KR19990051481A - Annealing Method of WY 308 Austenitic Stainless Steel with Excellent Surface Roughness - Google Patents

Abstract

The present invention relates to an annealing method of an austenitic wire rod used as a welding rod when welding stainless steel; The purpose is to provide an annealing method of Y308 austenitic stainless steel wire having excellent surface roughness.

The present invention for achieving the above object, by weight% C: 0.06% or less, Si: 0.65% or less, Mn: 1.00-2.50%, Cr: 19.50-22.00%, Ni: 9.50-10.50% and the remaining Fe and others In the method of wire-rolling and then annealing the austenitic stainless steel pieces composed of impurities inevitably contained, the annealing is carried out at a temperature of 1060-1100 ° C. in an atmosphere in which excess oxygen is maintained in the range of 1-3%. The gist of the annealing method of the Y308 austenitic stainless steel wire which has the outstanding surface roughness including heating is made into the summary.

Description

Annealing Method of W308 Austenitic Stainless Steel Wire with Excellent Surface Roughness

The present invention relates to an annealing method of a Y308 austenitic stainless steel wire used as a welding rod when welding stainless steel, and more particularly, to an annealing method capable of ensuring excellent surface roughness.

The welding rod used for welding stainless steel is Y308 austenitic stainless steel, the specific component of which is by weight, C: 0.06% or less, Si: 0.65% or less, Mn: 1.00-2.50%, Cr: 19.50- 22.00%, Ni: 9.50-10.50% and the rest of Fe and other unavoidable impurities.

This Y308 austenitic stainless steel wire is manufactured by a series of processes in which a wire rod is rolled to the required dimensions through a melt-casting-rolled steel rolling process, and then wound and cooled in the shape of a coil, in the same manner as a general wire rod manufacturing method. The wire rod thus manufactured is made of wire through secondary processing (fresh processing) after annealing heat treatment at a demand price and is used as a welding rod.

Surface roughness of the characteristics of the welding bar material means the surface roughness, the lower the surface roughness value is advantageous to the product characteristics. Actual surface roughness is an important property that determines the glossiness of the material after pickling, adhesion with lubricant and glossiness of wire rod after drawing.

During the manufacturing process mentioned above, the surface roughness of the wire before secondary processing is usually controlled by the winding condition control after the wire rolling and the annealing condition of the wound wire, which is greatly affected by the double annealing condition.

The annealing heat treatment is performed before the secondary processing (fresh processing), and the purpose is to remove various defects present on the surface of the wire rod during hot rolling, to uniform grains, and to remove carbide precipitated during cooling. At this time, the surface of the wire rod often has an adverse effect on the quality and error rate of the product due to the formation of an oxide scale during annealing. That is, the error rate decreases due to the loss of metal due to the annealing scale, and the non-uniformity of the oxidizing scale during annealing inhibits the surface roughness and surface gloss. .

In general, annealing of Y308 stainless steel is heated at a rate of 40 / ° C. to 900 ° C., which is a heating condition in which the temperature variation inside and outside the coil occurs below 10 ° C., and 5-8 ° C. / to a temperature of 1020-1050 ° C., which is the final annealing temperature. It is heated to minutes, and the annealing heat treatment is carried out at 120 minutes for the total annealing time. The annealing atmosphere at this time is a condition of 7-12% excess oxygen.

In the case of pickling the wire rod annealed under such annealing conditions, the surface roughness after pickling is very poor due to the scale and the formation of the scale formed during the annealing.

Recently, in order to solve such a problem, a method of controlling solution by controlling cooling conditions after wire rolling without separately performing annealing heat treatment, which is a cause of lowering the realization rate and surface roughness due to oxidation scale (hereinafter, referred to as 'direct heat treatment'). Are disclosed in Japanese Patent Publication Nos. 59-22773 and 55-5103.

Specifically, these methods are carried out in the filament rolling during wire rolling at 1100 ℃ or more, and then maintained at a temperature of 1100-1050 ℃ for a certain time to increase the size of the austenite grains ASTM No. After adjusting to 3.0-7.0 range, it quenched below 500 degreeC. That is, after cooling to room temperature, the annealing heat treatment process for removing various defects and desired mechanical properties is removed. This method is a method of direct solution treatment to improve the real error rate of the material, to save energy due to the use of rolling heating and to ensure the surface roughness of R _max 15㎛.

