 20 to 30% and annealing at about 650 ° C. were repeated, and after performing the fourth cold rolling, Examples 1 and 2 and Comparative Example 1 were performed. ~ 3 test pieces were obtained.

<Machinability test>
In each of the test pieces of Examples 1 and 2 and Comparative Examples 1 to 3, face milling was performed using a general-purpose lathe LPT-35C manufactured by Washino Machine Co., Ltd. at a rotation speed of 450 rpm, a feed pitch of 0.75 mm, and a cutting depth of 0.5 mm. did.

  Then, in Examples 1 and 2 and Comparative Examples 1 and 2, the mass of 10 pieces of cutting chips generated at the time of facing was measured with an electronic balance AUX120 manufactured by Shimadzu Corporation. Table 1 shows the above results. In Examples 1 and 2 and Comparative Example 3, the presence or absence of discoloration of the cutting chips was visually checked. Table 3 shows the above results.

<Cold workability evaluation>
In each of the test pieces of Examples 1 and 2 and the test piece of Comparative Example 3 used in the above-mentioned machinability test, the occurrence of cracks during cold rolling was visually evaluated according to the following evaluation criteria. Table 2 shows the above results.

No cracks occurred: ○
Cracks occurred: ×

  As shown in Table 1, in Examples 1 and 2 in which the content of nickel was 0.35% by mass or more, compared with Comparative Example 1 in which the content of nickel was less than 0.35% by mass, Ten pieces were small in mass, and the cuttings of Example 1 were finely divided than the cuttings of Comparative Example 1, and it can be seen that they had excellent machinability even without containing lead.

  Further, as shown in Table 2, in Comparative Example 3, since the content of nickel was more than 4.50% by mass, it was found that cracks occurred and the cold workability was reduced.

  That is, it can be seen that the lead-free free-cutting phosphor bronze rods of Examples 1 and 2 containing 0.35 to 4.50% by mass of nickel are excellent in machinability and cold workability.

  In addition, in Comparative Example 2, since the content of zinc is large (6.40 mass%), it can be seen that the mass of 10 cutting chips is large.

  Further, as shown in Table 3, in Comparative Example 3, since the content of zinc was small (0.01% by mass), it can be seen that the cutting chips thermally discolored.

  INDUSTRIAL APPLICABILITY As described above, the present invention is particularly useful for a lead-free free-cutting phosphor bronze rod wire requiring excellent machinability and cold workability.

Claims (1)

  3.00 to 7.00% by mass of tin, 1.00 to 5.50% by mass of zinc, 0.35 to 4.50% by mass of nickel, 0.05 to 0.70% by mass of sulfur, and phosphorus Of 0.06 to 0.50 mass%, and the balance is copper and inevitable impurities.