Galvanized open plate with flowers

The product is widely used in various industries, including hardware tools, clay and tile knives, putty knives, bricklaying knives, trowels, shovels, woodworking band saws, saw blades, hand board saws, circular saw blades, various garden saws, roller gate springs, fuel dispenser coil spring steel strips, brick mouth machine steel strips, automobile clutch plate steel strips, clock watch springs, various steel tape measures, lock making, shoe materials, textiles, sickle materials, standard stamping steel strips, as well as various materials such as blue painted packaging belts. It also produces steel strips used in other industries

65Mn spring steel (foreign name: 65Mn), also known as 65 manganese, is a spring steel material that complies with the GB/T 1222-2007 standard. This steel grade improves its hardenability by adding manganese element. The φ 12mm steel can be quenched in oil and has the characteristics of less surface decarburization tendency than silicon steel and better comprehensive mechanical properties than carbon steel. However, it has overheating sensitivity and temper brittleness tendency. It is mainly used in the manufacturing of elastic components such as spring rings, valve springs, clutch spring plates, and cold drawn steel wire coil springs.

The chemical composition of this material contains 0.62% -0.70% carbon and 0.90% -1.20% manganese, with a tensile strength of 825-925MPa and a hot rolling hardness of ≤ 302HB. The heat treatment specification is oil quenching at 830 ℃± 20 ℃, tempering at 540 ℃± 50 ℃, and the critical temperature Ac1 is 726 ℃. The product supply specifications include Φ 5.5-16mm disc and Φ 160-450mm forging, which can be pre treated using normalizing process (810 ℃± 10 ℃ air cooling).

Implement the standard GB/T 1222-2007

Yield strength 520~690 (MPa)

Rolled material with a diameter of 16 to 160mm

Execution standard: GB/T 1222-2007

Chemical composition:

Carbon C: 0.62-0.70

Silicon Si: 0.17-0.37

Manganese Mn: 0.90-1.20

Sulfur S: ≤ 0.035

Phosphorus P: ≤ 0.035

Chromium Cr: ≤ 0.25

Nickel Ni: ≤ 0.30

Copper Cu: ≤ 0.25

mechanical properties

Mechanical properties:

Tensile strength σ b (MPa): 825~925

Elongation rate δ 10 (%): 14~22.5

Shrinkage rate of cross-section (%): not greater than 10

Hardness: Hot rolled, ≤ 302HB; Hot rolled+heat treated, ≤ 321HB

Heat treatment specifications and metallographic structure:

Heat treatment specifications: quenching at 830 ℃± 20 ℃, oil cooling; Tempering at 540 ℃± 50 ℃ (± 30 ℃ if necessary).

Metallographic structure: martensite.

● Critical point temperatures (approximate values) Ac1=726 ℃, Ac3=765 ℃, Ar3=741 ℃, Ar1=689 ℃, Ms=270 ℃.

Normalization specification: temperature 810 ± 10 ℃, air cooling.  [1]

Delivery status: Hot rolled steel is delivered in a heat-treated or non heat-treated state, while cold drawn steel is delivered in a heat-treated state.

● Supply specifications:

Round disk: Φ 5.5-16mm

Forging material: Φ 160-450mm

Argon arc welding process

In order to reduce electrode consumption, direct current positive connection is selected for wire butt welding test, that is, a direct current power supply is selected, with the wire connected to the positive pole of the power supply and the tungsten electrode connected to the negative pole of the power supply.

Tungsten electrodes containing 1% or 2% thorium oxide have high electron emission efficiency, good current carrying capacity, good anti pollution performance, easy arc initiation, and relatively stable arc. For ease of operation, a thinner thorium tungsten electrode with a diameter of 2 mm is selected, and the front end of the electrode is sharpened.
Due to the lower arc voltage characteristics of argon gas, which is particularly beneficial for manual arc welding of thin plates and wires, argon gas is chosen as the shielding gas.

The experiment uses a DC manual argon arc welding machine. Before welding, the ends of the steel wire are carefully ground flat. To prevent porosity at the welding point, the oil stains on the ends are cleaned with acetone. Place the wire with both ends ground flat on a flat and clean alignment plate (Figure 1), aligning the ends without leaving any gap at the joint, and use a pressure iron to press down on both sides of the joint. Connect the wire to the positive pole of the welding machine and the tungsten pole to the negative pole. Adjust the current to 20 A, 15 A, 10 A, and 8 A respectively for welding. When welding, ignite an arc next to the joint and stabilize its combustion. Move the arc to the joint to melt the joint metal and quickly extinguish the arc. At the same time, apply a slight forging force and cool it down to complete the welding process. No filler wire is used during the welding process.