However, the process of controlling the size of austenite grains is very difficult by maintaining a constant temperature at a high temperature. The bigger problem is that it is inevitable that major equipments such as the installation of additional equipment in wire rod rolling mills are inevitable after maintenance rolling, and the maintenance costs of the conveyor equipments maintained at high temperature are inevitable. An increase in costs is incurred.

Therefore, the present inventors studied an annealing heat treatment process to secure the surface roughness of the wire rod produced without increasing the additional equipment or improvement of the equipment, and as a result, it is uniform by controlling the atmosphere excess oxygen and the annealing temperature during the annealing heat treatment of the Y308 steel. The present invention has been proposed on the basis that the scale can be obtained to improve the surface roughness.

The present invention provides an annealing heat treatment method that can secure the surface roughness of the wire rod by controlling the amount of excess oxygen and annealing temperature of the atmosphere gas during annealing of the Y308 stainless wire.

1 is a graph showing the size of nodule scale according to the amount of excess oxygen;

2 is a graph showing the size of the nodule scale according to the annealing temperature and the amount of excess oxygen;

3 is a graph showing the scale formation amount according to the annealing temperature and the excess oxygen amount.

The present invention for achieving the above object, by weight% C: 0.06% or less, Si: 0.65% or less, Mn: 1.00-2.50%, Cr: 19.50-22.00%, Ni: 9.50-10.50% and the remaining Fe and others Austenitic stainless steel pieces, which are inevitably contained in an impurity, are rolled and wire-wound and then annealed at a temperature of 1060-1100 ° C. in an atmosphere in which excess oxygen is maintained in the range of 1-3%.

Hereinafter, the present invention will be described in detail.

First, the target steel species of the present invention are known steels, which are called Y308 austenitic stainless steels. The specific components are by weight, C: 0.06% or less, Si: 0.65% or less, Mn: 1.00-2.50%, Cr: 19.50-22.00%, Ni: 9.50-10.50%, and the remaining Fe and other unavoidable impurities. Austenitic stainless steel.

The present invention is to control the annealing conditions when the steel pieces are formed as described above by wire-rolling in a conventional manner, then wound with a coil, and then annealing the wound coil in an annealing furnace. That is, by controlling the amount of excess oxygen in the annealing temperature and the annealing atmosphere to form a uniform scale to secure the surface roughness of the material, there is a feature of the present invention.

First, according to the present invention, when annealing the Y308 steel, it is preferable to control the amount of excess oxygen in the atmosphere gas to 1-3%. The reason is that if the excess oxygen is less than 1%, the amount of scale formed during annealing is small, so that it is impossible to remove various defects formed during wire rolling.In the case of LPG gas furnace, soot may occur due to combustion failure. to be. When the excess oxygen content exceeds 4%, it is difficult to remove various defects formed during wire rolling and transportation due to the reduction of the amount of annealing scale formed during annealing, and due to the lack of Fe oxide formation on the scale, This is because a large nodule-like scale may be formed, resulting in poor surface roughness after pickling.

When annealing in the above atmosphere conditions, the annealing temperature is preferably maintained at a temperature of 1060-1100 ℃. The reason is that when the annealing temperature is 1060 ℃ or less, the amount of scale formed on the surface of the wire rod is small, so that various defects formed during the wire rod rolling are inadequate. . If the annealing temperature exceeds 1100 ℃, the surface roughness is improved by the formation of uniform scale, but the mechanical property is poor due to the decrease of the real rate due to the formation of excessive scale and the grain coarsening, especially the coarse grain and the fine grain mixed Due to the non-uniformity of mechanical properties, the secondary workability worsens.

The wire rod annealed according to the present invention as described above is supplied to the demand after pickling in a conventional manner and used as a stainless steel welding rod after drawing.

Hereinafter, the present invention will be described in detail by way of examples.

Example 1

The SUS Y308 steel strip was rolled up to a diameter of 5.5 mm and wound up, and the cooled wire (which exists on a cooling scale) was heated to 900 ° C. at a rate of 40 ° C./min, and then 1080 at a speed of 5-8 ° C./min. After heating up to ℃, it was heated at this temperature for 120 minutes. At this time, the atmosphere gas used was mixed with LPG gas and air to use the combustion gas after combustion, and the amount of excess oxygen was adjusted by controlling the combustion ratio of fuel and air.

