Continuous quality and improvement technology of stainless steel spring wire

Fourth, the improvement plan

In line with the principle of 1S09001:2000 full participation, all relevant personnel are specially held to participate in the production site analysis meeting. The content of the meeting should be notified 3 days in advance, and more innovative measures are encouraged to promptly stop the negative evaluation of different views. Starting with the five factors of human, machine, material, law and environment, we have worked out improvement measures that are both in line with the actual production and practical.

1. The uniformity of the strength of the cleaning rod

YB(T)11-83 only stipulates the tensile strength range of steel wire, and does not specify the strength difference of a plate (batch) of steel wire. ASTM, BS, JIS, ISO and other standards all have different tensile strength of steel wire rods. In a nutshell, the dispersion of the tensile strength of a steel wire rod is ≤100MPa, and the dispersion of the strength of a batch of steel wire rod is ≤150MPa. The strength performance of the steel wire rod produced by Sanhe Company can also meet the above requirements. However, the strength difference of some foreign manufacturers’ cleaning rods is controlled within 50Mpa, and the current domestic spring steel wires cannot fully meet the requirements. It can be seen that domestic spring steel wires should not only meet relevant foreign standards, but also continue to improve their physical quality to reach the advanced level of foreign manufacturers’ physical quality. .While ensuring that the steel wire raw materials are imported high-quality wire rods, the following measures should be taken: (1) Improve the heat treatment temperature control and the precision of the winding equipment; (2) The wire drawing adopts a straight wire drawing machine; (3) The wire drawing machine coil The barrel and mold box should be cooled by circulating water; (4) The upper and lower ends of each finished steel wire are tested for tensile strength.

2. Flatness of steel wire

YB(T)11-83 stipulates: the wire reel should be regular, and when the wire reel is opened, it should not be scattered, twisted or shaped like “∞”. The steel wire with a diameter ≤ 4inm should be tested for flatness, that is, the length is about one and a half circle The sample is placed flat on the platform, and the maximum value of the tilt from the platform to the end of the steel wire is tested. The diameter is ≤0.50mm, the maximum value of the tilt is ≤40mm, the diameter>0.50mm, and the maximum value of the tilt is ≤30mm. The standard is as specified in ISO6931-1:1994: The steel wire should be wound in a regular manner after drawing, and the steel wire with a diameter of ≤5mm should meet the following requirements:

The distance between the shafts at both ends L=0.2D/d1/4 (1) In formula (1): D is the average free diameter of a single turn (turn) of the steel wire; d is the diameter of the steel wire.

Take a single turn (turn) of steel wire and hang it with a round rod. The axial distance L at both ends does not exceed the value calculated by formula (1), and 1 times the diameter of the reel D roll ≤ single turn (turn) of the steel wire average free diameter D ≤ Volume 1.5D is considered qualified.

Compared with well-known foreign manufacturers, the flatness of the steel wire is also behind them. A well-known foreign manufacturer of Φ1.0mm steel wire adopts the detection method shown in Figure 1, and the axial distance L value at both ends is almost zero. If the flatness of the steel wire is not good , It means that the residual stress on the surface of the wire drawing process is too large or uneven. During the coiling process, due to the residual force on the surface of the wire, the spring forming strain will be unstable, and the free height of the spring will rise and fall, and the size of the coil diameter will not change. 1. Defects such as loop cracks and axial twists. In order to further improve the flatness performance of the steel wire and narrow the gap, the following measures have been taken: (1) Improve the transmission accuracy of the wire drawing machine; (2) Modify the mold box to make It is more stable during drawing; (3) Find out a set of methods to adjust the mold box and straighteners by observing the upturn or downturn of the wire head on the wire drawing machine drum to make the wire regular and neat.

5. Evaluation effect

It is very important to evaluate the effect of the implementation of the above measures. If you exaggerate the improvement effect, you will mistakenly think that the problem has been solved, which will cause the problem to happen again; on the contrary, it will also lead to turning a blind eye to the improvement effect and damaging the enthusiasm for continuous improvement. Evaluate the effect using a bar chart. Compare the number and distribution of unqualified items detected by internal control before and after the implementation of the measures.

After the implementation of the measures, the quality of the cleaning rod strength and flatness of the steel wire has been improved significantly, but the effect of the surface quality of the steel wire is not ideal. In order to consolidate the results, the improvement measures have been standardized, and have been formulated or revised one after another. Use stainless steel wire production related work instructions, inspection procedures and other documents to provide the basis for the next continuous improvement.