The experiment found that when the welding current is 20 A, the arc combustion is intense, the metal splashing at the joint is severe, and the welding point collapses severely. When the current is adjusted to 15 A, the arc combustion is smoother and there is less splashing in the molten pool, but the weld still collapses. But when the current drops to 10 A, arc ignition is easy, arc combustion is stable, and there is no collapse phenomenon at the weld seam. Figure 2 shows the shape of the welded joint captured by a digital camera under a Leica MZ6 stereomicroscope at a welding current of 10A. It can be seen that the cylindricity of the joint is good, and after polishing it, it can meet the requirements of the wire saw. When the current is reduced to below 8 A, it is difficult to initiate the arc and the arc is unstable, making it difficult to complete the welding process.

Welding joint test

Due to the tendency of 65Mn steel to overheat, the welding heat affected zone has a significant impact on the mechanical properties of the joint. After argon arc welding, the joint of 65Mn steel wire with a diameter of 0.7 mm is very hard and brittle. Gently bending the welding point will cause brittle fracture at the fusion line or weld seam, and the fracture surface will show a clear brittle fracture morphology. The obtained joint consists of a weld seam and a heat affected zone, and the microhardness of each area from the center of the weld seam to the base metal is tested along the joint axis. The measurement results show that the microhardness increases sharply from the base metal to the heat affected zone and the middle of the weld, with a hardness of HV 1060 in the middle of the weld, indicating the formation of hard and brittle structures in the heat affected zone and the middle of the weld. For this type of joint with a hard and brittle structure, in order to improve its toughness and plasticity, reduce its hardness, and obtain an appropriate combination of hardness, strength, plasticity, and toughness, it is necessary to perform appropriate tempering treatment on the welded joint. After heat treatment, the brittleness of the heat affected zone should be eliminated, while maintaining a certain strength and elasticity of the base material. Tempering is carried out in a box type resistance furnace, and the tempering process is shown in Table 1. Carefully polish the welded joint of the tempered steel wire to make its diameter roughly equal to the diameter of the base metal, and then conduct a tensile test on the WE-50 tensile testing machine. Take three samples for each tempering treatment and take the average tensile strength.

From the experiment, it can be seen that after heat treatment above 330 ℃, the elasticity of the base material basically disappears, and the fracture occurs at the base material, rather than at the solder joint and its heat affected zone. This indicates that although the brittleness of the heat affected zone completely disappears after heat treatment, the strength of the base material is greatly reduced (according to the experiment, the tensile strength of the base material used is 1663 MPa). When kept at 260 ℃ for 10 minutes, although the elasticity of the material remains basically unchanged, the brittleness in the heat affected zone cannot be eliminated. When the heating temperature is 280 ℃ and the insulation time is 10 minutes, the best effect is achieved, and the tensile strength of the heat affected zone is only reduced by about 20% compared to the base material, while the elasticity of the base material disappears less. The microhardness of each zone on the longitudinal section of the welded joint tempered at 280 ℃ was tested along the axis direction, and it was found that the highest hardness value at the weld joint decreased to around HV 500, which was about twice the hardness of the untreated joint. The welded circular steel wire should not only meet certain strength and elasticity requirements, but also have a certain fatigue strength type

The traditional periodic spheroidization annealing process involves annealing at a temperature of 750 ℃, holding for 2 hours, furnace cooling to a temperature of (680 ± 10) ℃, holding for 3 hours, and then furnace cooling to 550 ℃ before being air cooled out of the furnace. The production efficiency is low, with an oxidation decarburization rate of 22% -40%, and the surface hardness and elasticity do not meet the requirements. Incomplete annealing new process, annealing temperature (740 ± 10) ℃, holding for 4 hours, furnace cooling to 550 ℃, then air cooling out of the furnace. The tensile strength is 600-620Mpa, the elongation is 53.5% -40%, and the hardness is 209-214HBW. The metallographic structure consists of spheroidized pearlite and a small amount of point like pearlite, which shortens the production cycle and saves energy.

The traditional annealing process involves annealing at 730 ℃ for 13 hours, followed by furnace cooling to 650 ℃ before being air cooled out of the furnace. New annealing process: Annealing temperature (860 ± 10) ℃, insulation for 45-60 minutes, furnace cooling to (750 ± 10) ℃, insulation for 3-3.5 hours, after furnace cooling to 650-660 ℃, it is cooled out of the furnace or slowly cooled in the insulation pit. The metallographic structure meets the requirements: the pearlite structure is between grade 2.5-6, with grade 4 being preferred. This process improves efficiency by 80% -100%.