The shape of the scale and the metal interface formed on the wire rod annealed under the conditions as described above was measured by the size of the nodule scale, and the results are shown in FIG. 1 according to the amount of excess oxygen.

Here, the shape of the scale and the metal interface is measured by the size of the nodule scale because the uniformity of the scale and the metal interface formed during annealing generally determines the surface roughness of the material after pickling. If large, it means that the surface roughness of the material after pickling deteriorates.

As shown in FIG. 1, when the amount of excess oxygen is 8%, the size of the nodule scale is about 50 μm. As a result, the interface between the metal and the scale is very nonuniform, and the scale of the large nodule shape is formed. Can be.

On the other hand, when the amount of excess oxygen decreases, the size of the nodule scale decreases, and when the amount of excess oxygen is about 3%, the size of the nodule scale is the smallest, and when the amount of excess oxygen is 3%, the interface between the metal and the scale is very uniform. It can be seen.

However, when the excess oxygen amount is 1% or less, a uniform scale layer is also formed, but an increase in fuel cost due to incomplete combustion of incomplete gas occurs. Therefore, the improvement of the surface roughness of the material was found to reduce the amount of excess oxygen in the annealing furnace to 1-3%, it can be seen that the annealing is preferable.

Example 2

The SUS Y308 steel was rolled and annealed in the same manner as in Example 1. However, at this time, while changing the annealing temperature and the amount of excess oxygen as shown in Figure 2 measured the size of the nodule scale according to the conditions and the results are shown in FIG.

As shown in FIG. 2, when the amount of excess oxygen is 8%, the size of the nodule scale does not change significantly as the annealing temperature increases to 40-50 μm, but the size of the nodule scale decreases significantly as the amount of excess oxygen decreases. Able to know.

In addition, in the case of 3% excess oxygen, when the annealing temperature is 1030 ° C., a nodule scale of 20 μm or more is formed, but the annealing temperature decreases to about 10 μm. Therefore, it can be seen that when the excess oxygen is low, the increase of the annealing temperature reduces the size of the nodule scale, thereby improving the surface roughness by improving the shape of the material scale and the metal interface.

Example 3

The SUS Y308 steel was rolled and annealed in the same manner as in Example 1. However, at this time, while changing the annealing temperature and the amount of excess oxygen as shown in Figure 3 the amount of scale according to the conditions were measured and the results are shown in FIG.

As shown in FIG. 3, at the same excess oxygen amount, an increase in annealing temperature increases the amount of scale formed during annealing, and in particular, an increase in annealing temperature in the case of excess oxygen amount of 4% or less leads to a rapid increase in the amount of oxidation. . In other words, the excess oxygen content of 4% or less means that the annealing rate of the material due to scale formation is drastically reduced when the annealing temperature is increased. In addition, in the case of excess oxygen amount of 4% or more, there is no significant change in oxidation amount according to the annealing temperature, but it can be seen that the oxidation amount gradually increases as the annealing temperature increases.

Therefore, the amount of excess oxygen of 1-3% to form a uniform scale in a range that does not reduce the real error rate of the material compared to the case of 1030-1050 ℃, the excess oxygen 7-12% of the annealing conditions of the normal annealing conditions In the case of, the heating temperature can be seen that the annealing temperature range of 1060-1100 ℃.

In summary, the surface roughness can be achieved by forming a uniform scale without reducing the error rate due to the scale formed when the annealing temperature is annealed in the range of 1060-1100 ° C. while maintaining an atmospheric excess oxygen amount of 1-3% in the annealing furnace. Improvements are possible.

As described above, the present invention can provide a Y308 stainless steel wire having excellent surface roughness by forming a uniform scale by controlling the annealing conditions, and thus has a very useful effect of improving the surface quality of the Y308 stainless steel wire. will be.

Claims (1)

Austenitic by weight of C: 0.06% or less, Si: 0.65% or less, Mn: 1.00-2.50%, Cr: 19.50-22.00%, Ni: 9.50-10.50% and the remaining Fe and other unavoidable impurities In the method of rolling and annealing a stainless steel piece by wire, The annealing is an annealing method of the Y308 stainless steel wire having excellent surface roughness, characterized in that the heating is carried out at a temperature of 1060-1100 ℃ in the atmosphere maintaining the amount of excess oxygen in the range of 1-3%.